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Sun G, He X, Feng M, Xu X, Chen J, Wang Y. Flavin mononucleotide in visible light photoinitiating systems for multiple-photocrosslinking and photoencapsulation strategies. Acta Biomater 2023; 172:272-279. [PMID: 37797710 DOI: 10.1016/j.actbio.2023.09.051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Revised: 09/26/2023] [Accepted: 09/28/2023] [Indexed: 10/07/2023]
Abstract
Visible light-induced photocrosslinking techniques have attracted significant attention for their flexibility, controllability, safety, and energy conservation, especially in tissue engineering and biofabrication, compared to UV photocrosslinking. Despite these advantages, current photoinitiators are constrained by various challenges, including inadequate photoinitiation efficiency, low biocompatibility, poor water solubility, and limited compatibility with diverse crosslinking systems. Here, a water-soluble derivative of riboflavin, flavin mononucleotide (FMN-), was used to assess its potential as an initiator in multiple-photocrosslinking systems, including radical photopolymerization, dityrosine, and ditryptophan coupling crosslinking, under blue light irradiation. Blue light irradiation facilitated an efficient electron transfer reaction between FMN- and persulfate, owing to their suitable spectral compatibility and photoactivity. The resulting oxidizing free radicals and excited triplet state of FMN- served as initiating active species for the multiple-photocrosslinking reactions. The combination of FMN- and potassium persulfate (KPS) exhibited exceptional photoinitiation efficiency for various biomaterials, including silk fibroin, gelatin, poly(ethylene glycol) diacrylate, and carboxymethyl cellulose modified with amino acids. Furthermore, the cytocompatibility of the FMN-/KPS photoinitiator was demonstrated by the survival rates of 3T3-LI fibroblasts encapsulated in it, which exceeded 95 % when compared to a commercial initiator. STATEMENT OF SIGNIFICANCE: By introducing persulfate, the photoinitiation efficiency of flavin mononucleotide was significantly improved. The application scenarios of flavin mononucleotide and persulfate combinations were also greatly extended, including radical photopolymerization, dityrosine, diphenylalanine, and ditryptophan coupling crosslinking. Among them, the coupling crosslinking of amino acids (di-phenylalanine, and di-tryptophan) modified carboxymethyl cellulose, to our knowledge, was first reported. The excellent cytocompatibility of cell encapsulation further proved that the combinations of flavin mononucleotide and persulfate have great potential in tissue engineering.
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Affiliation(s)
- Guangdong Sun
- The Institute of Sericulture and Tea, Zhejiang Academy of Agricultural Sciences, Hangzhou 310018, PR China; Engineering Research Center for Eco-Dyeing and Finishing of Textiles, Ministry of Education, Zhejiang Sci-Tech University, Hangzhou 310018, PR China
| | - Xiuling He
- The Institute of Sericulture and Tea, Zhejiang Academy of Agricultural Sciences, Hangzhou 310018, PR China
| | - Meilin Feng
- The Institute of Sericulture and Tea, Zhejiang Academy of Agricultural Sciences, Hangzhou 310018, PR China
| | - Xia Xu
- The Institute of Sericulture and Tea, Zhejiang Academy of Agricultural Sciences, Hangzhou 310018, PR China
| | - Jine Chen
- The Institute of Sericulture and Tea, Zhejiang Academy of Agricultural Sciences, Hangzhou 310018, PR China
| | - Yongqiang Wang
- The Institute of Sericulture and Tea, Zhejiang Academy of Agricultural Sciences, Hangzhou 310018, PR China.
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2
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Abstract
Endogenous photosensitizers play a critical role in both beneficial and harmful light-induced transformations in biological systems. Understanding their mode of action is essential for advancing fields such as photomedicine, photoredox catalysis, environmental science, and the development of sun care products. This review offers a comprehensive analysis of endogenous photosensitizers in human skin, investigating the connections between their electronic excitation and the subsequent activation or damage of organic biomolecules. We gather the physicochemical and photochemical properties of key endogenous photosensitizers and examine the relationships between their chemical reactivity, location within the skin, and the primary biochemical events following solar radiation exposure, along with their influence on skin physiology and pathology. An important take-home message of this review is that photosensitization allows visible light and UV-A radiation to have large effects on skin. The analysis presented here unveils potential causes for the continuous increase in global skin cancer cases and emphasizes the limitations of current sun protection approaches.
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Affiliation(s)
- Erick L Bastos
- Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, 05508-000 São Paulo, São Paulo, Brazil
| | - Frank H Quina
- Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, 05508-000 São Paulo, São Paulo, Brazil
- Department of Chemical Engineering, Polytechnic School, University of São Paulo, 05508-000 São Paulo, São Paulo, Brazil
| | - Maurício S Baptista
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, 05508-000 São Paulo, São Paulo, Brazil
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3
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Bradlaugh AA, Fedele G, Munro AL, Hansen CN, Hares JM, Patel S, Kyriacou CP, Jones AR, Rosato E, Baines RA. Essential elements of radical pair magnetosensitivity in Drosophila. Nature 2023; 615:111-116. [PMID: 36813962 PMCID: PMC9977682 DOI: 10.1038/s41586-023-05735-z] [Citation(s) in RCA: 21] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Accepted: 01/16/2023] [Indexed: 02/24/2023]
Abstract
Many animals use Earth's magnetic field (also known as the geomagnetic field) for navigation1. The favoured mechanism for magnetosensitivity involves a blue-light-activated electron-transfer reaction between flavin adenine dinucleotide (FAD) and a chain of tryptophan residues within the photoreceptor protein CRYPTOCHROME (CRY). The spin-state of the resultant radical pair, and therefore the concentration of CRY in its active state, is influenced by the geomagnetic field2. However, the canonical CRY-centric radical-pair mechanism does not explain many physiological and behavioural observations2-8. Here, using electrophysiology and behavioural analyses, we assay magnetic-field responses at the single-neuron and organismal levels. We show that the 52 C-terminal amino acid residues of Drosophila melanogaster CRY, lacking the canonical FAD-binding domain and tryptophan chain, are sufficient to facilitate magnetoreception. We also show that increasing intracellular FAD potentiates both blue-light-induced and magnetic-field-dependent effects on the activity mediated by the C terminus. High levels of FAD alone are sufficient to cause blue-light neuronal sensitivity and, notably, the potentiation of this response in the co-presence of a magnetic field. These results reveal the essential components of a primary magnetoreceptor in flies, providing strong evidence that non-canonical (that is, non-CRY-dependent) radical pairs can elicit magnetic-field responses in cells.
