1
|
Guo H, Liu S, Liu X, Zhang L. Lightening flavin by amination for fluorescent sensing. Phys Chem Chem Phys 2024; 26:19554-19563. [PMID: 38979978 DOI: 10.1039/d4cp01525h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/10/2024]
Abstract
Monitoring of reactive oxygen species (ROS), such as O2˙-, etc., in organisms is of great significance, not only for their essential role in biological processes, but their excessive production may also result in many diseases. Flavin (FL) is a fluorophore that naturally exists in flavoenzymes, and its fluorescent emission (FE) becomes negligible when reduced. This enables the application of FL derivatives as fluorescent sensors for ROS. We presented a theoretical investigation to address the impact of amino substitution on the photophysical properties of aminoflavins (AmFLs). Resulting from the interplay of electronic and positional effects, amination at C8 enhances the electronic coupling between the ground state and the first singlet excited state by enlarging the adiabatic energy change of the electronic transitions and the emission transition dipole moments, weakens the vibronic coupling by decreasing the contribution of isoalloxazine to the frontier molecular orbitals, redshifts the absorption band, and enhances the fluorescent emission drastically in 8AmFL. The theoretically estimated fluorescent emission intensity of 8AmFL is ∼40 times that of FL, suggesting its potential application as a fluorescent sensor.
Collapse
Affiliation(s)
- Huimin Guo
- School of Chemistry, Dalian University of Technology, No. 2, Linggong Road, Dalian, 116024, P. R. China.
| | - Siyu Liu
- School of Chemistry, Dalian University of Technology, No. 2, Linggong Road, Dalian, 116024, P. R. China.
| | - Xin Liu
- School of Chemistry, Dalian University of Technology, No. 2, Linggong Road, Dalian, 116024, P. R. China.
| | - Lijun Zhang
- Department of Ophthalmology, The Third People's Hospital of Dalian and Faculty of Medicine, Dalian University of Technology, No. 2, Linggong Road, Dalian, 116024, P. R. China
| |
Collapse
|
2
|
Wang J, Liu Y. Systematic Theoretical Study on the pH-Dependent Absorption and Fluorescence Spectra of Flavins. Molecules 2023; 28:molecules28083315. [PMID: 37110549 PMCID: PMC10146991 DOI: 10.3390/molecules28083315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Revised: 03/29/2023] [Accepted: 04/07/2023] [Indexed: 04/29/2023] Open
Abstract
Flavins are a class of organic compounds with the basic structure of 7,8-dimethy-10-alkyl isoalloxazine. They are ubiquitous in nature and participate in many biochemical reactions. Due to various existing forms, there is a lack of systematic research on the absorption and fluorescence spectra of flavins. In this study, employing the density functional theory (DFT) and time-dependent (TD) DFT, we calculated the pH-dependent absorption and fluorescence spectra of flavin of three redox states (quinone, semiquinone, and hydroquinone) in solvents. The chemical equilibrium of three redox states of flavins and the pH effect on the absorption spectra and fluorescence spectra of flavins were carefully discussed. The conclusion helps with identifying the existing forms of flavins in solvent with different pH values.
Collapse
Affiliation(s)
- Jinyu Wang
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Yajun Liu
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China
- Center for Advanced Materials Research, Beijing Normal University, Zhuhai 519087, China
| |
Collapse
|
3
|
Curtolo F, Arantes GM. Molecular properties and tautomeric equilibria of isolated flavins. J Comput Chem 2022; 43:1561-1572. [PMID: 35778728 DOI: 10.1002/jcc.26957] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Accepted: 06/09/2022] [Indexed: 11/05/2022]
Abstract
Flavins are employed as redox cofactors and chromophores in a plethora of flavoenzymes. Their versatility is an outcome of intrinsic molecular properties of the isoalloxazine ring modulated by the protein scaffold and surrounding solvent. Thus, an investigation of isolated flavins with high-level electronic-structure methods and with error assessment of the calculated properties will contribute to building better models of flavin reactivity. Here, we benchmarked ground-state properties such as electron affinity, gas-phase basicity, dipole moment, torsion energy, and tautomer stability for lumiflavins in all biologically relevant oxidation and charge states. Overall, multiconfigurational effects are small and chemical accuracy is achieved by coupled-cluster treatments of energetic properties. Augmented basis sets and extrapolations to the complete basis-set limit are necessary for consistent agreement with experimental energetics. Among DFT functionals tested, M06-2X shows the best performance for most properties, except gas-phase basicity, in which M06 and CAM-B3LYP perform better. Moreover, dipole moments of radical flavins show large deviations for all functionals studied. Tautomers with noncanonical protonation states are significantly populated at normal temperatures, adding to the complexity of modeling flavins. These results will guide future computational studies of flavoproteins and flavin chemistry by indicating the limitations of electronic-structure methodologies and the contributions of multiple tautomeric states.
