1
|
Calvo R, Sartoris RP, Nascimento OR, Šedivý M, Sojka A, Neugebauer P, Santana VT. Quantum phase transitions probed by EPR spectra in dimeric spin arrays with supramolecular couplings. Coord Chem Rev 2023. [DOI: 10.1016/j.ccr.2022.215007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
|
2
|
Witwicki M, Lewińska A, Ozarowski A. o-Semiquinone radical anion isolated as an amorphous porous solid. Phys Chem Chem Phys 2021; 23:17408-17419. [PMID: 34351330 DOI: 10.1039/d1cp01596f] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The use of metal cations is a commonly applied strategy to create S > 1/2 stable molecular systems containing semiquinone radicals. Persistent mono-semiquinonato complexes of diamagnetic metal ions (S = 1/2) have been hitherto less common and mostly limited to the complexes of heavy metal ions. In this work, a mono-semiquinonato complex of aluminum, derived from 1,2-dihydroxybenzene, is obtained using a surprisingly short and uncomplicated procedure. The isolated product is an amorphous and porous solid that exhibits very good stability under ambient conditions. To characterise its molecular and electronic structure, 9.7, 34 and 406 GHz EPR spectroscopy was used in concert with computational techniques (DFT and DLPNO-CCSD). It was revealed that the radical complex is composed of two chemically equivalent aluminum cations and two catechol-like ligands with the unpaired electron uniformly distributed between the two organic molecules. The good stability and porous structure make this complex applicable in heterogeneous aerobic reactions.
Collapse
Affiliation(s)
- Maciej Witwicki
- Faculty of Chemistry, Wroclaw University, Joliot-Curie 14, 50-383 Wroclaw, Poland.
| | | | | |
Collapse
|
3
|
Sartoris RP, Santana VT, Freire E, Baggio RF, Nascimento OR, Calvo R. Exchange couplings and quantum phases in two dissimilar arrays of similar copper dinuclear units. Dalton Trans 2020; 49:5228-5240. [DOI: 10.1039/d0dt00567c] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
X-ray structure and EPR spectra of two dinuclear copper compounds allow us to study spin entanglement and quantum phase transitions. Their different 3D arrays and interdinuclear exchange paths produce important effects.
Collapse
Affiliation(s)
- Rosana P. Sartoris
- Departamento de Física
- Facultad de Bioquímica y Ciencias Biológicas
- Universidad Nacional del Litoral
- Santa Fe
- Argentina
| | - Vinicius T. Santana
- CEITEC - Central European Institute of Technology
- Brno University of Technology
- Brno
- Czech Republic
| | - Eleonora Freire
- Gerencia de Investigación y Aplicaciones
- Centro Atómico Constituyentes
- Comisión Nacional de Energía Atómica
- Buenos Aires
- Argentina
| | - Ricardo F. Baggio
- Gerencia de Investigación y Aplicaciones
- Centro Atómico Constituyentes
- Comisión Nacional de Energía Atómica
- Buenos Aires
- Argentina
| | - Otaciro R. Nascimento
- Departamento de Física e Ciencias Interdisciplinares
- Instituto de Física de São Carlos
- Universidade de São Paulo - USP
- São Carlos
- Brazil
| | - Rafael Calvo
- Departamento de Física
- Facultad de Bioquímica y Ciencias Biológicas
- Universidad Nacional del Litoral
- Santa Fe
- Argentina
| |
Collapse
|
4
|
Maróti P. Thermodynamic View of Proton Activated Electron Transfer in the Reaction Center of Photosynthetic Bacteria. J Phys Chem B 2019; 123:5463-5473. [PMID: 31181159 DOI: 10.1021/acs.jpcb.9b03506] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The temperature dependence of the sequential coupling of proton transfer to the second interquinone electron transfer is studied in the reaction center proteins of photosynthetic bacteria modified by different mutations and treatment by divalent cations. The Eyring plots of kinetics were evaluated by the Marcus theory of electron and proton transfer. In mutants of electron transfer limitation (including the wild type), the observed thermodynamic parameters had to be corrected for those of the fast proton pre-equilibrium. The electron transfer is nonadiabatic with transmission coefficient 6 × 10-4, and the reorganization energy amounts to 1.2 eV. If the proton transfer is the rate limiting step, the reorganization energy and the works terms fall in the range of 200-500 meV, depending on the site of damage in the proton transfer chain. The product term is 100-150 meV larger than the reactant term. While the electron transfer mutants have a low free energy of activation (∼200 meV), the proton transfer variants show significantly elevated levels of the free energy barrier (∼500 meV). The second electron transfer in the bacterial reaction center can serve as a model system of coupled electron and proton transfer in other proteins or ion channels.