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Affiliation(s)
- Adam A Bradlaugh
- Division of Neuroscience, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, Manchester, UK
| | - Giorgio Fedele
- Department of Genetics and Genome Biology, University of Leicester, Leicester, UK
- Department of Biology, Ecology and Earth Sciences (DiBEST), University of Calabria, Rende, Italy
| | - Anna L Munro
- Division of Neuroscience, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, Manchester, UK
| | - Celia Napier Hansen
- Department of Genetics and Genome Biology, University of Leicester, Leicester, UK
| | - John M Hares
- Department of Genetics and Genome Biology, University of Leicester, Leicester, UK
- Pelican Healthcare, Cardiff, UK
| | - Sanjai Patel
- Manchester Fly Facility, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | | | - Alex R Jones
- Biometrology, Chemical and Biological Sciences Department, National Physical Laboratory, Teddington, UK
| | - Ezio Rosato
- Department of Genetics and Genome Biology, University of Leicester, Leicester, UK.
| | - Richard A Baines
- Division of Neuroscience, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, Manchester, UK.
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4
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Ciavardini A, Galdenzi F, Coreno M, Ninno GD, Grazioli C, de Simone M, Totani R, Piccirillo S, Plekan O, Ponzi A. Valence and core-level X-ray photoemission spectroscopy of light-sensitive molecules: Lumazine and alloxazine. Chem Phys 2022. [DOI: 10.1016/j.chemphys.2022.111757] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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5
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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]
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6
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Comparing ultrafast excited state quenching of flavin 1,N 6-ethenoadenine dinucleotide and flavin adenine dinucleotide by optical spectroscopy and DFT calculations. Photochem Photobiol Sci 2022; 21:959-982. [PMID: 35218554 DOI: 10.1007/s43630-022-00187-2] [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: 05/04/2021] [Accepted: 02/01/2022] [Indexed: 10/19/2022]
Abstract
Flavins are photoenzymatic cofactors often exploiting the absorption of light to energize photoinduced redox chemistry in a variety of contexts. Both flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN) are used for this function. The study of these photoenzymes has been facilitated using flavin analogs. Most of these analogs involve modification of the flavin ring, and there is recent evidence that adenine (Ade)-modified FAD can affect enzyme turnover, but so far this has only been shown for enzymes where the adenine and flavin rings are close to each other in a stacked conformation. FAD is also stacked in aqueous solution, and its photodynamics are quite different from unstacked FAD or FMN. Oxidized photoexcited FAD decays rapidly, presumably through PET with Ade as donor and Fl* as acceptor. Definitive identification of the spectral signatures of Ade∙+ and Fl∙- radicals is elusive. Here we use the FAD analog Flavin 1,N6-Ethenoadenine Dinucleotide (εFAD) to study how different photochemical outcomes depend on the identity of the Ade moiety in stacked FAD and its analog εFAD. We have used UV-Vis transient absorption spectroscopy complemented by TD-DFT calculations to investigate the excited state evolution of the flavins. In FAD*, no radicals were observed, suggesting that FAD* does not undergo PET. εFAD* kinetics showed a broad absorption band that suggests a charge transfer state exists upon photoexcitation with evidence for radical pair formation. Surprisingly, significant triplet flavin was produced from εFAD* We hypothesize that the dipolar (ε)Ade moieties differentially modulate the singlet-triplet energy gap, resulting in different intersystem crossing rates. The additional electron density on the etheno group of εFAD supplies better orbital overlap with the flavin S1 state, accelerating charge transfer in that molecule.
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7
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Campbell AC, Prater AR, Bogner AN, Quinn TP, Gates KS, Becker DF, Tanner JJ. Photoinduced Covalent Irreversible Inactivation of Proline Dehydrogenase by S-Heterocycles. ACS Chem Biol 2021; 16:2268-2279. [PMID: 34542291 DOI: 10.1021/acschembio.1c00427] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Proline dehydrogenase (PRODH) is a flavoenzyme that catalyzes the first step of proline catabolism, the oxidation of l-proline to Δ1-pyrroline-5-carboxylate. PRODH has emerged as a cancer therapy target because of its involvement in the metabolic reprogramming of cancer cells. Here, we report the discovery of a new class of PRODH inactivator, which covalently and irreversibly modifies the FAD in a light-dependent manner. Two examples, 1,3-dithiolane-2-carboxylate and tetrahydrothiophene-2-carboxylate, have been characterized using X-ray crystallography (1.52-1.85 Å resolution), absorbance spectroscopy, and enzyme kinetics. The structures reveal that in the dark, these compounds function as classical reversible, proline analogue inhibitors. However, exposure of enzyme-inhibitor cocrystals to bright white light induces decarboxylation of the inhibitor and covalent attachment of the residual S-heterocycle to the FAD N5 atom, locking the cofactor into a reduced, inactive state. Spectroscopic measurements of the inactivation process in solution confirm the requirement for light and show that blue light is preferred. Enzyme activity assays show that the rate of inactivation is enhanced by light and that the inactivation is irreversible. We also demonstrate the photosensitivity of cancer cells to one of these compounds. A possible mechanism is proposed involving photoexcitation of the FAD, while the inhibitor is noncovalently bound in the active site, followed by electron transfer, decarboxylation, and radical combination steps. Our results could lead to the development of photopharmacological drugs targeting PRODH.
