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Uzhytchak M, Smolková B, Frtús A, Stupakov A, Lunova M, Scollo F, Hof M, Jurkiewicz P, Sullivan GJ, Dejneka A, Lunov O. Sensitivity of endogenous autofluorescence in HeLa cells to the application of external magnetic fields. Sci Rep 2023; 13:10818. [PMID: 37402779 DOI: 10.1038/s41598-023-38015-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Accepted: 06/30/2023] [Indexed: 07/06/2023] Open
Abstract
Dramatically increased levels of electromagnetic radiation in the environment have raised concerns over the potential health hazards of electromagnetic fields. Various biological effects of magnetic fields have been proposed. Despite decades of intensive research, the molecular mechanisms procuring cellular responses remain largely unknown. The current literature is conflicting with regards to evidence that magnetic fields affect functionality directly at the cellular level. Therefore, a search for potential direct cellular effects of magnetic fields represents a cornerstone that may propose an explanation for potential health hazards associated with magnetic fields. It has been proposed that autofluorescence of HeLa cells is magnetic field sensitive, relying on single-cell imaging kinetic measurements. Here, we investigate the magnetic field sensitivity of an endogenous autofluorescence in HeLa cells. Under the experimental conditions used, magnetic field sensitivity of an endogenous autofluorescence was not observed in HeLa cells. We present a number of arguments indicating why this is the case in the analysis of magnetic field effects based on the imaging of cellular autofluorescence decay. Our work indicates that new methods are required to elucidate the effects of magnetic fields at the cellular level.
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Affiliation(s)
- Mariia Uzhytchak
- Department of Optical and Biophysical Systems, Institute of Physics of the Czech Academy of Sciences, Prague, 18221, Czech Republic
| | - Barbora Smolková
- Department of Optical and Biophysical Systems, Institute of Physics of the Czech Academy of Sciences, Prague, 18221, Czech Republic
| | - Adam Frtús
- Department of Optical and Biophysical Systems, Institute of Physics of the Czech Academy of Sciences, Prague, 18221, Czech Republic
| | - Alexandr Stupakov
- Department of Optical and Biophysical Systems, Institute of Physics of the Czech Academy of Sciences, Prague, 18221, Czech Republic
| | - Mariia Lunova
- Department of Optical and Biophysical Systems, Institute of Physics of the Czech Academy of Sciences, Prague, 18221, Czech Republic
- Institute for Clinical and Experimental Medicine (IKEM), Prague, 14021, Czech Republic
| | - Federica Scollo
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences, Prague, 18223, Czech Republic
| | - Martin Hof
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences, Prague, 18223, Czech Republic
| | - Piotr Jurkiewicz
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences, Prague, 18223, Czech Republic
| | - Gareth John Sullivan
- Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
- Department of Pediatric Research, Oslo University Hospital, Oslo, Norway
- Department of Immunology, Institute of Clinical Medicine, University of Oslo, Oslo, Norway
| | - Alexandr Dejneka
- Department of Optical and Biophysical Systems, Institute of Physics of the Czech Academy of Sciences, Prague, 18221, Czech Republic
| | - Oleg Lunov
- Department of Optical and Biophysical Systems, Institute of Physics of the Czech Academy of Sciences, Prague, 18221, Czech Republic.
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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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Kyriacou CP, Rosato E. Genetic analysis of cryptochrome in insect magnetosensitivity. Front Physiol 2022; 13:928416. [PMID: 36035470 PMCID: PMC9399412 DOI: 10.3389/fphys.2022.928416] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Accepted: 07/05/2022] [Indexed: 11/18/2022] Open
Abstract
The earth's magnetic field plays an important role in the spectacular migrations and navigational abilities of many higher animals, particularly birds. However, these organisms are not amenable to genetic analysis, unlike the model fruitfly, Drosophila melanogaster, which can respond to magnetic fields under laboratory conditions. We therefore review the field of insect magnetosensitivity focusing on the role of the Cryptochromes (CRYs) that were first identified in Arabidopsis and Drosophila as key molecular components of circadian photo-entrainment pathways. Physico-chemical studies suggest that photo-activation of flavin adenine dinucleotide (FAD) bound to CRY generates a FADo- Trpo+ radical pair as electrons skip along a chain of specific Trp residues and that the quantum spin chemistry of these radicals is sensitive to magnetic fields. The manipulation of CRY in several insect species has been performed using gene editing, replacement/rescue and knockdown methods. The effects of these various mutations on magnetosensitivity have revealed a number of surprises that are discussed in the light of recent developments from both in vivo and in vitro studies.