Collapse
Affiliation(s)
- Felipe Curtolo
- Department of Biochemistry, Instituto de Química, Universidade de São Paulo, São Paulo, SP, Brazil
| | - Guilherme M Arantes
- Department of Biochemistry, Instituto de Química, Universidade de São Paulo, São Paulo, SP, Brazil
| |
Collapse
|
4
|
Understanding flavin electronic structure and spectra. WIRES COMPUTATIONAL MOLECULAR SCIENCE 2022. [DOI: 10.1002/wcms.1541] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
|
5
|
Kar RK, Chasen S, Mroginski MA, Miller AF. Tuning the Quantum Chemical Properties of Flavins via Modification at C8. J Phys Chem B 2021; 125:12654-12669. [PMID: 34784473 DOI: 10.1021/acs.jpcb.1c07306] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Flavins are central to countless enzymes but display different reactivities depending on their environments. This is understood to reflect modulation of the flavin electronic structure. To understand changes in orbital natures, energies, and correlation over the ring system, we begin by comparing seven flavin variants differing at C8, exploiting their different electronic spectra to validate quantum chemical calculations. Ground state calculations replicate a Hammett trend and reveal the significance of the flavin π-system. Comparison of higher-level theories establishes CC2 and ACD(2) as methods of choice for characterization of electronic transitions. Charge transfer character and electron correlation prove responsive to the identity of the substituent at C8. Indeed, bond length alternation analysis demonstrates extensive conjugation and delocalization from the C8 position throughout the ring system. Moreover, we succeed in replicating a particularly challenging UV/Vis spectrum by implementing hybrid QM/MM in explicit solvents. Our calculations reveal that the presence of nonbonding lone pairs correlates with the change in the UV/Vis spectrum observed when the 8-methyl is replaced by NH2, OH, or SH. Thus, our computations offer routes to understanding the spectra of flavins with different modifications. This is a first step toward understanding how the same is accomplished by different binding environments.
Collapse
Affiliation(s)
- Rajiv K Kar
- Faculty II-Mathematics and Natural Sciences, Technische Universität Berlin, Sekr. PC 14, Strasse des 17. Juni 135, D-10623 Berlin, Germany
| | - Sam Chasen
- Department of Chemistry, University of Kentucky, Lexington, Kentucky 40506, United States
| | - Maria-Andrea Mroginski
- Faculty II-Mathematics and Natural Sciences, Technische Universität Berlin, Sekr. PC 14, Strasse des 17. Juni 135, D-10623 Berlin, Germany
| | - Anne-Frances Miller
- Faculty II-Mathematics and Natural Sciences, Technische Universität Berlin, Sekr. PC 14, Strasse des 17. Juni 135, D-10623 Berlin, Germany.,Department of Chemistry, University of Kentucky, Lexington, Kentucky 40506, United States
| |
Collapse
|
6
|
Dozova N, Lacombat F, Lombard M, Hamdane D, Plaza P. Ultrafast dynamics of fully reduced flavin in catalytic structures of thymidylate synthase ThyX. Phys Chem Chem Phys 2021; 23:22692-22702. [PMID: 34605505 DOI: 10.1039/d1cp03379d] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Thymidylate is a vital DNA precursor synthesized by thymidylate synthases. ThyX is a flavin-dependent thymidylate synthase found in several human pathogens and absent in humans, which makes it a potential target for antimicrobial drugs. This enzyme methylates the 2'-deoxyuridine 5'-monophosphate (dUMP) to 2'-deoxythymidine 5'-monophosphate (dTMP) using a reduced flavin adenine dinucleotide (FADH-) as prosthetic group and (6R)-N5,N10-methylene-5,6,7,8-tetrahydrofolate (CH2THF) as a methylene donor. Recently, it was shown that ThyX-catalyzed reaction is a complex process wherein FADH- promotes both methylene transfer and reduction of the transferred methylene into a methyl group. Here, we studied the dynamic and photophysics of FADH- bound to ThyX, in several substrate-binding states (no substrate, in the presence of dUMP or folate or both) by femtosecond transient absorption spectroscopy. This methodology provides valuable information about the ground-state configuration of the isoalloxazine moiety of FADH- and the rigidity of its local environment, through spectra shape and excited-state lifetime parameters. In the absence of substrate, the environment of FADH- in ThyX is only mildly more constrained than that of free FADH- in solution. The addition of dUMP however narrows the distribution of ground-state configurations and increases the constraints on the butterfly bending motion in the excited state. Folate binding results in the selection of new ground-state configurations, presumably located at a greater distance from the conical intersection where excited-state decay occurs. When both substrates are present, the ground-state configuration appears on the contrary rather limited to a geometry close to the conical intersection, which explains the relatively fast excited-state decay (100 ps on the average), even if the environment of the isoalloxazine is densely packed. Hence, although the environment of the flavin is dramatically constrained, FADH- retains a dynamic necessary to shuttle carbon from folate to dUMP. Our study demonstrates the high sensitivity of FADH- photophysics to the constraints exerted by its immediate surroundings.
Collapse
Affiliation(s)
- Nadia Dozova
- PASTEUR, Département de chimie, École normale supérieure, PSL University, Sorbonne Université, CNRS, 75005 Paris, France.
| | - Fabien Lacombat
- PASTEUR, Département de chimie, École normale supérieure, PSL University, Sorbonne Université, CNRS, 75005 Paris, France.
| | - Murielle Lombard
- Laboratoire de Chimie des Processus Biologiques, CNRS-UMR 8229, Collège de France, Sorbonne Université, 75005 Paris, France.
| | - Djemel Hamdane
- Laboratoire de Chimie des Processus Biologiques, CNRS-UMR 8229, Collège de France, Sorbonne Université, 75005 Paris, France.
| | - Pascal Plaza
- PASTEUR, Département de chimie, École normale supérieure, PSL University, Sorbonne Université, CNRS, 75005 Paris, France.
| |
Collapse
|
7
|
Dratch BD, Orozco-Gonzalez Y, Gadda G, Gozem S. Ionic Atmosphere Effect on the Absorption Spectrum of a Flavoprotein: A Reminder to Consider Solution Ions. J Phys Chem Lett 2021; 12:8384-8396. [PMID: 34435784 DOI: 10.1021/acs.jpclett.1c02173] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
This study utilizes the FMN-dependent NADH:quinone oxidoreductase from Pseudomonas aeruginosa PAO1 to investigate the effect of introducing an active site negative charge on the flavin absorption spectrum both in the absence and presence of a long-range electrostatic potential coming from solution ions. There were no observed changes in the flavin UV-visible spectrum when an active site tyrosine (Y277) becomes deprotonated in vitro. These results could only be reproduced computationally using average solvent electrostatic configuration (ASEC) QM/MM simulations that include both positive and negative solution ions. The same calculations performed with minimal ions to neutralize the total protein charge predicted that deprotonating Y277 would significantly alter the flavin absorption spectrum. Analyzing the distribution of solution ions indicated that the ions reorganize around the protein surface upon Y277 deprotonation to cancel the effect of the tyrosinate on the flavin absorption spectrum. Additional biochemical experiments were performed to test this hypothesis.