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Affiliation(s)
- Ashley C. Campbell
- Department of Biochemistry, University of Missouri, Columbia, Missouri 65211, United States
| | - Austin R. Prater
- Department of Biochemistry, University of Missouri, Columbia, Missouri 65211, United States
| | - Alexandra N. Bogner
- Department of Biochemistry, University of Missouri, Columbia, Missouri 65211, United States
| | - Thomas P. Quinn
- Department of Biochemistry, University of Missouri, Columbia, Missouri 65211, United States
| | - Kent S. Gates
- Department of Chemistry, University of Missouri, Columbia, Missouri 65211, United States
| | - Donald F. Becker
- Department of Biochemistry, Redox Biology Center, University of Nebraska, Lincoln, Nebraska 68588, United States
| | - John J. Tanner
- Department of Biochemistry, University of Missouri, Columbia, Missouri 65211, United States
- Department of Chemistry, University of Missouri, Columbia, Missouri 65211, United States
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8
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Hong P, Ning LC, Wu AA, Tan K, Lu X. Insights into the mechanism of fatty acid photodecarboxylase: A theoretical investigation. Chem Phys Lett 2021. [DOI: 10.1016/j.cplett.2021.138550] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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9
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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]
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10
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Nohr D, Weber S, Schleicher E. EPR spectroscopy on flavin radicals in flavoproteins. Methods Enzymol 2019; 620:251-275. [PMID: 31072489 DOI: 10.1016/bs.mie.2019.03.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Flavin semiquinone redox states are important intermediates in a broad variety of reactions catalyzed by flavoproteins. As paramagnetic states they can be favorably probed by EPR spectroscopy in all its flavors. This review summarizes recent results in the characterization of flavin radicals. On the one hand, flavin radical states, e.g., trapped as reaction intermediates, can be characterized using modern pulsed EPR methods to unravel their electronic structure and to gain information about the surrounding environment and its changes on protein action. On the other hand, short-lived intermediate flavin radical states generated, e.g., photochemically, can be followed by time-resolved EPR, which allows a direct tracking of flavin-dependent reactions with a temporal resolution reaching nanoseconds.
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Affiliation(s)
- Daniel Nohr
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Stefan Weber
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Erik Schleicher
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany.
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11
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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.
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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.
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12
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Reiffers A, Torres Ziegenbein C, Engelhardt A, Kühnemuth R, Gilch P, Czekelius C. Impact of Mono-Fluorination on the Photophysics of the Flavin Chromophore. Photochem Photobiol 2018; 94:667-676. [DOI: 10.1111/php.12921] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Accepted: 03/25/2018] [Indexed: 11/30/2022]
Affiliation(s)
- Anna Reiffers
- Institut für Physikalische Chemie; Heinrich-Heine-Universität Düsseldorf; Düsseldorf Germany
| | | | - Alyn Engelhardt
- Institut für Physikalische Chemie; Heinrich-Heine-Universität Düsseldorf; Düsseldorf Germany
| | - Ralf Kühnemuth
- Institut für Physikalische Chemie; Heinrich-Heine-Universität Düsseldorf; Düsseldorf Germany
| | - Peter Gilch
- Institut für Physikalische Chemie; Heinrich-Heine-Universität Düsseldorf; Düsseldorf Germany
| | - Constantin Czekelius
- Institut für Organische Chemie und Makromolekulare Chemie; Heinrich-Heine-Universität Düsseldorf; Düsseldorf Germany
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13
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Matsuoka H, Retegan M, Schmitt L, Höger S, Neese F, Schiemann O. Time-Resolved Electron Paramagnetic Resonance and Theoretical Investigations of Metal-Free Room-Temperature Triplet Emitters. J Am Chem Soc 2017; 139:12968-12975. [DOI: 10.1021/jacs.7b04561] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Hideto Matsuoka
- Institute
for Physical and Theoretical Chemistry, University of Bonn, Wegelerstr. 12, 53115 Bonn, Germany
| | - Marius Retegan
- Max Planck Institute for MPI for Chemical Energy Conversion, Stiftstr. 34−36, 45470 Mülheim an der Ruhr, Germany
| | - Lisa Schmitt
- Kekulé
Institute of Organic Chemistry and Biochemistry, University of Bonn, Gerhard-Domagk-Str. 1, 53121 Bonn, Germany
| | - Sigurd Höger
- Kekulé
Institute of Organic Chemistry and Biochemistry, University of Bonn, Gerhard-Domagk-Str. 1, 53121 Bonn, Germany
| | - Frank Neese
- Max Planck Institute for MPI for Chemical Energy Conversion, Stiftstr. 34−36, 45470 Mülheim an der Ruhr, Germany
| | - Olav Schiemann
- Institute
for Physical and Theoretical Chemistry, University of Bonn, Wegelerstr. 12, 53115 Bonn, Germany
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14
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Oxidation of alkyl benzenes by a flavin photooxidation catalyst on nanostructured metal-oxide films. Proc Natl Acad Sci U S A 2017; 114:9279-9283. [PMID: 28802257 DOI: 10.1073/pnas.1707318114] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
We describe here a surface-bound, oxide-based procedure for the photooxidation of a family of aromatic hydrocarbons by a phosphate-bearing flavin mononucleotide (FMN) photocatalyst on high surface area metal-oxide films.
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15
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Poly(ethylene glycol)/β-cyclodextrin covalent gel networks: host matrices for studying radical processes in plant extract–riboflavin systems following UV irradiation. CHEMICAL PAPERS 2016. [DOI: 10.1007/s11696-016-0047-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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Affiliation(s)
- P. J. Hore
- Department of Chemistry, University of Oxford, Oxford OX1 3QZ, United Kingdom;
| | - Henrik Mouritsen
- Institut für Biologie und Umweltwissenschaften, Carl von Ossietzky Universität Oldenburg, DE-26111 Oldenburg, Germany;
- Research Centre for Neurosensory Sciences, University of Oldenburg, DE-26111 Oldenburg, Germany
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17
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Metternich JB, Gilmour R. One Photocatalyst, n Activation Modes Strategy for Cascade Catalysis: Emulating Coumarin Biosynthesis with (-)-Riboflavin. J Am Chem Soc 2016; 138:1040-5. [PMID: 26714650 DOI: 10.1021/jacs.5b12081] [Citation(s) in RCA: 188] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Generating molecular complexity using a single catalyst, where the requisite activation modes are sequentially exploited as the reaction proceeds, is an attractive guiding principle in synthesis. This requires that each substrate transposition exposes a catalyst activation mode (AM) to which all preceding or future intermediates are resistant. While this concept is exemplified by MacMillan's beautiful merger of enamine and iminium ion activation, examples in other fields of contemporary catalysis remain elusive. Herein, we extend this tactic to organic photochemistry. By harnessing the two discrete photochemical activation modes of (-)-riboflavin, it is possible to sequentially induce isomerization and cyclization by energy transfer (ET) and single-electron transfer (SET) activation pathways, respectively. This catalytic approach has been utilized to emulate the coumarin biosynthesis pathway, which features a key photochemical E → Z isomerization step. Since the ensuing SET-based cyclization eliminates the need for a prefunctionalized aryl ring, this constitutes a novel disconnection of a pharmaceutically important scaffold.
