1
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Singha A, Sekretareva A, Tao L, Lim H, Ha Y, Braun A, Jones SM, Hedman B, Hodgson KO, Britt RD, Kosman DJ, Solomon EI. Tuning the Type 1 Reduction Potential of Multicopper Oxidases: Uncoupling the Effects of Electrostatics and H-Bonding to Histidine Ligands. J Am Chem Soc 2023. [PMID: 37294874 PMCID: PMC10392966 DOI: 10.1021/jacs.3c03241] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
In multicopper oxidases (MCOs), the type 1 (T1) Cu accepts electrons from the substrate and transfers these to the trinuclear Cu cluster (TNC) where O2 is reduced to H2O. The T1 potential in MCOs varies from 340 to 780 mV, a range not explained by the existing literature. This study focused on the ∼350 mV difference in potential of the T1 center in Fet3p and Trametes versicolor laccase (TvL) that have the same 2His1Cys ligand set. A range of spectroscopies performed on the oxidized and reduced T1 sites in these MCOs shows that they have equivalent geometric and electronic structures. However, the two His ligands of the T1 Cu in Fet3p are H-bonded to carboxylate residues, while in TvL they are H-bonded to noncharged groups. Electron spin echo envelope modulation spectroscopy shows that there are significant differences in the second-sphere H-bonding interactions in the two T1 centers. Redox titrations on type 2-depleted derivatives of Fet3p and its D409A and E185A variants reveal that the two carboxylates (D409 and E185) lower the T1 potential by 110 and 255-285 mV, respectively. Density functional theory calculations uncouple the effects of the charge of the carboxylates and their difference in H-bonding interactions with the His ligands on the T1 potential, indicating 90-150 mV for anionic charge and ∼100 mV for a strong H-bond. Finally, this study provides an explanation for the generally low potentials of metallooxidases relative to the wide range of potentials of the organic oxidases in terms of different oxidized states of their TNCs involved in catalytic turnover.
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Affiliation(s)
- Asmita Singha
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Alina Sekretareva
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Lizhi Tao
- Department of Chemistry, University of California at Davis, Davis, California 95616, United States
| | - Hyeongtaek Lim
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Yang Ha
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Augustin Braun
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Stephen M Jones
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Keith O Hodgson
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - R David Britt
- Department of Chemistry, University of California at Davis, Davis, California 95616, United States
| | - Daniel J Kosman
- Department of Biochemistry, The University at Buffalo, Buffalo, New York 14214, United States
| | - Edward I Solomon
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
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2
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Heck J, Metz F, Buchenau S, Teubner M, Grimm-Lebsanft B, Spaniol TP, Hoffmann A, Rübhausen MA, Herres-Pawlis S. Manipulating electron transfer – the influence of substituents on novel copper guanidine quinolinyl complexes. Chem Sci 2022; 13:8274-8288. [PMID: 35919707 PMCID: PMC9297705 DOI: 10.1039/d2sc02910c] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Accepted: 06/11/2022] [Indexed: 11/21/2022] Open
Abstract
Copper guanidine quinolinyl complexes act as good entatic state models due to their distorted structures leading to a high similarity between Cu(i) and Cu(ii) complexes. For a better understanding of the entatic state principle regarding electron transfer a series of guanidine quinolinyl ligands with different substituents in the 2- and 4-position were synthesized to examine the influence on the electron transfer properties of the corresponding copper complexes. Substituents with different steric or electronic influences were chosen. The effects on the properties of the copper complexes were studied applying different experimental and theoretical methods. The molecular structures of the bis(chelate) copper complexes were examined in the solid state by single-crystal X-ray diffraction and in solution by X-ray absorption spectroscopy and density functional theory (DFT) calculations revealing a significant impact of the substituents on the complex structures. For a better insight natural bond orbital (NBO) calculations of the ligands and copper complexes were performed. The electron transfer was analysed by the determination of the electron self-exchange rates following Marcus theory. The obtained results were correlated with the results of the structural analysis of the complexes and of the NBO calculations. Nelsen's four-point method calculations give a deeper understanding of the thermodynamic properties of the electron transfer. These studies reveal a significant impact of the substituents on the properties of the copper complexes. Copper guanidine quinolinyl complexes act as good entatic state models for the electron transfer due to a high similarity between the corresponding Cu(i) and Cu(ii) complexes. The introduction of substituents leads to a further enhancement.![]()
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Affiliation(s)
- Joshua Heck
- Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1a, 52074 Aachen, Germany
| | - Fabian Metz
- Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1a, 52074 Aachen, Germany
| | - Sören Buchenau
- Institute of Nanostructure and Solid State Physics, University of Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - Melissa Teubner
- Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1a, 52074 Aachen, Germany
- Institute of Nanostructure and Solid State Physics, University of Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - Benjamin Grimm-Lebsanft
- Institute of Nanostructure and Solid State Physics, University of Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - Thomas P. Spaniol
- Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1a, 52074 Aachen, Germany
| | - Alexander Hoffmann
- Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1a, 52074 Aachen, Germany
| | - Michael A. Rübhausen
- Institute of Nanostructure and Solid State Physics, University of Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - Sonja Herres-Pawlis
- Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1a, 52074 Aachen, Germany
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3
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King JD, Harrington L, Lada BM, He G, Cooley JW, Blankenship RE. Site-directed mutagenesis of the highly perturbed copper site of auracyanin D. Arch Biochem Biophys 2014; 564:237-43. [DOI: 10.1016/j.abb.2014.10.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Revised: 10/01/2014] [Accepted: 10/07/2014] [Indexed: 10/24/2022]
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4
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Liu J, Chakraborty S, Hosseinzadeh P, Yu Y, Tian S, Petrik I, Bhagi A, Lu Y. Metalloproteins containing cytochrome, iron-sulfur, or copper redox centers. Chem Rev 2014; 114:4366-469. [PMID: 24758379 PMCID: PMC4002152 DOI: 10.1021/cr400479b] [Citation(s) in RCA: 559] [Impact Index Per Article: 55.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2013] [Indexed: 02/07/2023]
Affiliation(s)
- Jing Liu
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Saumen Chakraborty
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Parisa Hosseinzadeh
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Yang Yu
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Shiliang Tian
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Igor Petrik
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Ambika Bhagi
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Yi Lu
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
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5
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King JD, McIntosh CL, Halsey CM, Lada BM, Niedzwiedzki DM, Cooley JW, Blankenship RE. Metalloproteins diversified: the auracyanins are a family of cupredoxins that stretch the spectral and redox limits of blue copper proteins. Biochemistry 2013; 52:8267-75. [PMID: 24147561 DOI: 10.1021/bi401163g] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The metal sites of electron transfer proteins are tuned for function. The type 1 copper site is one of the most utilized metal sites in electron transfer reactions. This site can be tuned by the protein environment from +80 mV to +680 mV in typical type 1 sites. Accompanying this huge variation in midpoint potentials are large changes in electronic structure, resulting in proteins that are blue, green, or even red. Here, we report a family of blue copper proteins, the auracyanins, from the filamentous anoxygenic phototroph Chloroflexus aurantiacus that display the entire known spectral and redox variations known in the type 1 copper site. C. aurantiacus encodes four auracyanins, labeled A-D. The midpoint potentials vary from +83 mV (auracyanin D) to +423 mV (auracyanin C). The electronic structures vary from classical blue copper UV-vis absorption spectra (auracyanin B) to highly perturbed spectra (auracyanins C and D). The spectrum of auracyanin C is temperature-dependent. The expansion and divergent nature of the auracyanins is a previously unseen phenomenon.
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Affiliation(s)
- Jeremy D King
- Graduate Program in Plant Biology, Departments of ‡Biology and §Chemistry, and ⊥Photosynthetic Antenna Research Center (PARC), Washington University in St. Louis , St. Louis, Missouri 63130, United States
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6
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Kurose S, Kataoka K, Shinohara N, Miura Y, Tsutsumi M, Tsujimura S, Kano K, Sakurai T. Modification of Spectroscopic Properties and Catalytic Activity ofEscherichia coliCueO by Mutations of Methionine 510, the Axial Ligand to the Type I Cu. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2009. [DOI: 10.1246/bcsj.82.504] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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7
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Kamitaka Y, Tsujimura S, Kataoka K, Sakurai T, Ikeda T, Kano K. Effects of axial ligand mutation of the type I copper site in bilirubin oxidase on direct electron transfer-type bioelectrocatalytic reduction of dioxygen. J Electroanal Chem (Lausanne) 2007. [DOI: 10.1016/j.jelechem.2006.10.035] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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8
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Garner DK, Vaughan MD, Hwang HJ, Savelieff MG, Berry SM, Honek JF, Lu Y. Reduction potential tuning of the blue copper center in Pseudomonas aeruginosa azurin by the axial methionine as probed by unnatural amino acids. J Am Chem Soc 2007; 128:15608-17. [PMID: 17147368 DOI: 10.1021/ja062732i] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The conserved axial ligand methionine 121 from Pseudomonas aeruginosa azurin (Az) has been replaced by isostructural unnatural amino acid analogues, oxomethionine (OxM), difluoromethionine (DFM), trifluoromethionine (TFM), selenomethionine (SeM), and norleucine (Nle) using expressed protein ligation. The replacements resulted in < 6 nm shifts in the S(Cys)-Cu charge transfer (CT) band in the electronic absorption spectra and < 8 gauss changes in the copper hyperfine coupling constants (AII) in the X-band electron paramagnetic resonance spectra, suggesting that isostructural replacement of Met resulted in minimal structural perturbation of the copper center. The slight blue shifts of the CT band follow the trend of stronger electronegativity of the ligands. This trend is supported by 19F NMR studies of the fluorinated methionine analogues. However, the order of AII differs, suggesting additional factors influencing AII. In contrast to the small changes in the UV-vis and EPR spectra, a large variation of > 227 mV in reduction potential was observed for the series of variants reported here. Additionally, a linear correlation was established between the reduction potentials and hydrophobicity of the variants. Extension of this analysis to other type 1 copper-containing proteins reveals a linear correlation between change in hydrophobicity and change in reduction potential, independent of the protein scaffold, experimental conditions, measurement techniques, and steric modifications. This analysis has also revealed for the first time high and low potential states for type 1 centers, and the difference may be attributable to destabilization of the protein fold by disruption of hydrophobic or hydrogen bonding interactions that stabilize the type 1 center.
