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Resonance Raman spectra of the neutral and anionic radical semiquinones of flavin adenine dinucleotide in glucose oxidase revisited
Author(s) -
Schelvis Johannes P. M.,
Pun Doris,
Goyal Neelam,
Sokolova Olga
Publication year - 2006
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.1509
Subject(s) - flavoprotein , semiquinone , flavin group , chemistry , flavin adenine dinucleotide , cofactor , photochemistry , resonance raman spectroscopy , protonation , redox , raman spectroscopy , enzyme , biochemistry , organic chemistry , ion , physics , optics
Flavin radical semiquinones are intermediates in important physiological processes. Resonance Raman (RR) spectroscopy is an important tool to determine the interactions between these radical intermediates and their protein environment that regulate their reactivity and role in the reaction mechanisms. RR spectra of flavin radical semiquinones have been available for several flavoproteins, and those in the glucose oxidase (GO) seem significantly different from all the other available data. Since GO is often used not only as a standard for flavin‐containing proteins but also in biotechnological applications, we decided to reexamine the RR spectra of the neutral and anionic radical semiquinone forms of the flavin adenine dinucleotide (FAD) cofactor in this enzyme. The new data show that the vibrational wavenumbers of the neutral and anionic radical semiquinone forms of FAD in GO are very similar to those in other flavoproteins. The discrepancies that were observed earlier seem related to contributions of the FAD in different redox and protonation states. We also obtained the first RR spectra of the oxidized FAD cofactor in GO. Analysis of the vibrations of the oxidized FAD and its anionic radical semiquinone in GO in H 2 O and D 2 O solutions indicates that the subtle differences between these spectra in GO and in other flavoproteins are related to the weak hydrogen‐bonding environment of the FAD cofactor in GO. Copyright © 2006 John Wiley & Sons, Ltd.