Determination of the g-matrix orientation in flavin radicals by high-field/high-frequency electron-nuclear double resonance.
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.
Kay
Christopher W M
CW
Freie Universität Berlin, Fachbereich Physik, Arnimallee 14, 14195 Berlin, Germany.
Schleicher
Erik
E
Hitomi
Kenichi
K
Todo
Takeshi
T
Bittl
Robert
R
Weber
Stefan
S
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
D005415:Flavins; D005609:Free Radicals