Collapse
Affiliation(s)
- Péter Maróti
- Institute of Medical Physics , University of Szeged , Rerrich Béla tér 1 , Szeged , H-6720 , Hungary
| |
Collapse
|
5
|
Study of the Cys-His bridge electron transfer pathway in a copper-containing nitrite reductase by site-directed mutagenesis, spectroscopic, and computational methods. Biochim Biophys Acta Gen Subj 2017; 1862:752-760. [PMID: 29051066 DOI: 10.1016/j.bbagen.2017.10.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2017] [Revised: 09/06/2017] [Accepted: 10/12/2017] [Indexed: 11/22/2022]
Abstract
The Cys-His bridge as electron transfer conduit in the enzymatic catalysis of nitrite to nitric oxide by nitrite reductase from Sinorhizobium meliloti 2011 (SmNir) was evaluated by site-directed mutagenesis, steady state kinetic studies, UV-vis and EPR spectroscopic measurements as well as computational calculations. The kinetic, structural and spectroscopic properties of the His171Asp (H171D) and Cys172Asp (C172D) SmNir variants were compared with the wild type enzyme. Molecular properties of H171D and C172D indicate that these point mutations have not visible effects on the quaternary structure of SmNir. Both variants are catalytically incompetent using the physiological electron donor pseudoazurin, though C172D presents catalytic activity with the artificial electron donor methyl viologen (kcat=3.9(4) s-1) lower than that of wt SmNir (kcat=240(50) s-1). QM/MM calculations indicate that the lack of activity of H171D may be ascribed to the Nδ1H…OC hydrogen bond that partially shortcuts the T1-T2 bridging Cys-His covalent pathway. The role of the Nδ1H…OC hydrogen bond in the pH-dependent catalytic activity of wt SmNir is also analyzed by monitoring the T1 and T2 oxidation states at the end of the catalytic reaction of wt SmNir at pH6 and 10 by UV-vis and EPR spectroscopies. These data provide insight into how changes in Cys-His bridge interrupts the electron transfer between T1 and T2 and how the pH-dependent catalytic activity of the enzyme are related to pH-dependent structural modifications of the T1-T2 bridging chemical pathway.
Collapse
|
6
|
Exchange interaction between S= 1/2 centers bridged by multiple noncovalent interactions: Contribution of the individual chemical pathways to the magnetic coupling. Polyhedron 2017. [DOI: 10.1016/j.poly.2016.12.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
|
7
|
Rizzi AC, Neuman NI, González PJ, Brondino CD. EPR as a Tool for Study of Isolated and Coupled Paramagnetic Centers in Coordination Compounds and Macromolecules of Biological Interest. Eur J Inorg Chem 2015. [DOI: 10.1002/ejic.201501111] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
8
|
Maróti Á, Wraight CA, Maróti P. Protonated rhodosemiquinone at the Q(B) binding site of the M265IT mutant reaction center of photosynthetic bacterium Rhodobacter sphaeroides. Biochemistry 2015; 54:2095-103. [PMID: 25760888 DOI: 10.1021/bi501553t] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The second electron transfer from primary ubiquinone Q(A) to secondary ubiquinone Q(B) in the reaction center (RC) from Rhodobacter sphaeroides involves a protonated Q(B)(-) intermediate state whose low pK(a) makes direct observation impossible. Here, we replaced the native ubiquinone with low-potential rhodoquinone at the Q(B) binding site of the M265IT mutant RC. Because the in situ midpoint redox potential of Q(A) of this mutant was lowered approximately the same extent (≈100 mV) as that of Q(B) upon exchange of ubiquinone with low-potential rhodoquinone, the inter-quinone (Q(A) → Q(B)) electron transfer became energetically favorable. After subsequent saturating flash excitations, a period of two damped oscillations of the protonated rhodosemiquinone was observed. The Q(B)H(•) was identified by (1) the characteristic band at 420 nm of the absorption spectrum after the second flash and (2) weaker damping of the oscillation at 420 nm (due to the neutral form) than at 460 nm (attributed to the anionic form). The appearance of the neutral semiquinone was restricted to the acidic pH range, indicating a functional pK(a) of <5.5, slightly higher than that of the native ubisemiquinone (pK(a) < 4.5) at pH 7. The analysis of the pH and temperature dependencies of the rates of the second electron transfer supports the concept of the pH-dependent pK(a) of the semiquinone at the Q(B) binding site. The local electrostatic potential is severely modified by the strongly interacting neighboring acidic cluster, and the pK(a) of the semiquinone is in the middle of the pH range of the complex titration. The kinetic and thermodynamic data are discussed according to the proton-activated electron transfer mechanism combined with the pH-dependent functional pK(a) of the semiquinone at the Q(B) site of the RC.