Collapse
Affiliation(s)
- Benjamin D Dratch
- Department of Chemistry, Georgia State University, Atlanta, Georgia 30302, United States
| | | | - Giovanni Gadda
- Department of Chemistry, Georgia State University, Atlanta, Georgia 30302, United States
- Department of Biology, Georgia State University, Atlanta, Georgia 30302, United States
- Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia 30302, United States
| | - Samer Gozem
- Department of Chemistry, Georgia State University, Atlanta, Georgia 30302, United States
| |
Collapse
|
8
|
Iyer A, Reis RAG, Gannavaram S, Momin M, Spring-Connell AM, Orozco-Gonzalez Y, Agniswamy J, Hamelberg D, Weber IT, Gozem S, Wang S, Germann MW, Gadda G. A Single-Point Mutation in d-Arginine Dehydrogenase Unlocks a Transient Conformational State Resulting in Altered Cofactor Reactivity. Biochemistry 2021; 60:711-724. [PMID: 33630571 DOI: 10.1021/acs.biochem.1c00054] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Proteins are inherently dynamic, and proper enzyme function relies on conformational flexibility. In this study, we demonstrated how an active site residue changes an enzyme's reactivity by modulating fluctuations between conformational states. Replacement of tyrosine 249 (Y249) with phenylalanine in the active site of the flavin-dependent d-arginine dehydrogenase yielded an enzyme with both an active yellow FAD (Y249F-y) and an inactive chemically modified green FAD, identified as 6-OH-FAD (Y249F-g) through various spectroscopic techniques. Structural investigation of Y249F-g and Y249F-y variants by comparison to the wild-type enzyme showed no differences in the overall protein structure and fold. A closer observation of the active site of the Y249F-y enzyme revealed an alternative conformation for some active site residues and the flavin cofactor. Molecular dynamics simulations probed the alternate conformations observed in the Y249F-y enzyme structure and showed that the enzyme variant with FAD samples a metastable conformational state, not available to the wild-type enzyme. Hybrid quantum/molecular mechanical calculations identified differences in flavin electronics between the wild type and the alternate conformation of the Y249F-y enzyme. The computational studies further indicated that the alternate conformation in the Y249F-y enzyme is responsible for the higher spin density at the C6 atom of flavin, which is consistent with the formation of 6-OH-FAD in the variant enzyme. The observations in this study are consistent with an alternate conformational space that results in fine-tuning the microenvironment around a versatile cofactor playing a critical role in enzyme function.
Collapse
Affiliation(s)
- Archana Iyer
- Department of Chemistry, Georgia State University, Atlanta, Georgia 30302, United States
| | - Renata A G Reis
- Department of Chemistry, Georgia State University, Atlanta, Georgia 30302, United States
| | - Swathi Gannavaram
- Department of Chemistry, Georgia State University, Atlanta, Georgia 30302, United States
| | - Mohamed Momin
- Department of Chemistry, Georgia State University, Atlanta, Georgia 30302, United States
| | | | | | - Johnson Agniswamy
- Department of Biology, Georgia State University, Atlanta, Georgia 30302, United States
| | - Donald Hamelberg
- Department of Chemistry, Georgia State University, Atlanta, Georgia 30302, United States
| | - Irene T Weber
- Department of Chemistry, Georgia State University, Atlanta, Georgia 30302, United States.,Department of Biology, Georgia State University, Atlanta, Georgia 30302, United States
| | - Samer Gozem
- Department of Chemistry, Georgia State University, Atlanta, Georgia 30302, United States
| | - Siming Wang
- Department of Chemistry, Georgia State University, Atlanta, Georgia 30302, United States
| | - Markus W Germann
- Department of Chemistry, Georgia State University, Atlanta, Georgia 30302, United States.,Department of Biology, Georgia State University, Atlanta, Georgia 30302, United States
| | - Giovanni Gadda
- Department of Chemistry, Georgia State University, Atlanta, Georgia 30302, United States.,Department of Biology, Georgia State University, Atlanta, Georgia 30302, United States.,Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia 30302, United States
| |
Collapse
|
9
|
Schwinn K, Ferré N, Huix-Rotllant M. UV-visible absorption spectrum of FAD and its reduced forms embedded in a cryptochrome protein. Phys Chem Chem Phys 2020; 22:12447-12455. [PMID: 32458897 DOI: 10.1039/d0cp01714k] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Cryptochromes are a class of flavoproteins proposed as candidates to explain magnetoreception of animals, plants and bacteria. The main hypothesis is that a biradical is formed upon blue-light absorption by flavin adenine dinucleotide (FAD). In a protein milieu, the oxidized form of FAD can be reduced, leading to four redox derivative forms: anionic and neutral semi-reduced radicals, and anionic and neutral fully reduced forms. All these forms have a characteristic electronic absorption spectrum, with a strong vibrational resolution. Here, we carried out a normal mode analysis at the electrostatic embedding QM/MM level of theory to compute the vibrationally resolved absorption spectra of the five redox forms of FAD embedded in a plant cryptochrome. We show that explicitly accounting for vibrational broadening contributions to electronic transitions is essential to reproduce the experimental spectra. In the case of the neutral radical form of FAD, the absorption spectrum is reproduced only if the presence of a tryptophan radical is considered.
