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Quechol R, Solomon JB, Liu YA, Lee CC, Jasniewski AJ, Górecki K, Oyala P, Hedman B, Hodgson KO, Ribbe MW, Hu Y. Heterologous synthesis of the complex homometallic cores of nitrogenase P- and M-clusters in Escherichia coli. Proc Natl Acad Sci U S A 2023; 120:e2314788120. [PMID: 37871225 PMCID: PMC10622910 DOI: 10.1073/pnas.2314788120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2023] [Accepted: 09/28/2023] [Indexed: 10/25/2023] Open
Abstract
Nitrogenase is an active target of heterologous expression because of its importance for areas related to agronomy, energy, and environment. One major hurdle for expressing an active Mo-nitrogenase in Escherichia coli is to generate the complex metalloclusters (P- and M-clusters) within this enzyme, which involves some highly unique bioinorganic chemistry/metalloenzyme biochemistry that is not generally dealt with in the heterologous expression of proteins via synthetic biology; in particular, the heterologous synthesis of the homometallic P-cluster ([Fe8S7]) and M-cluster core (or L-cluster; [Fe8S9C]) on their respective protein scaffolds, which represents two crucial checkpoints along the biosynthetic pathway of a complete nitrogenase, has yet to be demonstrated by biochemical and spectroscopic analyses of purified metalloproteins. Here, we report the heterologous formation of a P-cluster-containing NifDK protein upon coexpression of Azotobacter vinelandii nifD, nifK, nifH, nifM, and nifZ genes, and that of an L-cluster-containing NifB protein upon coexpression of Methanosarcina acetivorans nifB, nifS, and nifU genes alongside the A. vinelandii fdxN gene, in E. coli. Our metal content, activity, EPR, and XAS/EXAFS data provide conclusive evidence for the successful synthesis of P- and L-clusters in a nondiazotrophic host, thereby highlighting the effectiveness of our metallocentric, divide-and-conquer approach that individually tackles the key events of nitrogenase biosynthesis prior to piecing them together into a complete pathway for the heterologous expression of nitrogenase. As such, this work paves the way for the transgenic expression of an active nitrogenase while providing an effective tool for further tackling the biosynthetic mechanism of this important metalloenzyme.
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Affiliation(s)
- Robert Quechol
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA92697-3900
| | - Joseph B. Solomon
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA92697-3900
- Department of Chemistry, University of California, Irvine, CA92697-2025
| | - Yiling A. Liu
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA92697-3900
| | - Chi Chung Lee
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA92697-3900
| | - Andrew J. Jasniewski
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA92697-3900
| | - Kamil Górecki
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA92697-3900
| | - Paul Oyala
- Department of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA91125
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource, Stanford Linear Accelerator Center National Accelerator Laboratory, Stanford University, Menlo Park, CA94025
| | - Keith O. Hodgson
- Stanford Synchrotron Radiation Lightsource, Stanford Linear Accelerator Center National Accelerator Laboratory, Stanford University, Menlo Park, CA94025
- Department of Chemistry, Stanford University, Stanford, CA94305
| | - Markus W. Ribbe
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA92697-3900
- Department of Chemistry, University of California, Irvine, CA92697-2025
| | - Yilin Hu
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA92697-3900
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2
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Braun A, Gee LB, Mara MW, Hill EA, Kroll T, Nordlund D, Sokaras D, Glatzel P, Hedman B, Hodgson KO, Borovik AS, Baker ML, Solomon EI. X-ray Spectroscopic Study of the Electronic Structure of a Trigonal High-Spin Fe(IV)═O Complex Modeling Non-Heme Enzyme Intermediates and Their Reactivity. J Am Chem Soc 2023; 145:18977-18991. [PMID: 37590931 PMCID: PMC10631461 DOI: 10.1021/jacs.3c06181] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/19/2023]
Abstract
Fe K-edge X-ray absorption spectroscopy (XAS) has long been used for the study of high-valent iron intermediates in biological and artificial catalysts. 4p-mixing into the 3d orbitals complicates the pre-edge analysis but when correctly understood via 1s2p resonant inelastic X-ray scattering and Fe L-edge XAS, it enables deeper insight into the geometric structure and correlates with the electronic structure and reactivity. This study shows that in addition to the 4p-mixing into the 3dz2 orbital due to the short iron-oxo bond, the loss of inversion in the equatorial plane leads to 4p mixing into the 3dx2-y2,xy, providing structural insight and allowing the distinction of 6- vs 5-coordinate active sites as shown through application to the Fe(IV)═O intermediate of taurine dioxygenase. Combined with O K-edge XAS, this study gives an unprecedented experimental insight into the electronic structure of Fe(IV)═O active sites and their selectivity for reactivity enabled by the π-pathway involving the 3dxz/yz orbitals. Finally, the large effect of spin polarization is experimentally assigned in the pre-edge (i.e., the α/β splitting) and found to be better modeled by multiplet simulations rather than by commonly used time-dependent density functional theory.
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Affiliation(s)
- Augustin Braun
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Leland B Gee
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Michael W Mara
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Ethan A Hill
- Department of Chemistry, University of California, Irvine, California 92697, United States
| | - Thomas Kroll
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Dennis Nordlund
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Dimosthenis Sokaras
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Pieter Glatzel
- ESRF-The European Synchrotron Radiation Facility, 71 Avenue des Martyrs, Grenoble 38000, France
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Keith O Hodgson
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - A S Borovik
- Department of Chemistry, University of California, Irvine, California 92697, United States
| | - Michael L Baker
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
- Department of Chemistry, The University of Manchester, Manchester M13 9PL, U.K
- The University of Manchester at Harwell, Diamond Light Source, Harwell Campus, Didcot OX11 0DE, U.K
| | - Edward I Solomon
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
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3
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Lim H, Brueggemeyer MT, Transue WJ, Meier KK, Jones SM, Kroll T, Sokaras D, Kelemen B, Hedman B, Hodgson KO, Solomon EI. Kβ X-ray Emission Spectroscopy of Cu(I)-Lytic Polysaccharide Monooxygenase: Direct Observation of the Frontier Molecular Orbital for H 2O 2 Activation. J Am Chem Soc 2023; 145:16015-16025. [PMID: 37441786 PMCID: PMC10557184 DOI: 10.1021/jacs.3c04048] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/15/2023]
Abstract
Lytic polysaccharide monooxygenases (LPMOs) catalyze the degradation of recalcitrant carbohydrate polysaccharide substrates. These enzymes are characterized by a mononuclear Cu(I) active site with a three-coordinate T-shaped "His-brace" configuration including the N-terminal histidine and its amine group as ligands. This study explicitly investigates the electronic structure of the d10 Cu(I) active site in a LPMO using Kβ X-ray emission spectroscopy (XES). The lack of inversion symmetry in the His-brace site enables the 3d/p mixing required for intensity in the Kβ valence-to-core (VtC) XES spectrum of Cu(I)-LPMO. These Kβ XES data are correlated to density functional theory (DFT) calculations to define the bonding, and in particular, the frontier molecular orbital (FMO) of the Cu(I) site. These experimentally validated DFT calculations are used to evaluate the reaction coordinate for homolytic cleavage of the H2O2 O-O bond and understand the contribution of this FMO to the low barrier of this reaction and how the geometric and electronic structure of the Cu(I)-LPMO site is activated for rapid reactivity with H2O2.
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Affiliation(s)
- Hyeongtaek Lim
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | | | - Wesley J Transue
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Katlyn K Meier
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Stephen M Jones
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Thomas Kroll
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Dimosthenis Sokaras
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Bradley Kelemen
- IFF Health and Biosciences, Palo Alto, California 94304, United States
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Keith O Hodgson
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Edward I Solomon
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
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Singha A, Sekretareva A, Tao L, Lim H, Ha Y, Braun A, Jones SM, Hedman B, Hodgson KO, Britt RD, Kosman DJ, Solomon EI. Tuning the Type 1 Reduction Potential of Multicopper Oxidases: Uncoupling the Effects of Electrostatics and H-Bonding to Histidine Ligands. J Am Chem Soc 2023. [PMID: 37294874 PMCID: PMC10392966 DOI: 10.1021/jacs.3c03241] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
In multicopper oxidases (MCOs), the type 1 (T1) Cu accepts electrons from the substrate and transfers these to the trinuclear Cu cluster (TNC) where O2 is reduced to H2O. The T1 potential in MCOs varies from 340 to 780 mV, a range not explained by the existing literature. This study focused on the ∼350 mV difference in potential of the T1 center in Fet3p and Trametes versicolor laccase (TvL) that have the same 2His1Cys ligand set. A range of spectroscopies performed on the oxidized and reduced T1 sites in these MCOs shows that they have equivalent geometric and electronic structures. However, the two His ligands of the T1 Cu in Fet3p are H-bonded to carboxylate residues, while in TvL they are H-bonded to noncharged groups. Electron spin echo envelope modulation spectroscopy shows that there are significant differences in the second-sphere H-bonding interactions in the two T1 centers. Redox titrations on type 2-depleted derivatives of Fet3p and its D409A and E185A variants reveal that the two carboxylates (D409 and E185) lower the T1 potential by 110 and 255-285 mV, respectively. Density functional theory calculations uncouple the effects of the charge of the carboxylates and their difference in H-bonding interactions with the His ligands on the T1 potential, indicating 90-150 mV for anionic charge and ∼100 mV for a strong H-bond. Finally, this study provides an explanation for the generally low potentials of metallooxidases relative to the wide range of potentials of the organic oxidases in terms of different oxidized states of their TNCs involved in catalytic turnover.
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Affiliation(s)
- Asmita Singha
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Alina Sekretareva
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Lizhi Tao
- Department of Chemistry, University of California at Davis, Davis, California 95616, United States
| | - Hyeongtaek Lim
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Yang Ha
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Augustin Braun
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Stephen M Jones
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Keith O Hodgson
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - R David Britt
- Department of Chemistry, University of California at Davis, Davis, California 95616, United States
| | - Daniel J Kosman
- Department of Biochemistry, The University at Buffalo, Buffalo, New York 14214, United States
| | - Edward I Solomon
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
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5
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Heyer AJ, Plessers D, Braun A, Rhoda HM, Bols ML, Hedman B, Hodgson KO, Schoonheydt RA, Sels BF, Solomon EI. Methane Activation by a Mononuclear Copper Active Site in the Zeolite Mordenite: Effect of Metal Nuclearity on Reactivity. J Am Chem Soc 2022; 144:19305-19316. [PMID: 36219763 DOI: 10.1021/jacs.2c06269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The direct conversion of methane to methanol would have a wide reaching environmental and industrial impact. Copper-containing zeolites can perform this reaction at low temperatures and pressures at a previously defined O2-activated [Cu2O]2+ site. However, after autoreduction of the copper-containing zeolite mordenite and removal of the [Cu2O]2+ active site, the zeolite is still methane reactive. In this study, we use diffuse reflectance UV-vis spectroscopy, magnetic circular dichroism, resonance Raman spectroscopy, electron paramagnetic resonance, and X-ray absorption spectroscopy to unambiguously define a mononuclear [CuOH]+ as the CH4 reactive active site of the autoreduced zeolite. The rigorous identification of a mononuclear active site allows a reactivity comparison to the previously defined [Cu2O]2+ active site. We perform kinetic experiments to compare the reactivity of the [CuOH]+ and [Cu2O]2+ sites and find that the binuclear site is significantly more reactive. From the analysis of density functional theory calculations, we elucidate that this increased reactivity is a direct result of stabilization of the [Cu2OH]2+ H-atom abstraction product by electron delocalization over the two Cu cations via the bridging ligand. This significant increase in reactivity from electron delocalization over a binuclear active site provides new insights for the design of highly reactive oxidative catalysts.
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Affiliation(s)
- Alexander J Heyer
- Department of Chemistry, Stanford University, Stanford, California94305, United States
| | - Dieter Plessers
- Department of Microbial and Molecular Systems, Center for Sustainable Catalysis and Engineering, KU Leuven-University of Leuven, LeuvenB-3001, Belgium
| | - Augustin Braun
- Department of Chemistry, Stanford University, Stanford, California94305, United States
| | - Hannah M Rhoda
- Department of Chemistry, Stanford University, Stanford, California94305, United States
| | - Max L Bols
- Department of Microbial and Molecular Systems, Center for Sustainable Catalysis and Engineering, KU Leuven-University of Leuven, LeuvenB-3001, Belgium
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California94025, United States
| | - Keith O Hodgson
- Department of Chemistry, Stanford University, Stanford, California94305, United States.,Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California94025, United States
| | - Robert A Schoonheydt
- Department of Microbial and Molecular Systems, Center for Sustainable Catalysis and Engineering, KU Leuven-University of Leuven, LeuvenB-3001, Belgium
| | - Bert F Sels
- Department of Microbial and Molecular Systems, Center for Sustainable Catalysis and Engineering, KU Leuven-University of Leuven, LeuvenB-3001, Belgium
| | - Edward I Solomon
- Department of Chemistry, Stanford University, Stanford, California94305, United States.,Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California94025, United States
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6
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Tanifuji K, Jasniewski AJ, Lee CC, Solomon JB, Nagasawa T, Ohki Y, Tatsumi K, Hedman B, Hodgson KO, Hu Y, Ribbe MW. Incorporation of an Asymmetric Mo-Fe-S Cluster as an Artificial Cofactor into Nitrogenase. Chembiochem 2022; 23:e202200384. [PMID: 35925843 PMCID: PMC9547968 DOI: 10.1002/cbic.202200384] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Revised: 08/03/2022] [Indexed: 11/07/2022]
Abstract
Nitrogenase employs a sophisticated electron transfer system and a Mo-Fe-S-C cofactor, designated the M-cluster [(cit)MoFe7 S9 C]), to reduce atmospheric N2 to bioaccessible NH3 . Previously, we have shown that the cofactor-free form of nitrogenase can be repurposed as a protein scaffold for the incorporation of a synthetic Fe-S cluster [Fe6 S9 (SEt)2 ]4- . Here, we demonstrate the utility of an asymmetric Mo-Fe-S cluster [Cp*MoFe5 S9 (SH)]3- as an alternative artificial cofactor upon incorporation into the cofactor-free nitrogenase scaffold. The resultant semi-artificial enzyme catalytically reduces C2 H2 to C2 H4 , and CN- into short-chain hydrocarbons, yet it is clearly distinct in activity from its [Fe6 S9 (SEt)2 ]4- -reconstituted counterpart, pointing to the possibility to employ molecular design and cluster synthesis strategies to further develop semi-artificial or artificial systems with desired catalytic activities.