Collapse
Affiliation(s)
| | - Colin A Wraight
- §Center for Biophysics and Computational Biology and Department of Plant Biology, University of Illinois, Urbana, Illinois 61801-3838, United States
| | | |
Collapse
|
9
|
Khadir N, Boghaei DM, Assoud A, Nascimento OR, Nicotina A, Ghivelder L, Calvo R. The structure, magnetism and EPR spectra of a (μ-thiophenolato)(μ-pyrazolato-N,N') double bridged dicopper(II) complex. Dalton Trans 2015; 44:2431-8. [PMID: 25553757 DOI: 10.1039/c4dt03322a] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A new binuclear copper(ii) complex, namely [Cu2L(pz)(DMSO)], where L = 2,6-bis[(2-phenoxy)iminomethyl]-4-methylthiophenolate(3-) and pz = pyrazolate ligand, has been synthesized by a one-pot synthesis involving copper(ii) acetate monohydrate, the S-protected ligand precursor 2-(N,N-dimethylthiocarbamato)-5-methylisophthalaldehyde di-2'-hydroxy anil, (), and pyrazole, in which a metal-promoted S-deprotection reaction occurs during the formation of the complex. This was characterized by routine physicochemical studies, single crystal X-ray diffraction and electron paramagnetic resonance (EPR) techniques. The structure analysis reveals that there are copper centres in two different environments, a slightly distorted square planar and a distorted square-pyramidal, arranged in binuclear units. The EPR study of these binuclear units performed at 9.4 GHz in the temperature range between 4 and 293 K shows an antiferromagnetic interaction between Cu(II) ions, and allows evaluating g factors gx = 2.068(1), gy = 2.091(1) and gz = 2.165(1), with <g> = 2.108(1), an exchange coupling parameter J0 = -26(1) cm(-1) (defined as ), and a zero field splitting of the ground triplet state described by D = 86(2) × 10(-4) cm(-1) and E = -48(3) × 10(-4) cm(-1). These results are discussed and compared with the existing literature.
Collapse
Affiliation(s)
- Narjes Khadir
- Department of Chemistry, Sharif University of Technology, P.O. Box 11155-3516, Tehran, Iran.
| | | | | | | | | | | | | |
Collapse
|
10
|
Mukhopadhyay TK, Flores M, Feller RK, Scott BL, Taylor RD, Paz-Pasternak M, Henson NJ, Rein FN, Smythe NC, Trovitch RJ, Gordon JC. A New Spin on Cyclooctatetraene (COT) Redox Activity: Low-Spin Iron(I) Complexes That Exhibit Antiferromagnetic Coupling to a Singly Reduced η4-COT Ligand. Organometallics 2014. [DOI: 10.1021/om500909h] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Tufan K. Mukhopadhyay
- Department of Chemistry & Biochemistry, Arizona State University, Tempe, Arizona 85287, United States
| | - Marco Flores
- Department of Chemistry & Biochemistry, Arizona State University, Tempe, Arizona 85287, United States
| | - Russell K. Feller
- Materials
Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Brian L. Scott
- Materials
Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - R. Dean Taylor
- Materials
Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Moshe Paz-Pasternak
- School
of Physics and Astronomy, Tel Aviv University, 69978 Tel Aviv, Israel
| | - Neil J. Henson
- Theoretical
Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Francisca N. Rein
- Chemistry
Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Nathan C. Smythe
- Chemistry
Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Ryan J. Trovitch
- Department of Chemistry & Biochemistry, Arizona State University, Tempe, Arizona 85287, United States
| | - John C. Gordon
- Chemistry
Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| |
Collapse
|
11
|
Gómez MC, Neuman NI, Dalosto SD, González PJ, Moura JJG, Rizzi AC, Brondino CD. Isotropic exchange interaction between Mo and the proximal FeS center in the xanthine oxidase family member aldehyde oxidoreductase from Desulfovibrio gigas on native and polyalcohol inhibited samples: an EPR and QM/MM study. J Biol Inorg Chem 2014; 20:233-42. [PMID: 25344343 DOI: 10.1007/s00775-014-1204-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Accepted: 10/07/2014] [Indexed: 11/25/2022]
Abstract