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Affiliation(s)
- Jan B Metternich
- Institute for Organic Chemistry, Westfälische Wilhelms-Universität Münster , Corrensstrasse 40, 48149 Münster, Germany
| | - Ryan Gilmour
- Institute for Organic Chemistry, Westfälische Wilhelms-Universität Münster , Corrensstrasse 40, 48149 Münster, Germany
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18
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Domratcheva T, Fedorov R, Schlichting I. Analysis of the Primary Photocycle Reactions Occurring in the Light, Oxygen, and Voltage Blue-Light Receptor by Multiconfigurational Quantum-Chemical Methods. J Chem Theory Comput 2015; 2:1565-74. [PMID: 26627027 DOI: 10.1021/ct0600114] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The photocycle reactions occurring between the flavin mononucleotide cofactor and the reactive cysteine residue in the blue-light photoreceptor domain light, oxygen, and voltage (LOV) were modeled for a system consisting of lumiflavin and thiomethanol. The electronic structure and energies of the reactive species were estimated using the CASSCF and MCQDPT2 quantum-chemical methods. The reaction pathway for the S-C4a covalent adduct formation in the triplet state was determined. Concerted electron and proton transfer from the thiol to the flavin in the triplet electronic state results in a biradical complex that is, however, unstable because its structure corresponds to a triplet-singlet crossing. The covalent adduct dissociation in the ground electronic state is a reverse of the photoreaction proceeding via a single energy barrier for hydrogen transfer. Thus, both photo- and dark reactions were found to be single-step chemical transformations occurring without stable intermediates. The photoreaction yielding the S-C4a covalent adduct is an intrinsic property of the isoalloxazine-thiol complex in the specific geometry arranged by the protein in LOV. The S-C4a covalent adduct between lumiflavin and thiomethanol is rather stable implying that in LOV its dissociation is facilitated by the protein.
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Affiliation(s)
- Tatiana Domratcheva
- Max-Planck Institute for Medical Research, Department of Biomolecular Mechanisms, Jahnstrasse 29, 69120 Heidelberg, Germany
| | - Roman Fedorov
- Max-Planck Institute for Medical Research, Department of Biomolecular Mechanisms, Jahnstrasse 29, 69120 Heidelberg, Germany
| | - Ilme Schlichting
- Max-Planck Institute for Medical Research, Department of Biomolecular Mechanisms, Jahnstrasse 29, 69120 Heidelberg, Germany
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19
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Nohr D, Rodriguez R, Weber S, Schleicher E. How can EPR spectroscopy help to unravel molecular mechanisms of flavin-dependent photoreceptors? Front Mol Biosci 2015; 2:49. [PMID: 26389123 PMCID: PMC4555020 DOI: 10.3389/fmolb.2015.00049] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Accepted: 08/10/2015] [Indexed: 11/25/2022] Open
Abstract
Electron paramagnetic resonance (EPR) spectroscopy is a well-established spectroscopic method for the examination of paramagnetic molecules. Proteins can contain paramagnetic moieties in form of stable cofactors, transiently formed intermediates, or spin labels artificially introduced to cysteine sites. The focus of this review is to evaluate potential scopes of application of EPR to the emerging field of optogenetics. The main objective for EPR spectroscopy in this context is to unravel the complex mechanisms of light-active proteins, from their primary photoreaction to downstream signal transduction. An overview of recent results from the family of flavin-containing, blue-light dependent photoreceptors is given. In detail, mechanistic similarities and differences are condensed from the three classes of flavoproteins, the cryptochromes, LOV (Light-oxygen-voltage), and BLUF (blue-light using FAD) domains. Additionally, a concept that includes spin-labeled proteins and examination using modern pulsed EPR is introduced, which allows for a precise mapping of light-induced conformational changes.