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Affiliation(s)
- Kazuki Tanifuji
- Department of Molecular Biology & Biochemistry, University of California, Irvine, Irvine, CA, 92697-3900, USA
- Institute for Chemical Research, Kyoto University Gokasho, Uji, Kyoto, 611-0011, Japan
| | - Andrew J Jasniewski
- Department of Molecular Biology & Biochemistry, University of California, Irvine, Irvine, CA, 92697-3900, USA
| | - Chi Chung Lee
- Department of Molecular Biology & Biochemistry, University of California, Irvine, Irvine, CA, 92697-3900, USA
| | - Joseph B Solomon
- Department of Molecular Biology & Biochemistry, University of California, Irvine, Irvine, CA, 92697-3900, USA
- Department of Chemistry, University of California Irvine, Irvine, CA, 92697-2025, USA
| | - Takayuki Nagasawa
- Department of Chemistry Graduate School of Science and Research Center for Materials Science, Nagoya University, Furo-cho Chikusa-ku, Nagoya, 464-8602, Japan
| | - Yasuhiro Ohki
- Institute for Chemical Research, Kyoto University Gokasho, Uji, Kyoto, 611-0011, Japan
| | - Kazuyuki Tatsumi
- Department of Chemistry Graduate School of Science and Research Center for Materials Science, Nagoya University, Furo-cho Chikusa-ku, Nagoya, 464-8602, Japan
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA, 94025, USA
| | - Keith O Hodgson
- Stanford Synchrotron Radiation Lightsource SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA, 94025, USA
- Department of Chemistry, Stanford University, Stanford, CA, 94305, USA
| | - Yilin Hu
- Department of Molecular Biology & Biochemistry, University of California, Irvine, Irvine, CA, 92697-3900, USA
| | - Markus W Ribbe
- Department of Molecular Biology & Biochemistry, University of California, Irvine, Irvine, CA, 92697-3900, USA
- Department of Chemistry, University of California Irvine, Irvine, CA, 92697-2025, USA
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7
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Solomon JB, Tanifuji K, Lee CC, Jasniewski AJ, Hedman B, Hodgson KO, Hu Y, Ribbe MW. Characterization of a Nitrogenase Iron Protein Substituted with a Synthetic [Fe 4 Se 4 ] Cluster. Angew Chem Int Ed Engl 2022; 61:e202202271. [PMID: 35218104 PMCID: PMC9038695 DOI: 10.1002/anie.202202271] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Indexed: 11/08/2022]
Abstract
The Fe protein of nitrogenase plays multiple roles in substrate reduction and cluster maturation via its redox-active [Fe4 S4 ] cluster. Here we report the synthesis and characterization of a water-soluble [Fe4 Se4 ] cluster that is used to substitute the [Fe4 S4 ] cluster of the Azotobacter vinelandii Fe protein (AvNifH). Biochemical, EPR and XAS/EXAFS analyses demonstrate the ability of the [Fe4 Se4 ] cluster to adopt the super-reduced, all-ferrous state upon its incorporation into AvNifH. Moreover, these studies reveal that the [Fe4 Se4 ] cluster in AvNifH already assumes a partial all-ferrous state ([Fe4 Se4 ]0 ) in the presence of dithionite, where its [Fe4 S4 ] counterpart in AvNifH exists solely in the reduced state ([Fe4 S4 ]1+ ). Such a discrepancy in the redox properties of the AvNifH-associated [Fe4 Se4 ] and [Fe4 S4 ] clusters can be used to distinguish the differential redox requirements for the substrate reduction and cluster maturation of nitrogenase, pointing to the utility of chalcogen-substituted FeS clusters in future mechanistic studies of nitrogenase catalysis and assembly.
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Affiliation(s)
- Joseph B Solomon
- Department of Molecular Biology and Biochemistry, University of Califronia, Irvine, Irvine, CA 92697-3900, USA.,Department of Chemistry, University of California, Irvine, Irvine, CA 92697-2025, USA
| | - Kazuki Tanifuji
- Department of Molecular Biology and Biochemistry, University of Califronia, Irvine, Irvine, CA 92697-3900, USA.,Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto, 611-0011, Japan
| | - Chi Chung Lee
- Department of Molecular Biology and Biochemistry, University of Califronia, Irvine, Irvine, CA 92697-3900, USA
| | - Andrew J Jasniewski
- Department of Molecular Biology and Biochemistry, University of Califronia, Irvine, Irvine, CA 92697-3900, USA
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025, USA
| | - Keith O Hodgson
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025, USA.,Department of Chemistry, Stanford University, Stanford, CA 94305, USA
| | - Yilin Hu
- Department of Molecular Biology and Biochemistry, University of Califronia, Irvine, Irvine, CA 92697-3900, USA
| | - Markus W Ribbe
- Department of Molecular Biology and Biochemistry, University of Califronia, Irvine, Irvine, CA 92697-3900, USA.,Department of Chemistry, University of California, Irvine, Irvine, CA 92697-2025, USA
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8
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Ha Y, Dille SA, Braun A, Colston K, Hedman B, Hodgson KO, Basu P, Solomon EI. S K-edge XAS of Cu II, Cu I, and Zn II oxidized Dithiolene complexes: Covalent contributions to structure and the Jahn-Teller effect. J Inorg Biochem 2022; 230:111752. [PMID: 35202982 PMCID: PMC9680909 DOI: 10.1016/j.jinorgbio.2022.111752] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Revised: 02/01/2022] [Accepted: 02/03/2022] [Indexed: 11/26/2022]
Abstract
Reduced dithiolene ligands are bound to high valent Mo centers in the active site of the oxotransferase family of enzymes. Related model complexes have been studied with great insight by Prof. Holm and his colleagues. This study focuses on the other limit of dithiolene chemistry: an investigation of the 2-electron oxidized dithiolene bound to low-valent late transition metal (TM) ions (ZnII, CuI, and CuII). The bonding descriptions of the oxidized dithiolene [N,N-dimethyl piperazine 2,3-dithione (Me2Dt0)] complexes are probed using S K-edge X-ray absorption spectroscopy (XAS) and the results are correlated to density functional theory (DFT) calculations. These experimentally supported calculations are then extended to explain the different geometric structures of the three complexes. The ZnII(Me2Dt0)2 complex has only ligand-ligand repulsion so it is stabilized at the D2d symmetry limit. The CuI(Me2Dt0)2 complex has additional weak backbonding thus distorts somewhat from D2d toward D2h symmetry. The CuII(Me2Dt0)2 complex has a strong σ donor bond that leads to both a large Jahn-Teller stabilization to D2h and an additional covalent contribution to the geometry. The combined strong stabilization results in the square planar, D2h structure. This study quantifies the competition between the ligand-ligand repulsion and the change in electronic structures in determining the final geometric structures of the oxidized dithiolene complexes, and provides quantitative insights into the Jahn-Teller stabilization energy and its origin.
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Affiliation(s)
- Yang Ha
- Department of Chemistry, Stanford University, Stanford, CA 94035, United States; Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025, United States; Advanced Light Source, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, United States
| | - Sara A Dille
- Department of Chemistry and Chemical Biology, Indiana University-Purdue University Indianapolis, 402 N Blackford St, Indianapolis, IN 46202, United States
| | - Augustin Braun
- Department of Chemistry, Stanford University, Stanford, CA 94035, United States; Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025, United States
| | - Kyle Colston
- Department of Chemistry and Chemical Biology, Indiana University-Purdue University Indianapolis, 402 N Blackford St, Indianapolis, IN 46202, United States
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025, United States
| | - Keith O Hodgson
- Department of Chemistry, Stanford University, Stanford, CA 94035, United States; Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025, United States
| | - Partha Basu
- Department of Chemistry and Chemical Biology, Indiana University-Purdue University Indianapolis, 402 N Blackford St, Indianapolis, IN 46202, United States
| | - Edward I Solomon
- Department of Chemistry, Stanford University, Stanford, CA 94035, United States; Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025, United States.
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9
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Liu YA, Quechol R, Solomon JB, Lee CC, Ribbe MW, Hu Y, Hedman B, Hodgson KO. Radical SAM-dependent formation of a nitrogenase cofactor core on NifB. J Inorg Biochem 2022; 233:111837. [PMID: 35550498 PMCID: PMC9526504 DOI: 10.1016/j.jinorgbio.2022.111837] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Revised: 04/10/2022] [Accepted: 04/14/2022] [Indexed: 11/15/2022]
Abstract
Nitrogenase is a versatile metalloenzyme that reduces N2, CO and CO2 at its cofactor site. Designated the M-cluster, this complex cofactor has a composition of [(R-homocitrate)MoFe7S9C], and it is assembled through the generation of a unique [Fe8S9C] core prior to the insertion of Mo and homocitrate. NifB is a radical S-adenosyl-L-methionine (SAM) enzyme that is essential for nitrogenase cofactor assembly. This review focuses on the recent work that sheds light on the role of NifB in the formation of the [Fe8S9C] core of the nitrogenase cofactor, highlighting the structure, function and mechanism of this unique radical SAM methyltransferase.
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Affiliation(s)
- Yiling A Liu
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697-3900, United States of America
| | - Robert Quechol
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697-3900, United States of America
| | - Joseph B Solomon
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697-3900, United States of America; Department of Chemistry, University of California, Irvine, CA 92697-2025, United States of America
| | - Chi Chung Lee
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697-3900, United States of America
| | - Markus W Ribbe
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697-3900, United States of America; Department of Chemistry, University of California, Irvine, CA 92697-2025, United States of America.
| | - Yilin Hu
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697-3900, United States of America.
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025, United States of America.
| | - Keith O Hodgson
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025, United States of America; Department of Chemistry, Stanford University, Stanford, CA 94305, United States of America.
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10
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Kroll T, Baker ML, Wilson SA, Lundberg M, Juhin A, Arrio MA, Yan JJ, Gee LB, Braun A, Weng TC, Sokaras D, Hedman B, Hodgson KO, Solomon EI. Effect of 3d/4p Mixing on 1s2p Resonant Inelastic X-ray Scattering: Electronic Structure of Oxo-Bridged Iron Dimers. J Am Chem Soc 2021; 143:4569-4584. [PMID: 33730507 PMCID: PMC8018712 DOI: 10.1021/jacs.0c11193] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
1s2p resonant inelastic X-ray scattering (1s2p RIXS) has proven successful in the determination of the differential orbital covalency (DOC, the amount of metal vs ligand character in each d molecular orbital) of highly covalent centrosymmetric iron environments including heme models and enzymes. However, many reactive intermediates have noncentrosymmetric environments, e.g., the presence of strong metal-oxo bonds, which results in the mixing of metal 4p character into the 3d orbitals. This leads to significant intensity enhancement in the metal K-pre-edge and as shown here, the associated 1s2p RIXS features, which impact their insight into electronic structure. Binuclear oxo bridged high spin Fe(III) complexes are used to determine the effects of 4p mixing on 1s2p RIXS spectra. In addition to developing the analysis of 4p mixing on K-edge XAS and 1s2p RIXS data, this study explains the selective nature of the 4p mixing that also enhances the analysis of L-edge XAS intensity in terms of DOC. These 1s2p RIXS biferric model studies enable new structural insight from related data on peroxo bridged biferric enzyme intermediates. The dimeric nature of the oxo bridged Fe(III) complexes further results in ligand-to-ligand interactions between the Fe(III) sites and angle dependent features just above the pre-edge that reflect the superexchange pathway of the oxo bridge. Finally, we present a methodology that enables DOC to be obtained when L-edge XAS is inaccessible and only 1s2p RIXS experiments can be performed as in many metalloenzyme intermediates in solution.
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Affiliation(s)
- Thomas Kroll
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Michael L Baker
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
- Department of Chemistry, The University of Manchester, Manchester M13 9PL, United Kingdom
| | - Samuel A Wilson
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Marcus Lundberg
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
- Department of Chemistry - Ångström Laboratory, Uppsala University, SE-751 20 Uppsala, Sweden
| | - Amélie Juhin
- CNRS, Sorbonne Université, UMR7590, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie (IMPMC) Univ Paris 06, Muséum National d'Histoire Naturelle, IRD UMR206, 4 Place Jussieu, F-75005 Paris, France
| | - Marie-Anne Arrio
- CNRS, Sorbonne Université, UMR7590, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie (IMPMC) Univ Paris 06, Muséum National d'Histoire Naturelle, IRD UMR206, 4 Place Jussieu, F-75005 Paris, France
| | - James J Yan
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Leland B Gee
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Augustin Braun
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Tsu-Chien Weng
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Dimosthenis Sokaras
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Keith O Hodgson
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Edward I Solomon
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
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11
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Bhadra M, Transue WJ, Lim H, Cowley RE, Lee JYC, Siegler MA, Josephs P, Henkel G, Lerch M, Schindler S, Neuba A, Hodgson KO, Hedman B, Solomon EI, Karlin KD. A Thioether-Ligated Cupric Superoxide Model with Hydrogen Atom Abstraction Reactivity. J Am Chem Soc 2021; 143:3707-3713. [PMID: 33684290 DOI: 10.1021/jacs.1c00260] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The central role of cupric superoxide intermediates proposed in hormone and neurotransmitter biosynthesis by noncoupled binuclear copper monooxygenases like dopamine-β-monooxygenase has drawn significant attention to the unusual methionine ligation of the CuM ("CuB") active site characteristic of this class of enzymes. The copper-sulfur interaction has proven critical for turnover, raising still-unresolved questions concerning Nature's selection of an oxidizable Met residue to facilitate C-H oxygenation. We describe herein a model for CuM, [(TMGN3S)CuI]+ ([1]+), and its O2-bound analog [(TMGN3S)CuII(O2•-)]+ ([1·O2]+). The latter is the first reported cupric superoxide with an experimentally proven Cu-S bond which also possesses demonstrated hydrogen atom abstraction (HAA) reactivity. Introduction of O2 to a precooled solution of the cuprous precursor [1]B(C6F5)4 (-135 °C, 2-methyltetrahydrofuran (2-MeTHF)) reversibly forms [1·O2]B(C6F5)4 (UV/vis spectroscopy: λmax 442, 642, 742 nm). Resonance Raman studies (413 nm) using 16O2 [18O2] corroborated the identity of [1·O2]+ by revealing Cu-O (446 [425] cm-1) and O-O (1105 [1042] cm-1) stretches, and extended X-ray absorption fine structure (EXAFS) spectroscopy showed a Cu-S interatomic distance of 2.55 Å. HAA reactivity between [1·O2]+ and TEMPO-H proceeds rapidly (1.28 × 10-1 M-1 s-1, -135 °C, 2-MeTHF) with a primary kinetic isotope effect of kH/kD = 5.4. Comparisons of the O2-binding behavior and redox activity of [1]+ vs [2]+, the latter a close analog of [1]+ but with all N atom ligation (i.e., N3S vs N4), are presented.
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Affiliation(s)
- Mayukh Bhadra
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Wesley J Transue
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Hyeongtaek Lim
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Ryan E Cowley
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Jung Yoon C Lee
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Maxime A Siegler
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Patrick Josephs
- Department of Chemistry, University of Paderborn, Paderborn D-33098, Germany
| | - Gerald Henkel
- Department of Chemistry, University of Paderborn, Paderborn D-33098, Germany
| | - Markus Lerch
- Institute of Inorganic and Analytical Chemistry, Justus-Liebig University of Gießen, Giessen D-35392, Germany
| | - Siegfried Schindler
- Institute of Inorganic and Analytical Chemistry, Justus-Liebig University of Gießen, Giessen D-35392, Germany
| | - Adam Neuba
- Department of Chemistry, University of Paderborn, Paderborn D-33098, Germany
| | - Keith O Hodgson
- Department of Chemistry, Stanford University, Stanford, California 94305, United States.,Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Edward I Solomon
- Department of Chemistry, Stanford University, Stanford, California 94305, United States.,Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Kenneth D Karlin
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, United States
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12
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Lim H, Baker ML, Cowley RE, Kim S, Bhadra M, Siegler MA, Kroll T, Sokaras D, Weng TC, Biswas DR, Dooley DM, Karlin KD, Hedman B, Hodgson KO, Solomon EI. Kβ X-ray Emission Spectroscopy as a Probe of Cu(I) Sites: Application to the Cu(I) Site in Preprocessed Galactose Oxidase. Inorg Chem 2020; 59:16567-16581. [PMID: 33136386 DOI: 10.1021/acs.inorgchem.0c02495] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Cu(I) active sites in metalloproteins are involved in O2 activation, but their O2 reactivity is difficult to study due to the Cu(I) d10 closed shell which precludes the use of conventional spectroscopic methods. Kβ X-ray emission spectroscopy (XES) is a promising technique for investigating Cu(I) sites as it detects photons emitted by electronic transitions from occupied orbitals. Here, we demonstrate the utility of Kβ XES in probing Cu(I) sites in model complexes and a metalloprotein. Using Cu(I)Cl, emission features from double-ionization (DI) states are identified using varying incident X-ray photon energies, and a reasonable method to correct the data to remove DI contributions is presented. Kβ XES spectra of Cu(I) model complexes, having biologically relevant N/S ligands and different coordination numbers, are compared and analyzed, with the aid of density functional theory (DFT) calculations, to evaluate the sensitivity of the spectral features to the ligand environment. While the low-energy Kβ2,5 emission feature reflects the ionization energy of ligand np valence orbitals, the high-energy Kβ2,5 emission feature corresponds to transitions from molecular orbitals (MOs) having mainly Cu 3d character with the intensities determined by ligand-mediated d-p mixing. A Kβ XES spectrum of the Cu(I) site in preprocessed galactose oxidase (GOpre) supports the 1Tyr/2His structural model that was determined by our previous X-ray absorption spectroscopy and DFT study. The high-energy Kβ2,5 emission feature in the Cu(I)-GOpre data has information about the MO containing mostly Cu 3dx2-y2 character that is the frontier molecular orbital (FMO) for O2 activation, which shows the potential of Kβ XES in probing the Cu(I) FMO associated with small-molecule activation in metalloproteins.
