1
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Muralisankar M, Chen JR, Haribabu J, Ke SC. Effective and Selective Ru(II)-Arene Complexes Containing 4,4'-Substituted 2,2' Bipyridine Ligands Targeting Human Urinary Bladder Cancer Cells. Int J Mol Sci 2023; 24:11896. [PMID: 37569273 PMCID: PMC10418970 DOI: 10.3390/ijms241511896] [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: 06/29/2023] [Revised: 07/21/2023] [Accepted: 07/22/2023] [Indexed: 08/13/2023] Open
Abstract
Cisplatin-based chemotherapy is a common regimen for bladder cancer, a life-threatening cancer with more than 500,000 new cases worldwide annually. Like many other metallodrugs, cisplatin causes severe side effects for its general toxicity. Organoruthenium is known for its structural stability, good anticancer activity, and possible low general toxicity. Here, we have prepared and characterized a series of water-soluble ruthenium-arene complexes with N,N'-chelating ligands: [Ru(II)-η6-arene-(4,4'-(X)2-2,2'-bipyridine)Cl]Cl (arene = p-cymene, X = C4H9 (1), COOH (2), COOCH3 (3), COOC2H5 (4); arene = benzene, X = C4H9 (5), COOCH3 (6), COOC2H5 (7)). These complexes are carefully characterized using single-crystal X-ray diffraction, UV-vis, IR, 1H NMR, and MALDI-TOF MS spectroscopy. Their DFT-calculated structural and thermodynamic properties are consistent with the experimental observations. Biophysicochemical studies of complex interaction with CTDNA and BSA supported by molecular docking simulations reveal suitable properties of 1-7 as anticancer agents. Cytotoxicities of 1-7 are evaluated on healthy human MCF-10a-breast epithelial and African green monkey Vero cells, and carcinoma human HepG-2-hepatic, T24-bladder, and EAhy-926-endothelial cells. All complexes exhibit much higher cytotoxicity for T24 than cisplatin. Particularly, 1 and 2 are also highly selective toward T24. Fluorescence imaging and flow cytometry demonstrate that 1 and 2 penetrate T24 cell membrane and induce early apoptosis at their respective IC50 concentrations, which ultimately lead to cell death. Statistical analysis suggests that the order of importance for T24 cell antiproliferation is protein binding, Log p, Ru-Cl bond length, while DNA binding is the least important. This study is the first to report the anti-bladder cancer efficacy of Ru-arene-2,2'-bipyridine complexes, and may provide insights for rational design of organoruthenium drugs in the enduring search for new chemotherapeutic agents.
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Affiliation(s)
- Mathiyan Muralisankar
- Physics Department, National Dong Hwa University, Hualien 97401, Taiwan; (M.M.); (J.-R.C.)
| | - Jun-Ru Chen
- Physics Department, National Dong Hwa University, Hualien 97401, Taiwan; (M.M.); (J.-R.C.)
| | - Jebiti Haribabu
- Facultad de Medicina, Universidad de Atacama, Copayapu 485, Copiapo 1531772, Chile;
| | - Shyue-Chu Ke
- Physics Department, National Dong Hwa University, Hualien 97401, Taiwan; (M.M.); (J.-R.C.)
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2
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Koli VB, Murugan G, Ke SC. Self-Assembled Synthesis of Porous Iron-Doped Graphitic Carbon Nitride Nanostructures for Efficient Photocatalytic Hydrogen Evolution and Nitrogen Fixation. Nanomaterials (Basel) 2023; 13:275. [PMID: 36678029 PMCID: PMC9862282 DOI: 10.3390/nano13020275] [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] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 01/02/2023] [Accepted: 01/06/2023] [Indexed: 06/17/2023]
Abstract
In this study, Fe-doped graphitic carbon nitride (Fe-MCNC) with varying Fe contents was synthesized via a supramolecular approach, followed by thermal exfoliation, and was then used for accelerated photocatalytic hydrogen evolution and nitrogen fixation. Various techniques were used to study the physicochemical properties of the MCN (g-C3N4 from melamine) and Fe-MCNC (MCN for g-C3N4 and C for cyanuric acid) catalysts. The field emission scanning electron microscopy (FE-SEM) images clearly demonstrate that the morphology of Fe-MCNC changes from planar sheets to porous, partially twisted (partially developed nanotube and nanorod) nanostructures. The elemental mapping study confirms the uniform distribution of Fe on the MCNC surface. The X-ray photoelectron spectroscopy (XPS) and UV-visible diffuse reflectance spectroscopy (UV-DRS) results suggest that the Fe species might exist in the Fe3+ state and form Fe-N bonds with N atoms, thereby extending the visible light absorption areas and decreasing the band gap of MCN. Furthermore, doping with precise amounts of Fe might induce exfoliation and increase the specific surface area, but excessive Fe could destroy the MCN structure. The optimized Fe-MCNC nanostructure had a specific surface area of 23.6 m2 g-1, which was 8.1 times greater than that of MCN (2.89 m2 g-1). To study its photocatalytic properties, the nanostructure was tested for photocatalytic hydrogen evolution and nitrogen fixation; 2Fe-MCNC shows the highest photocatalytic activity, which is approximately 13.3 times and 2.4 times better, respectively, than MCN-1H. Due to its high efficiency and stability, the Fe-MCNC nanostructure is a promising and ideal photocatalyst for a wide range of applications.
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3
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Maity AN, Chen JR, Ke SC. Exploring the mechanism of action of lysine 5,6-aminomutase using EPR and ENDOR spectroscopies. Methods Enzymol 2022; 669:197-228. [PMID: 35644172 DOI: 10.1016/bs.mie.2021.12.021] [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] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Radical enzymes orchestrate challenging chemical transformations by devising strategies to tame the highly reactive radical intermediates. Electron paramagnetic resonance (EPR) spectroscopy is the most suitable technique to study various aspects of the radical enzymes. Lysine 5,6-aminomutase (5,6-LAM) is one such radical enzyme and employs coenzyme B12 and pyridoxal 5'-phosphate (PLP) to catalyze the 1,2-amino shift reaction through a radical mechanism. 5,6-LAM accepts either d-lysine or l-β-lysine as the substrate. EPR and electron nuclear double resonance (ENDOR) spectroscopies have played major roles in deciphering the mechanism of action of 5,6-LAM, while density functional theoretical (DFT) computation and synthetic isotopologues have played supporting roles. This comprehensive toolkit has revealed that 5,6-LAM undergoes large-scale conformational movement to bring PLP and coenzyme B12 close together, which allows the reaction to progress. The conformational change also closes the active site, which protects the radical intermediates and enables their transformation to product without unwanted side reactions. The substrate-related radical (S•), which is spin-coupled with Co2+ generated from homolysis of the CoC bond in coenzyme B12, was unequivocally characterized when a substrate analog, 4-thia-l-lysine, and isotopologues of it were reacted with 5,6-LAM. Studies with substrate analogs revealed a unique "odd-even" correlation with opening of the closed state. Moreover, mutagenesis studies identified the contributions that conserved residues in 5,6-LAM make toward binding of the substrate. Further studies with a cofactor analog, PLP-N-oxide, have shed light on various aspects of the mechanism of action of 5,6-LAM.
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Affiliation(s)
| | - Jun-Ru Chen
- Department of Physics, National Dong Hwa University, Hualien, Taiwan
| | - Shyue-Chu Ke
- Department of Physics, National Dong Hwa University, Hualien, Taiwan.
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4
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Maity AN, Chen JR, Li QY, Ke SC. The Nitrogen Atom of Vitamin B 6 Is Essential for the Catalysis of Radical Aminomutases. Int J Mol Sci 2022; 23:ijms23095210. [PMID: 35563602 PMCID: PMC9105233 DOI: 10.3390/ijms23095210] [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] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Revised: 05/03/2022] [Accepted: 05/04/2022] [Indexed: 11/16/2022] Open
Abstract
Radical aminomutases are pyridoxal 5'-phosphate (PLP, a B6 vitamer)-dependent enzymes that require the generation of a 5'-deoxyadenosyl radical to initiate the catalytic cycle, to perform a 1,2 amino group shift reaction. The role of the nitrogen atom of PLP in radical aminomutases has not been investigated extensively yet. We report an alternative synthetic procedure to provide easy access to 1-deazaPLP (dAPLP), an isosteric analog of PLP which acts as a probe for studying the role of the nitrogen atom. Our results revealed that lysine 5,6-aminomutase (5,6-LAM), a radical aminomutase, reconstituted with dAPLP cannot turn over a substrate, demonstrating that the nitrogen atom is essential for radical aminomutases. In contrast, biochemical and spectroscopic studies on the S238A variant reconstituted with PLP revealed a minuscule loss of activity. This apparent anomaly can be explained by a water-mediated rescue of activity in S238A, as if mimicking the active site of lysine 2,3-aminomutase. This study leads to a better comprehension of how enzymes harness the optimum capability of PLP to realize catalysis.