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Affiliation(s)
- Daniel Nohr
- Department of Physical Chemistry, Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg Freiburg, Germany
| | - Ryan Rodriguez
- Department of Physical Chemistry, Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg Freiburg, Germany
| | - Stefan Weber
- Department of Physical Chemistry, Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg Freiburg, Germany
| | - Erik Schleicher
- Department of Physical Chemistry, Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg Freiburg, Germany
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20
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Biskup T, Sommer M, Rein S, Meyer DL, Kohlstädt M, Würfel U, Weber S. Zeitaufgelöste Elektronenspinresonanz-Spektroskopie an Triplett-Exzitonen deckt Ordnung von PCDTBT auf. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201502241] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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21
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Biskup T, Sommer M, Rein S, Meyer DL, Kohlstädt M, Würfel U, Weber S. Ordering of PCDTBT Revealed by Time-Resolved Electron Paramagnetic Resonance Spectroscopy of Its Triplet Excitons. Angew Chem Int Ed Engl 2015; 54:7707-10. [DOI: 10.1002/anie.201502241] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Indexed: 01/17/2023]
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22
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Paulus B, Illarionov B, Nohr D, Roellinger G, Kacprzak S, Fischer M, Weber S, Bacher A, Schleicher E. One Protein, Two Chromophores: Comparative Spectroscopic Characterization of 6,7-Dimethyl-8-ribityllumazine and Riboflavin Bound to Lumazine Protein. J Phys Chem B 2014; 118:13092-105. [DOI: 10.1021/jp507618f] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Bernd Paulus
- Institute
of Physical Chemistry, Albert-Ludwigs-University Freiburg, Albertstrasse
21, 79104 Freiburg, Germany
| | - Boris Illarionov
- Institute for Biochemistry & Food Chemistry, University of Hamburg, Bundesstrasse 45, 20146 Hamburg, Germany
| | - Daniel Nohr
- Institute
of Physical Chemistry, Albert-Ludwigs-University Freiburg, Albertstrasse
21, 79104 Freiburg, Germany
| | - Guillaume Roellinger
- Institute
of Physical Chemistry, Albert-Ludwigs-University Freiburg, Albertstrasse
21, 79104 Freiburg, Germany
| | - Sylwia Kacprzak
- Institute
of Physical Chemistry, Albert-Ludwigs-University Freiburg, Albertstrasse
21, 79104 Freiburg, Germany
| | - Markus Fischer
- Institute for Biochemistry & Food Chemistry, University of Hamburg, Bundesstrasse 45, 20146 Hamburg, Germany
| | - Stefan Weber
- Institute
of Physical Chemistry, Albert-Ludwigs-University Freiburg, Albertstrasse
21, 79104 Freiburg, Germany
| | - Adelbert Bacher
- Institute for Biochemistry & Food Chemistry, University of Hamburg, Bundesstrasse 45, 20146 Hamburg, Germany
- Chemistry
Department, Technical University Munich, Lichtenbergstrasse 4, 85748 Garching, Germany
| | - Erik Schleicher
- Institute
of Physical Chemistry, Albert-Ludwigs-University Freiburg, Albertstrasse
21, 79104 Freiburg, Germany
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23
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Kothe G, Lukaschek M, Link G, Kacprzak S, Illarionov B, Fischer M, Eisenreich W, Bacher A, Weber S. Detecting a new source for photochemically induced dynamic nuclear polarization in the LOV2 domain of phototropin by magnetic-field dependent (13)C NMR spectroscopy. J Phys Chem B 2014; 118:11622-32. [PMID: 25207844 DOI: 10.1021/jp507134y] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Phototropin is a flavin mononucleotide (FMN) containing blue-light receptor, which regulates, governed by its two LOV domains, the phototropic response of higher plants. Upon photoexcitation, the FMN cofactor triplet state, (3)F, reacts with a nearby cysteine to form a covalent adduct. Cysteine-to-alanine mutants of LOV domains instead generate a flavin radical upon illumination. Here, we explore the formation of photochemically induced dynamic nuclear polarization (CIDNP) in LOV2-C450A of Avena sativa phototropin and demonstrate that photo-CIDNP observed in solution (13)C NMR spectra can reliably be interpreted in terms of solid-state mechanisms including a novel triplet mechanism. To minimize cross-polarization, which transfers light-induced magnetization to adjacent (13)C nuclei, our experiments were performed on proteins reconstituted with specifically (13)C-labeled flavins. Two potential sources for photo-CIDNP can be identified: The photogenerated triplet state, (3)F, and the triplet radical pair (3)(F(-•)W(+•)), formed by electron abstraction of (3)F from tryptophan W491. To separate the two contributions, photo-CIDNP studies were performed at four different magnetic fields ranging from 4.7 to 11.8 T. Analysis revealed that, at fields <9 T, both (3)(F(-•)W(+•)) and (3)F contribute to photo-CIDNP, whereas at high magnetic fields, the calculated enhancement factors of (3)F agree favorably with their experimental counterparts. Thus, we have for the first time detected that a triplet state is the major source for photo-CIDNP in a photoactive protein. Since triplet states are frequently encountered upon photoexcitation of flavoproteins, the novel triplet mechanism opens up new means of studying electronic structures of the active cofactors in these proteins at atomic resolution.
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Affiliation(s)
- Gerd Kothe
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg , Albertstr. 21, 79104 Freiburg, Germany
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24
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Langer J, Günther A, Seidenbecher S, Berden G, Oomens J, Dopfer O. Probing protonation sites of isolated flavins using IR spectroscopy: from lumichrome to the cofactor flavin mononucleotide. Chemphyschem 2014; 15:2550-62. [PMID: 24895155 DOI: 10.1002/cphc.201402146] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Indexed: 11/06/2022]
Abstract
Infrared spectra of the isolated protonated flavin molecules lumichrome, lumiflavin, riboflavin (vitamin B2), and the biologically important cofactor flavin mononucleotide are measured in the fingerprint region (600-1850 cm(-1)) by means of IR multiple-photon dissociation (IRMPD) spectroscopy. Using density functional theory calculations, the geometries, relative energies, and linear IR absorption spectra of several low-energy isomers are calculated. Comparison of the calculated IR spectra with the measured IRMPD spectra reveals that the N10 substituent on the isoalloxazine ring influences the protonation site of the flavin. Lumichrome, with a hydrogen substituent, is only stable as the N1-protonated tautomer and protonates at N5 of the pyrazine ring. The presence of the ribityl unit in riboflavin leads to protonation at N1 of the pyrimidinedione moiety, and methyl substitution in lumiflavin stabilizes the tautomer that is protonated at O2. In contrast, flavin mononucleotide exists as both the O2- and N1-protonated tautomers. The frequencies and relative intensities of the two C=O stretch vibrations in protonated flavins serve as reliable indicators for their protonation site.
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Affiliation(s)
- Judith Langer
- Technische Universität Berlin, Institut für Optik und Atomare Physik, Hardenbergstraße 36, D-10623 Berlin (Germany); Current address: Parque Tecnologico de San Sebastian, Paseo Miramon 182, Edif C, 20009 San Sebastian (Spain)
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25
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Biskup T. Time-resolved electron paramagnetic resonance of radical pair intermediates in cryptochromes. Mol Phys 2013. [DOI: 10.1080/00268976.2013.833350] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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26
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Evans EW, Dodson CA, Maeda K, Biskup T, Wedge CJ, Timmel CR. Magnetic field effects in flavoproteins and related systems. Interface Focus 2013; 3:20130037. [PMID: 24511388 PMCID: PMC3915827 DOI: 10.1098/rsfs.2013.0037] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Within the framework of the radical pair mechanism, magnetic fields may alter the rate and yields of chemical reactions involving spin-correlated radical pairs as intermediates. Such effects have been studied in detail in a variety of chemical systems both experimentally and theoretically. In recent years, there has been growing interest in whether such magnetic field effects (MFEs) also occur in biological systems, a question driven most notably by the increasing body of evidence for the involvement of such effects in the magnetic compass sense of animals. The blue-light photoreceptor cryptochrome is placed at the centre of this debate and photoexcitation of its bound flavin cofactor has indeed been shown to result in the formation of radical pairs. Here, we review studies of MFEs on free flavins in model systems as well as in blue-light photoreceptor proteins and discuss the properties that are crucial in determining the magnetosensitivity of these systems.