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Affiliation(s)
- Hyeongtaek Lim
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Michael L Baker
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Ryan E Cowley
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Sunghee Kim
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Mayukh Bhadra
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Maxime A Siegler
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Thomas Kroll
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Dimosthenis Sokaras
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Tsu-Chien Weng
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Dalia R Biswas
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| | - David M Dooley
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States.,University of Rhode Island, Kingston, Rhode Island 02881, United States
| | - Kenneth D Karlin
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Keith O Hodgson
- Department of Chemistry, Stanford University, Stanford, California 94305, United States.,Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Edward I Solomon
- Department of Chemistry, Stanford University, Stanford, California 94305, United States.,Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
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13
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Frank P, Carlson RMK, Carlson EJ, Hedman B, Hodgson KO. Biological sulfur in the blood cells of Ascidia ceratodes: XAS spectroscopy and a cellular-enzymatic hypothesis for vanadium reduction in the ascidians. J Inorg Biochem 2020; 205:110991. [PMID: 31945647 PMCID: PMC7033024 DOI: 10.1016/j.jinorgbio.2019.110991] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2019] [Revised: 12/12/2019] [Accepted: 12/31/2019] [Indexed: 10/25/2022]
Abstract
Two samples of living blood cells and of cleared blood plasma from the Phlebobranch tunicate Ascidia ceratodes from Bodega Bay, California, and one of fresh Henze solution from A. ceratodes of Monterey Bay, California, have been examined using sulfur K-edge x-ray absorption spectroscopy (XAS). Biological sulfur included sulfate esters, sulfate and bisulfate ions, benzothiazole, thianthrene, epi-sulfide, thiol and disulfide. Glutathione dominated reduced sulfur, from which an average intracellular Voltage of -0.21 V was calculated. Sulfate-bisulfate ratios yielded blood cell pH values of 2.0 and 2.8. Total blood cell [sulfur] was 373±9 mM or 296±73 mM from BaSO4 gravimetry. Two plasma samples (pH 6.9 or 7.0; [S] = 33±6 mM or 26±4 mM) were dominated by sulfate and disulfide. Fresh Henze solution evidenced a sulfur inventory similar to blood cells, with calculated pH = 2.7. A V(III)-sulfonate fraction varied systematically with intracellular pH across six independent blood cell samples, implying a vanadium mobilization pathway. Bodega Bay and Monterey Bay A. ceratodes appear to maintain alternative suites of low-valent sulfur. The significance of the vanabins to vanadium metabolism is critically examined in terms of known protein - V(IV) biochemistry. Finally, a detailed hypothesis for the reduction of [VO4]3- to V(III) in ascidians is introduced. A vanadium oxido-reductase is proposed to span the signet ring membrane and to release V(III) into the inner acidic vacuole. The V(V) to V(III) reduction is predicted require an inner-sphere mechanism, a thiol reductant, 7-coordinate V(III), a biologically accessible Voltage, and proton-facilitated release of V(III).
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Affiliation(s)
- Patrick Frank
- Stanford Synchrotron Radiation laboratory, SLAC, Stanford University, Menlo Park, CA 94025, United States of America; Department of Chemistry, Stanford University, Stanford, CA 94305, United States of America.
| | - Robert M K Carlson
- Institute for Materials and Energy Sciences, SLAC, Stanford University, Menlo Park, CA 94025, United States of America
| | - Elaine J Carlson
- University of California, San Francisco, CA 94143, United States of America
| | - Britt Hedman
- Stanford Synchrotron Radiation laboratory, SLAC, Stanford University, Menlo Park, CA 94025, United States of America
| | - Keith O Hodgson
- Stanford Synchrotron Radiation laboratory, SLAC, Stanford University, Menlo Park, CA 94025, United States of America; Department of Chemistry, Stanford University, Stanford, CA 94305, United States of America
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14
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Jasniewski AJ, Wilcoxen J, Tanifuji K, Hedman B, Hodgson KO, Britt RD, Hu Y, Ribbe MW. Spectroscopic Characterization of an Eight-Iron Nitrogenase Cofactor Precursor that Lacks the "9 th Sulfur". Angew Chem Int Ed Engl 2019; 58:14703-14707. [PMID: 31411369 DOI: 10.1002/anie.201907593] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Indexed: 01/09/2023]
Abstract
Nitrogenases catalyze the reduction of N2 to NH4 + at its cofactor site. Designated the M-cluster, this [MoFe7 S9 C(R-homocitrate)] cofactor is synthesized via the transformation of a [Fe4 S4 ] cluster pair into an [Fe8 S9 C] precursor (designated the L-cluster) prior to insertion of Mo and homocitrate. We report the characterization of an eight-iron cofactor precursor (designated the L*-cluster), which is proposed to have the composition [Fe8 S8 C] and lack the "9th sulfur" in the belt region of the L-cluster. Our X-ray absorption and electron spin echo envelope modulation (ESEEM) analyses strongly suggest that the L*-cluster represents a structural homologue to the l-cluster except for the missing belt sulfur. The absence of a belt sulfur from the L*-cluster may prove beneficial for labeling the catalytically important belt region, which could in turn facilitate investigations into the reaction mechanism of nitrogenases.
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Affiliation(s)
- Andrew J Jasniewski
- Department of Molecular Biology & Biochemistry, University of California, Irvine, Irvine, CA, 92697-3900, USA
| | - Jarett Wilcoxen
- Department of Chemistry, University of California, Davis, Davis, CA, 95616, USA
| | - Kazuki Tanifuji
- Department of Molecular Biology & Biochemistry, University of California, Irvine, Irvine, CA, 92697-3900, USA
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA, 94025, USA
| | - Keith O Hodgson
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA, 94025, USA.,Department of Chemistry, Stanford University, Stanford, CA, 94305, USA
| | - R David Britt
- Department of Chemistry, University of California, Davis, Davis, CA, 95616, USA
| | - Yilin Hu
- Department of Molecular Biology & Biochemistry, University of California, Irvine, Irvine, CA, 92697-3900, USA
| | - Markus W Ribbe
- Department of Molecular Biology & Biochemistry, University of California, Irvine, Irvine, CA, 92697-3900, USA.,Department Chemistry, University of California, Irvine, Irvine, CA, 92697-2025, USA
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15
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Jasniewski AJ, Wilcoxen J, Tanifuji K, Hedman B, Hodgson KO, Britt RD, Hu Y, Ribbe MW. Spectroscopic Characterization of an Eight‐Iron Nitrogenase Cofactor Precursor that Lacks the “9
th
Sulfur”. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201907593] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Andrew J. Jasniewski
- Department of Molecular Biology & Biochemistry University of California, Irvine Irvine CA 92697-3900 USA
| | - Jarett Wilcoxen
- Department of Chemistry University of California, Davis Davis CA 95616 USA
| | - Kazuki Tanifuji
- Department of Molecular Biology & Biochemistry University of California, Irvine Irvine CA 92697-3900 USA
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource SLAC National Accelerator Laboratory Stanford University Menlo Park CA 94025 USA
| | - Keith O. Hodgson
- Stanford Synchrotron Radiation Lightsource SLAC National Accelerator Laboratory Stanford University Menlo Park CA 94025 USA
- Department of Chemistry Stanford University Stanford CA 94305 USA
| | - R. David Britt
- Department of Chemistry University of California, Davis Davis CA 95616 USA
| | - Yilin Hu
- Department of Molecular Biology & Biochemistry University of California, Irvine Irvine CA 92697-3900 USA
| | - Markus W. Ribbe
- Department of Molecular Biology & Biochemistry University of California, Irvine Irvine CA 92697-3900 USA
- Department Chemistry University of California, Irvine Irvine CA 92697-2025 USA
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16
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Lim H, Thomas KE, Hedman B, Hodgson KO, Ghosh A, Solomon EI. X-ray Absorption Spectroscopy as a Probe of Ligand Noninnocence in Metallocorroles: The Case of Copper Corroles. Inorg Chem 2019; 58:6722-6730. [PMID: 31046257 PMCID: PMC6644708 DOI: 10.1021/acs.inorgchem.9b00128] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The question of ligand noninnocence in Cu corroles has long been a topic of discussion. Presented herein is a Cu K-edge X-ray absorption spectroscopy (XAS) study, which provides a direct probe of the metal oxidation state, of three Cu corroles, Cu[TPC], Cu[Br8TPC], and Cu[(CF3)8TPC] (TPC = meso-triphenylcorrole), and the analogous Cu(II) porphyrins, Cu[TPP], Cu[Br8TPP], and Cu[(CF3)8TPP] (TPP = meso-tetraphenylporphyrin). The Cu K rising-edges of the Cu corroles were found to be about 0-1 eV upshifted relative to the analogous porphyrins, which is substantially lower than the 1-2 eV shifts typically exhibited by authentic Cu(II)/Cu(III) model complex pairs. In an unusual twist, the Cu K pre-edge regions of both the Cu corroles and the Cu porphyrins exhibit two peaks split by 0.8-1.3 eV. Based on time-dependent density functional theory calculations, the lower- and higher-energy peaks were assigned to a Cu 1s → 3d x2- y2 transition and a Cu 1s → corrole/porphyrin π* transition, respectively. From the Cu(II) porphyrins to the corresponding Cu corroles, the energy of the Cu 1s → 3d x2- y2 transition peak was found to upshift by 0.6-0.8 eV. This shift is approximately half that observed between Cu(II) to Cu(III) states for well-defined complexes. The Cu K-edge XAS spectra thus show that although the metal sites in the Cu corroles are more oxidized relative to those in their Cu(II) porphyrin analogues, they are not oxidized to the Cu(III) level, consistent with the notion of a noninnocent corrole. The relative importance of σ-donation versus corrole π-radical character is discussed.
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Affiliation(s)
- Hyeongtaek Lim
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Kolle E. Thomas
- Department of Chemistry, UiT — The Arctic University of Norway, N-9037 Tromsø, Norway
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Keith O. Hodgson
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Abhik Ghosh
- Department of Chemistry, UiT — The Arctic University of Norway, N-9037 Tromsø, Norway
| | - Edward I. Solomon
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
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17
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Ehudin MA, Gee LB, Sabuncu S, Braun A, Moënne-Loccoz P, Hedman B, Hodgson KO, Solomon EI, Karlin KD. Tuning the Geometric and Electronic Structure of Synthetic High-Valent Heme Iron(IV)-Oxo Models in the Presence of a Lewis Acid and Various Axial Ligands. J Am Chem Soc 2019; 141:5942-5960. [PMID: 30860832 DOI: 10.1021/jacs.9b00795] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
High-valent ferryl species (e.g., (Por)FeIV═O, Cmpd-II) are observed or proposed key oxidizing intermediates in the catalytic cycles of heme-containing enzymes (P-450s, peroxidases, catalases, and cytochrome c oxidase) involved in biological respiration and oxidative metabolism. Herein, various axially ligated iron(IV)-oxo complexes were prepared to examine the influence of the identity of the base. These were generated by addition of various axial ligands (1,5-dicyclohexylimidazole (DCHIm), a tethered-imidazole system, and sodium derivatives of 3,5-dimethoxyphenolate and imidazolate). Characterization was carried out via UV-vis, electron paramagnetic resonance (EPR), 57Fe Mössbauer, Fe X-ray absorption (XAS), and 54/57Fe resonance Raman (rR) spectroscopies to confirm their formation and compare the axial ligand perturbation on the electronic and geometric structures of these heme iron(IV)-oxo species. Mössbauer studies confirmed that the axially ligated derivatives were iron(IV) and six-coordinate complexes. XAS and 54/57Fe rR data correlated with slight elongation of the iron-oxo bond with increasing donation from the axial ligands. The first reported synthetic H-bonded iron(IV)-oxo heme systems were made in the presence of the protic Lewis acid, 2,6-lutidinium triflate (LutH+), with (or without) DCHIm. Mössbauer, rR, and XAS spectroscopic data indicated the formation of molecular Lewis acid ferryl adducts (rather than full protonation). The reduction potentials of these novel Lewis acid adducts were bracketed through addition of outer-sphere reductants. The oxidizing capabilities of the ferryl species with or without Lewis acid vary drastically; addition of LutH+ to F8Cmpd-II (F8 = tetrakis(2,6-difluorophenyl)porphyrinate) increased its reduction potential by more than 890 mV, experimentally confirming that H-bonding interactions can increase the reactivity of ferryl species.
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Affiliation(s)
- Melanie A Ehudin
- Department of Chemistry , Johns Hopkins University , Baltimore , Maryland 21218 , United States
| | - Leland B Gee
- Department of Chemistry , Stanford University , Stanford , California 94305 , United States
| | - Sinan Sabuncu
- Department of Biochemistry & Molecular Biology , Oregon Health & Science University , Portland , Oregon 97239-3098 , United States
| | - Augustin Braun
- Department of Chemistry , Stanford University , Stanford , California 94305 , United States
| | - Pierre Moënne-Loccoz
- Department of Biochemistry & Molecular Biology , Oregon Health & Science University , Portland , Oregon 97239-3098 , United States
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory , Stanford University , Menlo Park , California 94025 , United States
| | - Keith O Hodgson
- Department of Chemistry , Stanford University , Stanford , California 94305 , United States.,Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory , Stanford University , Menlo Park , California 94025 , United States
| | - Edward I Solomon
- Department of Chemistry , Stanford University , Stanford , California 94305 , United States.,Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory , Stanford University , Menlo Park , California 94025 , United States
| | - Kenneth D Karlin
- Department of Chemistry , Johns Hopkins University , Baltimore , Maryland 21218 , United States
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18
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Frank P, Sarangi R, Hedman B, Hodgson KO. Synchrotron X-radiolysis of l-cysteine at the sulfur K-edge: Sulfurous products, experimental surprises, and dioxygen as an oxidoreductant. J Chem Phys 2019; 150:105101. [PMID: 30876351 PMCID: PMC7791807 DOI: 10.1063/1.5079419] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Accepted: 02/12/2019] [Indexed: 11/14/2022] Open
Abstract
In situ inventory of sulfurous products from the sulfur K-edge synchrotron X-radiolysis of l-cysteine in solid-phase and anaerobic (pH 5) and air-saturated (pH 5, 7, and 9) solutions without and with 40% glycerol is reported. Sequential K-edge X-ray Absorption Spectroscopic (XAS) spectra were acquired. l-cysteine degraded systematically in the X-ray beam. Radiolytic products were inventoried by fits using the XAS spectra of sulfur model compounds. Solid l-cysteine declined to 92% fraction after a single K-edge XAS scan. After six scans, 60% remained, accompanied by 14% cystine, 16% thioether, 5.4% elemental sulfur, and smaller fractions of more highly oxidized products. In air-saturated pH 5 solution, 73% of l-cysteine remained after ten scans, with 2% cystine and 19% elemental sulfur. Oxidation increased with 40% glycerol, yielding 67%, 5%, and 23% fractions, respectively, after ten scans. Higher pH solutions exhibited less radiolytic chemistry. All the reactivity followed first-order kinetics. The anaerobic experiment displayed two reaction phases, with sharp changes in kinetics and radiolytic chemistry. Unexpectedly, the radiolytic oxidation of l-cysteine was increased in anaerobic solution. After ten scans, only 60% of the l-cysteine remained, along with 17% cystine, 22% elemental sulfur, and traces of more highly oxidized products. A new aerobic reaction cycle is hypothesized, wherein dissolved dioxygen captures radiolytic H• or eaq -, enters HO2 •/O2 •-, reductively quenches cysteine thiyl radicals, and cycles back to O2. This cycle is suggested to suppress the radiolytic production of cystine in aerobic solution.