Collapse
|
10
|
Mondal P, Schwinn K, Huix-Rotllant M. Impact of the redox state of flavin chromophores on the UV–vis spectra, redox and acidity constants and electron affinities. J Photochem Photobiol A Chem 2020. [DOI: 10.1016/j.jphotochem.2019.112164] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
|
11
|
Brisker-Klaiman D, Dreuw A. On the influence of dimerisation of lumiflavin in aqueous solution on its optical spectra – a quantum chemical study. Mol Phys 2019. [DOI: 10.1080/00268976.2019.1616843] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Daria Brisker-Klaiman
- Interdisciplinary Center for Scientific Computing, Heidelberg University, Heidelberg, Germany
| | - Andreas Dreuw
- Interdisciplinary Center for Scientific Computing, Heidelberg University, Heidelberg, Germany
| |
Collapse
|
12
|
Su D, Kabir MP, Orozco-Gonzalez Y, Gozem S, Gadda G. Fluorescence Properties of Flavin Semiquinone Radicals in Nitronate Monooxygenase. Chembiochem 2019; 20:1646-1652. [PMID: 30748074 DOI: 10.1002/cbic.201900016] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2019] [Indexed: 11/09/2022]
Abstract
Fluorescent cofactors like flavins can be exploited to probe their local environment with spatial and temporal resolution. Although the fluorescence properties of the oxidized and two-electron-reduced states of flavins have been studied extensively, this is not the case for the one-electron-reduced state. Both the neutral and anionic semiquinones have proven particularly challenging to examine, as they are unstable in solution and are transient, short-lived species in many catalytic cycles. Here, we report that the nitronate monooxygenase (NMO) from Pseudomonas aeruginosa PAO1 is capable of stabilizing both semiquinone forms anaerobically for hours, thus enabling us to study their spectroscopy in a constant protein environment. We found that in the active site of NMO, the anionic semiquinone exhibits no fluorescence, whereas the neutral semiquinone radical shows a relatively strong fluorescence, with a behavior that violates the Kasha-Vavilov rule. These fluorescence properties are discussed in the context of time-dependent density functional theory calculations, which reveal low-lying dark states in both systems.
Collapse
Affiliation(s)
- Dan Su
- Department of Chemistry, Georgia State University, 50 Decatur St. SE, Atlanta, GA, 30302, USA
| | - Mohammad Pabel Kabir
- Department of Chemistry, Georgia State University, 50 Decatur St. SE, Atlanta, GA, 30302, USA
| | - Yoelvis Orozco-Gonzalez
- Department of Chemistry, Georgia State University, 50 Decatur St. SE, Atlanta, GA, 30302, USA
| | - Samer Gozem
- Department of Chemistry, Georgia State University, 50 Decatur St. SE, Atlanta, GA, 30302, USA
| | - Giovanni Gadda
- Department of Chemistry, Georgia State University, 50 Decatur St. SE, Atlanta, GA, 30302, USA.,Department of Biology, Georgia State University, 100 Piedmond Ave., Atlanta, GA, 30303, USA.,Center for Diagnostics and Therapeutics, Georgia State University, P.O. Box 5090, Atlanta, GA, 30303, USA.,Center for Biotechnology and Drug Design, Georgia State University, Atlanta, GA, 30302, USA
| |
Collapse
|
13
|
Kabir MP, Orozco-Gonzalez Y, Gozem S. Electronic spectra of flavin in different redox and protonation states: a computational perspective on the effect of the electrostatic environment. Phys Chem Chem Phys 2019; 21:16526-16537. [DOI: 10.1039/c9cp02230a] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
This study discusses how UV/vis absorption spectra of flavin in different redox and protonation states are shifted by the nearby electrostatic microenvironment.
Collapse
Affiliation(s)
| | | | - Samer Gozem
- Department of Chemistry
- Georgia State University
- Atlanta
- USA
| |
Collapse
|
14
|
Kar RK, Borin VA, Ding Y, Matysik J, Schapiro I. Spectroscopic Properties of Lumiflavin: A Quantum Chemical Study. Photochem Photobiol 2018; 95:662-674. [DOI: 10.1111/php.13023] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Accepted: 09/05/2018] [Indexed: 12/24/2022]
Affiliation(s)
- Rajiv Kumar Kar
- Fritz Haber Center for Molecular Dynamics Research Institute of Chemistry Hebrew University of Jerusalem Jerusalem Israel
| | - Veniamin A. Borin
- Fritz Haber Center for Molecular Dynamics Research Institute of Chemistry Hebrew University of Jerusalem Jerusalem Israel
| | - Yonghong Ding
- Institute of Analytical Chemistry University of Leipzig Leipzig Germany
| | - Jörg Matysik
- Institute of Analytical Chemistry University of Leipzig Leipzig Germany
| | - Igor Schapiro
- Fritz Haber Center for Molecular Dynamics Research Institute of Chemistry Hebrew University of Jerusalem Jerusalem Israel
| |
Collapse
|
15
|
Initial excited state structural dynamics of lumiflavin upon ultraviolet excitation. J Photochem Photobiol A Chem 2018. [DOI: 10.1016/j.jphotochem.2018.06.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
|
16
|
Bull JN, Carrascosa E, Giacomozzi L, Bieske EJ, Stockett MH. Ion mobility action spectroscopy of flavin dianions reveals deprotomer-dependent photochemistry. Phys Chem Chem Phys 2018; 20:19672-19681. [PMID: 30014081 PMCID: PMC6063075 DOI: 10.1039/c8cp03244k] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Photo-induced proton transfer, deprotomer-dependent photochemistry, and intramolecular charge transfer in flavin anions are investigated using action spectroscopy.