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5
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Chen JR, Ke TX, Frey PA, Ke SC. Electron Spin Echo Envelope Modulation Spectroscopy Reveals How Adenosylcobalamin-Dependent Lysine 5,6-Aminomutase Positions the Radical Pair Intermediates and Modulates Their Stabilities for Efficient Catalysis. ACS Catal 2021. [DOI: 10.1021/acscatal.1c03182] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jun-Ru Chen
- Physics Department, National Dong Hwa University, Hualien 974301, Taiwan
| | - Ting-Xi Ke
- Physics Department, National Dong Hwa University, Hualien 974301, Taiwan
| | - Perry A. Frey
- Department of Biochemistry, University of Wisconsin−Madison, Madison, Wisconsin 53726, United States
| | - Shyue-Chu Ke
- Physics Department, National Dong Hwa University, Hualien 974301, Taiwan
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Sahoo SR, Ke SC. Spin-Orbit Coupling Effects in Au 4f Core-Level Electronic Structures in Supported Low-Dimensional Gold Nanoparticles. Nanomaterials (Basel) 2021; 11:554. [PMID: 33672227 PMCID: PMC7926876 DOI: 10.3390/nano11020554] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Revised: 02/18/2021] [Accepted: 02/20/2021] [Indexed: 11/16/2022]
Abstract
Despite their many advantages, issues remain unresolved over the variability in catalytic activities in supported gold nanoparticle (AuNP)-based catalysts, which requires precise characterization to unravel the presence of any fine features. Herein, upon analyzing the Au 4f core-level spin-orbit components in many as-synthesized AuNP-based catalysts, we observed that like deviations in the Au 4f7/2 binding energy positions, both the Au 4f7/2-to-Au 4f5/2 peak intensity and linewidth ratios varied largely from the standard statistical bulk reference values. These deviations were observed in all the as-synthesized supported AuNPs irrespective of different synthesis conditions, variations in size, shape or morphology of the gold nanoparticles, and different support materials. On the other hand, the spin-orbit-splitting values remained almost unchanged and did not show any appreciable deviations from the atomic or bulk standard gold values. These deviations could originate due to alterations in the electronic band structures in the supported AuNPs and might be present in other NP-based catalyst systems as well, which could be the subject of future research interest.
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Affiliation(s)
| | - Shyue-Chu Ke
- Department of Physics, National Dong Hwa University, Hualien 974301, Taiwan;
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7
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Gandhi AC, Lai CY, Wu KT, Ramacharyulu PVRK, Koli VB, Cheng CL, Ke SC, Wu SY. Phase transformation and room temperature stabilization of various Bi 2O 3 nano-polymorphs: effect of oxygen-vacancy defects and reduced surface energy due to adsorbed carbon species. Nanoscale 2020; 12:24119-24137. [PMID: 33242052 DOI: 10.1039/d0nr06552h] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
We report the grain growth from the nanoscale to microscale and a transformation sequence from Bi →β-Bi2O3→γ-Bi2O3→α-Bi2O3 with the increase of annealing temperature. The room temperature (RT) stabilization of β-Bi2O3 nanoparticles (NPs) was attributed to the effect of reduced surface energy due to adsorbed carbon species, and oxygen vacancy defects may have played a significant role in the RT stabilization of γ-Bi2O3 NPs. An enhanced red emission band was evident from all the samples attributed to oxygen-vacancy defects formed during the growth process in contrast with the observed white emission band from the air annealed Bi ingots. Based on our experimental findings, the air annealing induced oxidation of Bi NPs and transformation mechanism within various Bi2O3 nano-polymorphs are presented. The outcome of this study suggests that oxygen vacancy defects at the nanoscale play a significant role in both structural stabilization and phase transformation within various Bi2O3 nano-polymorphs, which is significant from theoretical consideration.
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8
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Peng KC, Chang KC, Ke SC, Chen J, Liu SY. Novel protein photocleavers: Chrysophanol and pachybasin. Journal of Photochemistry and Photobiology 2020. [DOI: 10.1016/j.jpap.2020.100008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
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9
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Nimbalkar DB, Stas M, Hou SS, Ke SC, Wu JJ. Microscopic Revelation of Charge-Trapping Sites in Polymeric Carbon Nitrides for Enhanced Photocatalytic Activity by Correlating with Chemical and Electronic Structures. ACS Appl Mater Interfaces 2019; 11:19087-19095. [PMID: 31062573 DOI: 10.1021/acsami.9b02494] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The influences of chemical and electronic structures on the photophysical properties of polymeric carbon nitrides (PCNs) photocatalysts, which govern the microscopic mechanisms of the superior photocatalytic activity under visible-light irradiation, have been resolved in this work. Time-resolved photoluminescence and in situ electron paramagnetic resonance measurements indicate that the photoexcited electrons in the fractured PCNs swiftly transfer to the C2p-localized states where the trapped photoelectrons exhibit longer lifetime compared to those in the ordinary PCNs. Moreover, the structure deviation at the carbon (Cb) atoms around the bridging sites of heptazine ring units, where trapped photoelectrons are localized, has been determined in the fractured PCNs based on the 13C solid-state nuclear magnetic resonance spectra and the density functional theory calculations. Accordingly, the formation of fractured PCNs by breaking the in-plane hydrogen bonds at a high temperature is a promising strategy for the enhancement of photocatalytic activity.
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Affiliation(s)
- Dipak B Nimbalkar
- Department of Chemical Engineering , National Cheng Kung University , Tainan 70101 , Taiwan
- Department of Physics , National Dong Hwa University , Hualien 97401 , Taiwan
| | - Monika Stas
- Department of Physical Chemistry and Molecular Modeling , Opole University , Opole 45052 , Poland
| | - Sheng-Shu Hou
- Department of Chemical Engineering , National Cheng Kung University , Tainan 70101 , Taiwan
| | - Shyue-Chu Ke
- Department of Physics , National Dong Hwa University , Hualien 97401 , Taiwan
| | - Jih-Jen Wu
- Department of Chemical Engineering , National Cheng Kung University , Tainan 70101 , Taiwan
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10
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Chen FD, Chen HH, Ke SC, Zheng LR, Zheng XY. SLC27A2 regulates miR-411 to affect chemo-resistance in ovarian cancer. Neoplasma 2018; 65:915-924. [PMID: 30334452 DOI: 10.4149/neo_2018_180122n48] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2018] [Accepted: 05/02/2018] [Indexed: 11/08/2022]
Abstract
Although platinum-based chemotherapies have long been used as standard treatment in ovarian cancer, cisplatin resistance is a major problem that restricts its use. Herein, we investigate the biological function of SLC27A2 and its underlying mechanisms in regulating chemo-resistance in ovarian cancer. The findings show that SLC27A2 down-regulation in primary ovarian cancer tissues correlates with chemo-resistance and poor patient survival in our patient cohort. Significantly, we demonstrate that up-regulation of SLC27A2 by lentivirus-mediated p-SLC27A2 sensitizes ovarian cancer cells to cisplatin in vitro and in vivo via apoptosis. Mechanistic investigation reveals that miR-411 is the most strikingly over-expressed gene in response to ectopic expression of SLC27A2, but under-expressed in recurrent ovarian cancer tissues. Lower miR-411 expression contributes to ovarian cancer chemo-resistance in vitro and in vivo. Furthermore, SLC27A2 directly binds specific sites in the miR-411 promoter region and promoter activity decreases after mutation of putative SLC27A2-binding sites. This indicates that SLC27A2 is required for the transcriptional induction of miR-411. The luciferase assays also confirm that miR-411 directly targets ABCG2 in ovarian cancer, and overall findings establish the SLC27A2-miR-411-ABCG2 pathway in the regulation of ovarian cancer chemo-resistance with potential therapeutic applications.