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Affiliation(s)
- Charalambos P. Kyriacou
- Department of Genetics and Genome Biology, University of Leicester, Leicester, United Kingdom
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Zadeh-Haghighi H, Simon C. Magnetic field effects in biology from the perspective of the radical pair mechanism. J R Soc Interface 2022; 19:20220325. [PMID: 35919980 PMCID: PMC9346374 DOI: 10.1098/rsif.2022.0325] [Citation(s) in RCA: 34] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Accepted: 07/14/2022] [Indexed: 04/07/2023] Open
Abstract
Hundreds of studies have found that weak magnetic fields can significantly influence various biological systems. However, the underlying mechanisms behind these phenomena remain elusive. Remarkably, the magnetic energies implicated in these effects are much smaller than thermal energies. Here, we review these observations, and we suggest an explanation based on the radical pair mechanism, which involves the quantum dynamics of the electron and nuclear spins of transient radical molecules. While the radical pair mechanism has been studied in detail in the context of avian magnetoreception, the studies reviewed here show that magnetosensitivity is widespread throughout biology. We review magnetic field effects on various physiological functions, discussing static, hypomagnetic and oscillating magnetic fields, as well as isotope effects. We then review the radical pair mechanism as a potential unifying model for the described magnetic field effects, and we discuss plausible candidate molecules for the radical pairs. We review recent studies proposing that the radical pair mechanism provides explanations for isotope effects in xenon anaesthesia and lithium treatment of hyperactivity, magnetic field effects on the circadian clock, and hypomagnetic field effects on neurogenesis and microtubule assembly. We conclude by discussing future lines of investigation in this exciting new area of quantum biology.
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Affiliation(s)
- Hadi Zadeh-Haghighi
- Department of Physics and Astronomy, University of Calgary, Calgary, Alberta, Canada T2N 1N4
- Institute for Quantum Science and Technology, University of Calgary, Calgary, Alberta, Canada T2N 1N4
- Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada T2N 1N4
| | - Christoph Simon
- Department of Physics and Astronomy, University of Calgary, Calgary, Alberta, Canada T2N 1N4
- Institute for Quantum Science and Technology, University of Calgary, Calgary, Alberta, Canada T2N 1N4
- Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada T2N 1N4
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Jana R, Gautam RK, Bapli A, Seth D. Photodynamics of biological active flavin in the presence of zwitterionic surfactants. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2022; 264:120304. [PMID: 34464918 DOI: 10.1016/j.saa.2021.120304] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 08/16/2021] [Accepted: 08/17/2021] [Indexed: 06/13/2023]
Abstract
In the flavin family of photoactive biomolecules, lumichrome (LM) is a very important compound. It contains a tri-cyclic structure with methyl groups at two sides. It formed by the partial decomposition and biodegradation of riboflavin in both acidic as well as in neutral medium. Herein, we have studied the photophysical properties of LM in the presence of two zwitterionic surfactants, namely dodecyldimethyl(3-sulfopropyl) ammonium hydroxide inner salt (DSB), and tetradecyldimethyl(3-sulfopropyl) ammonium hydroxide inner salt (TSB), having the same head group but a different tail part. We have used steady-state absorption, fluorescence emission, and time-resolved fluorescence emission measurements. We observed that in the presence of zwitterionic surfactant aggregates LM shows excitation and emission wavelength dependent emission properties, which demonstrate the structural changes that take place from one form to another prototropic form of LM molecule. The higher rotational relaxation time of LM in the case of DSB compared to TSB demonstrated that LM is facing more rigid environment in DSB micelles compared to TSB micelles.