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Affiliation(s)
- Emrys W. Evans
- Centre for Advanced Electron Spin Resonance, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, UK
| | - Charlotte A. Dodson
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Mansfield Road, Oxford OX1 3TA, UK
| | - Kiminori Maeda
- Centre for Advanced Electron Spin Resonance, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, UK
| | - Till Biskup
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstraße 21, 79104 Freiburg, Germany
| | - C. J. Wedge
- Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, UK
| | - Christiane R. Timmel
- Centre for Advanced Electron Spin Resonance, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, UK
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27
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Quick M, Weigel A, Ernsting NP. Fluorescence following Excited-State Protonation of Riboflavin at N(5). J Phys Chem B 2013; 117:5441-7. [DOI: 10.1021/jp312571d] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Martin Quick
- Department
of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, D-12489 Berlin, Germany
| | - Alexander Weigel
- Department
of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, D-12489 Berlin, Germany
| | - Nikolaus P. Ernsting
- Department
of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, D-12489 Berlin, Germany
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28
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Biskup T, Paulus B, Okafuji A, Hitomi K, Getzoff ED, Weber S, Schleicher E. Variable electron transfer pathways in an amphibian cryptochrome: tryptophan versus tyrosine-based radical pairs. J Biol Chem 2013; 288:9249-60. [PMID: 23430261 DOI: 10.1074/jbc.m112.417725] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Electron transfer reactions play vital roles in many biological processes. Very often the transfer of charge(s) proceeds stepwise over large distances involving several amino acid residues. By using time-resolved electron paramagnetic resonance and optical spectroscopy, we have studied the mechanism of light-induced reduction of the FAD cofactor of cryptochrome/photolyase family proteins. In this study, we demonstrate that electron abstraction from a nearby amino acid by the excited FAD triggers further electron transfer steps even if the conserved chain of three tryptophans, known to be an effective electron transfer pathway in these proteins, is blocked. Furthermore, we were able to characterize this secondary electron transfer pathway and identify the amino acid partner of the resulting flavin-amino acid radical pair as a tyrosine located at the protein surface. This alternative electron transfer pathway could explain why interrupting the conserved tryptophan triad does not necessarily alter photoreactions of cryptochromes in vivo. Taken together, our results demonstrate that light-induced electron transfer is a robust property of cryptochromes and more intricate than commonly anticipated.
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Affiliation(s)
- Till Biskup
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, Oxford OX1 3QZ, United Kingdom
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29
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Hogben HJ, Biskup T, Hore PJ. Entanglement and sources of magnetic anisotropy in radical pair-based avian magnetoreceptors. PHYSICAL REVIEW LETTERS 2012; 109:220501. [PMID: 23368109 DOI: 10.1103/physrevlett.109.220501] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2012] [Indexed: 06/01/2023]
Abstract
One of the principal models of magnetic sensing in migratory birds rests on the quantum spin dynamics of transient radical pairs created photochemically in ocular cryptochrome proteins. We consider here the role of electron spin entanglement and coherence in determining the sensitivity of a radical pair-based geomagnetic compass and the origins of the directional response. It emerges that the anisotropy of radical pairs formed from spin-polarized molecular triplets could form the basis of a more sensitive compass sensor than one founded on the conventional hyperfine-anisotropy model. This property offers new and more flexible opportunities for the design of biologically inspired magnetic compass sensors.
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Affiliation(s)
- Hannah J Hogben
- Department of Chemistry, University of Oxford, Physical & Theoretical Chemistry Laboratory, Oxford OX1 3QZ, United Kingdom
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30
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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.
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Affiliation(s)
- Lydia Kammler
- Institut für Physikalische und Theoretische Chemie, Rheinische Friedrich-Wilhelms-Universität Bonn, Wegelerstrasse 12, 53115, Bonn, Germany
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31
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Penzkofer A. Photoluminescence behavior of riboflavin and lumiflavin in liquid solutions and solid films. Chem Phys 2012. [DOI: 10.1016/j.chemphys.2012.03.017] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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32
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Weber S, Schroeder C, Kacprzak S, Mathes T, Kowalczyk RM, Essen LO, Hegemann P, Schleicher E, Bittl R. Light-generated paramagnetic intermediates in BLUF domains. Photochem Photobiol 2011; 87:574-83. [PMID: 21198648 DOI: 10.1111/j.1751-1097.2010.00885.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Blue-light sensitive photoreceptory BLUF domains are flavoproteins, which regulate various, mostly stress-related processes in bacteria and eukaryotes. The photoreactivity of the flavin adenine dinucleotide (FAD) cofactor in three BLUF domains from Rhodobacter sphaeroides, Synechocystis sp. PCC 6803 and Escherichia coli have been studied at low temperature using time-resolved electron paramagnetic resonance. Photoinduced flavin triplet states and radical-pair species have been detected on a microsecond time scale. Differences in the electronic structures of the FAD cofactors as reflected by altered zero-field splitting parameters of the triplet states could be correlated with changes in the amino-acid composition of the various BLUF domains' cofactor binding pockets. For the generation of the light-induced, spin-correlated radical-pair species in the BLUF domain from Synechocystis sp. PCC 6803, a tyrosine residue near the flavin's isoalloxazine moiety plays a critical role.
