MO STUDY OF HYDRIDE TRANSFER BETWEEN NADH AND FLAVIN NUCLEOTIDES

The mechanism has been MO-theoretically described for the reaction of NADH and flavin nucleotides. Their bioactive regions were found to be the part forming transbutadiene type in the molecular by examing the r espective HOMO and LUMO electron densities of nicotinamide ring and is oalloxazine ring of flavin. The elecron densities of 1, 2, 3 and 4 pos itions of the transbutadiene part were found to be considerabiy larger than those of any other positions in the molecules. A loose molecular complex, which stacks with congruity between C(4) of nicotinamide rin g and N(5) of the isoalloxazine ring, was estimated to be formed by ca lculating the quantities of charge transfer occuring through 1, 2, 3 a nd 4 positions between them. Accordingly, we propose the mechanism tha t molecular complex first would be formed and follwed by the hydride t ransfer.