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Affiliation(s)
- F D Chen
- Department of Obstetrics and Gynecology, the Third Affiliated Hospital of Wenzhou Medical University, Wenzhou, China
| | - H H Chen
- Department of Obstetrics and Gynecology, the Third Affiliated Hospital of Wenzhou Medical University, Wenzhou, China
| | - S C Ke
- Department of Obstetrics and Gynecology, the Third Affiliated Hospital of Wenzhou Medical University, Wenzhou, China
| | - L R Zheng
- Department of Obstetrics and Gynecology, the Third Affiliated Hospital of Wenzhou Medical University, Wenzhou, China
| | - X Y Zheng
- Department of Obstetrics and Gynecology, the Third Affiliated Hospital of Wenzhou Medical University, Wenzhou, China
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11
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Sahoo SR, Ramacharyulu PVRK, Ke SC. Correction to Impact of Nonideal Nanoparticles on X-ray Photoelectron Spectroscopic Quantitation: An Investigation Using Simulation and Modeling of Gold Nanoparticles. Anal Chem 2018. [DOI: 10.1021/acs.analchem.8b00832] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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12
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Sahoo SR, Ramacharyulu PVRK, Ke SC. Impact of Nonideal Nanoparticles on X-ray Photoelectron Spectroscopic Quantitation: An Investigation Using Simulation and Modeling of Gold Nanoparticles. Anal Chem 2018; 90:1621-1627. [PMID: 29332393 DOI: 10.1021/acs.analchem.7b02837] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Quantitative X-ray photoelectron spectroscopic (XPS) analysis combined with spectral modeling of photoelectrons can be valuable while investigating the surface chemistry of nanoparticles (NPs) with different morphologies. Herein, with the use of NIST Simulation of Electron Spectra for Surface Analysis (SESSA), a comparative analysis of experimental and simulated photoelectron peak intensities in gold nanoparticles (AuNPs) of different morphologies is presented. Three sets of supported AuNPs with different morphologies were selected from a series of as synthesized Au-TiO2 catalyst samples. Using transmission electron microscopy (TEM) analyzed morphological information on the AuNPs as input model parameters in SESSA, XPS spectra were generated from the respective input NP morphologies. A degree of greater mismatch between SESSA simulated and experimental XPS spectra was observed while using the TEM obtained average diameter of the nanoparticles. The degree of mismatch lowered when the true nonspherical shape of the nanoparticles as obtained from TEM images was taken into account for the simulation. This demonstrates the impact of surface morphology on the XPS peak intensities which needs to be incorporated to obtain precise quantified information from the supported nanoparticles. This work demonstrates the applicability of SESSA in combination with experimental XPS and TEM measurements for precise quantification of XPS spectra from complex, nonideal shaped nanoparticles. This study can be extended to include a broad range of nanoparticles with ideal or nonideal geometries, thus providing a simple method to utilize quantitative XPS analysis to a wide range of nanomaterials.
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Affiliation(s)
- Smruti R Sahoo
- Department of Physics, National Dong Hwa University , Hualien 97401, Taiwan
| | | | - Shyue-Chu Ke
- Department of Physics, National Dong Hwa University , Hualien 97401, Taiwan
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13
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Chen JR, Ke SC. Magnetic field effects on coenzyme B12- and B6-dependent lysine 5,6-aminomutase: switching of the J-resonance through a kinetically competent radical-pair intermediate. Phys Chem Chem Phys 2018; 20:13068-13074. [DOI: 10.1039/c8cp01497c] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
External magnetic fields interact with lysine 5,6-aminomutase, through an immobilized radical-pair with constant and large exchange interaction, to switch on J-resonance between singlet and triplet spin states, which have different reactive fates.
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Affiliation(s)
- Jun-Ru Chen
- Department of Physics
- National Dong Hwa University
- Hualien
- Taiwan
| | - Shyue-Chu Ke
- Department of Physics
- National Dong Hwa University
- Hualien
- Taiwan
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14
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Ramacharyulu PVRK, Abbas SJ, Sahoo SR, Ke SC. Mechanistic insights into 4-nitrophenol degradation and benzyl alcohol oxidation pathways over MgO/g-C3N4 model catalyst systems. Catal Sci Technol 2018. [DOI: 10.1039/c8cy00431e] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Visible light active MgO/g-C3N4 composites for 4-nitrophenol degradation and selective oxidation of benzyl alcohol.
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Affiliation(s)
| | - Sk Jahir Abbas
- Department of Physics
- National Dong Hwa University
- Hualien
- 97401 Taiwan
| | - Smruti R. Sahoo
- Department of Physics
- National Dong Hwa University
- Hualien
- 97401 Taiwan
| | - Shyue-Chu Ke
- Department of Physics
- National Dong Hwa University
- Hualien
- 97401 Taiwan
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15
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Ramacharyulu PVRK, Abbas SJ, Ke SC. Enhanced charge separation and photoactivity in heterostructured g-C3N4: a synergistic interaction in environmental friendly CaO/g-C3N4. Catal Sci Technol 2017. [DOI: 10.1039/c7cy01623a] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
CaO/g-C3N4, an eco-friendly heterostructure to unreveal the mechanism for enhanced charge separation and photocatalysis. The picture illustrates electron density on CaO/g-C3N4.
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Affiliation(s)
| | - Sk Jahir Abbas
- Physics Department
- National Dong Hwa University
- Hualien
- 97401 Taiwan
| | - Shyue-Chu Ke
- Physics Department
- National Dong Hwa University
- Hualien
- 97401 Taiwan
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16
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Huang JY, Chiu YF, Ortega JM, Wang HT, Tseng TS, Ke SC, Roncel M, Chu HA. Mutations of Cytochrome b559 and PsbJ on and near the QC Site in Photosystem II Influence the Regulation of Short-Term Light Response and Photosynthetic Growth of the Cyanobacterium Synechocystis sp. PCC 6803. Biochemistry 2016; 55:2214-26. [DOI: 10.1021/acs.biochem.6b00133] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- Jine-Yung Huang
- Institute
of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Yi-Fang Chiu
- Institute
of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan
| | - José M. Ortega
- Instituto
de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla-CSIC, Avda. Américo Vespucio 49, 41092 Seville, Spain
| | - Hsing-Ting Wang
- Institute
of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Tien-Sheng Tseng
- Institute
of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Shyue-Chu Ke
- Department
of Physics, National Dong Hwa University, Hualien 97401, Taiwan
| | - Mercedes Roncel
- Instituto
de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla-CSIC, Avda. Américo Vespucio 49, 41092 Seville, Spain
| | - Hsiu-An Chu
- Institute
of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan
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17
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Abbas SJ, Ramacharyulu PVRK, Ke SC. MnO2/TiO2 catalyzed synthesis of coenzyme pyridoxamine-5′-phosphate analogues: 3-deoxypyridoxamine-5′-phosphate. RSC Adv 2016. [DOI: 10.1039/c5ra25779d] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The highly efficient-selective synthetic route of the pyridoxal-5′-phosphate (vitamin B6, PLP) analogues: C3 substituted deoxy derivatives were developed via reduction and followed by selective oxidation in one pot using solid supported nanoparticles.
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Affiliation(s)
- Sk Jahir Abbas
- Department of Physics
- National Dong Hwa University
- Hualien
- Taiwan 97401
| | | | - Shyue-Chu Ke
- Department of Physics
- National Dong Hwa University
- Hualien
- Taiwan 97401
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18
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Abstract
Interfacial charge transfer from TiO2 nanoparticles to layered MoS2 surface active sites via RGO nanosheets by suppressing the recombination rate of electron–hole pairs for enhanced photocatalytic activity.