The intrinsic optical properties and photochemistry of flavin adenine dinucleotide (FAD) dianions are investigated using a combination of tandem ion mobility spectrometry and action spectroscopy. Two principal isomers are observed, the more stable form being deprotonated on the isoalloxazine group and a phosphate (N-3,PO4 deprotomer), and the other on the two phosphates (PO4,PO4 deprotomer). Ion mobility data and electronic action spectra suggest that photo-induced proton transfer occurs from the isoalloxazine group to a phosphate group, converting the PO4,PO4 deprotomer to the N-3,PO4 deprotomer. Comparisons of the isomer selective action spectra of FAD dianions and flavin monoanions with solution spectra and gas-phase photodissociation action spectra suggests that solvation shifts the electronic absorption of the deprotonated isoalloxazine group to higher energy. This is interpreted as evidence for significant charge transfer in the lowest optical transition of deprotonated isoalloxazine. Overall, this work demonstrates that the site of deprotonation of flavin anions strongly affects their electronic absorptions and photochemistry.
Collapse
Affiliation(s)
- James N Bull
- School of Chemistry, University of Melbourne, Melbourne, VIC 3010, Australia
| | - Eduardo Carrascosa
- School of Chemistry, University of Melbourne, Melbourne, VIC 3010, Australia
| | | | - Evan J Bieske
- School of Chemistry, University of Melbourne, Melbourne, VIC 3010, Australia
| | - Mark H Stockett
- School of Chemistry, University of Melbourne, Melbourne, VIC 3010, Australia and Department of Physics, Stockholm University, Stockholm, Sweden.
| |
Collapse
|
17
|
Giacomozzi L, Kjær C, Langeland Knudsen J, Andersen LH, Brøndsted Nielsen S, Stockett MH. Absorption and luminescence spectroscopy of mass-selected flavin adenine dinucleotide mono-anions. J Chem Phys 2018; 148:214309. [PMID: 29884035 DOI: 10.1063/1.5024028] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
We report the absorption profile of isolated Flavin Adenine Dinucleotide (FAD) mono-anions recorded using photo-induced dissociation action spectroscopy. In this charge state, one of the phosphoric acid groups is deprotonated and the chromophore itself is in its neutral oxidized state. These measurements cover the first four optical transitions of FAD with excitation energies from 2.3 to 6.0 eV (210-550 nm). The S0 → S2 transition is strongly blue shifted relative to aqueous solution, supporting the view that this transition has a significant charge-transfer character. The remaining bands are close to their solution-phase positions. This confirms that the large discrepancy between quantum chemical calculations of vertical transition energies and solution-phase band maxima cannot be explained by solvent effects. We also report the luminescence spectrum of FAD mono-anions in vacuo. The gas-phase Stokes shift for S1 is 3000 cm-1, which is considerably larger than any previously reported for other molecular ions and consistent with a significant displacement of the ground and excited state potential energy surfaces. Consideration of the vibronic structure is thus essential for simulating the absorption and luminescence spectra of flavins.
Collapse
Affiliation(s)
- L Giacomozzi
- Department of Physics, Stockholm University, Stockholm, Sweden
| | - C Kjær
- Department of Physics and Astronomy, Aarhus University, Aarhus, Denmark
| | | | - L H Andersen
- Department of Physics and Astronomy, Aarhus University, Aarhus, Denmark
| | | | - M H Stockett
- Department of Physics, Stockholm University, Stockholm, Sweden
| |
Collapse
|
18
|
Pauszek RF, Kodali G, Siddiqui MSU, Stanley RJ. Overlapping Electronic States with Nearly Parallel Transition Dipole Moments in Reduced Anionic Flavin Can Distort Photobiological Dynamics. J Am Chem Soc 2016; 138:14880-14889. [PMID: 27686753 DOI: 10.1021/jacs.6b06449] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Chromophoric biomolecules are exploited as reporters of a diverse set of phenomena, acting as internal distance monitors, environment and redox sensors, and endogenous imaging probes. The extent to which they can be exploited is dependent on an accurate knowledge of their fundamental electronic properties. Arguably of greatest importance is a precise knowledge of the direction(s) of the absorption transition dipole moment(s) (TDMs) in the molecular frame of reference. Such is the case for flavins, fluorescent redox cofactors utilized for ground- and excited-state redox and photochemical processes. The directions of the TDMs in oxidized and semiquinone flavins were characterized decades ago, and the details of charge redistribution in these forms have also been studied by Stark spectroscopy. The electronic structure of the fully reduced hydroquinone anionic state, FlH-, however, has been the subject of unfounded assumptions and estimates about the number and direction of TDMs in FlH-, as well the electronic structure changes that occur upon light absorption. Here we have used Stark spectroscopy to measure the magnitude and direction of charge redistribution in FlH- upon optical excitation. These data were analyzed using TD-DFT calculations. The results show unequivocally that not one but two nearly orientation-degenerate electronic transitions are required to explain the 340-500 nm absorption spectral range, demolishing the commonly held assumption of a single transition. The difference dipole moments for these states show that electron density shifts toward the xylene ring for both transitions. These measurements force a reappraisal of previous studies that have used erroneous assumptions and unsubstantiated estimates of these quantities. The results put future optical studies of reduced flavins/flavoproteins on a firm photophysical footing.