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Affiliation(s)
- Stefan Weber
- Albert-Ludwigs-Universität Freiburg, Institut für Physikalische Chemie, Freiburg, Germany
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33
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34
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Weber S, Biskup T, Okafuji A, Marino AR, Berthold T, Link G, Hitomi K, Getzoff ED, Schleicher E, Norris JR. Origin of light-induced spin-correlated radical pairs in cryptochrome. J Phys Chem B 2010; 114:14745-54. [PMID: 20684534 DOI: 10.1021/jp103401u] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Blue-light excitation of cryptochromes and homologues uniformly triggers electron transfer (ET) from the protein surface to the flavin adenine dinucleotide (FAD) cofactor. A cascade of three conserved tryptophan residues has been considered to be critically involved in this photoreaction. If the FAD is initially in its fully oxidized (diamagnetic) redox state, light-induced ET via the tryptophan triad generates a series of short-lived spin-correlated radical pairs comprising an FAD radical and a tryptophan radical. Coupled doublet-pair species of this type have been proposed as the basis, for example, of a biological magnetic compass in migratory birds, and were found critical for some cryptochrome functions in vivo. In this contribution, a cryptochrome-like protein (CRYD) derived from Xenopus laevis has been examined as a representative system. The terminal radical-pair state FAD(•)···W324(•) of X. laevis CRYD has been characterized in detail by time-resolved electron-paramagnetic resonance (TREPR) at X-band microwave frequency (9.68 GHz) and magnetic fields around 345 mT, and at Q-band (34.08 GHz) at around 1215 mT. Different precursor states, singlet versus triplet, of radical-pair formation have been considered in spectral simulations of the experimental electron-spin polarized TREPR signals. Conclusively, we present evidence for a singlet-state precursor of FAD(•)···W324(•) radical-pair generation because at both magnetic fields, where radical pairs were studied by TREPR, net-zero electron-spin polarization has been detected. Neither a spin-polarized triplet precursor nor a triplet at thermal equilibrium can explain such an electron-spin polarization. It turns out that a two-microwave-frequency TREPR approach is essential to draw conclusions on the nature of the precursor electronic states in light-induced spin-correlated radical pair formations.
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Affiliation(s)
- Stefan Weber
- Institute of Physical Chemistry, Albert-Ludwigs-Universität Freiburg, 79104 Freiburg, Germany.
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35
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Tyagi A, Penzkofer A, Mathes T, Hegemann P. Photophysical characterisation and photo-cycle dynamics of LOV1-His domain of phototropin from Chlamydomonas reinhardtii with roseoflavin monophosphate cofactor. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2010; 101:76-88. [PMID: 20655238 DOI: 10.1016/j.jphotobiol.2010.06.014] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2010] [Revised: 06/29/2010] [Accepted: 06/29/2010] [Indexed: 11/19/2022]
Abstract
The wild-type phototropin protein phot from the green alga Chlamydomonas reinhardtii with the blue-light photoreceptor domains LOV1 and LOV2 has flavin mononucleotide (FMN) as cofactor. For the LOV1-His domain from phot of C. reinhardtii studied here, the FMN chromophore was replaced by roseoflavin monophosphate (8-dimethylamino-8-demethyl-FMN, RoFMN) during heterologous expression in a riboflavin auxotropic Escherichia coli strain. An absorption and emission spectroscopic characterisation of the cofactor exchanged-LOV1-His (RoLOV1) domain was carried out in aqueous pH 8 phosphate buffer. The fluorescence of RoLOV1 is quenched by photo-induced charge transfer at room temperature. The photo-cyclic dynamics of RoLOV1 was observed by blue-light induced hypochromic and bathochromic absorption changes which recover on a minute timescale in the dark. Photo-excited RoFMN is thought to cause reversible protein and cofactor structural changes. Prolonged intense blue-light exposure caused photo-degradation of RoFMN in RoLOV1 to fully reduced flavin and lumichrome derivatives. Photo-cycle schemes of RoLOV1 and LOV1 are presented, and the photo-degradation dynamics of RoLOV1 is discussed.
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Affiliation(s)
- A Tyagi
- Fakultät für Physik, Universität Regensburg, Universitätsstrasse 31, D-93053 Regensburg, Germany
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36
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Schleicher E, Bittl R, Weber S. New roles of flavoproteins in molecular cell biology: Blue-light active flavoproteins studied by electron paramagnetic resonance. FEBS J 2009; 276:4290-303. [DOI: 10.1111/j.1742-4658.2009.07141.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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37
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Zhang Y, Görner H. Flavin-sensitized Photo-oxidation of Lysozyme and Serum Albumin. Photochem Photobiol 2009; 85:943-8. [DOI: 10.1111/j.1751-1097.2009.00547.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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38
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Accorsi G, Barigelletti F, Farrán A, Herranz F, Claramunt RM, Marcaccio M, Valenti G, Paolucci F, Pinilla E, Torres MR. Intramolecular interactions and photoinduced electron transfer in isoalloxazine-naphthalene bichromophores. J Photochem Photobiol A Chem 2009. [DOI: 10.1016/j.jphotochem.2009.01.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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39
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Efficient photocleavage of DNA utilizing water soluble riboflavin/naphthaleneacetate substituted fullerene complex. J Photochem Photobiol A Chem 2009. [DOI: 10.1016/j.jphotochem.2008.12.026] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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40
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Biskup T, Schleicher E, Okafuji A, Link G, Hitomi K, Getzoff ED, Weber S. Direct observation of a photoinduced radical pair in a cryptochrome blue-light photoreceptor. Angew Chem Int Ed Engl 2009; 48:404-7. [PMID: 19058271 DOI: 10.1002/anie.200803102] [Citation(s) in RCA: 123] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- Till Biskup
- Department of Physics, Free University Berlin, Germany
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41
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Biskup T, Schleicher E, Okafuji A, Link G, Hitomi K, Getzoff E, Weber S. Direkte Detektion eines lichtinduzierten Radikalpaars in einem Cryptochrom-Blaulichtrezeptor. Angew Chem Int Ed Engl 2009. [DOI: 10.1002/ange.200803102] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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42
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Salzmann S, Marian CM. Effects of protonation and deprotonation on the excitation energies of lumiflavin. Chem Phys Lett 2008. [DOI: 10.1016/j.cplett.2008.08.050] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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43
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Photostability and Photoreactivity in Biomolecules: Quantum Chemistry of Nucleic Acid Base Monomers and Dimers. CHALLENGES AND ADVANCES IN COMPUTATIONAL CHEMISTRY AND PHYSICS 2008. [DOI: 10.1007/978-1-4020-8184-2_16] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
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44
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Dittrich M, Freddolino PL, Schulten K. When light falls in LOV: a quantum mechanical/molecular mechanical study of photoexcitation in Phot-LOV1 of Chlamydomonas reinhardtii. J Phys Chem B 2007; 109:13006-13. [PMID: 16852614 PMCID: PMC2453334 DOI: 10.1021/jp050943o] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Plants use sophisticated photosensing mechanisms to maximize their utilization of the available sunlight and to control developmental processes. The plant blue-light receptors of the Phot family mediate plant phototropism and contain two light, oxygen, and voltage (LOV)-sensitive domains as photoactive elements. Here, we report combined quantum mechanical/molecular mechanical simulations of the photocycle of a complete Phot-LOV1 domain from Chlamydomonas reinhardtii. We have investigated the electronic properties and structural changes that follow blue-light absorption. This permitted us to characterize the pathway for flavin-cysteinyl adduct formation, which was found to proceed via a neutral radical state generated by hydrogen atom transfer from the reactive cysteine residue, Cys57, to the chromophore flavin mononucleotide. Interestingly, we find that adduct formation does not cause any larger scale conformational changes in Phot-LOV1, which suggests that dynamic effects mediate signal transmission following the initial photoexcitation event.
