title: Determination of the g-matrix orientation in flavin radicals by high-field/high-frequency electron-nuclear double resonance.
abstract: A high-microwave-frequency/high-magnetic-field pulsed electron-nuclear double resonance (ENDOR) study performed at 94 GHz on the flavin semiquinone cofactor of Xenopus laevis (6-4) photolyase in its neutral radical state is presented. Although the principal values of the flavin radical's g-matrix are not fully resolved in the 94-GHz EPR spectrum in a nonoriented sample, the orientation of the principal axes of g is obtained by exploiting the orientation selection of the proton ENDOR signals from the methyl protons at C-8alpha and the deuteron ENDOR signals from D-5 in an enzyme sample in deuterated buffer. This procedure for assigning the orientation of g relative to the molecular frame makes use of commercially available ENDOR instrumentation without the necessity to perform single-crystal studies.
authors.affiliation: Freie Universität Berlin, Fachbereich Physik, Arnimallee 14, 14195 Berlin, Germany.
authors.forename: Christopher W M
authors.initials: CW
authors.lastname: Kay
authors.forename: Erik
authors.initials: E
authors.lastname: Schleicher
authors.forename: Kenichi
authors.initials: K
authors.lastname: Hitomi
authors.forename: Takeshi
authors.initials: T
authors.lastname: Todo
authors.forename: Robert
authors.initials: R
authors.lastname: Bittl
authors.forename: Stefan
authors.initials: S
authors.lastname: Weber
mesh_terms: D000818:Animals; D004578:Electron Spin Resonance Spectroscopy; D005415:Flavins / Q000737:chemistry*; D005609:Free Radicals / Q000737:chemistry*; D008280:Magnetics; D008872:Microwaves; D015394:Molecular Structure; D014982:Xenopus laevis
chemical_list: D005415:Flavins; D005609:Free Radicals