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Affiliation(s)
- Rabindranath Jana
- Department of Chemistry, Indian Institute of Technology Patna, Patna 801103, Bihar, India
| | - Rajesh Kumar Gautam
- Department of Chemistry, Indian Institute of Technology Patna, Patna 801103, Bihar, India
| | - Aloke Bapli
- Department of Chemistry, Indian Institute of Technology Patna, Patna 801103, Bihar, India
| | - Debabrata Seth
- Department of Chemistry, Indian Institute of Technology Patna, Patna 801103, Bihar, India.
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Abstract
We demonstrate, by direct, single-cell imaging kinetic measurements, that endogenous autofluorescence in HeLa cells is sensitive to the application of external magnetic fields of 25 mT and less. We provide spectroscopic and mechanistic evidence that our findings can be explained in terms of magnetic field effects on photoinduced electron transfer reactions to flavins, through the radical pair mechanism. The observed magnetic field dependence is consistent with a triplet-born radical pair and a B1/2 value of 18.0 mT with a saturation value of 3.7%.
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Zhukov I, Kiryutin A, Panov M, Fishman N, Morozova O, Lukzen N, Ivanov K, Vieth HM, Sagdeev R, Yurkovskaya A. Exchange interaction in short-lived flavine adenine dinucleotide biradical in aqueous solution revisited by CIDNP (chemically induced dynamic nuclear polarization) and nuclear magnetic relaxation dispersion. MAGNETIC RESONANCE (GOTTINGEN, GERMANY) 2021; 2:139-148. [PMID: 37904760 PMCID: PMC10539776 DOI: 10.5194/mr-2-139-2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Accepted: 03/29/2021] [Indexed: 11/01/2023]
Abstract
Flavin adenine dinucleotide (FAD) is an important cofactor in many light-sensitive enzymes. The role of the adenine moiety of FAD in light-induced electron transfer was obscured, because it involves an adenine radical, which is short-lived with a weak chromophore. However, an intramolecular electron transfer from adenine to flavin was revealed several years ago by Robert Kaptein by using chemically induced dynamic nuclear polarization (CIDNP). The question of whether one or two types of biradicals of FAD in aqueous solution are formed stays unresolved so far. In the present work, we revisited the CIDNP study of FAD using a robust mechanical sample shuttling setup covering a wide magnetic field range with sample illumination by a light-emitting diode. Also, a cost efficient fast field cycling apparatus with high spectral resolution detection up to 16.4 T for nuclear magnetic relaxation dispersion studies was built based on a 700 MHz NMR spectrometer. Site-specific proton relaxation dispersion data for FAD show a strong restriction of the relative motion of its isoalloxazine and adenine rings with coincident correlation times for adenine, flavin, and their ribityl phosphate linker. This finding is consistent with the assumption that the molecular structure of FAD is rigid and compact. The structure with close proximity of the isoalloxazine and purine moieties is favorable for reversible light-induced intramolecular electron transfer from adenine to triplet excited flavin with formation of a transient spin-correlated triplet biradical F⚫ - -A⚫ + . Spin-selective recombination of the biradical leads to the formation of CIDNP with a common emissive maximum at 4.0 mT detected for adenine and flavin protons. Careful correction of the CIDNP data for relaxation losses during sample shuttling shows that only a single maximum of CIDNP is formed in the magnetic field range from 0.1 mT to 9 T; thus, only one type of FAD biradical is detectable. Modeling of the CIDNP field dependence provides good agreement with the experimental data for a normal distance distribution between the two radical centers around 0.89 nm and an effective electron exchange interaction of - 2.0 mT.
