Excited-state properties of flavin radicals in flavoproteins: Femtosecond spectroscopy of DNA photolyase, glucose oxidase, and flavodoxin

Abstract : In isolated, catalytically inactive, DNA photolyase from Escherichia coli (E. coli), the flavin adenine dinucleotide cofactor is in its neutral radical state FAD?. It can be activated by a unique light-induced reduction of the flavin, a process initiated by the formation of the excited-state FAD?*. As the photophysical properties of this state are essentially unknown, we performed a comparative characterization by femtosecond transient absorption spectroscopy of FAD?* in DNA photolyase from E. coli and glucose oxidase from Aspergillus niger, and of the excited neutral radical flavin mononucleotide (FMN?*) in flavodoxin from Desulfovibrio gigas. In contrast to photolyase, in glucose oxidase and flavodoxin no electron-transfer products are observed after selective excitation of the flavin radical. In glucose oxidase, FAD?* decays to the ground state in 59 ± 5 ps, close to the 80-ps intrinsic lifetime of the excited state in photolyase, and we discuss that the intrinsic lifetime of the excited state of flavin radical in protein environment is in the 50-80 ps range. FMN?* in flavodoxin decays much faster (2.3 ± 0.3 ps), possibly because of quenching by formation of a very short-lived (INF 0.7 ps) electron-transfer intermediate. Spectroscopically, the excited state of FAD? in photolyase displays a pronounced spectral feature that is absent in the other systems studied. Further characterization by polarized photoselection experiments identifies the feature as an additional induced absorption band at ~ 550 nm superimposed on the ground-state bleaching signal. In view of the unique U-shape configuration of FAD in photolyase, we suggest it to reflect a flavin-adenine charge-transfer interaction.
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Submitted on : Tuesday, June 18, 2013 - 9:25:00 PM
Last modification on : Thursday, July 18, 2019 - 2:54:09 PM

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  • HAL Id : hal-00831842, version 1

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Jie Pan, Martin Byrdin, Corinne Aubert, André Eker, Klaus Brettel, et al.. Excited-state properties of flavin radicals in flavoproteins: Femtosecond spectroscopy of DNA photolyase, glucose oxidase, and flavodoxin. Journal of Physical Chemistry B, American Chemical Society, 2004, 108 (28), pp.10160. ⟨hal-00831842⟩

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