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Affiliation(s)
- Dewain K Garner
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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9
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Astier Y, Canters GW, Davis JJ, Hill HAO, Verbeet MP, Wijma HJ. Sensing nitrite through a pseudoazurin-nitrite reductase electron transfer relay. Chemphyschem 2006; 6:1114-20. [PMID: 15900523 DOI: 10.1002/cphc.200400384] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Nitrite is converted to nitric oxide by haem or copper-containing enzymes in denitrifying bacteria during the process of denitrification. In designing an efficient biosensor, this enzymic turnover must be quantitatively assessed. The enzyme nitrite reductase from Alcaligenes faecalis contains a redox-active blue copper centre and a nonblue enzyme-active copper centre. It can be covalently tethered to modified gold-electrode surfaces in configurations in which direct electron transfer is possible. A surface cysteine mutant of the enzyme can be similarly immobilised on bare electroactive gold substrates. Under such circumstances, however, electron transfer cannot be effectively coupled with substrate catalytic turnover. In using either the natural redox partner, pseudoazurin, or ruthenium hexammine as an "electron-shuttle" or "conduit" between enzyme and a peptide-modified electrode surface, the coupling of electron transfer to catalysis can be utilised in the development of an amperometric nitrite sensor.
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Affiliation(s)
- Yann Astier
- Inorganic Chemistry Laboratory, University of Oxford, UK
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10
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Wijma HJ, Macpherson I, Alexandre M, Diederix REM, Canters GW, Murphy MEP, Verbeet MP. A Rearranging Ligand Enables Allosteric Control of Catalytic Activity in Copper-containing Nitrite Reductase. J Mol Biol 2006; 358:1081-93. [PMID: 16574144 DOI: 10.1016/j.jmb.2006.02.042] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2005] [Revised: 02/13/2006] [Accepted: 02/15/2006] [Indexed: 11/26/2022]
Abstract
In Cu-containing nitrite reductase from Alcaligenes faecalis S-6 the axial methionine ligand of the type-1 site was replaced (M150G) to make the copper ion accessible to external ligands that might affect the enzyme's catalytic activity. The type-1 site optical spectrum of M150G (A(460)/A(600)=0.71) differs significantly from that of the native nitrite reductase (A(460)/A(600)=1.3). The midpoint potential of the type-1 site of nitrite reductase M150G (E(M)=312(+/-5)mV versus hydrogen) is higher than that of the native enzyme (E(M)=213(+/-5)mV). M150G has a lower catalytic activity (k(cat)=133(+/-6)s(-1)) than the wild-type nitrite reductase (k(cat)=416(+/-10)s(-1)). The binding of external ligands to M150G restores spectral properties, midpoint potential (E(M)<225mV), and catalytic activity (k(cat)=374(+/-28)s(-1)). Also the M150H (A(460)/A(600)=7.7, E(M)=104(+/-5)mV, k(cat)=0.099(+/-0.006)s(-1)) and M150T (A(460)/A(600)=0.085, E(M)=340(+/-5)mV, k(cat)=126(+/-2)s(-1)) variants were characterized. Crystal structures show that the ligands act as allosteric effectors by displacing Met62, which moves to bind to the Cu in the position emptied by the M150G mutation. The reconstituted type-1 site has an otherwise unaltered geometry. The observation that removal of an endogenous ligand can introduce allosteric control in a redox enzyme suggests potential for structural and functional flexibility of copper-containing redox sites.