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Affiliation(s)
- Ivan V. Zhukov
- International Tomography Center, Siberian Branch of the Russian
Academy of Sciences, Novosibirsk, 630090, Russia
- Department of Natural Sciences, Novosibirsk State University, Novosibirsk, 630090, Russia
| | - Alexey S. Kiryutin
- International Tomography Center, Siberian Branch of the Russian
Academy of Sciences, Novosibirsk, 630090, Russia
- Department of Natural Sciences, Novosibirsk State University, Novosibirsk, 630090, Russia
| | - Mikhail S. Panov
- International Tomography Center, Siberian Branch of the Russian
Academy of Sciences, Novosibirsk, 630090, Russia
- Department of Natural Sciences, Novosibirsk State University, Novosibirsk, 630090, Russia
| | - Natalya N. Fishman
- International Tomography Center, Siberian Branch of the Russian
Academy of Sciences, Novosibirsk, 630090, Russia
- Department of Natural Sciences, Novosibirsk State University, Novosibirsk, 630090, Russia
| | - Olga B. Morozova
- International Tomography Center, Siberian Branch of the Russian
Academy of Sciences, Novosibirsk, 630090, Russia
- Department of Natural Sciences, Novosibirsk State University, Novosibirsk, 630090, Russia
| | - Nikita N. Lukzen
- International Tomography Center, Siberian Branch of the Russian
Academy of Sciences, Novosibirsk, 630090, Russia
- Department of Natural Sciences, Novosibirsk State University, Novosibirsk, 630090, Russia
| | - Konstantin L. Ivanov
- International Tomography Center, Siberian Branch of the Russian
Academy of Sciences, Novosibirsk, 630090, Russia
- Department of Natural Sciences, Novosibirsk State University, Novosibirsk, 630090, Russia
| | - Hans-Martin Vieth
- International Tomography Center, Siberian Branch of the Russian
Academy of Sciences, Novosibirsk, 630090, Russia
- Institut für Experimentalphysik, Freie Universität Berlin, 14195 Berlin, Germany
| | - Renad Z. Sagdeev
- International Tomography Center, Siberian Branch of the Russian
Academy of Sciences, Novosibirsk, 630090, Russia
- Department of Natural Sciences, Novosibirsk State University, Novosibirsk, 630090, Russia
| | - Alexandra V. Yurkovskaya
- International Tomography Center, Siberian Branch of the Russian
Academy of Sciences, Novosibirsk, 630090, Russia
- Department of Natural Sciences, Novosibirsk State University, Novosibirsk, 630090, Russia
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Kimura S, Kimura S, Kato K, Teki Y, Nishihara H, Kusamoto T. A ground-state-dominated magnetic field effect on the luminescence of stable organic radicals. Chem Sci 2021; 12:2025-2029. [PMID: 34163964 PMCID: PMC8179284 DOI: 10.1039/d0sc05965j] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 12/16/2020] [Indexed: 11/21/2022] Open
Abstract
Organic radicals are an emerging class of luminophores possessing multiplet spin states and potentially showing spin-luminescence correlated properties. We investigated the mechanism of recently reported magnetic field sensitivity in the emission of a photostable luminescent radical, (3,5-dichloro-4-pyridyl)bis(2,4,6-trichlorophenyl)methyl radical (PyBTM) doped into host αH-PyBTM molecular crystals. The magnetic field (0-14 T), temperature (4.2-20 K), and the doping concentration (0.1, 4, 10, and 22 wt%) dependence on the time-resolved emission were examined by measuring emission decays of the monomer and excimer. Quantum mechanical simulations on the decay curves disclosed the role of the magnetic field; it dominantly affects the spin sublevel population of radical dimers in the ground states. This situation is distinctly different from that in conventional closed-shell luminophores, where the magnetic field modulates their excited-state spin multiplicity. Namely, the spin degree of freedom of ground-state open-shell molecules is a new key for achieving magnetic-field-controlled molecular photofunctions.