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Affiliation(s)
- Patrick Frank
- Author to whom correspondence should be addressed: . Tel.: 650-723-2479
| | - Ritimukta Sarangi
- Stanford Synchrotron Radiation Lightsource, SLAC, Stanford University, Menlo Park, California 94025, USA
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource, SLAC, Stanford University, Menlo Park, California 94025, USA
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19
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Hong S, Yan JJ, Karmalkar DG, Sutherlin KD, Kim J, Lee YM, Goo Y, Mascharak PK, Hedman B, Hodgson KO, Karlin KD, Solomon EI, Nam W. A mononuclear nonheme {FeNO} 6 complex: synthesis and structural and spectroscopic characterization. Chem Sci 2018; 9:6952-6960. [PMID: 30210769 PMCID: PMC6124912 DOI: 10.1039/c8sc01962b] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Accepted: 07/18/2018] [Indexed: 01/19/2023] Open
Abstract
While the synthesis and characterization of {FeNO}7,8,9 complexes have been well documented in heme and nonheme iron models, {FeNO}6 complexes have been less clearly understood. Herein, we report the synthesis and structural and spectroscopic characterization of mononuclear nonheme {FeNO}6 and iron(iii)-nitrito complexes bearing a tetraamido macrocyclic ligand (TAML), such as [(TAML)FeIII(NO)]- and [(TAML)FeIII(NO2)]2-, respectively. First, direct addition of NO(g) to [FeIII(TAML)]- results in the formation of [(TAML)FeIII(NO)]-, which is sensitive to moisture and air. The spectroscopic data of [(TAML)FeIII(NO)]-, such as 1H nuclear magnetic resonance and X-ray absorption spectroscopies, combined with computational study suggest the neutral nature of nitric oxide with a diamagnetic Fe center (S = 0). We also provide alternative pathways for the generation of [(TAML)FeIII(NO)]-, such as the iron-nitrite reduction triggered by protonation in the presence of ferrocene, which acts as an electron donor, and the photochemical iron-nitrite reduction. To the best of our knowledge, the present study reports the first photochemical nitrite reduction in nonheme iron models.
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Affiliation(s)
- Seungwoo Hong
- Department of Chemistry and Nano Science , Ewha Womans University , Seoul 03760 , Korea . .,Department of Chemistry , Sookmyung Women's University , Seoul 04310 , Korea
| | - James J Yan
- Department of Chemistry , Stanford University , Stanford , California 94305 , USA .
| | - Deepika G Karmalkar
- Department of Chemistry and Nano Science , Ewha Womans University , Seoul 03760 , Korea .
| | - Kyle D Sutherlin
- Department of Chemistry , Stanford University , Stanford , California 94305 , USA .
| | - Jin Kim
- Department of Chemistry and Nano Science , Ewha Womans University , Seoul 03760 , Korea .
| | - Yong-Min Lee
- Department of Chemistry and Nano Science , Ewha Womans University , Seoul 03760 , Korea .
| | - Yire Goo
- Department of Chemistry and Nano Science , Ewha Womans University , Seoul 03760 , Korea .
| | - Pradip K Mascharak
- Department of Chemistry and Biochemistry , University of California , Santa Cruz , California 95064 , USA
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource , SLAC National Accelerator Laboratory , Stanford University , California 94025 , USA . ;
| | - Keith O Hodgson
- Department of Chemistry , Stanford University , Stanford , California 94305 , USA . .,Stanford Synchrotron Radiation Lightsource , SLAC National Accelerator Laboratory , Stanford University , California 94025 , USA . ;
| | - Kenneth D Karlin
- Department of Chemistry , The Johns Hopkins University , Baltimore , Maryland 21218 , USA .
| | - Edward I Solomon
- Department of Chemistry , Stanford University , Stanford , California 94305 , USA . .,Stanford Synchrotron Radiation Lightsource , SLAC National Accelerator Laboratory , Stanford University , California 94025 , USA . ;
| | - Wonwoo Nam
- Department of Chemistry and Nano Science , Ewha Womans University , Seoul 03760 , Korea . .,School of Chemistry and Chemical Engineering , Shaanxi Normal University , Xi'an 710119 , P. R. China
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20
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Jeong D, Yan JJ, Noh H, Hedman B, Hodgson KO, Solomon EI, Cho J. Oxidation of Naphthalene with a Manganese(IV) Bis(hydroxo) Complex in the Presence of Acid. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201802641] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Donghyun Jeong
- Department of Emerging Materials Science DGIST Daegu 42988 Korea
| | - James J. Yan
- Department of Chemistry Stanford University Stanford CA 94305 USA
| | - Hyeonju Noh
- Department of Emerging Materials Science DGIST Daegu 42988 Korea
| | - Britt Hedman
- Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Menlo Park CA 94025 USA
| | - Keith O. Hodgson
- Department of Chemistry Stanford University Stanford CA 94305 USA
- Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Menlo Park CA 94025 USA
| | - Edward I. Solomon
- Department of Chemistry Stanford University Stanford CA 94305 USA
- Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Menlo Park CA 94025 USA
| | - Jaeheung Cho
- Department of Emerging Materials Science DGIST Daegu 42988 Korea
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21
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Jeong D, Yan JJ, Noh H, Hedman B, Hodgson KO, Solomon EI, Cho J. Oxidation of Naphthalene with a Manganese(IV) Bis(hydroxo) Complex in the Presence of Acid. Angew Chem Int Ed Engl 2018; 57:7764-7768. [PMID: 29701293 PMCID: PMC6013404 DOI: 10.1002/anie.201802641] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Revised: 04/05/2018] [Indexed: 11/06/2022]
Abstract
Naphthalene oxidation with metal-oxygen intermediates is a difficult reaction in environmental and biological chemistry. Herein, we report that a MnIV bis(hydroxo) complex, which was fully characterized by various physicochemical methods, such as ESI-MS, UV/Vis, and EPR analysis, X-ray diffraction, and XAS, can be employed for the oxidation of naphthalene in the presence of acid to afford 1,4-naphthoquinone. Redox titration of the MnIV bis(hydroxo) complex gave a one-electron reduction potential of 1.09 V, which is the most positive potential for all reported nonheme MnIV bis(hydroxo) species as well as MnIV oxo analogues. Kinetic studies, including kinetic isotope effect analysis, suggest that the naphthalene oxidation occurs through a rate-determining electron transfer process.
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Affiliation(s)
- Donghyun Jeong
- Department of Emerging Materials Science, DGIST, Daegu, 42988, Korea
| | - James J Yan
- Department of Chemistry, Stanford University, Stanford, CA, 94305, USA
| | - Hyeonju Noh
- Department of Emerging Materials Science, DGIST, Daegu, 42988, Korea
| | - Britt Hedman
- Stanford Synchrotron Radiation Laboratory, Stanford Linear Accelerator Center, Menlo Park, CA, 94025, USA
| | - Keith O Hodgson
- Department of Chemistry, Stanford University, Stanford, CA, 94305, USA
- Stanford Synchrotron Radiation Laboratory, Stanford Linear Accelerator Center, Menlo Park, CA, 94025, USA
| | - Edward I Solomon
- Department of Chemistry, Stanford University, Stanford, CA, 94305, USA
- Stanford Synchrotron Radiation Laboratory, Stanford Linear Accelerator Center, Menlo Park, CA, 94025, USA
| | - Jaeheung Cho
- Department of Emerging Materials Science, DGIST, Daegu, 42988, Korea
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22
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Mara MW, Hadt RG, Reinhard ME, Kroll T, Lim H, Hartsock RW, Alonso-Mori R, Chollet M, Glownia JM, Nelson S, Sokaras D, Kunnus K, Hodgson KO, Hedman B, Bergmann U, Gaffney KJ, Solomon EI. Metalloprotein entatic control of ligand-metal bonds quantified by ultrafast x-ray spectroscopy. Science 2018. [PMID: 28642436 DOI: 10.1126/science.aam6203] [Citation(s) in RCA: 91] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The multifunctional protein cytochrome c (cyt c) plays key roles in electron transport and apoptosis, switching function by modulating bonding between a heme iron and the sulfur in a methionine residue. This Fe-S(Met) bond is too weak to persist in the absence of protein constraints. We ruptured the bond in ferrous cyt c using an optical laser pulse and monitored the bond reformation within the protein active site using ultrafast x-ray pulses from an x-ray free-electron laser, determining that the Fe-S(Met) bond enthalpy is ~4 kcal/mol stronger than in the absence of protein constraints. The 4 kcal/mol is comparable with calculations of stabilization effects in other systems, demonstrating how biological systems use an entatic state for modest yet accessible energetics to modulate chemical function.
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Affiliation(s)
- Michael W Mara
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA.,Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
| | - Ryan G Hadt
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
| | - Marco Eli Reinhard
- PULSE Institute, SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305, USA
| | - Thomas Kroll
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, 2575 Sand Hill Road, Menlo Park, CA 94025, USA.,Linac Coherent Light Source, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025, USA
| | - Hyeongtaek Lim
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA.,Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
| | - Robert W Hartsock
- PULSE Institute, SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305, USA
| | - Roberto Alonso-Mori
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025, USA
| | - Matthieu Chollet
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025, USA
| | - James M Glownia
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025, USA
| | - Silke Nelson
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025, USA
| | - Dimosthenis Sokaras
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, 2575 Sand Hill Road, Menlo Park, CA 94025, USA.,Linac Coherent Light Source, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025, USA
| | - Kristjan Kunnus
- PULSE Institute, SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305, USA
| | - Keith O Hodgson
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA.,Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
| | - Uwe Bergmann
- PULSE Institute, SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305, USA.,Linac Coherent Light Source, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025, USA
| | - Kelly J Gaffney
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, 2575 Sand Hill Road, Menlo Park, CA 94025, USA.,PULSE Institute, SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305, USA
| | - Edward I Solomon
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA. .,Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
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23
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Sharma SK, Schaefer AW, Lim H, Matsumura H, Moënne-Loccoz P, Hedman B, Hodgson KO, Solomon EI, Karlin KD. A Six-Coordinate Peroxynitrite Low-Spin Iron(III) Porphyrinate Complex-The Product of the Reaction of Nitrogen Monoxide (·NO (g)) with a Ferric-Superoxide Species. J Am Chem Soc 2017; 139:17421-17430. [PMID: 29091732 PMCID: PMC5783694 DOI: 10.1021/jacs.7b08468] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Peroxynitrite (-OON═O, PN) is a reactive nitrogen species (RNS) which can effect deleterious nitrative or oxidative (bio)chemistry. It may derive from reaction of superoxide anion (O2•-) with nitric oxide (·NO) and has been suggested to form an as-yet unobserved bound heme-iron-PN intermediate in the catalytic cycle of nitric oxide dioxygenase (NOD) enzymes, which facilitate a ·NO homeostatic process, i.e., its oxidation to the nitrate anion. Here, a discrete six-coordinate low-spin porphyrinate-FeIII complex [(PIm)FeIII(-OON═O)] (3) (PIm; a porphyrin moiety with a covalently tethered imidazole axial "base" donor ligand) has been identified and characterized by various spectroscopies (UV-vis, NMR, EPR, XAS, resonance Raman) and DFT calculations, following its formation at -80 °C by addition of ·NO(g) to the heme-superoxo species, [(PIm)FeIII(O2•-)] (2). DFT calculations confirm that 3 is a six-coordinate low-spin species with the PN ligand coordinated to iron via its terminal peroxidic anionic O atom with the overall geometry being in a cis-configuration. Complex 3 thermally transforms to its isomeric low-spin nitrato form [(PIm)FeIII(NO3-)] (4a). While previous (bio)chemical studies show that phenolic substrates undergo nitration in the presence of PN or PN-metal complexes, in the present system, addition of 2,4-di-tert-butylphenol (2,4DTBP) to complex 3 does not lead to nitrated phenol; the nitrate complex 4a still forms. DFT calculations reveal that the phenolic H atom approaches the terminal PN O atom (farthest from the metal center and ring core), effecting O-O cleavage, giving nitrogen dioxide (·NO2) plus a ferryl compound [(PIm)FeIV═O] (7); this rebounds to give [(PIm)FeIII(NO3-)] (4a).The generation and characterization of the long sought after ferriheme peroxynitrite complex has been accomplished.
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Affiliation(s)
- Savita K. Sharma
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Andrew W. Schaefer
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Hyeongtaek Lim
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Hirotoshi Matsumura
- Division of Environmental & Biomolecular Systems, Oregon Health & Science University, Portland, Oregon 97239-3098, United States
| | - Pierre Moënne-Loccoz
- Division of Environmental & Biomolecular Systems, Oregon Health & Science University, Portland, Oregon 97239-3098, United States
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Keith O. Hodgson
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Edward I. Solomon
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Kenneth D. Karlin
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
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24
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Ha Y, Arnold AR, Nuñez NN, Bartels PL, Zhou A, David SS, Barton JK, Hedman B, Hodgson KO, Solomon EI. Sulfur K-Edge XAS Studies of the Effect of DNA Binding on the [Fe 4S 4] Site in EndoIII and MutY. J Am Chem Soc 2017; 139:11434-11442. [PMID: 28715891 DOI: 10.1021/jacs.7b03966] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
S K-edge X-ray absorption spectroscopy (XAS) was used to study the [Fe4S4] clusters in the DNA repair glycosylases EndoIII and MutY to evaluate the effects of DNA binding and solvation on Fe-S bond covalencies (i.e., the amount of S 3p character mixed into the Fe 3d valence orbitals). Increased covalencies in both iron-thiolate and iron-sulfide bonds would stabilize the oxidized state of the [Fe4S4] clusters. The results are compared to those on previously studied [Fe4S4] model complexes, ferredoxin (Fd), and to new data on high-potential iron-sulfur protein (HiPIP). A limited decrease in covalency is observed upon removal of solvent water from EndoIII and MutY, opposite to the significant increase observed for Fd, where the [Fe4S4] cluster is solvent exposed. Importantly, in EndoIII and MutY, a large increase in covalency is observed upon DNA binding, which is due to the effect of its negative charge on the iron-sulfur bonds. In EndoIII, this change in covalency can be quantified and makes a significant contribution to the observed decrease in reduction potential found experimentally in DNA repair proteins, enabling their HiPIP-like redox behavior.