Collapse
Affiliation(s)
- Raymond F Pauszek
- Department of Chemistry, Temple University , 250B Beury Hall, 1901 North 13th Street, Philadelphia, Pennsylvania 19122, United States
| | - Goutham Kodali
- Department of Chemistry, Temple University , 250B Beury Hall, 1901 North 13th Street, Philadelphia, Pennsylvania 19122, United States
| | - M Salim U Siddiqui
- Department of Chemistry, Temple University , 250B Beury Hall, 1901 North 13th Street, Philadelphia, Pennsylvania 19122, United States
| | - Robert J Stanley
- Department of Chemistry, Temple University , 250B Beury Hall, 1901 North 13th Street, Philadelphia, Pennsylvania 19122, United States
| |
Collapse
|
19
|
Karasulu B, Götze JP, Thiel W. Assessment of Franck-Condon Methods for Computing Vibrationally Broadened UV-vis Absorption Spectra of Flavin Derivatives: Riboflavin, Roseoflavin, and 5-Thioflavin. J Chem Theory Comput 2015; 10:5549-66. [PMID: 26583238 DOI: 10.1021/ct500830a] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We address the performance of the vertical and adiabatic Franck-Condon (VFC/AFC) approaches combined with time-independent or time-dependent (TI/TD) formalisms in simulating the one-photon absorption spectra of three flavin compounds with distinct structural features. Calculations were done in the gas phase and in two solvents (water, benzene) for which experimental reference measurements are available. We utilized the independent mode displaced harmonic oscillator model without or with frequency alteration (IMDHO/IMDHO-FA) and also accounted for Duschinsky mixing effects. In the initial validation on the first excited singlet state of riboflavin, the range-separated functionals, CAM-B3LYP and ωB97xD, showed the best performance, but B3LYP also gave a good compromise between peak positions and spectral topology. Large basis sets were not mandatory to obtain high-quality spectra for the selected systems. The presence of a symmetry plane facilitated the computation of vibrationally broadened spectra, since different FC variants yield similar results and the harmonic approximation holds rather well. Compared with the AFC approach, the VFC approach performed equally well or even better for all three flavins while offering several advantages, such as avoiding error-prone geometry optimization procedures on excited-state surfaces. We also explored the advantages of curvilinear displacements and of a Duschinsky treatment for the AFC spectra in cases when a rotatable group is present on the chromophore. Taken together, our findings indicate that the combination of the VFC approach with the TD formalism and the IMDHO-FA model offers the best overall performance.
Collapse
Affiliation(s)
- Bora Karasulu
- Max-Planck-Institut für Kohlenforschung , Kaiser-Wilhelm-Platz 1, 45470, Mülheim an der Ruhr, Germany
| | - Jan Philipp Götze
- Max-Planck-Institut für Kohlenforschung , Kaiser-Wilhelm-Platz 1, 45470, Mülheim an der Ruhr, Germany
| | - Walter Thiel
- Max-Planck-Institut für Kohlenforschung , Kaiser-Wilhelm-Platz 1, 45470, Mülheim an der Ruhr, Germany
| |
Collapse
|
20
|
Karasulu B, Thiel W. Photoinduced Intramolecular Charge Transfer in an Electronically Modified Flavin Derivative: Roseoflavin. J Phys Chem B 2014; 119:928-43. [DOI: 10.1021/jp506101x] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Bora Karasulu
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz
1, 45470, Mülheim, Germany
| | - Walter Thiel
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz
1, 45470, Mülheim, Germany
| |
Collapse
|
21
|
Tan C, Guo L, Ai Y, Li J, Wang L, Sancar A, Luo Y, Zhong D. Direct determination of resonance energy transfer in photolyase: structural alignment for the functional state. J Phys Chem A 2014; 118:10522-30. [PMID: 25000823 PMCID: PMC4234433 DOI: 10.1021/jp504349b] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
Photoantenna is essential to energy
transduction in photoinduced
biological machinery. A photoenzyme, photolyase, has a light-harvesting
pigment of methenyltetrahydrofolate (MTHF) that transfers its excitation
energy to the catalytic flavin cofactor FADH¯ to enhance DNA-repair
efficiency. Here we report our systematic characterization and direct
determination of the ultrafast dynamics of resonance energy transfer
from excited MTHF to three flavin redox states in E. coli photolyase by capturing the intermediates formed through the energy
transfer and thus excluding the electron-transfer quenching pathway.
We observed 170 ps for excitation energy transferring to the fully
reduced hydroquinone FADH¯, 20 ps to the fully oxidized FAD,
and 18 ps to the neutral semiquinone FADH•, and
the corresponding orientation factors (κ2) were determined
to be 2.84, 1.53 and 1.26, respectively, perfectly matching with our
calculated theoretical values. Thus, under physiological conditions
and over the course of evolution, photolyase has adopted the optimized
orientation of its photopigment to efficiently convert solar energy
for repair of damaged DNA.
Collapse
Affiliation(s)
- Chuang Tan
- Department of Physics, Department of Chemistry and Biochemistry, and Programs of Biophysics, Chemical Physics, and Biochemistry, The Ohio State University , 191 West Woodruff Avenue, Columbus, Ohio 43210, United States
| | | | | | | | | | | | | | | |
Collapse
|
22
|
Domratcheva T, Udvarhelyi A, Shahi ARM. Computational spectroscopy, dynamics, and photochemistry of photosensory flavoproteins. Methods Mol Biol 2014; 1146:191-228. [PMID: 24764094 DOI: 10.1007/978-1-4939-0452-5_10] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Extensive interest in photosensory proteins stimulated computational studies of flavins and flavoproteins in the past decade. This review is dedicated to the three central topics of these studies: calculations of flavin UV-visible and IR spectra, simulated dynamics of photoreceptor proteins, and flavin photochemistry. Accordingly, this chapter is divided into three parts; each part describes corresponding computational protocols, summarizes computational results, and discusses the emerging mechanistic picture.