Aldehyde oxidoreductase from Desulfovibrio gigas (DgAOR) is a homodimeric molybdenum-containing protein that catalyzes the hydroxylation of aldehydes to carboxylic acids and contains a Mo-pyranopterin active site and two FeS centers called FeS 1 and FeS 2. The electron transfer reaction inside DgAOR is proposed to be performed through a chemical pathway linking Mo and the two FeS clusters involving the pyranopterin ligand. EPR studies performed on reduced as-prepared DgAOR showed that this pathway is able to transmit very weak exchange interactions between Mo(V) and reduced FeS 1. Similar EPR studies but performed on DgAOR samples inhibited with glycerol and ethylene glycol showed that the value of the exchange coupling constant J increases ~2 times upon alcohol inhibition. Structural studies in these DgAOR samples have demonstrated that the Mo-FeS 1 bridging pathway does not show significant differences, confirming that the changes in J observed upon inhibition cannot be ascribed to structural changes associated neither with pyranopterin and FeS 1 nor with changes in the electronic structure of FeS 1, as its EPR properties remain unchanged. Theoretical calculations indicate that the changes in J detected by EPR are related to changes in the electronic structure of Mo(V) determined by the replacement of the OHx labile ligand for an alcohol molecule. Since the relationship between electron transfer rate and isotropic exchange interaction, the present results suggest that the intraenzyme electron transfer process mediated by the pyranopterin moiety is governed by a Mo ligand-based regulatory mechanism.
Collapse
Affiliation(s)
- María C Gómez
- Departamento de Física, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Ciudad Universitaria, Paraje El Pozo, S3000ZAA, Santa Fe, Argentina
| | | | | | | | | | | | | |
Collapse
|
12
|
Okamura M. George Feher: a pioneer in reaction center research. PHOTOSYNTHESIS RESEARCH 2014; 120:29-42. [PMID: 24104959 DOI: 10.1007/s11120-013-9927-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Accepted: 09/16/2013] [Indexed: 06/02/2023]
Abstract
Our understanding of photosynthesis has been greatly advanced by the elucidation of the structure and function of the reaction center (RC), the membrane protein responsible for the initial light-induced charge separation in photosynthetic bacteria and green plants. Although today we know a great deal about the details of the primary processes in photosynthesis, little was known in the early days. George Feher made pioneering contributions to photosynthesis research in characterizing RCs from photosynthetic bacteria following the ground-breaking work of Lou Duysens and Rod Clayton (see articles in this issue by van Gorkom and Wraight). The work in his laboratory at the University of California, San Diego, started in the late 1960s and continued for over 30 years. He isolated a pure RC protein and used magnetic resonance spectroscopy to study the primary reactants. Following this pioneering work, Feher studied the detailed structure of the RC and the basic electron and proton transfer functions that it performs using a wide variety of biophysical and biochemical techniques. These studies, together with work from many other researchers, have led to our present detailed understanding of these proteins and their function in photosynthesis. The present article is a brief historical account of his pioneering contributions to photosynthesis research. A more detailed description of his work can be found in an earlier biographical paper (Feher in Photosynth Res 55:1-40, 1998a).
Collapse
Affiliation(s)
- Melvin Okamura
- Department of Physics, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093-0354, USA,
| |
Collapse
|
13
|
Neuman NI, Franco VG, Ferroni FM, Baggio R, Passeggi MCG, Rizzi AC, Brondino CD. Single Crystal EPR of the Mixed-Ligand Complex of Copper(II) with l-Glutamic Acid and 1,10-Phenanthroline: A Study on the Narrowing of the Hyperfine Structure by Exchange. J Phys Chem A 2012. [DOI: 10.1021/jp308745e] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- Nicolás I. Neuman
- Departamento de Física,
Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Ciudad Universitaria,
Paraje El Pozo, S3000ZAA Santa Fe, Argentina
| | - Vanina G. Franco
- Departamento de Física,
Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Ciudad Universitaria,
Paraje El Pozo, S3000ZAA Santa Fe, Argentina