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Affiliation(s)
- Yang Ha
- Department of Chemistry, Stanford University , Stanford, California 94035, United States.,Stanford Synchrotron Radiation Lightsource, SLAC, Stanford University , Menlo Park, California 94025, United States
| | - Anna R Arnold
- Division of Chemistry and Chemical Engineering, California Institute of Technology , Pasadena, California 91125, United States
| | - Nicole N Nuñez
- Department of Chemistry, University of California Davis , Davis, California 95616, United States
| | - Phillip L Bartels
- Division of Chemistry and Chemical Engineering, California Institute of Technology , Pasadena, California 91125, United States
| | - Andy Zhou
- Division of Chemistry and Chemical Engineering, California Institute of Technology , Pasadena, California 91125, United States
| | - Sheila S David
- Department of Chemistry, University of California Davis , Davis, California 95616, United States
| | - Jacqueline K Barton
- Division of Chemistry and Chemical Engineering, California Institute of Technology , Pasadena, California 91125, United States
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource, SLAC, Stanford University , Menlo Park, California 94025, United States
| | - Keith O Hodgson
- Department of Chemistry, Stanford University , Stanford, California 94035, United States.,Stanford Synchrotron Radiation Lightsource, SLAC, Stanford University , Menlo Park, California 94025, United States
| | - Edward I Solomon
- Department of Chemistry, Stanford University , Stanford, California 94035, United States.,Stanford Synchrotron Radiation Lightsource, SLAC, Stanford University , Menlo Park, California 94025, United States
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25
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Frank P, Szilagyi RK, Gramlich V, Hsu HF, Hedman B, Hodgson KO. Spin-Polarization-Induced Preedge Transitions in the Sulfur K-Edge XAS Spectra of Open-Shell Transition-Metal Sulfates: Spectroscopic Validation of σ-Bond Electron Transfer. Inorg Chem 2017; 56:1080-1093. [PMID: 28068071 PMCID: PMC5733802 DOI: 10.1021/acs.inorgchem.6b00991] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Sulfur K-edge X-ray absorption spectroscopy (XAS) spectra of the monodentate sulfate complexes [MII(itao)(SO4)(H2O)0,1] (M = Co, Ni, Cu) and [Cu(Me6tren)(SO4)] exhibit well-defined preedge transitions at 2479.4, 2479.9, 2478.4, and 2477.7 eV, respectively, despite having no direct metal-sulfur bond, while the XAS preedge of [Zn(itao)(SO4)] is featureless. The sulfur K-edge XAS of [Cu(itao)(SO4)] but not of [Cu(Me6tren)(SO4)] uniquely exhibits a weak transition at 2472.1 eV, an extraordinary 8.7 eV below the first inflection of the rising K-edge. Preedge transitions also appear in the sulfur K-edge XAS of crystalline [MII(SO4)(H2O)] (M = Fe, Co, Ni, and Cu, but not Zn) and in sulfates of higher-valent early transition metals. Ground-state density functional theory (DFT) and time-dependent DFT (TDDFT) calculations show that charge transfer from coordinated sulfate to paramagnetic late transition metals produces spin polarization that differentially mixes the spin-up (α) and spin-down (β) spin orbitals of the sulfate ligand, inducing negative spin density at the sulfate sulfur. Ground-state DFT calculations show that sulfur 3p character then mixes into metal 4s and 4p valence orbitals and various combinations of ligand antibonding orbitals, producing measurable sulfur XAS transitions. TDDFT calculations confirm the presence of XAS preedge features 0.5-2 eV below the rising sulfur K-edge energy. The 2472.1 eV feature arises when orbitals at lower energy than the frontier occupied orbitals with S 3p character mix with the copper(II) electron hole. Transmission of spin polarization and thus of radical character through several bonds between the sulfur and electron hole provides a new mechanism for the counterintuitive appearance of preedge transitions in the XAS spectra of transition-metal oxoanion ligands in the absence of any direct metal-absorber bond. The 2472.1 eV transition is evidence for further radicalization from copper(II), which extends across a hydrogen-bond bridge between sulfate and the itao ligand and involves orbitals at energies below the frontier set. This electronic structure feature provides a direct spectroscopic confirmation of the through-bond electron-transfer mechanism of redox-active metalloproteins.
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Affiliation(s)
- Patrick Frank
- Department of Chemistry, Stanford University, Stanford CA, 94305 USA
- Stanford Synchrotron Radiation Lightsource, SLAC, Stanford University, Stanford CA, 94309 USA
| | - Robert K. Szilagyi
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717 and MTA-ELTE “Momentum” Chemical Structure/Function Laboratory, Budapest, 1117, Hungary
| | - Volker Gramlich
- Laboratorium fuer Kristallographie, Sonneggstrasse 5, ETH-Zentrum, No. G 62, CH-8092 Zürich, Switzerland
| | - Hua-Fen Hsu
- Department of Chemistry, National Cheng-Kung University, Tainan City 701, Taiwan
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource, SLAC, Stanford University, Stanford CA, 94309 USA
| | - Keith O. Hodgson
- Department of Chemistry, Stanford University, Stanford CA, 94305 USA
- SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025, USA
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26
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Yan JJ, Gonzales MA, Mascharak PK, Hedman B, Hodgson KO, Solomon EI. L-Edge X-ray Absorption Spectroscopic Investigation of {FeNO} 6: Delocalization vs Antiferromagnetic Coupling. J Am Chem Soc 2017; 139:1215-1225. [PMID: 28006897 DOI: 10.1021/jacs.6b11260] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
NO is a classic non-innocent ligand, and iron nitrosyls can have different electronic structure descriptions depending on their spin state and coordination environment. These highly covalent ligands are found in metalloproteins and are also used as models for Fe-O2 systems. This study utilizes iron L-edge X-ray absorption spectroscopy (XAS), interpreted using a valence bond configuration interaction multiplet model, to directly experimentally probe the electronic structure of the S = 0 {FeNO}6 compound [Fe(PaPy3)NO]2+ (PaPy3 = N,N-bis(2-pyridylmethyl)amine-N-ethyl-2-pyridine-2-carboxamide) and the S = 0 [Fe(PaPy3)CO]+ reference compound. This method allows separation of the σ-donation and π-acceptor interactions of the ligand through ligand-to-metal and metal-to-ligand charge-transfer mixing pathways. The analysis shows that the {FeNO}6 electronic structure is best described as FeIII-NO(neutral), with no localized electron in an NO π* orbital or electron hole in an Fe dπ orbital. This delocalization comes from the large energy gap between the Fe-NO π-bonding and antibonding molecular orbitals relative to the exchange interactions between electrons in these orbitals. This study demonstrates the utility of L-edge XAS in experimentally defining highly delocalized electronic structures.
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Affiliation(s)
- James J Yan
- Department of Chemistry, Stanford University , Stanford, California 94305, United States
| | - Margarita A Gonzales
- Department of Chemistry, Foothill College , Los Altos Hills, California 94022, United States
| | - Pradip K Mascharak
- Department of Chemistry and Biochemistry, University of California , Santa Cruz, California 95064, United States
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University , Menlo Park, California 94025, United States
| | - Keith O Hodgson
- Department of Chemistry, Stanford University , Stanford, California 94305, United States.,Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University , Menlo Park, California 94025, United States
| | - Edward I Solomon
- Department of Chemistry, Stanford University , Stanford, California 94305, United States.,Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University , Menlo Park, California 94025, United States
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27
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Cowley RE, Cirera J, Qayyum MF, Rokhsana D, Hedman B, Hodgson KO, Dooley DM, Solomon EI. Structure of the Reduced Copper Active Site in Preprocessed Galactose Oxidase: Ligand Tuning for One-Electron O 2 Activation in Cofactor Biogenesis. J Am Chem Soc 2016; 138:13219-13229. [PMID: 27626829 DOI: 10.1021/jacs.6b05792] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Galactose oxidase (GO) is a copper-dependent enzyme that accomplishes 2e- substrate oxidation by pairing a single copper with an unusual cysteinylated tyrosine (Cys-Tyr) redox cofactor. Previous studies have demonstrated that the post-translational biogenesis of Cys-Tyr is copper- and O2-dependent, resulting in a self-processing enzyme system. To investigate the mechanism of cofactor biogenesis in GO, the active-site structure of Cu(I)-loaded GO was determined using X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy, and density-functional theory (DFT) calculations were performed on this model. Our results show that the active-site tyrosine lowers the Cu potential to enable the thermodynamically unfavorable 1e- reduction of O2, and the resulting Cu(II)-O2•- is activated toward H atom abstraction from cysteine. The final step of biogenesis is a concerted reaction involving coordinated Tyr ring deprotonation where Cu(II) coordination enables formation of the Cys-Tyr cross-link. These spectroscopic and computational results highlight the role of the Cu(I) in enabling O2 activation by 1e- and the role of the resulting Cu(II) in enabling substrate activation for biogenesis.
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Affiliation(s)
- Ryan E Cowley
- Department of Chemistry, Stanford University , Stanford, California 94305, United States
| | - Jordi Cirera
- Department of Chemistry, Stanford University , Stanford, California 94305, United States
| | - Munzarin F Qayyum
- Department of Chemistry, Stanford University , Stanford, California 94305, United States
| | - Dalia Rokhsana
- Department of Chemistry and Biochemistry, Montana State University , Bozeman, Montana 59717, United States
| | - Britt Hedman
- Department of Chemistry, Stanford University , Stanford, California 94305, United States.,Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University , Menlo Park, California 94025, United States
| | - Keith O Hodgson
- Department of Chemistry, Stanford University , Stanford, California 94305, United States.,Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University , Menlo Park, California 94025, United States
| | - David M Dooley
- Department of Chemistry and Biochemistry, Montana State University , Bozeman, Montana 59717, United States.,University of Rhode Island , Kingston, Rhode Island 02881, United States
| | - Edward I Solomon
- Department of Chemistry, Stanford University , Stanford, California 94305, United States.,Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University , Menlo Park, California 94025, United States
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28
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Antalek M, Pace E, Hedman B, Hodgson KO, Chillemi G, Benfatto M, Sarangi R, Frank P. Solvation structure of the halides from x-ray absorption spectroscopy. J Chem Phys 2016; 145:044318. [PMID: 27475372 PMCID: PMC4967075 DOI: 10.1063/1.4959589] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Accepted: 07/11/2016] [Indexed: 11/14/2022] Open
Abstract
Three-dimensional models for the aqueous solvation structures of chloride, bromide, and iodide are reported. K-edge extended X-ray absorption fine structure (EXAFS) and Minuit X-ray absorption near edge (MXAN) analyses found well-defined single shell solvation spheres for bromide and iodide. However, dissolved chloride proved structurally distinct, with two solvation shells needed to explain its strikingly different X-ray absorption near edge structure (XANES) spectrum. Final solvation models were as follows: iodide, 8 water molecules at 3.60 ± 0.13 Å and bromide, 8 water molecules at 3.40 ± 0.14 Å, while chloride solvation included 7 water molecules at 3.15 ± 0.10 Å, and a second shell of 7 water molecules at 4.14 ± 0.30 Å. Each of the three derived solvation shells is approximately uniformly disposed about the halides, with no global asymmetry. Time-dependent density functional theory calculations simulating the chloride XANES spectra following from alternative solvation spheres revealed surprising sensitivity of the electronic state to 6-, 7-, or 8-coordination, implying a strongly bounded phase space for the correct structure during an MXAN fit. MXAN analysis further showed that the asymmetric solvation predicted from molecular dynamics simulations using halide polarization can play no significant part in bulk solvation. Classical molecular dynamics used to explore chloride solvation found a 7-water solvation shell at 3.12 (-0.04/+0.3) Å, supporting the experimental result. These experiments provide the first fully three-dimensional structures presenting to atomic resolution the aqueous solvation spheres of the larger halide ions.
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Affiliation(s)
- Matthew Antalek
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, USA
| | - Elisabetta Pace
- Laboratori Nazionali di Frascati-INFN, P.O. Box 13, 00044 Frascati, Italy
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, USA
| | - Keith O Hodgson
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
| | - Giovanni Chillemi
- CINECA, SCAI-SuperComputing Applications and Innovation Department, Via dei Tizii 6, 00185 Roma, Italy
| | - Maurizio Benfatto
- Laboratori Nazionali di Frascati-INFN, P.O. Box 13, 00044 Frascati, Italy
| | - Ritimukta Sarangi
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, USA
| | - Patrick Frank
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, USA
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29
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Arcos-López T, Qayyum M, Rivillas-Acevedo L, Miotto MC, Grande-Aztatzi R, Fernández CO, Hedman B, Hodgson KO, Vela A, Solomon EI, Quintanar L. Spectroscopic and Theoretical Study of Cu(I) Binding to His111 in the Human Prion Protein Fragment 106-115. Inorg Chem 2016; 55:2909-22. [PMID: 26930130 PMCID: PMC4804749 DOI: 10.1021/acs.inorgchem.5b02794] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
![]()
The ability of the cellular prion
protein (PrPC) to bind copper in vivo points to a physiological
role for PrPC in copper transport. Six copper binding sites
have been identified in the nonstructured N-terminal region of human
PrPC. Among these sites, the His111 site is unique in that
it contains a MKHM motif that would confer interesting CuI and CuII binding properties. We have evaluated CuI coordination to the PrP(106–115) fragment of the human
PrP protein, using NMR and X-ray absorption spectroscopies and electronic
structure calculations. We find that Met109 and Met112 play an important
role in anchoring this metal ion. CuI coordination to His111
is pH-dependent: at pH >8, 2N1O1S species are formed with one Met
ligand; in the range of pH 5–8, both methionine (Met) residues
bind to CuI, forming a 1N1O2S species, where N is from
His111 and O is from a backbone carbonyl or a water molecule; at pH
<5, only the two Met residues remain coordinated. Thus, even upon
drastic changes in the chemical environment, such as those occurring
during endocytosis of PrPC (decreased pH and a reducing
potential), the two Met residues in the MKHM motif enable PrPC to maintain the bound CuI ions, consistent with
a copper transport function for this protein. We also find that the
physiologically relevant CuI-1N1O2S species activates dioxygen
via an inner-sphere mechanism, likely involving the formation of a
copper(II) superoxide complex. In this process, the Met residues are
partially oxidized to sulfoxide; this ability to scavenge superoxide
may play a role in the proposed antioxidant properties of PrPC. This study provides further insight into the CuI coordination properties of His111 in human PrPC and the
molecular mechanism of oxygen activation by this site. CuI coordination to the His111 site in the HuPrP protein
is highly dependent on the pH: at pH <5, two methionine (Met) residues
bind CuI; in the range of pH 5−8, both Met residues
remain coordinated, forming a 1N1O2S species, with N from His111 and
O from a backbone carbonyl or a water molecule; at pH >8, 2N1O1S
species are formed with only a Met ligand. The CuI-1N1O2S
species activates dioxygen, and in this process, the Met residues
are partially oxidized to sulfoxide.
