Partially deuterated and various substituted flavin and thiaflavin model compounds have been synthesized. For the first time, high-resolution H, D, and 14N ENDOR and TRIPLE resonance experiments in fluid solutions have been performed on the paramagnetic derivatives of these compounds. Additionally, valuable information has been obtained about hyperfine anisotropies and molecular structures from ENDOR in rigid matrices. Solid matrix ENDOR studies of native flavoenzymes, namely, "Old Yellow Enzyme" (NADPH dehydrogenase), two flavodoxins, and a methanol oxidase are reported. The ENDOR matrix signals of the various flavoproteins are different in intensity, suggesting that the microenvironments are remarkably different. Applicabilities and limitations of the ENDOR technique in the studies of flavins and flavoenzymes are discussed.
Riboflavin‐binding apoprotein isolated from egg white has been used as a protein matrix for a variety of substituted and/or deuterated flavins. The neutral radical states of the reconstituted flavoproteins were studied by ENDOR (electron nuclear double resonance) spectroscopy in disordered solids. For the first time all major hyperfine coupling constants of a flavin cofactor embedded within a protein could be measured and unambiguously assigned to molecular positions. Some conclusions about the geometrical arrangement of the flavin within the protein pocket and about molecular motions could be drawn.
Phytochrome controlled chloroplast movement in Mougeotia is induced by flashes of polarized red light. Two subsequent flashes, separated by a dark interval of a few seconds, are much more effective than two simultaneous flashes; a maximal cumulative effect is reached if the duration of the dark interval is 30 ms or longer. We propose two light reactions in series, separated by a very fast dark reaction. Preliminary evidence is given that the energy requirement for these light reactions is different. It is suggested that the two reactions are related in some way to free and bound phytochrome.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.