| | - Felix M. Ferroni
- Departamento de Física,
Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Ciudad Universitaria,
Paraje El Pozo, S3000ZAA Santa Fe, Argentina
| | - Ricardo Baggio
- Gerencia de Investigación
y Aplicaciones, Comisión Nacional de Energía Atómica, Avenida Gral Paz y Constituyentes,
San Martín, Buenos Aires, Argentina
| | - Mario C. G. Passeggi
- Departamento de Física,
Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Ciudad Universitaria,
Paraje El Pozo, S3000ZAA Santa Fe, Argentina
| | - Alberto C. Rizzi
- Departamento de Física,
Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Ciudad Universitaria,
Paraje El Pozo, S3000ZAA Santa Fe, Argentina
| | - Carlos D. Brondino
- Departamento de Física,
Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Ciudad Universitaria,
Paraje El Pozo, S3000ZAA Santa Fe, Argentina
| |
Collapse
|
14
|
Single crystal electron paramagnetic resonance spectra of CuII ions in Cu(tyrosine)2. J Inorg Biochem 2012; 114:75-81. [DOI: 10.1016/j.jinorgbio.2012.04.013] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2011] [Revised: 04/10/2012] [Accepted: 04/11/2012] [Indexed: 11/17/2022]
|
15
|
Leonova MM, Fufina TY, Vasilieva LG, Shuvalov VA. Structure-function investigations of bacterial photosynthetic reaction centers. BIOCHEMISTRY (MOSCOW) 2012; 76:1465-83. [DOI: 10.1134/s0006297911130074] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
16
|
Venegas-Yazigi D, Brown KA, Vega A, Calvo R, Aliaga C, Santana RC, Cardoso-Gil R, Kniep R, Schnelle W, Spodine E. Exchange Interactions Through π–π Stacking in the Lamellar Compound [{Cu(bipy)(en)}{Cu(bipy)(H2O)}{VO3}4]n. Inorg Chem 2011; 50:11461-71. [DOI: 10.1021/ic201278a] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Diego Venegas-Yazigi
- Facultad de Química y
Biología, Universidad de Santiago de Chile, USACH, Santiago,
Chile
- Centro para el Desarrollo de
Nanociencias y Nanotecnología, CEDENNA, Santiago, Chile
| | - Kareen A. Brown
- Centro para el Desarrollo de
Nanociencias y Nanotecnología, CEDENNA, Santiago, Chile
- Facultad de Ciencias Químicas
y Farmacéuticas, Universidad de Chile, Santiago, Chile
| | - Andrés Vega
- Centro para el Desarrollo de
Nanociencias y Nanotecnología, CEDENNA, Santiago, Chile
- Departamento de Ciencias Químicas,
Universidad Andres Bello, Santiago, Chile
| | - Rafael Calvo
- Facultad de Bioquímica
y Ciencias Biológicas and INTEC, CONICET-Universidad Nacional
del Litoral, 3000 Santa Fe, Argentina
| | - Carolina Aliaga
- Facultad de Química y
Biología, Universidad de Santiago de Chile, USACH, Santiago,
Chile
- Centro para el Desarrollo de
Nanociencias y Nanotecnología, CEDENNA, Santiago, Chile
| | - Ricardo C. Santana
- Instituto de Física,
Universidade Federal de Goiás, CP 131, 74001-970 Goiânia,
Brazil
| | - Raul Cardoso-Gil
- Max-Planck-Institut für
Chemische Physik fester Stoffe, Dresden, Germany
| | - Rüdiger Kniep
- Max-Planck-Institut für
Chemische Physik fester Stoffe, Dresden, Germany
| | - Walter Schnelle
- Max-Planck-Institut für
Chemische Physik fester Stoffe, Dresden, Germany
| | - Evgenia Spodine
- Centro para el Desarrollo de
Nanociencias y Nanotecnología, CEDENNA, Santiago, Chile
- Facultad de Ciencias Químicas
y Farmacéuticas, Universidad de Chile, Santiago, Chile
| |
Collapse
|
17
|
Witwicki M, Jezierska J. Effects of Solvents, Ligand Aromaticity, and Coordination Sphere on the g Tensor of Anionic o-Semiquinone Radicals Complexed by Mg2+ Ions: DFT Studies. J Phys Chem B 2011; 115:3172-84. [DOI: 10.1021/jp110515j] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Maciej Witwicki
- Faculty of Chemistry, Wroclaw University, 14 F. Joliot-Curie St., Wroclaw 50-283, Poland
| | - Julia Jezierska
- Faculty of Chemistry, Wroclaw University, 14 F. Joliot-Curie St., Wroclaw 50-283, Poland
| |
Collapse
|
18
|
Jones MR. Structural Plasticity of Reaction Centers from Purple Bacteria. THE PURPLE PHOTOTROPHIC BACTERIA 2009. [DOI: 10.1007/978-1-4020-8815-5_16] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
|
19
|