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Affiliation(s)
| | - Hsin-Hsi Lo
- Department of Physics
- National Dong Hwa University
- Hualien
- Taiwan 974-01
| | | | - Shyue-Chu Ke
- Department of Physics
- National Dong Hwa University
- Hualien
- Taiwan 974-01
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19
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Lo HH, Lin HH, Maity AN, Ke SC. The molecular mechanism of the open–closed protein conformational cycle transitions and coupled substrate binding, activation and product release events in lysine 5,6-aminomutase. Chem Commun (Camb) 2016; 52:6399-402. [DOI: 10.1039/c6cc01888b] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The contributions of Lys370α and Asp298α to the critical Co–C bond cleavage trigger and open–closed cycle transitions of lysine 5,6-aminomutase.
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Affiliation(s)
- Hsin-Hsi Lo
- Physics Department
- National Dong Hwa University
- Hualien
- Taiwan 97401
| | - Hsin-Hua Lin
- Physics Department
- National Dong Hwa University
- Hualien
- Taiwan 97401
| | | | - Shyue-Chu Ke
- Physics Department
- National Dong Hwa University
- Hualien
- Taiwan 97401
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Maity AN, Lin HH, Chiang HS, Lo HH, Ke SC. Reaction of Pyridoxal-5′-phosphate-N-oxide with Lysine 5,6-Aminomutase: Enzyme Flexibility toward Cofactor Analog. ACS Catal 2015. [DOI: 10.1021/acscatal.5b00671] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
| | - Hsin-Hua Lin
- Department
of Physics, National Dong Hwa University, Hualien, Taiwan 97401
| | | | - Hsin-Hsi Lo
- Department
of Physics, National Dong Hwa University, Hualien, Taiwan 97401
| | - Shyue-Chu Ke
- Department
of Physics, National Dong Hwa University, Hualien, Taiwan 97401
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21
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Maity AN, Ke SC. 4'-CyanoPLP presents better prospect for the experimental detection of elusive cyclic intermediate radical in the reaction of lysine 5,6-aminomutase. Biochem Biophys Res Commun 2015; 457:161-4. [PMID: 25542154 DOI: 10.1016/j.bbrc.2014.12.076] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [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: 12/02/2014] [Accepted: 12/15/2014] [Indexed: 11/26/2022]
Abstract
The results of our calculations suggest that the reaction of 4'-cyanoPLP with lysine 5,6-aminomutase offers better prospect for the experimental detection of elusive cyclic azacyclopropylcarbinyl radical (I), which is proposed to be a key intermediate in the reaction of pyridoxal-5'-phosphate dependent radical aminomutases. We have calculated the corresponding hyperfine coupling constants (HFCCs) for (14)N and (13)C of cyano group using several basis sets to help the characterization of 4'-cyanoI.
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Affiliation(s)
| | - Shyue-Chu Ke
- Department of Physics, National Dong Hwa University, Hualien 97401, Taiwan.
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22
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Ramacharyulu PVRK, Nimbalkar DB, Kumar JP, Prasad GK, Ke SC. N-doped, S-doped TiO2nanocatalysts: synthesis, characterization and photocatalytic activity in the presence of sunlight. RSC Adv 2015. [DOI: 10.1039/c4ra08858a] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
N doped and S doped nano TiO2catalysts were synthesized by a sol–gel process followed by hydrothermal treatment at low temperature and tested for catalytic activity by natural sunlight photocatalytic degradation of a toxic chemical warfare agent.
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Affiliation(s)
| | | | - J. Praveen Kumar
- Defence Research & Development Establishment
- Gwalior 474 002
- India
| | - G. K. Prasad
- Defence Research & Development Establishment
- Gwalior 474 002
- India
| | - Shyue-Chu Ke
- Department of Physics
- National Dong Hwa University
- Hualien 974-01
- Taiwan
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23
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Huang SH, Ke SC, Lin TH, Huang HB, Chen YC. Effect of C-terminal residues of Aβ on copper binding affinity, structural conversion and aggregation. PLoS One 2014; 9:e90385. [PMID: 24594588 PMCID: PMC3940864 DOI: 10.1371/journal.pone.0090385] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Accepted: 01/29/2014] [Indexed: 12/31/2022] Open
Abstract
Many properties of Aβ such as toxicity, aggregation and ROS formation are modulated by Cu2+. Previously, the coordination configuration and interaction of Cu2+ with the Aβ N-terminus has been extensively studied. However, the effect of Aβ C-terminal residues on related properties is still unclear. In the present study, several C-terminus-truncated Aβ peptides, including Aβ1-40, Aβ1-35, Aβ1-29, Aβ1-24 and Aβ1-16, were synthesized to characterize the effect of Aβ C-terminal residues on Cu2+ binding affinity, structure, aggregation ability and ROS formation. Results show that the Aβ C-terminal residues have effect on Cu2+ binding affinity, aggregation ability and inhibitory ability of ROS formation. Compared to the key residues responsible for Aβ aggregation and structure in the absence of Cu2+, it is more likely that residues 36-40, rather than residues 17-21 and 30-35, play a key role on the related properties of Aβ in the presence of Cu2+.
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Affiliation(s)
- Shu-Hsiang Huang
- Department of Medicine, MacKay Medical College, New Taipei City, Taiwan
| | - Shyue-Chu Ke
- Department of Physics, National Dong Hwa University, Hualien, Taiwan
| | - Ta-Hsin Lin
- Department of Medical Research & Education, Taipei Veterans General Hospital, Taipei city, Taiwan
- Institute of Biochemistry, National Yang-Ming University, Taipei, Taiwan
| | - Hsin-Bin Huang
- Institute of Molecular Biology, National Chung-Cheng University, Chiayi, Taiwan
| | - Yi-Cheng Chen
- Department of Medicine, MacKay Medical College, New Taipei City, Taiwan
- * E-mail:
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24
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Maity AN, Chen YH, Ke SC. Large-scale domain motions and pyridoxal-5'-phosphate assisted radical catalysis in coenzyme B12-dependent aminomutases. Int J Mol Sci 2014; 15:3064-87. [PMID: 24562332 PMCID: PMC3958899 DOI: 10.3390/ijms15023064] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Revised: 12/25/2013] [Accepted: 01/22/2014] [Indexed: 12/31/2022] Open
Abstract
Lysine 5,6-aminomutase (5,6-LAM) and ornithine 4,5-aminomutase (4,5-OAM) are two of the rare enzymes that use assistance of two vitamins as cofactors. These enzymes employ radical generating capability of coenzyme B12 (5'-deoxyadenosylcobalamin, dAdoCbl) and ability of pyridoxal-5'-phosphate (PLP, vitamin B6) to stabilize high-energy intermediates for performing challenging 1,2-amino rearrangements between adjacent carbons. A large-scale domain movement is required for interconversion between the catalytically inactive open form and the catalytically active closed form. In spite of all the similarities, these enzymes differ in substrate specificities. 4,5-OAM is highly specific for D-ornithine as a substrate while 5,6-LAM can accept D-lysine and L-β-lysine. This review focuses on recent computational, spectroscopic and structural studies of these enzymes and their implications on the related enzymes. Additionally, we also discuss the potential biosynthetic application of 5,6-LAM.
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Affiliation(s)
| | - Yung-Han Chen
- Physics Department, National Dong Hwa University, Hualien 97401, Taiwan.
| | - Shyue-Chu Ke
- Physics Department, National Dong Hwa University, Hualien 97401, Taiwan.