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Affiliation(s)
| | - Munzarin Qayyum
- Department of Chemistry, Stanford University , Stanford, California 94395, United States
| | | | - Marco C Miotto
- Max Planck Laboratory for Structural Biology, Chemistry and Molecular Biophysics of Rosario (MPLbioR, UNR-MPIbpC) and Instituto de Investigaciones para el Descubrimiento de Fármacos de Rosario (IIDEFAR, UNR-CONICET), Universidad Nacional de Rosario, Ocampo y Esmeralda , S2002LRK Rosario, Argentina
| | | | - Claudio O Fernández
- Max Planck Laboratory for Structural Biology, Chemistry and Molecular Biophysics of Rosario (MPLbioR, UNR-MPIbpC) and Instituto de Investigaciones para el Descubrimiento de Fármacos de Rosario (IIDEFAR, UNR-CONICET), Universidad Nacional de Rosario, Ocampo y Esmeralda , S2002LRK Rosario, Argentina
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource (SSRL), SLAC, Stanford University , Menlo Park, California 94025, United States
| | - Keith O Hodgson
- Department of Chemistry, Stanford University , Stanford, California 94395, United States.,Stanford Synchrotron Radiation Lightsource (SSRL), SLAC, Stanford University , Menlo Park, California 94025, United States
| | - Alberto Vela
- Departamento de Química, Cinvestav , Gustavo A. Madero, 07360 México
| | - Edward I Solomon
- Department of Chemistry, Stanford University , Stanford, California 94395, United States.,Stanford Synchrotron Radiation Lightsource (SSRL), SLAC, Stanford University , Menlo Park, California 94025, United States
| | - Liliana Quintanar
- Departamento de Química, Cinvestav , Gustavo A. Madero, 07360 México
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30
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Frank P, Benfatto M, Qayyam M, Hedman B, Hodgson KO. A high-resolution XAS study of aqueous Cu(II) in liquid and frozen solutions: pyramidal, polymorphic, and non-centrosymmetric. J Chem Phys 2015; 142:084310. [PMID: 25725734 PMCID: PMC4349298 DOI: 10.1063/1.4908266] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2014] [Accepted: 02/04/2015] [Indexed: 11/15/2022] Open
Abstract
High-resolution EXAFS (k = 18 Å(-1)) and MXAN XAS analyses show that axially elongated square pyramidal [Cu(H2O)5](2+) dominates the structure of Cu(II) in aqueous solution, rather than 6-coordinate JT-octahedral [Cu(H2O)6](2+). Freezing produced a shoulder at 8989.6 eV on the rising XAS edge and an altered EXAFS spectrum, while 1s → 3d transitions remained invariant in energy position and intensity. Core square pyramidal [Cu(H2O)5](2+) also dominates frozen solution. Solvation shells were found at ∼3.6 Å (EXAFS) or ∼3.8 Å (MXAN) in both liquid and frozen phases. However, MXAN analysis revealed that about half the time in liquid solution, [Cu(H2O)5](2+) associates with an axially non-bonding 2.9 Å water molecule. This distant water apparently organizes the solvation shell. When the 2.9 Å water molecule is absent, the second shell is undetectable to MXAN. The two structural arrangements may represent energetic minima of fluxional dissolved aqueous [Cu(H2O)5](2+). The 2.9 Å trans-axial water resolves an apparent conflict of the [Cu(H2O)5](2+) core model with a dissociational exchange mechanism. In frozen solution, [Cu(H2O)5](2+) is associated with either a 3.0 Å axial non-bonded water molecule or an axial ClO4(-) at 3.2 Å. Both structures are again of approximately equal presence. When the axial ClO4(-) is present, Cu(II) is ∼0.5 Å above the mean O4 plane. This study establishes [Cu(H2O)5](2+) as the dominant core structure for Cu(II) in water solution, and is the first to both empirically resolve multiple extended solution structures for fluxional [Cu(H2O)5](2+) and to provide direct evidence for second shell dynamics.
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Affiliation(s)
- Patrick Frank
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
| | - Maurizio Benfatto
- Laboratori Nazionali di Frascati-INFN, P.O. Box 13, 00044 Frascati, Italy
| | - Munzarin Qayyam
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, USA
| | - Keith O Hodgson
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
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31
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Kroll T, Hadt RG, Wilson SA, Lundberg M, Yan JJ, Weng TC, Sokaras D, Alonso-Mori R, Casa D, Upton MH, Hedman B, Hodgson KO, Solomon EI. Resonant inelastic X-ray scattering on ferrous and ferric bis-imidazole porphyrin and cytochrome c: nature and role of the axial methionine-Fe bond. J Am Chem Soc 2014; 136:18087-99. [PMID: 25475739 PMCID: PMC4291809 DOI: 10.1021/ja5100367] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Axial Cu-S(Met) bonds in electron transfer (ET) active sites are generally found to lower their reduction potentials. An axial S(Met) bond is also present in cytochrome c (cyt c) and is generally thought to increase the reduction potential. The highly covalent nature of the porphyrin environment in heme proteins precludes using many spectroscopic approaches to directly study the Fe site to experimentally quantify this bond. Alternatively, L-edge X-ray absorption spectroscopy (XAS) enables one to directly focus on the 3d-orbitals in a highly covalent environment and has previously been successfully applied to porphyrin model complexes. However, this technique cannot be extended to metalloproteins in solution. Here, we use metal K-edge XAS to obtain L-edge like data through 1s2p resonance inelastic X-ray scattering (RIXS). It has been applied here to a bis-imidazole porphyrin model complex and cyt c. The RIXS data on the model complex are directly correlated to L-edge XAS data to develop the complementary nature of these two spectroscopic methods. Comparison between the bis-imidazole model complex and cyt c in ferrous and ferric oxidation states show quantitative differences that reflect differences in axial ligand covalency. The data reveal an increased covalency for the S(Met) relative to N(His) axial ligand and a higher degree of covalency for the ferric states relative to the ferrous states. These results are reproduced by DFT calculations, which are used to evaluate the thermodynamics of the Fe-S(Met) bond and its dependence on redox state. These results provide insight into a number of previous chemical and physical results on cyt c.
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Affiliation(s)
- Thomas Kroll
- Department of Chemistry, Stanford University , Stanford, California 94305, United States
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32
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Cohen AE, Soltis SM, González A, Aguila L, Alonso-Mori R, Barnes CO, Baxter EL, Brehmer W, Brewster AS, Brunger AT, Calero G, Chang JF, Chollet M, Ehrensberger P, Eriksson TL, Feng Y, Hattne J, Hedman B, Hollenbeck M, Holton JM, Keable S, Kobilka BK, Kovaleva EG, Kruse AC, Lemke HT, Lin G, Lyubimov AY, Manglik A, Mathews II, McPhillips SE, Nelson S, Peters JW, Sauter NK, Smith CA, Song J, Stevenson HP, Tsai Y, Uervirojnangkoorn M, Vinetsky V, Wakatsuki S, Weis WI, Zadvornyy OA, Zeldin OB, Zhu D, Hodgson KO. Goniometer-based femtosecond crystallography with X-ray free electron lasers. Proc Natl Acad Sci U S A 2014; 111:17122-7. [PMID: 25362050 PMCID: PMC4260607 DOI: 10.1073/pnas.1418733111] [Citation(s) in RCA: 102] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The emerging method of femtosecond crystallography (FX) may extend the diffraction resolution accessible from small radiation-sensitive crystals and provides a means to determine catalytically accurate structures of acutely radiation-sensitive metalloenzymes. Automated goniometer-based instrumentation developed for use at the Linac Coherent Light Source enabled efficient and flexible FX experiments to be performed on a variety of sample types. In the case of rod-shaped Cpl hydrogenase crystals, only five crystals and about 30 min of beam time were used to obtain the 125 still diffraction patterns used to produce a 1.6-Å resolution electron density map. For smaller crystals, high-density grids were used to increase sample throughput; 930 myoglobin crystals mounted at random orientation inside 32 grids were exposed, demonstrating the utility of this approach. Screening results from cryocooled crystals of β2-adrenoreceptor and an RNA polymerase II complex indicate the potential to extend the diffraction resolution obtainable from very radiation-sensitive samples beyond that possible with undulator-based synchrotron sources.
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Affiliation(s)
| | | | | | | | | | - Christopher O Barnes
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261
| | | | | | - Aaron S Brewster
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720
| | - Axel T Brunger
- Molecular and Cellular Physiology, and Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305
| | - Guillermo Calero
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261
| | | | | | | | | | | | - Johan Hattne
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720
| | | | | | - James M Holton
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720; Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94158; and
| | - Stephen Keable
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59715
| | | | | | | | | | - Guowu Lin
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261
| | - Artem Y Lyubimov
- Molecular and Cellular Physiology, and Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305
| | | | | | | | | | - John W Peters
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59715
| | - Nicholas K Sauter
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720
| | | | - Jinhu Song
- Stanford Synchrotron Radiation Lightsource
| | - Hilary P Stevenson
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261
| | - Yingssu Tsai
- Stanford Synchrotron Radiation Lightsource, Departments of Chemistry
| | - Monarin Uervirojnangkoorn
- Molecular and Cellular Physiology, and Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305
| | | | - Soichi Wakatsuki
- Photon Science, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025; Structural Biology, and
| | - William I Weis
- Molecular and Cellular Physiology, and Structural Biology, and
| | - Oleg A Zadvornyy
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59715
| | - Oliver B Zeldin
- Molecular and Cellular Physiology, and Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305
| | | | - Keith O Hodgson
- Stanford Synchrotron Radiation Lightsource, Departments of Chemistry,
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33
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Peterson RL, Ginsbach JW, Cowley RE, Qayyum MF, Himes RA, Siegler MA, Moore CD, Hedman B, Hodgson KO, Fukuzumi S, Solomon EI, Karlin KD. Stepwise protonation and electron-transfer reduction of a primary copper-dioxygen adduct. J Am Chem Soc 2014; 135:16454-67. [PMID: 24164682 DOI: 10.1021/ja4065377] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The protonation–reduction of a dioxygen adduct with [LCu(I)][B(C6F5)4], cupric superoxo complex [LCu(II)(O2(•–))]+ (1) (L = TMG3tren (1,1,1-tris[2-[N(2)-(1,1,3,3-tetramethylguanidino)]ethyl]amine)) has been investigated. Trifluoroacetic acid (HOAcF) reversibly associates with the superoxo ligand in ([LCu(II)(O2(•–))]+) in a 1:1 adduct [LCu(II)(O2(•–))(HOAcF)](+) (2), as characterized by UV–visible, resonance Raman (rR), nuclear magnetic resonance (NMR), and X-ray absorption (XAS) spectroscopies, along with density functional theory (DFT) calculations. Chemical studies reveal that for the binding of HOAcF with 1 to give 2, Keq = 1.2 × 10(5) M(–1) (−130 °C) and ΔH° = −6.9(7) kcal/mol, ΔS° = −26(4) cal mol(–1) K(–1)). Vibrational (rR) data reveal a significant increase (29 cm(–1)) in vO–O (= 1149 cm(–1)) compared to that known for [LCu(II)(O2(•–))](+) (1). Along with results obtained from XAS and DFT calculations, hydrogen bonding of HOAcF to a superoxo O-atom in 2 is established. Results from NMR spectroscopy of 2 at −120 °C in 2-methyltetrahydrofuran are also consistent with 1/HOAcF = 1:1 formulation of 2 and with this complex possessing a triplet (S = 1) ground state electronic configuration, as previously determined for 1. The pre-equilibrium acid association to 1 is followed by outer-sphere electron-transfer reduction of 2 by decamethylferrocene (Me10Fc) or octamethylferrocene (Me8Fc), leading to the products H2O2, the corresponding ferrocenium salt, and [LCu(II)(OAcF)](+). Second-order rate constants for electron transfer (ket) were determined to be 1365 M(–1) s(–1) (Me10Fc) and 225 M(–1) s(–1) (Me8Fc) at −80 °C. The (bio)chemical relevance of the proton-triggered reduction of the metal-bound dioxygen-derived fragment is discussed.
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34
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Ha Y, Tenderholt AL, Holm RH, Hedman B, Hodgson KO, Solomon EI. Sulfur K-edge X-ray absorption spectroscopy and density functional theory calculations on monooxo Mo(IV) and bisoxo Mo(VI) bis-dithiolenes: insights into the mechanism of oxo transfer in sulfite oxidase and its relation to the mechanism of DMSO reductase. J Am Chem Soc 2014; 136:9094-105. [PMID: 24884723 PMCID: PMC4073832 DOI: 10.1021/ja503316p] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Indexed: 12/25/2022]
Abstract
Sulfur K-edge X-ray absorption spectroscopy (XAS) and density functional theory (DFT) calculations have been used to determine the electronic structures of two complexes [Mo(IV)O(bdt)2](2-) and [Mo(VI)O2(bdt)2](2-) (bdt = benzene-1,2-dithiolate(2-)) that relate to the reduced and oxidized forms of sulfite oxidase (SO). These are compared with those of previously studied dimethyl sulfoxide reductase (DMSOr) models. DFT calculations supported by the data are extended to evaluate the reaction coordinate for oxo transfer to a phosphite ester substrate. Three possible transition states are found with the one at lowest energy, stabilized by a P-S interaction, in good agreement with experimental kinetics data. Comparison of both oxo transfer reactions shows that in DMSOr, where the oxo is transferred from the substrate to the metal ion, the oxo transfer induces electron transfer, while in SO, where the oxo transfer is from the metal site to the substrate, the electron transfer initiates oxo transfer. This difference in reactivity is related to the difference in frontier molecular orbitals (FMO) of the metal-oxo and substrate-oxo bonds. Finally, these experimentally related calculations are extended to oxo transfer by sulfite oxidase. The presence of only one dithiolene at the enzyme active site selectively activates the equatorial oxo for transfer, and allows facile structural reorganization during turnover.
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Affiliation(s)
- Yang Ha
- Department
of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Adam L. Tenderholt
- Department
of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Richard H. Holm
- Department
of Chemistry and Chemical Biology, Harvard
University, Cambridge, Massachusetts 02138, United States
| | - Britt Hedman
- Stanford
Synchrotron Radiation Lightsource, SLAC, Stanford University, Menlo Park, California 94025, United States
| | - Keith O. Hodgson
- Department
of Chemistry, Stanford University, Stanford, California 94305, United States
- Stanford
Synchrotron Radiation Lightsource, SLAC, Stanford University, Menlo Park, California 94025, United States
| | - Edward I. Solomon
- Department
of Chemistry, Stanford University, Stanford, California 94305, United States
- Stanford
Synchrotron Radiation Lightsource, SLAC, Stanford University, Menlo Park, California 94025, United States
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35
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Engstrom LM, Brinkmeyer MK, Ha Y, Raetz AG, Hedman B, Hodgson KO, Solomon EI, David SS. A zinc linchpin motif in the MUTYH glycosylase interdomain connector is required for efficient repair of DNA damage. J Am Chem Soc 2014; 136:7829-32. [PMID: 24841533 PMCID: PMC4063174 DOI: 10.1021/ja502942d] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Mammalian MutY glycosylases have a unique architecture that features an interdomain connector (IDC) that joins the catalytic N-terminal domain and 8-oxoguanine (OG) recognition C-terminal domain. The IDC has been shown to be a hub for interactions with protein partners involved in coordinating downstream repair events and signaling apoptosis. Herein, a previously unidentified zinc ion and its coordination by three Cys residues of the IDC region of eukaryotic MutY organisms were characterized by mutagenesis, ICP-MS, and EXAFS. In vitro kinetics and cellular assays on WT and Cys to Ser mutants have revealed an important function for zinc coordination on overall protein stability, iron-sulfur cluster insertion, and ability to mediate DNA damage repair. We propose that this "zinc linchpin" motif serves to structurally organize the IDC and coordinate the damage recognition and base excision functions of the C- and N-terminal domains.
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Affiliation(s)
- Lisa M Engstrom
- Department of Chemistry, University of California, Davis , One Shields Avenue, Davis, California 95616, United States
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36
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Halvagar M, Solntsev PV, Lim H, Hedman B, Hodgson KO, Solomon E, Cramer CJ, Tolman WB. Hydroxo-bridged dicopper(II,III) and -(III,III) complexes: models for putative intermediates in oxidation catalysis. J Am Chem Soc 2014; 136:7269-72. [PMID: 24821432 PMCID: PMC4046753 DOI: 10.1021/ja503629r] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2014] [Indexed: 12/21/2022]
Abstract
A macrocyclic ligand (L(4-)) comprising two pyridine(dicarboxamide) donors was used to target reactive copper species relevant to proposed intermediates in catalytic hydrocarbon oxidations by particulate methane monooxygenase and heterogeneous zeolite systems. Treatment of LH4 with base and Cu(OAc)2·H2O yielded (Me4N)2[L2Cu4(μ4-O)] (1) or (Me4N)[LCu2(μ-OH)] (2), depending on conditions. Complex 2 was found to undergo two reversible 1-electron oxidations via cyclic voltammetry and low-temperature chemical reactions. On the basis of spectroscopy and theory, the oxidation products were identified as novel hydroxo-bridged mixed-valent Cu(II)Cu(III) and symmetric Cu(III)2 species, respectively, that provide the first precedence for such moieties as oxidation catalysis intermediates.
