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Fatima S, Olshansky L. Conformational control over proton-coupled electron transfer in metalloenzymes. Nat Rev Chem 2024; 8:762-775. [PMID: 39223400 DOI: 10.1038/s41570-024-00646-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/29/2024] [Indexed: 09/04/2024]
Abstract
From the reduction of dinitrogen to the oxidation of water, the chemical transformations catalysed by metalloenzymes underlie global geochemical and biochemical cycles. These reactions represent some of the most kinetically and thermodynamically challenging processes known and require the complex choreography of the fundamental building blocks of nature, electrons and protons, to be carried out with utmost precision and accuracy. The rate-determining step of catalysis in many metalloenzymes consists of a protein structural rearrangement, suggesting that nature has evolved to leverage macroscopic changes in protein molecular structure to control subatomic changes in metallocofactor electronic structure. The proton-coupled electron transfer mechanisms operative in nitrogenase, photosystem II and ribonucleotide reductase exemplify this interplay between molecular and electronic structural control. We present the culmination of decades of study on each of these systems and clarify what is known regarding the interplay between structural changes and functional outcomes in these metalloenzyme linchpins.
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Affiliation(s)
- Saman Fatima
- Department of Chemistry, College of Liberal Arts and Sciences, University of Illinois Urbana-Champaign, Urbana, IL, USA
| | - Lisa Olshansky
- Department of Chemistry, College of Liberal Arts and Sciences, University of Illinois Urbana-Champaign, Urbana, IL, USA.
- Center for Biophysics and Quantitative Biology, University of Illinois Urbana-Champaign, Urbana, IL, USA.
- Materials Research Laboratory, The Grainger College of Engineering, University of Illinois Urbana-Champaign, Urbana, IL, USA.
- The Beckman Institute for Advanced Science and Technology, University of Illinois Urbana-Champaign, Urbana, IL, USA.
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2
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Griffin PJ, Charette BJ, Burke JH, Vura-Weis J, Schaller RD, Gosztola DJ, Olshansky L. Toward Improved Charge Separation through Conformational Control in Copper Coordination Complexes. J Am Chem Soc 2022; 144:12116-12126. [PMID: 35762527 DOI: 10.1021/jacs.2c02580] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The continued development of solar energy as a renewable resource necessitates new approaches to sustaining photodriven charge separation (CS). We present a bioinspired approach in which photoinduced conformational rearrangements at a ligand are translated into changes in coordination geometry and environment about a bound metal ion. Taking advantage of the differential coordination properties of CuI and CuII, these dynamics aim to facilitate intramolecular electron transfer (ET) from CuI to the ligand to create a CS state. The synthesis and photophysical characterization of CuCl(dpaaR) (dpaa = dipicolylaminoacetophenone, with R = H and OMe) are presented. These ligands incorporate a fluorophore that gives rise to a twisted intramolecular charge transfer (TICT) excited state. Excited-state ligand twisting provides a tetragonal coordination geometry capable of capturing CuII when an internal ortho-OMe binding site is present. NMR, IR, electron paramagnetic resonance (EPR), and optical spectroscopies, X-ray diffraction, and electrochemical methods establish the ground-state properties of these CuI and CuII complexes. The photophysical dynamics of the CuI complexes are explored by time-resolved photoluminescence and optical transient absorption spectroscopies. Relative to control complexes lacking a TICT-active ligand, the lifetimes of CS states are enhanced ∼1000-fold. Further, the presence of the ortho-OMe substituent greatly enhances the lifetime of the TICT* state and biases the coordination environment toward CuII. The presence of CuI decreases photoinduced degradation from 14 to <2% but does not result in significant quenching via ET. Factors affecting CS in these systems are discussed, laying the groundwork for our strategy toward solar energy conversion.
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Affiliation(s)
- Paul J Griffin
- Department of Chemistry, University of Illinois Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United States
| | - Bronte J Charette
- Department of Chemistry, University of Illinois Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United States
| | - John H Burke
- Department of Chemistry, University of Illinois Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United States
| | - Josh Vura-Weis
- Department of Chemistry, University of Illinois Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United States
| | - Richard D Schaller
- Center for Nanoscale Materials, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - David J Gosztola
- Center for Nanoscale Materials, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Lisa Olshansky
- Department of Chemistry, University of Illinois Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United States
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3
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Properties Assessment by Quantum Mechanical Calculations for Azulenes Substituted with Thiophen– or Furan–Vinyl–Pyridine. Symmetry (Basel) 2022. [DOI: 10.3390/sym14020354] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
In this paper, azulenes substituted with thiophen– or furan–vinyl–pyridine are reported as heavy metal ligands in systems based on chemically modified electrodes. We undertook a computational study of their structures using density functional theory (DFT). Based on these computations, we obtained properties and key molecular descriptors related to chemical reactivity and electrochemical behavior. We investigated the correlation between some quantum parameters associated with the chemical reactivity and the complexing properties of the modified electrodes based on these ligands. The best correlations for the parameters were retained. We showed that the linear correlation between DFT-computed HOMO/LUMO energies and experimental redox potentials is very good.