Flores M, Isaacson R, Abresch E, Calvo R, Lubitz W, Feher G. Protein-cofactor interactions in bacterial reaction centers from Rhodobacter sphaeroides R-26: II. Geometry of the hydrogen bonds to the primary quinone formula by 1H and 2H ENDOR spectroscopy. Biophys J 2006; 92:671-82. [PMID: 17071655 PMCID: PMC1751397 DOI: 10.1529/biophysj.106.092460] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The geometry of the hydrogen bonds to the two carbonyl oxygens of the semiquinone Q(A)(. -) in the reaction center (RC) from the photosynthetic purple bacterium Rhodobacter sphaeroides R-26 were determined by fitting a spin Hamiltonian to the data derived from (1)H and (2)H ENDOR spectroscopies at 35 GHz and 80 K. The experiments were performed on RCs in which the native Fe(2+) (high spin) was replaced by diamagnetic Zn(2+) to prevent spectral line broadening of the Q(A)(. -) due to magnetic coupling with the iron. The principal components of the hyperfine coupling and nuclear quadrupolar coupling tensors of the hydrogen-bonded protons (deuterons) and their principal directions with respect to the quinone axes were obtained by spectral simulations of ENDOR spectra at different magnetic fields on frozen solutions of deuterated Q(A)(. -) in H(2)O buffer and protonated Q(A)(. -) in D(2)O buffer. Hydrogen-bond lengths were obtained from the nuclear quadrupolar couplings. The two hydrogen bonds were found to be nonequivalent, having different directions and different bond lengths. The H-bond lengths r(OH) are 1.73 +/- 0.03 Angstrom and 1.60 +/- 0.04 Angstrom, from the carbonyl oxygens O(1) and O(4) to the NH group of Ala M260 and the imidazole nitrogen N(delta) of His M219, respectively. The asymmetric hydrogen bonds of Q(A)(. -) affect the spin density distribution in the quinone radical and its electronic structure. It is proposed that the H-bonds play an important role in defining the physical properties of the primary quinone, which affect the electron transfer processes in the RC.
Collapse
Affiliation(s)
- M Flores
- Department of Physics, University of California at San Diego, La Jolla, California, USA
| | | | | | | | | | | |
Collapse
|
20
|
Sinnecker S, Flores M, Lubitz W. Protein–cofactor interactions in bacterial reaction centers from Rhodobacter sphaeroides R-26: Effect of hydrogen bonding on the electronic and geometric structure of the primary quinone. A density functional theory study. Phys Chem Chem Phys 2006; 8:5659-70. [PMID: 17149487 DOI: 10.1039/b612568a] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The effect of hydrogen bonding to the primary quinone (Q(A) and Q(*)(-)(A)) in bacterial reaction centers was studied using density functional theory (DFT) calculations. The charge neutral state Q(A) was investigated by optimizing the hydrogen atom positions of model systems extracted from 15 different X-ray structures. From this analysis, mean values of the H-bond lengths and directions were derived. It was found that the N(delta)-H of His M219 forms a shorter H-bond to Q(A) than the N-H of Ala M260. The H-bond of His M219 is linear and more twisted out of the quinone plane. The radical anion Q(*)(-)(A) in the protein environment was investigated by using a mixed quantum mechanics/molecular mechanics (QM/MM) approach. Two geometry optimizations with a different number of flexible atoms were performed. H-bond lengths were obtained and spectroscopic parameters calculated, i.e. the hyperfine and nuclear quadrupole couplings of magnetic nuclei coupled to the radical. Good agreement was found with the results provided by EPR/ENDOR spectroscopy. This implies that the calculated lengths and directions of the H-bonds to Q(*)(-)(A) are reliable values. From a comparison of the neutral and reduced state of Q(A) it was concluded that the H-bond distances are shortened by approximately 0.17 Angstroms (His M219) and approximately 0.13 Angstroms (Ala M260) upon single reduction of the quinone. It is shown that the point-dipole approximation can not be used for an estimation of H-bond lengths from measured hyperfine couplings in a system with out-of-plane H-bonding. In contrast, the evaluation of the nuclear quadrupole couplings of (2)H nuclei substituted in the hydrogen bonds yields H-bond lengths close to the values that were deduced from DFT geometry optimizations. The significance of hydrogen bonding to the quinone cofactors in biological systems is discussed.