Collapse
Affiliation(s)
- Tatiana Domratcheva
- Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, Jahnstraße 29, 69120, Heidelberg, Germany,
| | | | | |
Collapse
|
23
|
Pauszek RF, Kodali G, Caldwell ST, Fitzpatrick B, Zainalabdeen NY, Cooke G, Rotello VM, Stanley RJ. Excited state charge redistribution and dynamics in the donor-π-acceptor flavin derivative ABFL. J Phys Chem B 2013; 117:15684-94. [PMID: 24020957 DOI: 10.1021/jp406420h] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Chromophores containing a donor-π-acceptor (D-π-A) motif have been shown to exhibit many interesting photophysical properties. The lowest electronic transition of a flavin derivative containing this motif, azobenzylflavin (ABFL), has previously been shown to be highly sensitive to solvent environment and hydrogen bonding ligands. To better understand this sensitivity, we have investigated the excited state charge redistribution and dynamics of ABFL in a low-dielectric, non-hydrogen bonding solvent by steady-state Stark and femtosecond optical transient absorption spectroscopies. The Stark measurements reveal the difference dipole moment, Δμ01, between the ground and first excited states to be 22.3 ± 0.9 D. The direction of Δμ01 in the molecular frame was assigned with the aid of TD-DFT and finite field calculations, verifying the hypothesis that electron density moves from the diethylaniline donor to the flavin acceptor in the excited state. The magnitude of the difference dipole moment was used to estimate the hyperpolarizability of ABFL, β0 = 720 × 10(-30) esu. Subsequent excited state decay via charge recombination was shown to take place in a few picoseconds. The data was best fit to a kinetic model composed of a sub-picosecond internal conversion step from S2→S1, followed by a 5 ps decay to the ground state. A competing process involving formation of an additional long-lived state from S1 was also observed. Cyclic voltammetry shows one oxidation and two reduction waves and is completely reversible. This analysis lays the groundwork for developing new flavin dyads with the desired excited electronic state properties for applications such as nonlinear optical devices, molecular electronics applications, or dye-sensitized solar cells.
Collapse
Affiliation(s)
- Raymond F Pauszek
- Department of Chemistry, Temple University , Philadelphia, Pennsylvania 19122, United States
| | | | | | | | | | | | | | | |
Collapse
|
24
|
Kammler L, van Gastel M. Electronic structure of the lowest triplet state of flavin mononucleotide. J Phys Chem A 2012; 116:10090-8. [PMID: 22998491 DOI: 10.1021/jp305778v] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The electronic structure of flavin mononucleotide (FMN), an organic cofactor that plays a role in many important enzymatic reactions, has been investigated by electron paramagnetic resonance (EPR) spectroscopy, optical spectroscopy, and quantum chemistry. In particular, the triplet state of FMN, which is paramagnetic (total spin S = 1), allows an investigation of the zero field splitting parameters D and E, which are directly related to the two singly occupied molecular orbitals. Triplet EPR spectra and optical absorption spectra at different pH values in combination with time dependent density functional theory (TDDFT) reveal that the highest occupied orbital (HOMO) and lowest unoccupied orbital (LUMO) of FMN are largely unaffected by changes in the protonation state of FMN. Rather, the orbital structure of the lower lying doubly occupied orbitals changes dramatically. Additional EPR experiments have been carried out in the presence of AgNO(3), which allows the formation of an Ag-FMN triplet state with different zero field splitting parameters and population and depopulation rates. Addition of AgNO(3) only induces small changes in the optical spectrum, indicating that the Ag(+) ion only contributes to the zero field splitting by second order spin-orbit coupling and leaves the orbital structure unaffected. By a combination of the three employed methods, the observed bands in the UV/vis spectra of FMN at different pH values are assigned to electronic transitions.
Collapse
Affiliation(s)
- Lydia Kammler
- Institut für Physikalische und Theoretische Chemie, Rheinische Friedrich-Wilhelms-Universität Bonn, Wegelerstrasse 12, 53115, Bonn, Germany
| | | |
Collapse
|
25
|
Iida H, Iwahana S, Mizoguchi T, Yashima E. Main-Chain Optically Active Riboflavin Polymer for Asymmetric Catalysis and Its Vapochromic Behavior. J Am Chem Soc 2012; 134:15103-13. [DOI: 10.1021/ja306159t] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Hiroki Iida
- Department of Molecular
Design and Engineering, Graduate
School of Engineering, Nagoya University, Nagoya 464-8603, Japan
| | - Soichiro Iwahana
- Department of Molecular
Design and Engineering, Graduate
School of Engineering, Nagoya University, Nagoya 464-8603, Japan
| | - Tomohisa Mizoguchi
- Department of Molecular
Design and Engineering, Graduate
School of Engineering, Nagoya University, Nagoya 464-8603, Japan
| | - Eiji Yashima
- Department of Molecular
Design and Engineering, Graduate
School of Engineering, Nagoya University, Nagoya 464-8603, Japan
| |
Collapse
|
26
|
Murugan NA. Modeling Solvatochromism of a Quinolinium Betaine Dye in Water Solvent Using Sequential Hybrid QM/MM and Semicontinuum Approach. J Phys Chem B 2011; 115:1056-61. [DOI: 10.1021/jp1049342] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- N. Arul Murugan
- Department of Theoretical Chemistry, School of Biotechnology, Royal Institute of Technology, SE-10691 Stockholm, Sweden
| |
Collapse
|
27
|
Arul Murugan N, Kongsted J, Rinkevicius Z, Aidas K, Ågren H. Modeling the Structure and Absorption Spectra of Stilbazolium Merocyanine in Polar and Nonpolar Solvents Using Hybrid QM/MM Techniques. J Phys Chem B 2010; 114:13349-57. [DOI: 10.1021/jp1060717] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Affiliation(s)
- N. Arul Murugan