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Affiliation(s)
- Hein J Wijma
- Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands
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11
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12
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Dennison C. Ligand and loop variations at type 1 copper sites: influence on structure and reactivity. Dalton Trans 2005:3436-42. [PMID: 16234922 DOI: 10.1039/b507440c] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Type 1 (T1) copper sites promote biological electron transfer and are found in the cupredoxins and a number of copper-containing enzymes including the multi-copper oxidases. A T1 copper site usually has a distorted tetrahedral geometry with strong ligands provided by the thiolate sulfur of a Cys and the imidazole nitrogens of two His residues. The active site structure is typically completed by a weak axial Met ligand (a second weak axial interaction is found in azurin resulting in a trigonal bipyramidal geometry). The axial Met is not conserved and Gln, Phe, Leu and Val are also found in this position. Three of the four ligands at a T1 copper site are situated on a single C-terminal loop whose length and structure varies. Studies are discussed which investigate both the influence of physiologically relevant axial ligand alterations, and also of mutations to the length and structure of the ligand-containing loop, on the properties of T1 copper sites.
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Affiliation(s)
- Christopher Dennison
- Institute for Cell and Molecular Biosciences, Medical School, University of Newcastle upon Tyne, Newcastle upon Tyne, UK NE2 4HH.
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13
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Kataoka K, Yamaguchi K, Kobayashi M, Mori T, Bokui N, Suzuki S. Structure-based Engineering of Alcaligenes xylosoxidans Copper-containing Nitrite Reductase Enhances Intermolecular Electron Transfer Reaction with Pseudoazurin. J Biol Chem 2004; 279:53374-8. [PMID: 15475344 DOI: 10.1074/jbc.m410198200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The intermolecular electron transfer from Achromobacter cycloclastes pseudoazurin (AcPAZ) to wild-type and mutant Alcaligenes xylosoxidans nitrite reductases (AxNIRs) was investigated using steady-state kinetics and electrochemical methods. The affinity and the electron transfer reaction constant (k(ET)) are considerably lower between AcPAZ and AxNIR (K(m) = 1.34 mM and k(ET) = 0.87 x 10(5) M(-1) s(-1)) than between AcPAZ and its cognate nitrite reductase (AcNIR) (K(m) = 20 microM and k(ET) = 7.3 x 10(5) M(-1) s(-1)). A negatively charged hydrophobic patch, comprising seven acidic residues around the type 1 copper site in AcNIR, is the site of protein-protein interaction with a positively charged hydrophobic patch on AcPAZ. In AxNIR, four of the negatively charged residues (Glu-112, Glu-133, Glu-195, and Asp-199) are conserved at the corresponding positions of AcNIR, whereas the other three residues are not acidic amino acids but neutral amino acids (Ala-83, Ala-191, and Gly-198). Seven mutant AxNIRs with additional negatively charged residues surrounding the hydrophobic patch of AxNIR (A83D, A191E, G198E, A83D/A191E, A93D/G198E, A191E/G198E, and A83D/A191E/G198E) were prepared to enhance the specificity of the electron transport reaction between AcPAZ and AxNIR. The k(ET) values of these mutants become progressively larger as the number of mutated residues increases. The K(m) and k(ET) values of A83D/A191E/G198E (K(m) = 88 microM and k(ET) = 4.1 x 10(5) M(-1) s(-1)) are 15-fold smaller and 4.7-fold larger than those of wild-type AxNIR, respectively. These results suggest that the introduction of negatively charged residues into the docking surface of AxNIR facilitates both the formation of electron transport complex and the electron transfer reaction.
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Affiliation(s)
- Kunishige Kataoka
- Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa 920-1192, Japan
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14
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Kataoka K, Yamaguchi K, Sakai S, Takagi K, Suzuki S. Characterization and function of Met150Gln mutant of copper-containing nitrite reductase from Achromobacter cycloclastes IAM1013. Biochem Biophys Res Commun 2003; 303:519-24. [PMID: 12659849 DOI: 10.1016/s0006-291x(03)00381-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The mutant (M150Q-NIR) replacing the Met150 ligand of the type 1 Cu center in Achromobacter cycloclastes nitrite reductase (AcNIR) with Gln has been physicochemically and functionally characterized. The electronic absorption and CD spectra of M150Q-NIR are similar to those of mavicyanin and stellacyanin having the 2His, Cys, and Gln ligands, but the EPR signal has an axial character, although their blue copper proteins show rhombic EPR signals. The mutant has about 80% catalytic activity of AcNIR. Moreover, the midpoint potential (E(1/2)) of M150Q-NIR is +113 mV vs. NHE at pH 7.0, being negatively shifted compared to that of AcNIR (+240 mV). Although the intermolecular electron-transfer process from Achromobacter cycloclastes pseudoazurin (pAz) to M150Q-NIR was not detected, the pAz mutant (M86Q-pAz) replacing the Met86 ligand with Gln transfers one electron to the NIR mutant with an intermolecular electron-transfer rate constant (k(ET)) of 2.3 x 10(5)M(-1)s(-1).
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Affiliation(s)
- Kunishige Kataoka
- Department of Chemistry, Faculty of Science, Kanazawa University, Kakuma, Kanazawa 920-1192, Japan
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