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25
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Chen KHC, Chen CL, Tseng CF, Yu SSF, Ke SC, Lee JF, Nguyen HT, Elliott SJ, Alben JO, Chan SI. The Copper Clusters in the Particulate Methane Monooxygenase (pMMO) fromMethylococcus Capsulatus(Bath). J CHIN CHEM SOC-TAIP 2013. [DOI: 10.1002/jccs.200400162] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Chiu YF, Chen YH, Roncel M, Dilbeck PL, Huang JY, Ke SC, Ortega JM, Burnap RL, Chu HA. Spectroscopic and functional characterization of cyanobacterium Synechocystis PCC 6803 mutants on the cytoplasmic-side of cytochrome b559 in photosystem II. Biochim Biophys Acta 2013; 1827:507-19. [PMID: 23399490 DOI: 10.1016/j.bbabio.2013.01.016] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2012] [Revised: 01/18/2013] [Accepted: 01/30/2013] [Indexed: 11/19/2022]
Abstract
We performed spectroscopic and functional characterization on cyanobacterium Synechocystis PCC6803 with mutations of charged residues of the cytoplasmic side of cytochrome (Cyt) b559 in photosystem II (PSII). All of the mutant cells grew photoautotrophically and assembled stable PSII. However, R7Eα, R17Eα and R17Lβ mutant cells grew significantly slower and were more susceptible to photoinhibition than wild-type cells. The adverse effects of the arginine mutations on the activity and the stability of PSII were in the following order (R17Lβ>R7Eα>R17Eα and R17Aα). All these arginine mutants exhibited normal period-four oscillation in oxygen yield. Thermoluminescence characteristics indicated a slight decrease in the stability of the S3QB(-)/S2QB(-) charge pairs in the R7Eα and R17Lβ mutant cells. R7Eα and R17Lβ PSII core complexes contained predominantly the low potential form of Cyt b559. EPR results indicated the displacement of one of the two axial ligands to the heme of Cyt b559 in R7Eα and R17Lβ mutant reaction centers. Our results demonstrate that the electrostatic interactions between these arginine residues and the heme propionates of Cyt b559 are important to the structure and redox properties of Cyt b559. In addition, the blue light-induced nonphotochemical quenching was significantly attenuated and its recovery was accelerated in the R7Lα and R17Lβ mutant cells. Furthermore, ultra performance liquid chromatography-mass spectrometry results showed that the PQ pool was more reduced in the R7Eα and R17Lβ mutant cells than wild-type cells in the dark. Our data support a functional role of Cyt b559 in protection of PSII under photoinhibition conditions in vivo.
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Affiliation(s)
- Yi-Fang Chiu
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei, 11529, Taiwan
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28
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Biswas MK, Patra SC, Maity AN, Ke SC, Weyhermüller T, Ghosh P. 9,10-Phenanthrenesemiquinone radical complexes of ruthenium(iii), osmium(iii) and rhodium(iii) and redox series. Dalton Trans 2013; 42:6538-52. [DOI: 10.1039/c3dt00038a] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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30
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Biswas MK, Patra SC, Maity AN, Ke SC, Weyhermüller T, Ghosh P. Asymmetric cleavage of 2,2′-pyridil to a picolinic acid anion radical coordinated to ruthenium(ii): splitting of water to hydrogen. Chem Commun (Camb) 2013; 49:4522-4. [DOI: 10.1039/c3cc40956b] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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31
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Chen YH, Maity AN, Frey PA, Ke SC. Mechanism-based Inhibition Reveals Transitions between Two Conformational States in the Action of Lysine 5,6-Aminomutase: A Combination of Electron Paramagnetic Resonance Spectroscopy, Electron Nuclear Double Resonance Spectroscopy, and Density Functional Theory Study. J Am Chem Soc 2012; 135:788-94. [DOI: 10.1021/ja309603a] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- Yung-Han Chen
- Physics Department, National Dong Hwa University, Hualien, Taiwan 97401
| | | | - Perry A. Frey
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin
53726, United States
| | - Shyue-Chu Ke
- Physics Department, National Dong Hwa University, Hualien, Taiwan 97401
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Biswas MK, Patra SC, Maity AN, Ke SC, Adhikary ND, Ghosh P. Electronic Structures of Ruthenium and Osmium Complexes of 9,10-Phenanthrenequinone. Inorg Chem 2012; 51:6687-99. [DOI: 10.1021/ic300327x] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Manas Kumar Biswas
- Department of Chemistry, R. K. Mission Residential College, Narendrapur,
Kolkata 103, India
| | - Sarat Chandra Patra
- Department of Chemistry, R. K. Mission Residential College, Narendrapur,
Kolkata 103, India
| | - Amarendra Nath Maity
- Department of Physics, National Dong Hwa University, Shou-Feng,
Hualien 97401, Taiwan
| | - Shyue-Chu Ke
- Department of Physics, National Dong Hwa University, Shou-Feng,
Hualien 97401, Taiwan
| | | | - Prasanta Ghosh
- Department of Chemistry, R. K. Mission Residential College, Narendrapur,
Kolkata 103, India
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33
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Chen YH, Maity AN, Pan YC, Frey PA, Ke SC. Radical stabilization is crucial in the mechanism of action of lysine 5,6-aminomutase: role of tyrosine-263α as revealed by electron paramagnetic resonance spectroscopy. J Am Chem Soc 2011; 133:17152-5. [PMID: 21939264 DOI: 10.1021/ja207766c] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [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
Adenosylcobalamin- and pyridoxal-5'-phosphate-dependent lysine 5,6-aminomutase utilizes free radical intermediates to mediate 1,2-amino group rearrangement, during which an elusive high-energy aziridincarbinyl radical is proposed to be central in the mechanism of action. Understanding how the enzyme participates in stabilizing any of the radical intermediates is fundamentally significant. Y263F mutation abolished the enzymatic activity. With isotope-edited EPR methods, the roles of the Tyr263α residue in the putative active site are revealed. The Tyr263α residue stabilizes a radical intermediate, which most likely is the aziridincarbinyl radical, either by acting as a spin-relay device or serving as an anchor for the pyridine ring of pyridoxal-5'-phosphate through aromatic π-stacking interactions during spin transfer. The Tyr263α residue also protects the radical intermediate from interception by molecular oxygen. This study supports the proposed reaction mechanism, including the aziridincarbinyl radical, which has eluded detection for more than two decades.
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Affiliation(s)
- Yung-Han Chen
- Physics Department, National Dong Hwa University, Hualien, Taiwan 97401
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34
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Wang TH, Chen YH, Huang JY, Liu KC, Ke SC, Chu HA. Enzyme kinetics, inhibitors, mutagenesis and electron paramagnetic resonance analysis of dual-affinity nitrate reductase in unicellular N(2)-fixing cyanobacterium Cyanothece sp. PCC 8801. Plant Physiol Biochem 2011; 49:1369-1376. [PMID: 21821424 DOI: 10.1016/j.plaphy.2011.07.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2011] [Accepted: 07/12/2011] [Indexed: 05/31/2023]
Abstract
The assimilatory nitrate reductase (NarB) of N(2)-fixing cyanobacterium Cyanothece sp. PCC 8801 is a monomeric enzyme with dual affinity for substrate nitrate. We purified the recombinant NarB of Cyanothece sp. PCC 8801 and further investigated it by enzyme kinetics analysis, site-directed mutagenesis, inhibitor kinetics analysis, and electron paramagnetic resonance (EPR) spectroscopy. The NarB showed 2 kinetic regimes at pH 10.5 or 8 and electron-donor conditions methyl viologen or ferredoxin (Fd). Fd-dependent NR assay revealed NarB with very high affinity for nitrate (K(m)1, ∼1μM; K(m)2, ∼270μM). Metal analysis and EPR results showed that NarB contains a Mo cofactor and a [4Fe-4S] cluster. In addition, the R352A mutation on the proposed nitrate-binding site of NarB greatly altered both high- and low-affinity kinetic components. Furthermore, the effect of azide on the NarB of Cyanothece sp. PCC 8801 was more complex than that on the NarB of Synechococcus sp. PCC 7942 with its single kinetic regime. With 1mM azide, the kinetics of the wild-type NarB was transformed from 2 kinetic regimes to hyperbolic kinetics, and its activity was enhanced significantly under medium nitrate concentrations. Moreover, EPR results also suggested a structural difference between the two NarBs. Taken together, our results show that the NarB of Cyanothece sp. PCC 8801 contains only a single Mo-catalytic center, and we rule out that the enzyme has 2 independent, distinct catalytic sites. In addition, the NarB of Cyanothece sp. PCC 8801 may have a regulatory nitrate-binding site.
