ESR and ENDOR at 9 and 35 GHz on a powder of the enzyme methanol dehydrogenase from H y p h o m i c r o b i u m X

Abstract
ESR and ENDOR at 9 and 35 GHz have been applied to a powder of the enzyme methanol dehydrogenase from Hyphomicrobium X. The observed g‐tensor and ESR linewidth suggest that the protein‐bonded free radical originates from a quinone. ENDOR measurements at 35 GHz show that there are two strongly coupled protons in the free radical. The ENDOR response of the proton with the largest hyperfine coupling has been simulated by means of a line shape model. From this simulation the principal values of the hyperfine tensor could be extracted. The derived values indicate that the proton concerned is attached directly to a carbon of the quinoid ring.