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Short‐Lived Radical Intermediates in the Photochemistry of Glucose Oxidase
Author(s) -
Nag Lipsa,
Lukacs Andras,
Vos Marten H.
Publication year - 2019
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201900329
Subject(s) - chemistry , flavin group , photochemistry , electron transfer , flavoprotein , ultrafast laser spectroscopy , radical ion , proton coupled electron transfer , femtochemistry , radical , electron transport chain , picosecond , flavin adenine dinucleotide , spectroscopy , femtosecond , cofactor , organic chemistry , ion , biochemistry , physics , quantum mechanics , enzyme , laser , optics
Glucose oxidase is a flavoprotein that is relatively well‐studied as a physico‐chemical model system. The flavin cofactor is surrounded by several aromatic acid residues that can act as direct and indirect electron donors to photoexcited flavin. Yet, the identity of the photochemical product states is not well established. We present a detailed full spectral reinvestigation of this issue using femtosecond fluorescence and absorption spectroscopy. Based on a recent characterization of the unstable tyrosine cation radical TyrOH •+ , we now propose that the primary photoproduct involves this species, which was previously not considered. Formation of this product is followed by competing charge recombination and radical pair stabilization reactions that involve proton transfer and radical transfer to tryptophan. A minimal kinetic model is proposed, including a fraction of TyrOH .+ that is stabilized up to the tens of picoseconds timescale, suggesting a potential role of this species as intermediate in biochemical electron transfer reactions.