Collapse
Affiliation(s)
- Sebastian Sinnecker
- Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34-36, D-45470, Mülheim an der Ruhr, Germany
| | | | | |
Collapse
|
21
|
Santana RC, Cunha RO, Carvalho JF, Vencato I, Calvo R. Single crystal EPR study of electronic structure and exchange interactions for copper(II)(L-arginine)2(SO4).(H2O)6: a model system to study exchange interactions between unpaired spins in proteins. J Inorg Biochem 2005; 99:415-23. [PMID: 15621273 DOI: 10.1016/j.jinorgbio.2004.10.014] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2004] [Revised: 10/04/2004] [Accepted: 10/13/2004] [Indexed: 11/15/2022]
Abstract
We report EPR measurements at 9.77 and 34.1 GHz in powder and single crystal samples of the ternary copper amino acid complex Cu(L-arginine)(2)(SO(4)).(H(2)O)(6). The single crystal Electron Paramagnetic Resonance spectra display a single resonance for all magnetic field orientations in the ca and cb crystal planes. In the ab plane they display two resonances for most orientations of the magnetic field, and only one resonance for orientations close to the crystal axes. This behavior is a result of the selective collapse of the resonances corresponding to the four copper sites in the unit cell produced by the exchange interactions between copper ions. From the characteristics of the collapse and the angular dependences of the position and width of the resonances we evaluate the g-tensors of the copper molecules and estimate exchange interactions |J(1)/k(B)|=0.9 K and |J(2)/k(B)|=0.009 K between copper neighbors at 5.908 A and at 15.684 A, respectively. J(1) is assigned to a syn-anti equatorial-apical carboxylate bridge with a total bond length of 7.133 A. J(2) is assigned to a long bridge of 12 atoms with a total bond length of 19.789 A, that includes two hydrogen bonds. The results are discussed in terms of the crystal and electronic structure of Cu(L-arginine)(2)(SO(4)).(H(2)O)(6). We show that J(2) is in excellent agreement with the observed magnetic interaction between the reduced quinone acceptors in the photosynthetic reaction center protein of the bacterium Rb. sphaeroides, which is transmitted along a similar chemical path containing two hydrogen bonds. Our findings indicate that it is valid to estimate values for the exchange interactions between redox centers in proteins transmitted along long chemical paths containing sigma and H-bonds, from data obtained in model systems, and emphasize the importance of measuring exchange interactions in biologically relevant model systems.
Collapse
Affiliation(s)
- R C Santana
- Universidade Federal de Goiás, Instituto de Física, CP 131, Goiânia, Goiás 74001-970, Brazil.
| | | | | | | | | |
Collapse
|
22
|
Costa-Filho AJ, Nascimento OR, Calvo R. Electron Paramagnetic Resonance Study of Weak Exchange Interactions between Metal Ions in a Model System: CuIIGly-Trp. J Phys Chem B 2004. [DOI: 10.1021/jp037271r] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Antonio J. Costa-Filho
- Departamento de Física e Informática, Instituto de Física de São Carlos, Universidade de São Paulo, C.P. 369, CEP 13560-970, São Carlos, SP, Brazil, and Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral and INTEC (CONICET-UNL), Güemes 3450, 3000 Santa Fe, Argentina
| | - Otaciro R. Nascimento
- Departamento de Física e Informática, Instituto de Física de São Carlos, Universidade de São Paulo, C.P. 369, CEP 13560-970, São Carlos, SP, Brazil, and Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral and INTEC (CONICET-UNL), Güemes 3450, 3000 Santa Fe, Argentina
| | - Rafael Calvo
- Departamento de Física e Informática, Instituto de Física de São Carlos, Universidade de São Paulo, C.P. 369, CEP 13560-970, São Carlos, SP, Brazil, and Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral and INTEC (CONICET-UNL), Güemes 3450, 3000 Santa Fe, Argentina
| |
Collapse
|
23
|
Photo- and chemically-produced phylloquinone biradicals: EPR and ENDOR study. J Photochem Photobiol A Chem 2004. [DOI: 10.1016/j.nainr.2003.08.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
|
24
|
|
25
|
Zeng R, Budil DE. A re-examination of spin–orbit coupling in the triplet state of the primary donor in photosynthetic reaction centers. Chem Phys 2003. [DOI: 10.1016/s0301-0104(03)00286-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
26
|
Andersson KK, Schmidt PP, Katterle B, Strand KR, Palmer AE, Lee SK, Solomon EI, Gräslund A, Barra AL. Examples of high-frequency EPR studies in bioinorganic chemistry. J Biol Inorg Chem 2003; 8:235-47. [PMID: 12589559 DOI: 10.1007/s00775-002-0429-0] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2002] [Accepted: 11/04/2002] [Indexed: 10/18/2022]