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Affiliation(s)
- Tung-Hei Wang
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan
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35
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Affiliation(s)
| | - Shyue-Chu Ke
- Department of Physics; National Dong Hwa University; Hualien; 974-01; Taiwan
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36
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Yang CA, Chen YH, Ke SC, Chen YR, Huang HB, Lin TH, Chen YC. Correlation of copper interaction, copper-driven aggregation, and copper-driven h(2)o(2) formation with aβ40 conformation. Int J Alzheimers Dis 2010; 2011:607861. [PMID: 21234305 PMCID: PMC3018625 DOI: 10.4061/2011/607861] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [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: 09/15/2010] [Accepted: 11/15/2010] [Indexed: 11/24/2022] Open
Abstract
The neurotoxicity of Aβ is associated with the formation of free radical by interacting with redox active metals such as Cu2+. However, the relationship between ion-interaction, ion-driven free radical formation, and Aβ conformation remains to be further elucidated. In the present study, we investigated the correlation of Cu2+ interaction and Cu2+-driven free radical formation with Aβ40 conformation. The Cu2+-binding affinity for Aβ40 in random coiled form is 3-fold higher than that in stable helical form. Unexpectedly but interestingly, we demonstrate in the first time that the stable helical form of Aβ40 can induce the formation of H2O2 by interacting with Cu2+. On the other hand, the H2O2 generation is repressed at Aβ/Cu2+ molar ratio ≥1 when Aβ40 adopts random coiled structure. Taken together, our result demonstrates that Aβ40 adopted a helical structure that may play a key factor for the formation of free radical with Cu2+ ions.
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Affiliation(s)
- Chia-Anne Yang
- Institute of Life Science, Tzu Chi University, Hualien 970, Taiwan
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Maity AN, Shaikh AC, Srimurugan S, Wu CJ, Chen C, Ke SC. Synthesis of 4-thia-[6-(13)C]lysine from [2- (13)C]glycine: access to site-directed isotopomers of 2-aminoethanol, 2-bromoethylamine and 4-thialysine. Amino Acids 2010; 42:309-15. [PMID: 21103898 DOI: 10.1007/s00726-010-0808-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2010] [Accepted: 11/02/2010] [Indexed: 11/28/2022]
Abstract
4-Thialysine (S-(2-aminoethyl)-L: -cysteine) is an analog of lysine. It has been used as an alternative substrate for lysine in enzymatic reactions. Site-directed isotopomers are often needed for elucidation of mechanism of reactions. 4-Thialysine can be synthesized by reacting cysteine with 2-bromoethylamine, an important reagent in chemical-modification rescue (CMR) of proteins. Here, we present the synthesis of 4-thia-[6-(13)C]lysine, one of the isotopomers of 4-thialysine, from commercially available starting material [2-(13)C]glycine via formation of five intermediates including 2-amino[2-(13)C]ethanol and 2-bromo[1-(13)C]ethylamine. The compounds were characterized using various spectroscopic techniques. Moreover, we discuss that our strategy would provide access to site-directed isotopomers of 2-aminoethanol, 2-bromoethylamine and 4-thialysine. Biological activity of 4-thia-[6-(13)C]lysine was tested in the enzymatic reaction of lysine 5,6-aminomutase.
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38
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Gopal NO, Lo HH, Sheu SC, Ke SC. A Potential Site for Trapping Photogenerated Holes on Rutile TiO2 Surface as Revealed by EPR Spectroscopy: An Avenue for Enhancing Photocatalytic Activity. J Am Chem Soc 2010; 132:10982-3. [DOI: 10.1021/ja909901f] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Neeruganti O. Gopal
- Physics Department and Nanotechnology Research Center, National Dong Hwa University, Hualien, Taiwan 97401, and Department of Occupational Safety and Health, Chang Jung Christian University, Tainan, Taiwan 711
| | - Hsin-Hsi Lo
- Physics Department and Nanotechnology Research Center, National Dong Hwa University, Hualien, Taiwan 97401, and Department of Occupational Safety and Health, Chang Jung Christian University, Tainan, Taiwan 711
| | - Shiann-Cherng Sheu
- Physics Department and Nanotechnology Research Center, National Dong Hwa University, Hualien, Taiwan 97401, and Department of Occupational Safety and Health, Chang Jung Christian University, Tainan, Taiwan 711
| | - Shyue-Chu Ke
- Physics Department and Nanotechnology Research Center, National Dong Hwa University, Hualien, Taiwan 97401, and Department of Occupational Safety and Health, Chang Jung Christian University, Tainan, Taiwan 711
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39
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Hung CH, Hwang HJ, Chen YH, Chiu YF, Ke SC, Burnap RL, Chu HA. Spectroscopic and functional characterizations of cyanobacterium Synechocystis PCC 6803 mutants on and near the heme axial ligand of cytochrome b559 in photosystem II. J Biol Chem 2009; 285:5653-63. [PMID: 20007972 DOI: 10.1074/jbc.m109.044719] [Citation(s) in RCA: 17] [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: 01/31/2023] Open
Abstract
The functional role of cytochrome (cyt) b(559) in photosystem II (PSII) was investigated in H22K alpha and Y18S alpha cyt b(559) mutants of the cyanobacterium Synechocystis sp. PCC6803. H22K alpha and Y18S alpha cyt b(559) mutant carries one amino acid substitution on and near one of heme axial ligands of cyt b(559) in PSII, respectively. Both mutants grew photoautotrophically, assembled stable PSII, and exhibited the normal period-four oscillation in oxygen yield. However, both mutants showed several distinct chlorophyll a fluorescence properties and were more susceptible to photoinhibition than wild type. EPR results indicated the displacement of one of the two axial ligands to the heme of cyt b(559) in H22K alpha mutant reaction centers, at least in isolated reaction centers. The maximum absorption of cyt b(559) in Y18S alpha mutant PSII core complexes was shifted to 561 nm. Y18S alpha and H22K alpha mutant PSII core complexes contained predominately the low potential form of cyt b(559). The findings lend support to the concept that the redox properties of cyt b(559) are strongly influenced by the hydrophobicity and ligation environment of the heme. When the cyt b(559) mutations placed in a D1-D170A genetic background that prevents assembly of the manganese cluster, accumulation of PSII is almost completely abolished. Overall, our data support a functional role of cyt b(559) in protection of PSII under photoinhibition conditions in vivo.
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Affiliation(s)
- Chung-Hsien Hung
- Institute of Plant and Microbial Biology, Taiwan International Graduate Program, Academia Sinica, Taipei 11529, Taiwan
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40
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Maity AN, Hsieh CP, Huang MH, Chen YH, Tang KH, Behshad E, Frey PA, Ke SC. Evidence for Conformational Movement and Radical Mechanism in the Reaction of 4-Thia-l-lysine with Lysine 5,6-Aminomutase. J Phys Chem B 2009; 113:12161-3. [DOI: 10.1021/jp905357a] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Amarendra N. Maity
- Physics Department, National Dong Hwa University, Hualien, Taiwan 974-01, Department of Biochemistry, University of Wisconsin—Madison, Madison, Wisconsin 53726
| | - Chih-Pin Hsieh
- Physics Department, National Dong Hwa University, Hualien, Taiwan 974-01, Department of Biochemistry, University of Wisconsin—Madison, Madison, Wisconsin 53726
| | - Ming-Hui Huang
- Physics Department, National Dong Hwa University, Hualien, Taiwan 974-01, Department of Biochemistry, University of Wisconsin—Madison, Madison, Wisconsin 53726
| | - Yung-Han Chen
- Physics Department, National Dong Hwa University, Hualien, Taiwan 974-01, Department of Biochemistry, University of Wisconsin—Madison, Madison, Wisconsin 53726
| | - Kuo-Hsiang Tang
- Physics Department, National Dong Hwa University, Hualien, Taiwan 974-01, Department of Biochemistry, University of Wisconsin—Madison, Madison, Wisconsin 53726
| | - Elham Behshad
- Physics Department, National Dong Hwa University, Hualien, Taiwan 974-01, Department of Biochemistry, University of Wisconsin—Madison, Madison, Wisconsin 53726
| | - Perry A. Frey
- Physics Department, National Dong Hwa University, Hualien, Taiwan 974-01, Department of Biochemistry, University of Wisconsin—Madison, Madison, Wisconsin 53726
| | - Shyue-Chu Ke
- Physics Department, National Dong Hwa University, Hualien, Taiwan 974-01, Department of Biochemistry, University of Wisconsin—Madison, Madison, Wisconsin 53726
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Chiu YF, Lin WC, Wu CM, Chen YH, Hung CH, Ke SC, Chu HA. Identification and characterization of a cytochrome b559 Synechocystis 6803 mutant spontaneously generated from DCMU-inhibited photoheterotrophical growth conditions. Biochim Biophys Acta 2009; 1787:1179-88. [PMID: 19464256 DOI: 10.1016/j.bbabio.2009.05.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2008] [Revised: 05/12/2009] [Accepted: 05/14/2009] [Indexed: 11/29/2022]
Abstract
We identified a spontaneously generated mutant from Synechocystis sp. PCC6803 wild-type cells grown in BG-11 agar plates containing 5 mM Glu and 10 microM DCMU. This mutant carries an R7L mutation on the alpha-subunit of cyt b559 in photosystem II (PSII). In the recent 2.9 A PSII crystal structural model, the side chain of this arginine residue is in close contact with the heme propionates of cyt b559. We called this mutant WR7Lalpha cyt b559. This mutant grew at about the same rate as wild-type cells under photoautotrophical conditions but grew faster than wild-type cells under photoheterotrophical conditions. In addition, 77 K fluorescence and 295 K chlorophyll a fluorescence spectral results indicated that the energy delivery from phycobilisomes to PSII reaction centers was partially inhibited or uncoupled in this mutant. Moreover, WR7Lalpha cyt b559 mutant cells were more susceptible to photoinhibition than wild-type cells under high light conditions. Furthermore, our EPR results indicated that in a significant fraction of mutant reaction centers, the R7Lalpha cyt b559 mutation induced the displacement of one of the axial histidine ligands to the heme of cyt b559. On the basis of these results, we propose that the Arg7Leu mutation on the alpha-subunit of cyt b559 alters the interaction between the APC core complex and PSII reaction centers, which reduces energy delivery from the antenna to the reaction center and thus protects mutant cells from DCMU-induced photo-oxidative stress.