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Affiliation(s)
- Mohammad
Reza Halvagar
- Department
of Chemistry, Center for Metals in Biocatalysis, Chemical Theory Center,
and Minnesota Supercomputing Institute, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States
| | - Pavlo V. Solntsev
- Department
of Chemistry, Center for Metals in Biocatalysis, Chemical Theory Center,
and Minnesota Supercomputing Institute, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States
| | - Hyeongtaek Lim
- Department
of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Britt Hedman
- Stanford
Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Keith O. Hodgson
- Department
of Chemistry, Stanford University, Stanford, California 94305, United States
- Stanford
Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Edward
I. Solomon
- Department
of Chemistry, Stanford University, Stanford, California 94305, United States
- Stanford
Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Christopher J. Cramer
- Department
of Chemistry, Center for Metals in Biocatalysis, Chemical Theory Center,
and Minnesota Supercomputing Institute, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States
| | - William B. Tolman
- Department
of Chemistry, Center for Metals in Biocatalysis, Chemical Theory Center,
and Minnesota Supercomputing Institute, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States
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37
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Frank P, Hedman B, Hodgson KO. XAS spectroscopy, sulfur, and the brew within blood cells from Ascidia ceratodes. J Inorg Biochem 2014; 131:99-108. [PMID: 24333825 PMCID: PMC3913562 DOI: 10.1016/j.jinorgbio.2013.11.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2013] [Revised: 11/06/2013] [Accepted: 11/08/2013] [Indexed: 02/02/2023]
Abstract
We report the first use of K-edge X-ray absorption spectroscopy (XAS) as a direct spectroscopic probe of pH and cytosolic emf within living cells. A new accuracy metric of model-based fits to K-edge spectra is further developed. Sulfur functional groups in three collections of living blood cells and one sample of cleared blood plasma from the tunicate Ascidia ceratodes were speciated using K-edge XAS. Cysteine and cystine, the preferred thiol-disulfide model, averaged about 12% of total sulfur. Sulfate monoesters and cyclic diesters unexpectedly constituted 36% of blood cell sulfur. Soluble sulfate averaged about 25% across the three blood cell samples, while the ratio of SO4(2-) to HSO4(-) implied average signet ring vacuolar pH values of 0.85, 1.4, or 3.1. Intracellular (VSO4)(+) was unobserved, while [V(RSO3)n]((3-n)+) was detected in the two lowest pH blood cell samples. About 5% of sulfur was distributed as mono- or dibenzothiophene or ethylene-epi-sulfide, or as a thiadiazole reminiscent of the polycarpathiamines. Blood plasma was dominated by sulfate (83%), but with 15% of an alkylsulfate ester and about 2% of low-valent sulfur. Gravimetric analysis of soluble sulfate yielded average concentrations of blood cell sulfur. Average [cysteine] and [cystine] (ranging ~10-30 mM and ~20-90 mM, respectively) implied blood-cell cytosolic emf values of approximately -0.20 V. High cellular [cysteine] is consistent with the proposed model for enzymatic reduction of vanadate by endogenous thiol, wherein the trajectory of metal site-symmetry is controlled and directed through to a thermodynamically favored 7-coordinate V(III) product.
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Affiliation(s)
- Patrick Frank
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA; Stanford Synchrotron Radiation Lightsource, SLAC, Stanford University, Stanford, CA 94309, USA.
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource, SLAC, Stanford University, Stanford, CA 94309, USA
| | - Keith O Hodgson
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA; SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94309, USA
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38
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Affiliation(s)
- Markus W Ribbe
- Department of Molecular Biology and Biochemistry, University of California , Irvine, California 92697-3900, United States
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39
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Qayyum MF, Sarangi R, Fujisawa K, Stack TDP, Karlin KD, Hodgson KO, Hedman B, Solomon EI. L-edge X-ray absorption spectroscopy and DFT calculations on Cu2O2 species: direct electrophilic aromatic attack by side-on peroxo bridged dicopper(II) complexes. J Am Chem Soc 2013; 135:17417-31. [PMID: 24102191 PMCID: PMC3891796 DOI: 10.1021/ja4078717] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The hydroxylation of aromatic substrates catalyzed by coupled binuclear copper enzymes has been observed with side-on-peroxo-dicopper(II) (P) and bis-μ-oxo-dicopper(III) (O) model complexes. The substrate-bound-O intermediate in [Cu(II)2(DBED)2(O)2](2+) (DBED = N,N'-di-tert-butyl-ethylenediamine) was shown to perform aromatic hydroxylation. For the [Cu(II)2(NO2-XYL)(O2)](2+) complex, only a P species was spectroscopically observed. However, it was not clear whether this O-O bond cleaves to proceed through an O-type structure along the reaction coordinate for hydroxylation of the aromatic xylyl linker. Accurate evaluation of these reaction coordinates requires reasonable quantitative descriptions of the electronic structures of the P and O species. We have performed Cu L-edge XAS on two well-characterized P and O species to experimentally quantify the Cu 3d character in their ground state wave functions. The lower per-hole Cu character (40 ± 6%) corresponding to higher covalency in the O species compared to the P species (52 ± 4%) reflects a stronger bonding interaction of the bis-μ-oxo core with the Cu(III) centers. DFT calculations show that 10-20% Hartree-Fock (HF) mixing for P and ~38% for O species are required to reproduce the Cu-O bonding; for the P species this HF mixing is also required for an antiferromagnetically coupled description of the two Cu(II) centers. B3LYP (with 20% HF) was, therefore, used to calculate the hydroxylation reaction coordinate of P in [Cu(II)2(NO2-XYL)(O2)](2+). These experimentally calibrated calculations indicate that the electrophilic attack on the aromatic ring does not involve formation of a Cu(III)2(O(2-))2 species. Rather, there is direct electron donation from the aromatic ring into the peroxo σ* orbital of the Cu(II)2(O2(2-)) species, leading to concerted C-O bond formation with O-O bond cleavage. Thus, species P is capable of direct hydroxylation of aromatic substrates without the intermediacy of an O-type species.
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40
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Lundberg M, Kroll T, DeBeer S, Bergmann U, Wilson SA, Glatzel P, Nordlund D, Hedman B, Hodgson KO, Solomon EI. Metal-ligand covalency of iron complexes from high-resolution resonant inelastic X-ray scattering. J Am Chem Soc 2013; 135:17121-34. [PMID: 24131028 PMCID: PMC3920600 DOI: 10.1021/ja408072q] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Data from Kα resonant inelastic X-ray scattering (RIXS) have been used to extract electronic structure information, i.e., the covalency of metal-ligand bonds, for four iron complexes using an experimentally based theoretical model. Kα RIXS involves resonant 1s→3d excitation and detection of the 2p→1s (Kα) emission. This two-photon process reaches similar final states as single-photon L-edge (2p→3d) X-ray absorption spectroscopy (XAS), but involves only hard X-rays and can therefore be used to get high-resolution L-edge-like spectra for metal proteins, solution catalysts and their intermediates. To analyze the information content of Kα RIXS spectra, data have been collected for four characteristic σ-donor and π-back-donation complexes: ferrous tacn [Fe(II)(tacn)2]Br2, ferrocyanide [Fe(II)(CN)6]K4, ferric tacn [Fe(III)(tacn)2]Br3 and ferricyanide [Fe(III)(CN)6]K3. From these spectra metal-ligand covalencies can be extracted using a charge-transfer multiplet model, without previous information from the L-edge XAS experiment. A direct comparison of L-edge XAS and Kα RIXS spectra show that the latter reaches additional final states, e.g., when exciting into the e(g) (σ*) orbitals, and the splitting between final states of different symmetry provides an extra dimension that makes Kα RIXS a more sensitive probe of σ-bonding. Another key difference between L-edge XAS and Kα RIXS is the π-back-bonding features in ferro- and ferricyanide that are significantly more intense in L-edge XAS compared to Kα RIXS. This shows that two methods are complementary in assigning electronic structure. The Kα RIXS approach can thus be used as a stand-alone method, in combination with L-edge XAS for strongly covalent systems that are difficult to probe by UV/vis spectroscopy, or as an extension to conventional absorption spectroscopy for a wide range of transition metal enzymes and catalysts.
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Affiliation(s)
- Marcus Lundberg
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
| | - Thomas Kroll
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
| | - Serena DeBeer
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025, USA
| | - Uwe Bergmann
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025, USA
| | - Samuel A. Wilson
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
| | | | - Dennis Nordlund
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025, USA
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025, USA
| | - Keith O. Hodgson
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025, USA
| | - Edward I. Solomon
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025, USA
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41
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McQuilken AC, Ha Y, Sutherlin KD, Siegler MA, Hodgson KO, Hedman B, Solomon EI, Jameson GNL, Goldberg DP. Preparation of non-heme {FeNO}7 models of cysteine dioxygenase: sulfur versus nitrogen ligation and photorelease of nitric oxide. J Am Chem Soc 2013; 135:14024-7. [PMID: 24040838 DOI: 10.1021/ja4064487] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
We present the synthesis and spectroscopic characterization of [Fe(NO)(N3PyS)]BF4 (3), the first structural and electronic model of NO-bound cysteine dioxygenase. The nearly isostructural all-N-donor analogue [Fe(NO)(N4Py)](BF4)2 (4) was also prepared, and comparisons of 3 and 4 provide insight regarding the influence of S vs N ligation in {FeNO}(7) species. One key difference occurs upon photoirradiation, which causes the fully reversible release of NO from 3, but not from 4.
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Affiliation(s)
- Alison C McQuilken
- Department of Chemistry, The Johns Hopkins University , Baltimore, Maryland 21218, United States
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42
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Kjaergaard CH, Qayyum MF, Augustine AJ, Ziegler L, Kosman DJ, Hodgson KO, Hedman B, Solomon EI. Modified reactivity toward O2 in first shell variants of Fet3p: geometric and electronic structure requirements for a functioning trinuclear copper cluster. Biochemistry 2013; 52:3702-11. [PMID: 23631422 DOI: 10.1021/bi4002826] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Multicopper oxidases (MCOs) carry out the most energy efficient reduction of O2 to H2O known, i.e., with the lowest overpotential. This four-electron process requires an electron mediating type 1 (T1) Cu site and an oxygen reducing trinuclear Cu cluster (TNC), consisting of a binuclear type 3 (T3)- and a mononuclear type 2 (T2) Cu center. The rate-determining step in O2 reduction is the first two-electron transfer from one of the T3 Cu's (T3β) and the T2 Cu, forming a bridged peroxide intermediate (PI). This reaction has been investigated in T3β Cu variants of the Fet3p, where a first shell His ligand is mutated to Glu or Gln. This converts the fast two-electron reaction of the wild-type (WT) enzyme to a slow one-electron oxidation of the TNC. Both variants initially react to form a common T3β Cu(II) intermediate that converts to the Glu or Gln bound resting state. From spectroscopic evaluation, the nonmutated His ligands coordinate linearly to the T3β Cu in the reduced TNCs in the two variants, in contrast to the trigonal arrangement observed in the WT enzyme. This structural perturbation is found to significantly alter the electronic structure of the reduced TNC, which is no longer capable of rapidly transferring two electrons to the two perpendicular half occupied π*-orbitals of O2, in contrast to the WT enzyme. This study provides new insight into the geometric and electronic structure requirements of a fully functional TNC for the rate determining two-electron reduction of O2 in the MCOs.
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Affiliation(s)
- Christian H Kjaergaard
- Department of Chemistry, Stanford University , Stanford, California 94305, United States
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43
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Sarangi R, Frank P, Benfatto M, Morante S, Minicozzi V, Hedman B, Hodgson KO. The x-ray absorption spectroscopy model of solvation about sulfur in aqueous L-cysteine. J Chem Phys 2013. [PMID: 23206038 DOI: 10.1063/1.4767350] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
The environment of sulfur in dissolved aqueous L-cysteine has been examined using K-edge x-ray absorption spectroscopy (XAS), extended continuum multiple scattering (ECMS) theory, and density functional theory (DFT). For the first time, bound-state and continuum transitions representing the entire XAS spectrum of L-cysteine sulfur are accurately reproduced by theory. Sulfur K-edge absorption features at 2473.3 eV and 2474.2 eV represent transitions to LUMOs that are mixtures of S-C and S-H σ∗ orbitals significantly delocalized over the entire L-cysteine molecule. Continuum features at 2479, 2489, and 2530 eV were successfully reproduced using extended continuum theory. The full L-cysteine sulfur K-edge XAS spectrum could not be reproduced without addition of a water-sulfur hydrogen bond. Density functional theory analysis shows that although the Cys(H)S⋯H-OH hydrogen bond is weak (∼2 kcal) the atomic charge on sulfur is significantly affected by this water. MXAN analysis of hydrogen-bonding structures for L-cysteine and water yielded a best fit model featuring a tandem of two water molecules, 2.9 Å and 5.8 Å from sulfur. The model included a S(cys)⋯H-O(w1)H hydrogen-bond of 2.19 Å and of 2.16 Å for H(2)O(w1)⋯H-O(w2)H. One hydrogen-bonding water-sulfur interaction alone was insufficient to fully describe the continuum XAS spectrum. However, density functional theoretical results are convincing that the water-sulfur interaction is weak and should be only transient in water solution. The durable water-sulfur hydrogen bond in aqueous L-cysteine reported here therefore represents a break with theoretical studies indicating its absence. Reconciling the apparent disparity between theory and result remains the continuing challenge.
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Affiliation(s)
- Ritimukta Sarangi
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
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44
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Tsai Y, McPhillips SE, González A, McPhillips TM, Zinn D, Cohen AE, Feese MD, Bushnell D, Tiefenbrunn T, Stout CD, Ludaescher B, Hedman B, Hodgson KO, Soltis SM. AutoDrug: fully automated macromolecular crystallography workflows for fragment-based drug discovery. Acta Crystallogr D Biol Crystallogr 2013; 69:796-803. [PMID: 23633588 PMCID: PMC3640469 DOI: 10.1107/s0907444913001984] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2013] [Accepted: 01/20/2013] [Indexed: 11/10/2022]
Abstract
AutoDrug is software based upon the scientific workflow paradigm that integrates the Stanford Synchrotron Radiation Lightsource macromolecular crystallography beamlines and third-party processing software to automate the crystallography steps of the fragment-based drug-discovery process. AutoDrug screens a cassette of fragment-soaked crystals, selects crystals for data collection based on screening results and user-specified criteria and determines optimal data-collection strategies. It then collects and processes diffraction data, performs molecular replacement using provided models and detects electron density that is likely to arise from bound fragments. All processes are fully automated, i.e. are performed without user interaction or supervision. Samples can be screened in groups corresponding to particular proteins, crystal forms and/or soaking conditions. A single AutoDrug run is only limited by the capacity of the sample-storage dewar at the beamline: currently 288 samples. AutoDrug was developed in conjunction with RestFlow, a new scientific workflow-automation framework. RestFlow simplifies the design of AutoDrug by managing the flow of data and the organization of results and by orchestrating the execution of computational pipeline steps. It also simplifies the execution and interaction of third-party programs and the beamline-control system. Modeling AutoDrug as a scientific workflow enables multiple variants that meet the requirements of different user groups to be developed and supported. A workflow tailored to mimic the crystallography stages comprising the drug-discovery pipeline of CoCrystal Discovery Inc. has been deployed and successfully demonstrated. This workflow was run once on the same 96 samples that the group had examined manually and the workflow cycled successfully through all of the samples, collected data from the same samples that were selected manually and located the same peaks of unmodeled density in the resulting difference Fourier maps.