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Affiliation(s)
- Shun Kimura
- Department of Life and Coordination-Complex Molecular Science, Institute for Molecular Science 5-1 Higashiyama, Myodaiji Okazaki Aichi 444-8787 Japan
- Department of Chemistry, Graduate School of Science, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku Tokyo 113-0033 Japan
| | - Shojiro Kimura
- Institute for Materials Research, Tohoku University 2-1-1 Katahira, Aoba-ku Sendai 980-8577 Japan
| | - Ken Kato
- Division of Molecular Materials Science, Graduate School of Science, Osaka City University 3-3-138 Sugimoto, Sumiyoshi-ku Osaka 558-8585 Japan
| | - Yoshio Teki
- Division of Molecular Materials Science, Graduate School of Science, Osaka City University 3-3-138 Sugimoto, Sumiyoshi-ku Osaka 558-8585 Japan
| | - Hiroshi Nishihara
- Department of Chemistry, Graduate School of Science, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku Tokyo 113-0033 Japan
- Research Center for Science and Technology, Tokyo University of Science 2641 Yamazaki Noda Chiba 278-8510 Japan
| | - Tetsuro Kusamoto
- Department of Life and Coordination-Complex Molecular Science, Institute for Molecular Science 5-1 Higashiyama, Myodaiji Okazaki Aichi 444-8787 Japan
- SOKENDAI (The Graduate University for Advanced Studies) Shonan Village, Hayama 240-0193 Kanagawa Japan
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Hughes JA, Hardman SJO, Scrutton NS, Graham DM, Woodward JR, Jones AR. Observation of the Δg mechanism resulting from the ultrafast spin dynamics that follow the photolysis of coenzyme B 12. J Chem Phys 2019; 151:201102. [PMID: 31779325 DOI: 10.1063/1.5127258] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Throughout nature, both free radicals and transient radical reaction intermediates are vital to many biological functions. Coenzyme B12 is a case in point. This organometallic cofactor generates a radical pair upon activation in its dependent enzymes by substrate binding and following photolysis. The resulting cob(ii)alamin/5'-deoxyadenosyl radical pair has unusual magnetic properties that present a challenge to detailed investigation at ambient temperatures. Here, we use femtosecond transient absorption spectroscopy adapted for magnetic field exposure to reveal that the spin dynamics of the B12 radical pair are sufficiently fast for magnetic field effects to be observed on the ultrafast reaction kinetics. Moreover, the large difference in g-values between the radicals of the pair means that effects of the Δg mechanism are observed for the first time for a radical pair system exposed to magnetic fields below 1 T. Spin dynamic simulations allow a value of the cob(ii)alamin radical g-value (2.105) at ambient temperature to be extracted and, because the spin dynamic time scale is faster than the diffusional rotation of the cob(ii)alamin radical, the observed value corresponds to the anisotropic g|| value for this radical.
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Affiliation(s)
- Joanna A Hughes
- Manchester Institute of Biotechnology and Department of Chemistry, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
| | - Samantha J O Hardman
- Manchester Institute of Biotechnology and Department of Chemistry, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
| | - Nigel S Scrutton
- Manchester Institute of Biotechnology and Department of Chemistry, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
| | - Darren M Graham
- Photon Science Institute, The University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
| | - Jonathan R Woodward
- Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Japan
| | - Alex R Jones
- Manchester Institute of Biotechnology and Department of Chemistry, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
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Matthews E, Dessent CEH. Observation of Near-Threshold Resonances in the Flavin Chromophore Anions Alloxazine and Lumichrome. J Phys Chem Lett 2018; 9:6124-6130. [PMID: 30277786 DOI: 10.1021/acs.jpclett.8b02529] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Lumichrome (LC) is the chromophore of the flavin family of photoactive biomolecules, where key biochemical activity involves interplay between redox and photophysical events. Questions remain about the relationship between the redox status of the ground and excited states and demand an improved understanding of the intrinsic photochemistry. Using anion photodissociation spectroscopy, we have measured the intrinsic electronic spectroscopy (564-220 nm) and accompanying photodegradation pathways of the deprotonated anionic form of LC. Experiments were also performed on alloxazine (AL), which is equivalent to LC minus two methyl groups. We observe a resonance state close to 3.8 eV for both anions for the first time, which we tentatively assign to dipole-bound excited states. For AL this state is sufficiently long-lived to facilitate dissociative electron attachment. Our results suggest that the presence of methyl group rotors at key positions along the molecular dipole may reduce the lifetime of the resonance state and hence provide a structural barrier to valence electron capture, and ensuing molecular dissociation.
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Affiliation(s)
- Edward Matthews
- Department of Chemistry , University of York , Heslington, York YO10 5DD , U.K
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