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Affiliation(s)
- Yi-Fang Chiu
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan
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Warncke K, Schmidt JC, Ke SC. Identification of a Rearranged-Substrate, Product Radical Intermediate and the Contribution of a Product Radical Trap in Vitamin B 12 Coenzyme-Dependent Ethanolamine Deaminase Catalysis. J Am Chem Soc 2008. [DOI: 10.1021/ja801780x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Gopal NO, Lo HH, Ke SC. Chemical State and Environment of Boron Dopant in B,N-Codoped Anatase TiO2 Nanoparticles: An Avenue for Probing Diamagnetic Dopants in TiO2 by Electron Paramagnetic Resonance Spectroscopy. J Am Chem Soc 2008; 130:2760-1. [DOI: 10.1021/ja711424d] [Citation(s) in RCA: 103] [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)
- Neeruganti O. Gopal
- Physics Department and Nanotechnology Research Center, National Dong Hwa University, Hualien, Taiwan 974-01
| | - Hsin-Hsi Lo
- Physics Department and Nanotechnology Research Center, National Dong Hwa University, Hualien, Taiwan 974-01
| | - Shyue-Chu Ke
- Physics Department and Nanotechnology Research Center, National Dong Hwa University, Hualien, Taiwan 974-01
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Hsu IJ, Hsieh CH, Ke SC, Chiang KA, Lee JM, Chen JM, Jang LY, Lee GH, Wang Y, Liaw WF. New Members of a Class of Iron−Thiolate−Nitrosyl Compounds: Trinuclear Iron−Thiolate−Nitrosyl Complexes Containing Fe3S6 Core. J Am Chem Soc 2007; 129:1151-9. [PMID: 17263396 DOI: 10.1021/ja065401e] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The neutral trinuclear iron-thiolate-nitrosyl, [(ON)Fe(mu-S,S-C(6)H(4))](3) (1), and its oxidation product, [(ON)Fe(mu-S,S-C(6)H(4))](3)[PF(6)] (2), were synthesized and characterized by IR, X-ray diffraction, X-ray absorption, electron paramagnetic resonance (EPR), and magnetic measurement. The five-coordinated, square pyramidal geometry around each iron atom in complex 1 remains intact when complex 1 is oxidized to yield complex 2. Magnetic measurements and EPR results show that there is only one unpaired electron in complex 1 (S(total) = 1/2) and no unpaired electron (S(total) = 0) in 2. The detailed geometric comparisons between complexes 1 and 2 provide understanding of the role that the unpaired electron plays in the chemical bonding of this trinuclear complex. Significant shortening of the Fe-Fe, Fe-N, and Fe-S distances around Fe(1) is observed when complex 1 is oxidized to 2. This result implicates that the removal of the unpaired electron does induce the strengthening of the Fe-Fe, Fe-N, and Fe-S bonds in the Fe(1) fragment. A significant shift of the nuNO stretching frequency from 1751 cm(-1) (1) to 1821, 1857 cm(-1) (2) (KBr) also indicates the strengthening of the N-O bonds in complex 2. The EPR, X-ray absorption, magnetic measurements, and molecular orbital calculations lead to the conclusion that the unpaired electron in complex 1 is mainly allocated in the Fe(1) fragment and is best described as {Fe(1)NO}7, so that the unpaired electron is delocalized between Fe and NO via d-pi* orbital interaction; some contributions from [Fe(2)NO] and [Fe(3)NO] as well as the thiolates associated with Fe (1) are also realized. According to MO calculations, the spin density of complex 1 is predominantly located at the Fe atoms with 0.60, -0.15, and 0.25 at Fe(1), Fe(2), and Fe(3), respectively.
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Affiliation(s)
- I-Jui Hsu
- Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan
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Ke SC, Wang TC, Wong MS, Gopal NO. Low Temperature Kinetics and Energetics of the Electron and Hole Traps in Irradiated TiO2 Nanoparticles as Revealed by EPR Spectroscopy. J Phys Chem B 2006; 110:11628-34. [PMID: 16800456 DOI: 10.1021/jp0612578] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [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
We have monitored exclusively the dynamics of photogenerated charge carriers trapping in deep traps and trapped electron-hole recombination in UV irradiated anatase TiO2 powders by electron paramagnetic resonance (EPR) spectroscopy at 10 K. The results reveal that the strategy of using low temperatures contributes to the stabilization of the charged pair states for hours by reducing the rate of electron-hole recombination processes. Since only the localized states such as holes trapped at oxygen anions and electrons trapped at coordinatively unsaturated cations are accessible to EPR spectroscopy, the time-dependent population and depopulation of these EPR signals reflect the kinetics and energetics of these trap states. The data support a model of sequential accumulation of deep trap site populations in which the initial fast direct trapping into a deep trap site is followed by slower carrier trap-to-trap hopping until a deep trap is encountered for both photogenerated electrons and holes. Effective modeling of the subsequent decay of trapped-holes is achieved by employing a first-order kinetics, whereas the decay of either surface- or inner-trapped electrons has both a fast and a slow component. The fast component is attributed to a trapped-electron and a free-hole recombination, and the slow component is attributed to trapped electron-hole recombination. The activation energies for the process of diffusion of trapped electrons from their Ti3+ trapping sites are estimated.
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Affiliation(s)
- Shyue-Chu Ke
- Physics Department, National Dong Hwa University, Hualien, Taiwan 974-01.