Abstract
Low-temperature EPR spectroscopy with frequencies between 95 and 345 GHz and magnetic fields up to 12 T has been used to study metal sites in proteins or inorganic complexes and free radicals. The high-field EPR method was used to resolve g-value anisotropy by separating it from overlapping hyperfine couplings. The presence of hydrogen bonding interactions to the tyrosyl radical oxygens in ribonucleotide reductases were detected. At 285 GHz the g-value anisotropy from the rhombic type 2 Cu(II) signal in the enzyme laccase has its g-value anisotropy clearly resolved from slightly different overlapping axial species. Simple metal site systems with S>1/2 undergo a zero-field splitting, which can be described by the spin Hamiltonian. From high-frequency EPR, the D values that are small compared to the frequency (high-field limit) can be determined directly by measuring the distance of the outermost signal to the center of the spectrum, which corresponds to (2 S-1)* mid R: Dmid R: For example, D values of 0.8 and 0.3 cm(-1) are observed for S=5/2 Fe(III)-EDTA and transferrin, respectively. When D values are larger compared to the frequency and in the case of half-integer spin systems, they can be obtained from the frequency dependence of the shifts of g(eff), as observed for myoglobin in the presence ( D=5 cm(-1)) or absence ( D=9.5 cm(-1)) of fluoride. The 285 and 345 GHz spectra of the Fe(II)-NO-EDTA complex show that it is best described as a S=3/2 system with D=11.5 cm(-1), E=0.1 cm(-1), and g(x)= g(y)= g(z)=2.0. Finally, the effects of HF-EPR on X-band EPR silent states and weak magnetic interactions are demonstrated.
Collapse
Affiliation(s)
- K Kristoffer Andersson
- Department of Biochemistry, University of Oslo, Blindern, PO Box 1041, 0316, Oslo, Norway.
| | | | | | | | | | | | | | | | | |
Collapse
|
27
|
Calvo R, Isaacson RA, Abresch EC, Okamura MY, Feher G. Spin-lattice relaxation of coupled metal-radical spin-dimers in proteins: application to Fe(2+)-cofactor (Q(A)(-.), Q(B)(-.), phi(-.)) dimers in reaction centers from photosynthetic bacteria. Biophys J 2002; 83:2440-56. [PMID: 12414679 PMCID: PMC1302331 DOI: 10.1016/s0006-3495(02)75256-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The spin-lattice relaxation times (T(1)) for the reduced quinone acceptors Q(A)(-.) and Q(B)(-.), and the intermediate pheophytin acceptor phi(-.), were measured in native photosynthetic reaction centers (RC) containing a high spin Fe(2+) (S = 2) and in RCs in which Fe(2+) was replaced by diamagnetic Zn(2+). From these data, the contribution of the Fe(2+) to the spin-lattice relaxation of the cofactors was determined. To relate the spin-lattice relaxation rate to the spin-spin interaction between the Fe(2+) and the cofactors, we developed a spin-dimer model that takes into account the zero field splitting and the rhombicity of the Fe(2+) ion. The relaxation mechanism of the spin-dimer involves a two-phonon process that couples the fast relaxing Fe(2+) spin to the cofactor spin. The process is analogous to the one proposed by R. Orbach (Proc. R. Soc. A. (Lond.). 264:458-484) for rare earth ions. The spin-spin interactions are, in general, composed of exchange and dipolar contributions. For the spin dimers studied in this work the exchange interaction, J(o), is predominant. The values of J(o) for Q(A)(-.)Fe(2+), Q(B)(-.)Fe(2+), and phi(-.)Fe(2+) were determined to be (in kelvin) -0.58, -0.92, and -1.3 x 10(-3), respectively. The |J(o)| of the various cofactors (obtained in this work and those of others) could be fitted with the relation exp(-beta(J)d), where d is the distance between cofactor spins and beta(J) had a value of (0.66-0.86) A(-1). The relation between J(o) and the matrix element |V(ij)|(2) involved in electron transfer rates is discussed.
Collapse
Affiliation(s)
- Rafael Calvo
- Departamento de Física, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral and INTEC, 3000 Santa Fe, Argentina
| | | | | | | | | |
Collapse
|
28
|
Feher G. My road to biophysics: picking flowers on the way to photosynthesis. ANNUAL REVIEW OF BIOPHYSICS AND BIOMOLECULAR STRUCTURE 2002; 31:1-44. [PMID: 11988461 DOI: 10.1146/annurev.biophys.31.082901.134147] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- George Feher
- Department of Physics, University of California-San Diego, La Jolla, CA 92037, USA.
| |
Collapse
|
29
|
Current awareness in phytochemical analysis. PHYTOCHEMICAL ANALYSIS : PCA 2001; 12:347-354. [PMID: 11708298 DOI: 10.1002/pca.557] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
|