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Published on: July 27, 2018
Determination of the g-matrix orientation in flavin radicals by high-field/high-frequency electron-nuclear double
Christopher W M Kay1, Erik Schleicher, Kenichi Hitomi
1Freie Universität Berlin, Fachbereich Physik, Arnimallee 14, 14195 Berlin, Germany.
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.
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