- Department of Theoretical Chemistry, School of Biotechnology, Royal Institute of Technology, SE-10691 Stockholm, Sweden, Department of Physics and Chemistry, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark, and Department of Chemistry, H. C. ⌀rsted Institute, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen ⌀, Denmark
| | - Jacob Kongsted
- Department of Theoretical Chemistry, School of Biotechnology, Royal Institute of Technology, SE-10691 Stockholm, Sweden, Department of Physics and Chemistry, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark, and Department of Chemistry, H. C. ⌀rsted Institute, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen ⌀, Denmark
| | - Zilvinas Rinkevicius
- Department of Theoretical Chemistry, School of Biotechnology, Royal Institute of Technology, SE-10691 Stockholm, Sweden, Department of Physics and Chemistry, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark, and Department of Chemistry, H. C. ⌀rsted Institute, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen ⌀, Denmark
| | - Kestutis Aidas
- Department of Theoretical Chemistry, School of Biotechnology, Royal Institute of Technology, SE-10691 Stockholm, Sweden, Department of Physics and Chemistry, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark, and Department of Chemistry, H. C. ⌀rsted Institute, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen ⌀, Denmark
| | - Hans Ågren
- Department of Theoretical Chemistry, School of Biotechnology, Royal Institute of Technology, SE-10691 Stockholm, Sweden, Department of Physics and Chemistry, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark, and Department of Chemistry, H. C. ⌀rsted Institute, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen ⌀, Denmark
| |
Collapse
|
28
|
Iida H, Mizoguchi T, Oh SD, Yashima E. Redox-triggered switching of helical chirality of poly(phenylacetylene)s bearing riboflavin pendants. Polym Chem 2010. [DOI: 10.1039/c0py00044b] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
29
|
Hu B, Zhang J. Theoretical investigation on the white-light emission from a single-polymer system with simultaneous blue and orange emission. POLYMER 2009. [DOI: 10.1016/j.polymer.2009.10.034] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
30
|
Kodali G, Siddiqui SU, Stanley RJ. Charge redistribution in oxidized and semiquinone E. coli DNA photolyase upon photoexcitation: stark spectroscopy reveals a rationale for the position of Trp382. J Am Chem Soc 2009; 131:4795-807. [PMID: 19292445 DOI: 10.1021/ja809214r] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The electronic structure of the two lowest excited electronic states of FAD and FADH(*) in folate-depleted E. coli DNA photolyase (PL(OX) and PL(SQ), respectively) was measured using absorption Stark spectroscopy. The experimental analysis was supported by TDDFT calculations of both the charge redistribution and the difference dipole moments for the transitions of both oxidation states using lumiflavin as a model. The difference dipole moments and polarizabilities for PL(OX) are similar to those obtained in our previous work for flavins in simple solvents and in an FMN-containing flavoprotein. No such comparison can be made for PL(SQ), as we believe this to be the first experimental report of the direction and magnitude of excited-state charge redistribution in any flavosemiquinone. The picture that emerges from these studies is discussed in the context of electron transfer in photolyase, particularly for the semiquinone photoreduction process, which involves nearby tryptophan residues as electron donors. The direction of charge displacement derived from an analysis of the Stark spectra rationalizes the positioning of the critical Trp382 residue relative to the flavin for efficient vectorial electron transfer leading to photoreduction. The ramifications of vectorial charge redistribution are discussed in the context of the wider class of flavoprotein blue light photoreceptors.
Collapse
Affiliation(s)
- Goutham Kodali
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, USA
| | | | | |
Collapse
|
31
|
Kao YT, Saxena C, He TF, Guo L, Wang L, Sancar A, Zhong D. Ultrafast dynamics of flavins in five redox states. J Am Chem Soc 2008; 130:13132-9. [PMID: 18767842 DOI: 10.1021/ja8045469] [Citation(s) in RCA: 179] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We report here our systematic studies of excited-state dynamics of two common flavin molecules, FMN and FAD, in five redox states--oxidized form, neutral and anionic semiquinones, and neutral and anionic fully reduced hydroquinones--in solution and in inert protein environments with femtosecond resolution. Using protein environments, we were able to stabilize two semiquinone radicals and thus observed their weak emission spectra. Significantly, we observed a strong correlation between their excited-state dynamics and the planarity of their flavin isoalloxazine ring. For a bent ring structure, we observed ultrafast dynamics from a few to hundreds of picoseconds and strong excitation-wavelength dependence of emission spectra, indicating deactivation during relaxation. A butterfly bending motion is invoked to get access to conical intersection(s) to facilitate deactivation. These states include the anionic semiquinone radical and fully reduced neutral and anionic hydroquinones in solution. In a planar configuration, flavins have a long lifetime of nanoseconds, except for the stacked conformation of FAD, where intramolecular electron transfer between the ring and the adenine moiety in 5-9 ps as well as subsequent charge recombination in 30-40 ps were observed. These observed distinct dynamics, controlled by the flavin ring flexibility, are fundamental to flavoenzyme's functions, as observed in photolyase with a planar structure to lengthen the lifetime to maximize DNA repair efficiency and in insect type 1 cryptochrome with a flexible structure to vary the excited-state deactivation to modulate the functional channel.
Collapse
Affiliation(s)
- Ya-Ting Kao
- Department of Physics, The Ohio State University, 191 West Woodruff Avenue, Columbus, Ohio 43210, USA
| | | | | | | | | | | | | |
Collapse
|