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Affiliation(s)
- Markus Dittrich
- Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Peter L. Freddolino
- Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Klaus Schulten
- Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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45
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Choe YK, Nagase S, Nishimoto K. Theoretical study of the electronic spectra of oxidized and reduced states of lumiflavin and its derivative. J Comput Chem 2007; 28:727-39. [PMID: 17226839 DOI: 10.1002/jcc.20533] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Time-dependent density functional theory has been applied to investigate the electronic absorption spectrum of oxidized and reduced lumiflavin and its derivative, 8-NH(2)-lumiflavin. The calculations allow the authors to explain the origin of the difference in spectral features between oxidized and reduced states of lumiflavin. For the reduced lumiflavin, a reasonable assignment of the experimental spectrum has been made for the first time. Furthermore, the results obtained reveal that the NH(2) group plays a critical role in shaping the spectral features of 8-NH(2)-lumiflavin, and offer a reasonable explanation for the spectral changes upon substituting the NH(2) group for the CH(3) group of lumiflavin.
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Affiliation(s)
- Yoong-Kee Choe
- Research Institute for Computational Sciences (RICS), National Institute of Advanced Industrial Science and Technology (AIST), Centeral-2, Umezono 1-1-1, Tsukuba 305-8578, Japan.
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Climent T, González-Luque R, Merchán M, Serrano-Andrés L. Theoretical Insight into the Spectroscopy and Photochemistry of Isoalloxazine, the Flavin Core Ring. J Phys Chem A 2006; 110:13584-90. [PMID: 17165886 DOI: 10.1021/jp065772h] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The electronic singlet-singlet and singlet-triplet electronic transitions of the isoalloxazine ring of the flavin core are studied using second-order perturbation theory within the framework of the CASPT2//CASSCF protocol. The main features of the absorption spectrum are computed at 3.09, 4.28, 4.69, 5.00, and 5.37 eV. The lowest singlet (S1) and triplet (T1) excited states are found to be both of pi character with a singlet-triplet splitting of 0.57 eV. On the basis of the analysis of the computed spin-orbit couplings and the potential energy hypersurfaces built for the relevant excited states, the intrinsic mechanism for photoinduced population of T1 is discussed. Upon light absorption, evolution of the lowest singlet excited state along the relaxation pathway leads ultimately to the population of the lowest triplet state, which is mediated by a singlet-triplet crossing with a state of npi* type. Subsequently a radiationless decay toward T1 through a conical intersection takes place. The intersystem crossing mechanism and the internal conversion processes documented here provide a plausible route to access the lowest triplet state, which has a key role in the photochemistry of the flavin core ring and is mainly responsible for the reactivity of the system.
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Affiliation(s)
- Teresa Climent
- Instituto de Ciencia Molecular, Universitat de València, Apartado 22085, ES-46071 Valencia, Spain
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Wondrak GT, Jacobson MK, Jacobson EL. Endogenous UVA-photosensitizers: mediators of skin photodamage and novel targets for skin photoprotection. Photochem Photobiol Sci 2006; 5:215-37. [PMID: 16465308 DOI: 10.1039/b504573h] [Citation(s) in RCA: 273] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Endogenous chromophores in human skin serve as photosensitizers involved in skin photocarcinogenesis and photoaging. Absorption of solar photons, particularly in the UVA region, induces the formation of photoexcited states of skin photosensitizers with subsequent generation of reactive oxygen species (ROS), organic free radicals and other toxic photoproducts that mediate skin photooxidative stress. The complexity of endogenous skin photosensitizers with regard to molecular structure, pathways of formation, mechanisms of action, and the diversity of relevant skin targets has hampered progress in this area of photobiology and most likely contributed to an underestimation of the importance of endogenous sensitizers in skin photodamage. Recently, UVA-fluorophores in extracellular matrix proteins formed posttranslationally as a consequence of enzymatic maturation or spontaneous chemical damage during chronological and actinic aging have been identified as an abundant source of light-driven ROS formation in skin upstream of photooxidative cellular stress. Importantly, sensitized skin cell photodamage by this bystander mechanism occurs after photoexcitation of sensitizers contained in skin structural proteins without direct cellular photon absorption thereby enhancing the potency and range of phototoxic UVA action in deeper layers of skin. The causative role of photoexcited states in skin photodamage suggests that direct molecular antagonism of photosensitization reactions using physical quenchers of photoexcited states offers a novel chemopreventive opportunity for skin photoprotection.
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Affiliation(s)
- Georg T Wondrak
- Department of Pharmacology and Toxicology, College of Pharmacy, Arizona Cancer Center, University of Arizona, 1515 North Campbell Avenue, Tucson, AZ, USA
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