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Hsu HF, Su CL, Gopal NO, Wu CC, Chu WC, Tsai YF, Chang YH, Liu YH, Kuo TS, Ke SC. Redox Chemistry in the Reaction of Oxovanadium(V) with Thiolate-Containing Ligands: the Isolation and Characterization of Non-Oxo Vanadium(IV) Complexes Containing Disulfide and Thioether Groups. Eur J Inorg Chem 2006. [DOI: 10.1002/ejic.200500874] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Fang CH, Chiang KA, Hung CH, Chang K, Ke SC, Chu HA. Effects of Ethylene Glycol and Methanol on Ammonia-Induced Structural Changes of the Oxygen-Evolving Complex in Photosystem II. Biochemistry 2005; 44:9758-65. [PMID: 16008360 DOI: 10.1021/bi050030k] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Ammonia is an inhibitor of water oxidation and a structural analogue for substrate water, making it a valuable probe for the structural properties of the possible substrate-binding site on the oxygen-evolving complex (OEC) in photosystem II (PSII). By using the NH(3)-induced upshift of the 1365 cm(-)(1) IR mode in the S(2)Q(A)(-)/S(1)Q(A) spectrum and the NH(3)-modified S(2) state EPR signals of PSII as spectral probes, we found that ethylene glycol has clear effects on the binding properties of the NH(3)-specific site on the OEC. Our results show that in PSII samples containing 30% (v/v) ethylene glycol, the affinity of the NH(3)-specific binding site on the OEC is estimated to be more than 10 times lower than that in PSII samples containing 0.4 M sucrose. In addition, our results show that the NH(3)-induced upshift of the 1365 cm(-)(1) IR mode in the S(2)Q(A)(-)/S(1)Q(A) spectrum is dependent on the concentration of ethylene glycol, but not dependent on the concentration of sucrose (up to 1.5 M) or methanol (up to 5.4 M). By comparing the concentration dependence of sucrose and ethylene glycol on NH(3)-induced spectral change and also by comparing the sucrose and ethylene glycol data at similar concentrations ( approximately 1 M), we conclude that ethylene glycol has a clear effect on the NH(3)-induced spectral changes. Furthermore, our results also show that ethylene glycol alters the steric requirement of the amine effect on the upshift of the 1365 cm(-)(1) mode in the S(2)Q(A)(-)/S(1)Q(A) spectrum. In PSII samples containing 30% (v/v) ethylene glycol, only NH(3), not other bulkier amines (e.g., Tris, AEPD, and CH(3)NH(2)), has a clear effect on the upshift of the 1365 cm(-)(1) mode in the S(2)Q(A)(-)/S(1)Q(A) spectrum; in contrast, in PSII samples containing 0.4 M sucrose, both NH(3) and CH(3)NH(2) have a clear effect. On the basis of the results mentioned above, we propose that ethylene glycol acts directly or indirectly to decrease the affinity or limit the accessibility of NH(3) and CH(3)NH(2) to the NH(3)-specific binding site on the OEC in PSII. Finally, we also applied the same approach to test whether methanol is able to compete with ammonia on its binding site on the OEC. We found that 4% (v/v) methanol does not have any significant effect on the NH(3)-induced upshift of the 1365 cm(-)(1) mode in the S(2)Q(A)(-)/S(1)Q(A) spectrum and the NH(3)-modified S(2) state g = 2 multiline EPR signal. Our results suggest that methanol is unable to compete with NH(3) upon binding to the Mn site of the OEC that gives rise to the altered S(2) state g = 2 multiline EPR signal.
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Affiliation(s)
- Cheng-Hao Fang
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan 11529, Republic of China
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Chen CL, Chen KHC, Ke SC, Yu SSF, Chan SI. Preparation and characterization of a (Cu,Zn)-pMMO from Methylococcus capsulatus (Bath). J Inorg Biochem 2004; 98:2125-30. [PMID: 15541502 DOI: 10.1016/j.jinorgbio.2004.09.021] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2004] [Revised: 09/13/2004] [Accepted: 09/23/2004] [Indexed: 11/23/2022]
Abstract
We report the preparation of a (Cu,Zn)-particulate methane monooxygenase (pMMO) in which the bulk of the copper ions of the electron-transfer clusters (E-clusters) has been replaced by divalent Zn ions. The Cu and Zn contents in the (Cu,Zn)-pMMO were determined by both inductively coupled plasma mass spectroscopy (ICP-MS) and X-ray absorption K-edge spectroscopy. Further characterization of the (Cu,Zn)-pMMO was provided by pMMO-activity assays as well as low-temperature electron paramagnetic resonance (EPR) spectroscopy following reductive titration and incubation in air or air/propylene mixtures. The pMMO-activity assays indicated that the (Cu,Zn)-pMMO was no longer capable of supporting catalytic turnover of hydrocarbon substrates. However, the EPR studies revealed that the catalytic cluster (C-cluster) copper ions in the (Cu,Zn)-pMMO were still capable of supporting the activation of dioxygen when reduced, and that the 14N-superhyperfine features associated with one of the type 2 Cu(II) centers in the hydroxylation C-cluster remained unperturbed. The replacement of the E-cluster copper ions by Zn ions did compromise the ability of the protein to mediate the transfer of reducing equivalents from exogenous reductants to the C-clusters. These observations provide strong support for the electron transfer and catalytic roles for the E-cluster and C-cluster copper ions, respectively.
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Affiliation(s)
- Chang-Li Chen
- Institute of Chemistry, Academia Sinica, 128 Academia Road Section 2, Nankang, Taipei 115, Taiwan
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Chu HA, Feng YW, Wang CM, Chiang KA, Ke SC. Ammonia-Induced Structural Changes of the Oxygen-Evolving Complex in Photosystem II As Revealed by Light-Induced FTIR Difference Spectroscopy. Biochemistry 2004; 43:10877-85. [PMID: 15323548 DOI: 10.1021/bi0499260] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Light-induced Fourier transform infrared difference spectroscopy has been applied to studies of ammonia effects on the oxygen-evolving complex (OEC) of photosystem II (PSII). We found that NH(3) induced characteristic spectral changes in the region of the symmetric carboxylate stretching modes (1450-1300 cm(-1)) of the S(2)Q(A)(-)/S(1)Q(A) FTIR difference spectra of PSII. The S(2) state carboxylate mode at 1365 cm(-1) in the S(2)Q(A)(-)/S(1)Q(A) spectrum of the controlled samples was very likely upshifted to 1379 cm(-1) in that of NH(3)-treated samples; however, the frequency of the corresponding S(1) carboxylate mode at 1402 cm(-1) in the same spectrum was not significantly affected. These two carboxylate modes have been assigned to a Mn-ligating carboxylate whose coordination mode changes from bridging or chelating to unidentate ligation during the S(1) to S(2) transition [Noguchi, T., Ono, T., and Inoue, Y. (1995) Biochim. Biophys. Acta 1228, 189-200; Kimura, Y., and Ono, T.-A. (2001) Biochemistry 40, 14061-14068]. Therefore, our results show that NH(3) induced significant structural changes of the OEC in the S(2) state. In addition, our results also indicated that the NH(3)-induced spectral changes of the S(2)Q(A)(-)/S(1)Q(A) spectrum of PSII are dependent on the temperature of the FTIR measurement. Among the temperatures we measured, the strongest effect was seen at 250 K, a lesser effect was seen at 225 K, and little or no effect was seen at 200 K. Furthermore, our results also showed that the NH(3) effects on the S(2)Q(A)(-)/S(1)Q(A) spectrum of PSII are dependent on the concentrations of NH(4)Cl. The NH(3)-induced upshift of the 1365 cm(-1) mode is apparent at 5 mM NH(4)Cl and is completely saturated at 100 mM NH(4)Cl concentration. Finally, we found that CH(3)NH(2) has a small but clear effect on the spectral change of the S(2)Q(A)(-)/S(1)Q(A) FTIR difference spectrum of PSII. The effects of amines on the S(2)Q(A)(-)/S(1)Q(A) FTIR difference spectra (NH(3) > CH(3)NH(2) > AEPD and Tris) are inverse proportional to their size (Tris approximately AEPD > CH(3)NH(2) > NH(3)). Therefore, our results showed that the effects of amines on the S(2)Q(A)(-)/S(1)Q(A) spectrum of PSII are sterically selective for small amines. On the basis of the correlations between the conditions (dependences on the excitation temperature and NH(3) concentration and the steric requirement for the amine effects) that give rise to the NH(3)-induced upshift of the 1365 cm(-)(1) mode in the S(2)Q(A)(-)/S(1)Q(A) spectrum of PSII and the conditions that give rise to the altered S(2) state multiline EPR signal, we propose that the NH(3)-induced upshift of the 1365 cm(-1) mode is caused by the binding of NH(3) to the site on the Mn cluster that gives rise to the altered S(2) state multiline EPR signal. In addition, we found no significant NH(3)-induced change in the S(2)Q(A)(-)/S(1)Q(A) FTIR difference spectrum at 200 K. Under this condition, the OEC gives rise to the NH(3)-stabilized g = 4.1 EPR signal and a suppressed g = 2 multiline EPR signal. Our results suggest that the structural difference of the OEC between the normal g = 2 multiline form and the NH(3)-stabilized g = 4.1 form is small.
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Affiliation(s)
- Hsiu-An Chu
- Institute of Botany, Academia Sinica, Taipei, Taiwan 11529, Republic of China.
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