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Tilly DP, Cullen W, Zhong H, Jamagne R, Vitórica-Yrezábal I, Webb SJ. α-Amino-iso-butyric acid foldamers terminated with rhodium(I) N-heterocyclic carbene catalysts. Chemistry 2021; 28:e202104293. [PMID: 34932229 PMCID: PMC9305545 DOI: 10.1002/chem.202104293] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Indexed: 12/01/2022]
Abstract
To investigate how remotely induced changes in ligand folding might affect catalysis by organometallic complexes, dynamic α‐amino‐iso‐butyric acid (Aib) peptide foldamers bearing rhodium(I) N‐heterocyclic carbene (NHC) complexes have been synthesized and studied. X‐ray crystallography of a foldamer with an N‐terminal azide and a C‐terminal Rh(NHC)(Cl)(diene) complex showed a racemate with a chiral axis in the Rh(NHC) complex and a distorted 310 helical body. Replacing the azide with either one or two chiral L‐α‐methylvaline (L‐αMeVal) residues gave diastereoisomeric foldamers that each possessed point, helical and axial chirality. NMR spectroscopy revealed an unequal ratio of diastereoisomers for some foldamers, indicating that the chiral conformational preference of the N‐terminal residue(s) was relayed down the 1 nm helical body to the axially chiral Rh(NHC) complex. Although the remote chiral residue(s) did not affect the stereoselectivity of hydrosilylation reactions catalysed by these foldamers, these studies suggest a potential pathway towards remote conformational control of organometallic catalysts.
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Affiliation(s)
- David P Tilly
- The University of Manchester, Department of Chemistry, UNITED KINGDOM
| | - William Cullen
- The University of Manchester, Department of Chemistry, UNITED KINGDOM
| | - Heng Zhong
- The University of Manchester, Department of Chemistry, UNITED KINGDOM
| | - Romain Jamagne
- The University of Manchester, Department of Chemistry, UNITED KINGDOM
| | | | - Simon John Webb
- University of Manchester, School of Chemistry and MIB, 131 Princess St, M1 7DN, Manchester, UNITED KINGDOM
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5
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Conrad KS, Jordan CD, Brown KL, Brunold TC. Spectroscopic and Computational Studies of Cobalamin Species with Variable Lower Axial Ligation: Implications for the Mechanism of Co–C Bond Activation by Class I Cobalamin-Dependent Isomerases. Inorg Chem 2015; 54:3736-47. [DOI: 10.1021/ic502665x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Karen S. Conrad
- Department
of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Christopher D. Jordan
- Department
of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Kenneth L. Brown
- Department of Chemistry and Biochemistry, Ohio University, Athens, Ohio 45701, United States
| | - Thomas C. Brunold
- Department
of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
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Barcena HS, Liu B, Mirkin MV, Canary JW. An electrochiroptical molecular switch: mechanistic and kinetic studies. Inorg Chem 2006; 44:7652-60. [PMID: 16212392 DOI: 10.1021/ic051048m] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Previously, we reported the synthesis and preliminary characterization of Cu(I/II) complexes of N,N-bis(2-quinilylmethyl)-(l)-methionine (Zahn, S.; Canary, J. W. Science 2000, 288, 1404-7). The chemically oxidized and reduced forms of the complexes gave nearly mirror image circular dichroism (CD) spectra as a result of reorganization of the inner coordination sphere of the copper atom. The reorganization involved exchange of oxygen for sulfur in proceeding from the Cu(II) to Cu(I) oxidation state and corresponding ligand conformational changes required to accommodate this exchange. In this paper, we demonstrate that the complex can be triggered by electrochemical means. The electrochemical and stereochemical details of the redox-induced ligand reorganization were probed by independent synthesis of alternative chemical intermediates, CD spectroelectrochemistry, curve fitting of cyclic voltammograms, CD titration, and scanning electrochemical microscopy (SECM). A square-type mechanism was most consistent with the data: the Cu(II) complex is reduced followed by a ligand reorganization step to give the stable reduced form of the complex. The Cu(I) complex is then oxidized in a fast step followed by another ligand reorganization. A millisecond time scale rate was found by SECM for one of the key conformational conversion steps.