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Affiliation(s)
- Yingssu Tsai
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
- Department of Chemistry, Stanford University, 333 Campus Drive, Mudd Building, Stanford, CA 94305-5080, USA
| | - Scott E. McPhillips
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
| | - Ana González
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
| | - Timothy M. McPhillips
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
| | - Daniel Zinn
- LogicBlox Inc., 1349 West Peachtree Street NW, Atlanta, GA 30309, USA
| | - Aina E. Cohen
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
| | - Michael D. Feese
- Cocrystal Discovery Inc., 19805 North Creek Parkway, Bothell, WA 98011, USA
| | - David Bushnell
- Cocrystal Discovery Inc., 19805 North Creek Parkway, Bothell, WA 98011, USA
| | - Theresa Tiefenbrunn
- Department of Molecular Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - C. David Stout
- Department of Molecular Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Bertram Ludaescher
- Department of Computer Science and Genome Center, University of California, One Shields Avenue, Davis, CA 95616, USA
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
- Department of Chemistry, Stanford University, 333 Campus Drive, Mudd Building, Stanford, CA 94305-5080, USA
| | - Keith O. Hodgson
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
- Department of Chemistry, Stanford University, 333 Campus Drive, Mudd Building, Stanford, CA 94305-5080, USA
| | - S. Michael Soltis
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
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45
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Wilson SA, Kroll T, Decreau RA, Hocking RK, Lundberg M, Hedman B, Hodgson KO, Solomon EI. Iron L-edge X-ray absorption spectroscopy of oxy-picket fence porphyrin: experimental insight into Fe-O2 bonding. J Am Chem Soc 2013; 135:1124-36. [PMID: 23259487 PMCID: PMC3614349 DOI: 10.1021/ja3103583] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The electronic structure of the Fe-O(2) center in oxy-hemoglobin and oxy-myoglobin is a long-standing issue in the field of bioinorganic chemistry. Spectroscopic studies have been complicated by the highly delocalized nature of the porphyrin, and calculations require interpretation of multideterminant wave functions for a highly covalent metal site. Here, iron L-edge X-ray absorption spectroscopy, interpreted using a valence bond configuration interaction multiplet model, is applied to directly probe the electronic structure of the iron in the biomimetic Fe-O(2) heme complex [Fe(pfp)(1-MeIm)O(2)] (pfp ("picket fence porphyrin") = meso-tetra(α,α,α,α-o-pivalamidophenyl)porphyrin or TpivPP). This method allows separate estimates of σ-donor, π-donor, and π-acceptor interactions through ligand-to-metal charge transfer and metal-to-ligand charge transfer mixing pathways. The L-edge spectrum of [Fe(pfp)(1-MeIm)O(2)] is further compared to those of [Fe(II)(pfp)(1-MeIm)(2)], [Fe(II)(pfp)], and [Fe(III)(tpp)(ImH)(2)]Cl (tpp = meso-tetraphenylporphyrin) which have Fe(II)S = 0, Fe(II)S = 1, and Fe(III)S = 1/2 ground states, respectively. These serve as references for the three possible contributions to the ground state of oxy-pfp. The Fe-O(2) pfp site is experimentally determined to have both significant σ-donation and a strong π-interaction of the O(2) with the iron, with the latter having implications with respect to the spin polarization of the ground state.
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Affiliation(s)
- Samuel A. Wilson
- Department of Chemistry, Stanford University, Stanford, CA 94305, U.S.A
| | - Thomas Kroll
- Department of Chemistry, Stanford University, Stanford, CA 94305, U.S.A
| | | | | | - Marcus Lundberg
- Department of Chemistry, Stanford University, Stanford, CA 94305, U.S.A
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025-7015, U.S.A
| | - Keith O. Hodgson
- Department of Chemistry, Stanford University, Stanford, CA 94305, U.S.A
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025-7015, U.S.A
| | - Edward I. Solomon
- Department of Chemistry, Stanford University, Stanford, CA 94305, U.S.A
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025-7015, U.S.A
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46
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George GN, Pickering IJ, Pushie MJ, Nienaber K, Hackett MJ, Ascone I, Hedman B, Hodgson KO, Aitken JB, Levina A, Glover C, Lay PA. X-ray-induced photo-chemistry and X-ray absorption spectroscopy of biological samples. J Synchrotron Radiat 2012; 19:875-86. [PMID: 23093745 PMCID: PMC3480274 DOI: 10.1107/s090904951203943x] [Citation(s) in RCA: 101] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2012] [Accepted: 09/16/2012] [Indexed: 05/03/2023]
Abstract
As synchrotron light sources and optics deliver greater photon flux on samples, X-ray-induced photo-chemistry is increasingly encountered in X-ray absorption spectroscopy (XAS) experiments. The resulting problems are particularly pronounced for biological XAS experiments. This is because biological samples are very often quite dilute and therefore require signal averaging to achieve adequate signal-to-noise ratios, with correspondingly greater exposures to the X-ray beam. This paper reviews the origins of photo-reduction and photo-oxidation, the impact that they can have on active site structure, and the methods that can be used to provide relief from X-ray-induced photo-chemical artifacts.
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Affiliation(s)
- Graham N. George
- Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 5E2
| | - Ingrid J. Pickering
- Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 5E2
| | - M. Jake Pushie
- Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 5E2
| | - Kurt Nienaber
- Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 5E2
| | - Mark J. Hackett
- Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 5E2
| | - Isabella Ascone
- ENSCP Chimie ParisTech, LCF, CNRS, UMR 7223, 75005 Paris, France
| | - Britt Hedman
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
| | - Keith O. Hodgson
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
| | - Jade B. Aitken
- School of Chemistry, The University of Sydney, Sydney, NSW 2006, Australia
- Australian Synchrotron, Clayton, VIC 3168, Australia
- Institute of Materials Structure Science, KEK, Tsukuba, Ibaraki 305-0801, Japan
| | - Aviva Levina
- School of Chemistry, The University of Sydney, Sydney, NSW 2006, Australia
| | | | - Peter A. Lay
- School of Chemistry, The University of Sydney, Sydney, NSW 2006, Australia
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47
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Hadt RG, Sun N, Marshall NM, Hodgson KO, Hedman B, Lu Y, Solomon EI. Spectroscopic and DFT studies of second-sphere variants of the type 1 copper site in azurin: covalent and nonlocal electrostatic contributions to reduction potentials. J Am Chem Soc 2012; 134:16701-16. [PMID: 22985400 PMCID: PMC3506006 DOI: 10.1021/ja306438n] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The reduction potentials (E(0)) of type 1 (T1) or blue copper (BC) sites in proteins and enzymes with identical first coordination spheres around the redox active copper ion can vary by ~400 mV. Here, we use a combination of low-temperature electronic absorption and magnetic circular dichroism, electron paramagnetic resonance, resonance Raman, and S K-edge X-ray absorption spectroscopies to investigate a series of second-sphere variants--F114P, N47S, and F114N in Pseudomonas aeruginosa azurin--which modulate hydrogen bonding to and protein-derived dipoles nearby the Cu-S(Cys) bond. Density functional theory calculations correlated to the experimental data allow for the fractionation of the contributions to tuning E(0) into covalent and nonlocal electrostatic components. These are found to be significant, comparable in magnitude, and additive for active H-bonds, while passive H-bonds are mostly nonlocal electrostatic in nature. For dipoles, these terms can be additive to or oppose one another. This study provides a methodology for uncoupling covalency from nonlocal electrostatics, which, when coupled to X-ray crystallographic data, distinguishes specific local interactions from more long-range protein/active interactions, while affording further insight into the second-sphere mechanisms available to the protein to tune the E(0) of electron-transfer sites in biology.
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Affiliation(s)
- Ryan G. Hadt
- Department of Chemistry, Stanford University, Stanford, CA 94305
| | - Ning Sun
- Department of Chemistry, Stanford University, Stanford, CA 94305
| | - Nicholas M. Marshall
- Department of Chemistry, University of Illinois, Urbana-Champaign, Illinois 61801
| | - Keith O. Hodgson
- Department of Chemistry, Stanford University, Stanford, CA 94305
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025
| | - Yi Lu
- Department of Chemistry, University of Illinois, Urbana-Champaign, Illinois 61801
| | - Edward I. Solomon
- Department of Chemistry, Stanford University, Stanford, CA 94305
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025
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48
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Wilson SA, Chen J, Hong S, Lee YM, Clémancey M, Garcia-Serres R, Nomura T, Ogura T, Latour JM, Hedman B, Hodgson KO, Nam W, Solomon EI. [Fe(IV)═O(TBC)(CH3CN)]2+: comparative reactivity of iron(IV)-oxo species with constrained equatorial cyclam ligation. J Am Chem Soc 2012; 134:11791-806. [PMID: 22708532 DOI: 10.1021/ja3046298] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
[Fe(IV)═O(TBC)(CH(3)CN)](2+) (TBC = 1,4,8,11-tetrabenzyl-1,4,8,11-tetraazacyclotetradecane) is characterized, and its reactivity differences relative to [Fe(IV)═O(TMC)(CH(3)CN)](2+) (TMC = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane) are evaluated in hydrogen atom (H-atom) abstraction and oxo-transfer reactions. Structural differences are defined using X-ray absorption spectroscopy and correlated to reactivities using density functional theory. The S = 1 ground states are highly similar and result in large activation barriers (~25 kcal/mol) due to steric interactions between the cyclam chelate and the substrate (e.g., ethylbenzene) associated with the equatorial π-attack required by this spin state. Conversely, H-atom abstraction reactivity on an S = 2 surface allows for a σ-attack with an axial substrate approach. This results in decreased steric interactions with the cyclam and a lower barrier (~9 kcal/mol). For [Fe(IV)═O(TBC)(CH(3)CN)](2+), the S = 2 excited state in the reactant is lower in energy and therefore more accessible at the transition state due to a weaker ligand field associated with the steric interactions of the benzyl substituents with the trans-axial ligand. This study is further extended to the oxo-transfer reaction, which is a two-electron process requiring both σ- and π-electron transfer and thus a nonlinear transition state. In oxo-transfer, the S = 2 has a lower barrier due to sequential vs concerted (S = 1) two electron transfer which gives a high-spin ferric intermediate at the transition state. The [Fe(IV)═O(TBC)(CH(3)CN)](2+) complex is more distorted at the transition state, with the iron farther out of the equatorial plane due to the steric interaction of the benzyl groups with the trans-axial ligand. This allows for better orbital overlap with the substrate, a lower barrier, and an increased rate of oxo-transfer.
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Affiliation(s)
- Samuel A Wilson
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
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49
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Loh ND, Hampton CY, Martin AV, Starodub D, Sierra RG, Barty A, Aquila A, Schulz J, Lomb L, Steinbrener J, Shoeman RL, Kassemeyer S, Bostedt C, Bozek J, Epp SW, Erk B, Hartmann R, Rolles D, Rudenko A, Rudek B, Foucar L, Kimmel N, Weidenspointner G, Hauser G, Holl P, Pedersoli E, Liang M, Hunter MS, Hunter MM, Gumprecht L, Coppola N, Wunderer C, Graafsma H, Maia FRNC, Ekeberg T, Hantke M, Fleckenstein H, Hirsemann H, Nass K, White TA, Tobias HJ, Farquar GR, Benner WH, Hau-Riege SP, Reich C, Hartmann A, Soltau H, Marchesini S, Bajt S, Barthelmess M, Bucksbaum P, Hodgson KO, Strüder L, Ullrich J, Frank M, Schlichting I, Chapman HN, Bogan MJ. Fractal morphology, imaging and mass spectrometry of single aerosol particles in flight. Nature 2012; 486:513-7. [PMID: 22739316 DOI: 10.1038/nature11222] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2011] [Accepted: 05/09/2012] [Indexed: 11/09/2022]
Abstract
The morphology of micrometre-size particulate matter is of critical importance in fields ranging from toxicology to climate science, yet these properties are surprisingly difficult to measure in the particles' native environment. Electron microscopy requires collection of particles on a substrate; visible light scattering provides insufficient resolution; and X-ray synchrotron studies have been limited to ensembles of particles. Here we demonstrate an in situ method for imaging individual sub-micrometre particles to nanometre resolution in their native environment, using intense, coherent X-ray pulses from the Linac Coherent Light Source free-electron laser. We introduced individual aerosol particles into the pulsed X-ray beam, which is sufficiently intense that diffraction from individual particles can be measured for morphological analysis. At the same time, ion fragments ejected from the beam were analysed using mass spectrometry, to determine the composition of single aerosol particles. Our results show the extent of internal dilation symmetry of individual soot particles subject to non-equilibrium aggregation, and the surprisingly large variability in their fractal dimensions. More broadly, our methods can be extended to resolve both static and dynamic morphology of general ensembles of disordered particles. Such general morphology has implications in topics such as solvent accessibilities in proteins, vibrational energy transfer by the hydrodynamic interaction of amino acids, and large-scale production of nanoscale structures by flame synthesis.
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Affiliation(s)
- N D Loh
- PULSE Institute, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
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50
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O’Halloran KP, Zhao C, Ando NS, Schultz AJ, Koetzle TF, Piccoli PMB, Hedman B, Hodgson KO, Bobyr E, Kirk ML, Knottenbelt S, Depperman EC, Stein B, Anderson TM, Cao R, Geletii YV, Hardcastle KI, Musaev DG, Neiwert WA, Fang X, Morokuma K, Wu S, Kögerler P, Hill CL. Revisiting the Polyoxometalate-Based Late-Transition-Metal-Oxo Complexes: The “Oxo Wall” Stands. Inorg Chem 2012; 51:7025-31. [DOI: 10.1021/ic2008914] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Kevin P. O’Halloran
- Department of Chemistry, Emory
University, Atlanta, Georgia 30322, United States
| | - Chongchao Zhao
- Department of Chemistry, Emory
University, Atlanta, Georgia 30322, United States
| | - Nicole S. Ando
- Department of Chemistry, Emory
University, Atlanta, Georgia 30322, United States
| | - Arthur J. Schultz
- Intense Pulsed Neutron Source,
Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Thomas F. Koetzle
- Intense Pulsed Neutron Source,
Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Paula M. B. Piccoli
- Intense Pulsed Neutron Source,
Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Britt Hedman
- Department of Chemistry and Stanford
Synchrotron Radiation Lightsource, SLAC, Stanford University, Stanford,
California 94305, United Statess
| | - Keith O. Hodgson
- Department of Chemistry and Stanford
Synchrotron Radiation Lightsource, SLAC, Stanford University, Stanford,
California 94305, United Statess
| | - Elena Bobyr
- Department of Chemistry and Stanford
Synchrotron Radiation Lightsource, SLAC, Stanford University, Stanford,
California 94305, United Statess
| | - Martin L. Kirk
- Department of Chemistry and
Chemical Biology, The University of New Mexico, Albuquerque, New Mexico
87131-0001, United States
| | - Sushilla Knottenbelt
- Department of Chemistry and
Chemical Biology, The University of New Mexico, Albuquerque, New Mexico
87131-0001, United States
| | - Ezra C. Depperman
- Department of Chemistry and
Chemical Biology, The University of New Mexico, Albuquerque, New Mexico
87131-0001, United States
| | - Benjamin Stein
- Department of Chemistry and
Chemical Biology, The University of New Mexico, Albuquerque, New Mexico
87131-0001, United States
| | - Travis M. Anderson
- Department of Chemistry, Emory
University, Atlanta, Georgia 30322, United States
| | - Rui Cao
- Department of Chemistry, Emory
University, Atlanta, Georgia 30322, United States
| | - Yurii V. Geletii
- Department of Chemistry, Emory
University, Atlanta, Georgia 30322, United States
| | | | - Djamaladdin G. Musaev
- Cherry L. Emerson Center for
Scientific Computation, Emory University, Atlanta, Georgia 30322,
United States
| | - Wade A. Neiwert
- Department of Chemistry, Emory
University, Atlanta, Georgia 30322, United States
| | - Xikui Fang
- Department of Chemistry, Emory
University, Atlanta, Georgia 30322, United States
| | - Keiji Morokuma
- Department of Chemistry, Emory
University, Atlanta, Georgia 30322, United States
- Cherry L. Emerson Center for
Scientific Computation, Emory University, Atlanta, Georgia 30322,
United States
| | - Shaoxiong Wu
- Department of Chemistry, Emory
University, Atlanta, Georgia 30322, United States
| | - Paul Kögerler
- Ames Laboratory, Iowa State University,
Ames, Iowa 50011, United States
| | - Craig L. Hill
- Department of Chemistry, Emory
University, Atlanta, Georgia 30322, United States
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