Open AccessComparative Electron‐Nuclear Double Resonance Study of Two Flavoproteins
Author(s) -
Eriksson L. E. Göran,
Ehrenberg Anders,
Hyde James S.
Publication year - 1970
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1970.tb01198.x
Subject(s) - flavoprotein , chemistry , flavin group , azotobacter vinelandii , protonation , electron paramagnetic resonance , radical , resonance (particle physics) , ubiquinol , cofactor , photochemistry , hyperfine structure , electron nuclear double resonance , dehydrogenase , nuclear magnetic resonance , crystallography , cytochrome c , ion , enzyme , coenzyme q – cytochrome c reductase , biochemistry , nitrogenase , physics , atomic physics , nitrogen , organic chemistry , nitrogen fixation , mitochondrion
The proton electron‐nuclear double resonance (ENDOR) of flavin radicals in NADPH dehydrogenase and a flavoprotein from Azotobacter vinelandii have been studied at −160 and −120°. By combination of the apoprotein of NADPH dehydrogenase with [ 8‐Me ‐ 2 H 3 ]FMN, it was demonstrated that the CH 3 (8) group of the coenzyme gives an ENDOR signal. The ENDOR signals from CH 3 (8) of the two proteins showed different hyperfine couplings which are consistent with the assignments of a radical anion, or a neutral radical enolized at 0(4), in NADPH dehydrogenase and a neutral radical protonated at N(5) in the Azotobacter flavoprotein. Analysis of the matrix‐ENDOR signals in H 2 O and 2 H 2 O yields information concerning the exchangeability of protons both in the constituent water and on the apoprotein in the vicinity of the radical.