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Affiliation(s)
- Homar S Barcena
- Department of Chemistry, New York University, New York, New York 10003, USA
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Affiliation(s)
- David B Rorabacher
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA.
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8
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Li S, McGrath DV. Effect of Macromolecular Isomerism on the Photomodulation of Dendrimer Properties. J Am Chem Soc 2000. [DOI: 10.1021/ja0015085] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Affiliation(s)
- Sheng Li
- Department of Chemistry, University of Arizona Tucson, Arizona 85721
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Andrews ER, Pratt JM, Brown KL. Molecular recognition in the binding of vitamin B12 by the cobalamin-specific Intrinsic Factor. FEBS Lett 1991; 281:90-2. [PMID: 2015914 DOI: 10.1016/0014-5793(91)80365-a] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Equilibrium constants (given as log K/M-1) have been determined at pH 7.4 and 4 degrees C for binding by porcine Intrinsic Factor (B12-binding protein from the gut, specific for the 'cobalamin' series of Co corrinoids) of vitamin B12 or cyanocobalamin (10.5), cyanocobinamide, alpha-ribazole and alpha-ribazole-phosphate (main fragments produced by cleaving off the 'cobalamin' side-chain, all less than or equal to 3), and cyanocobinamide in the presence of greater than or equal to 10(-9) M ribazole (5.6 and independent of ribazole concentration), i.e. ribazole catalyses the binding of the cobinamide. It is proposed that the specificity of Intrinsic Factor for the cobalamins depends on the presence of the ribazole fragment in the cobalamin side-chain to promote an essential change in conformation before the corrinoid fragment can be bound.
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Affiliation(s)
- E R Andrews
- Department of Chemistry, University of Surrey, Guildford, UK
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Miller MA, Coletta M, Mauro JM, Putnam LD, Farnum MF, Kraut J, Traylor TG. CO recombination in cytochrome c peroxidase: effect of the local heme environment on CO binding explored through site-directed mutagenesis. Biochemistry 1990; 29:1777-91. [PMID: 2158813 DOI: 10.1021/bi00459a017] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
CO recombination to the cloned cytochrome c peroxidase [CCP(MI)] and mutants of CCP(MI) prepared by site-directed mutagenesis was examined as a function of pH by flash photolysis. The mutants examined included distal Arg 48----Leu, Lys; proximal Asp 235----Asn; and His 181----Gly. At alkaline pH, ferrous CCP(MI) was converted to a hexacoordinate form by a cooperative two-proton ionization, apparent pK(a) = 8.0. This change was observed in all of the mutants, although in the His 181----Gly mutant, the conversion to the hexacoordinate form was the result of a single-proton ionization, implicating His 181 as one of the two residues deprotonated in this isomerization. The pH-dependent conversion of CO ferrous CCP(MI) from acidic to alkaline forms was also observed and was similar to that reported for cytochrome c peroxidase from bakers' yeast [Iizuka, T., Makino, R., Ishimura, Y., & Yonetani, T. (1985) J. Biol. Chem. 260, 1407-1412]. Photolysis of the acidic form of the CO complex of CCP(MI) produces a kinetic form of the ferrous enzyme (form A) which exhibits the slow rate of CO recombination (l1' approximately 10(3) M-1 s-1) characteristic of peroxidases, while photolysis of the alkaline form of the CO complex produces a second kinetic form (form B), which exhibits a much faster rate of recombination (l2' approximately 10(5) M-1 s-1). Kinetic forms analogous to forms A and B were observed in all of the mutants examined. A third kinetic form (form B*) with a bimolecular rate constant l3' approximately 10(6) M-1 s-1 was also observed in the mutants at alkaline pH. Although the pH dependence for the conversion of form A to form B with increasing pH was altered by changes in the local heme environment, the rate of CO recombination by the respective forms was not dramatically altered in the mutants. Transient spectra of the reaction of CO with ferrous CCP(MI) after photolysis show that equilibrium between penta- and hexacoordinate ferrous enzyme is rapid relative to CO recombination. The presence of the internal sixth ligand has no discernible effect on the observed rate of recombination, however. The results presented indicate that in CCP(MI) the rate of ligand binding is determined primarily by isomerization of the protein from a closed conformation at acidic pH to an open conformation at alkaline pH and that polar effects of proximal Asp 235 and distal Arg 48 are of minor significance in the rate of CO recombination in both conformations.
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Affiliation(s)
- M A Miller
- Department of Chemistry, University of California, San Diego, La Jolla 92093
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