Flavins contain  isoalloxazine as chromophore and function as reaction centers of oxido-reduction reactions in various flavoproteins. Fluorescence dynamics of  FAD is described in the time domain from nanoseconds to femtoseconds. The quenching mechanism of  free flavins by aromatic amino acids and of flavodoxin, Desulfovibrio vulgaris strain Miyazaki was investigated by means of transient  absorption spectroscopy in picosecond time again. Photoinduced electron transfer from tyrosine and tryptophan to the excited flavins is responsible for the quenching.

D-amino acid oxidase contains one mole of FAD per monomer and in an equilibrium state between monomer and dimer or origomer depending on its concentration. It was found that fluorescence lifetime of the monomer is 180 ps and that of dimer 44 ps. Temperature transition in the protein structure of D-amino acid oxidase is also investigated by picosecond-resolved fluorescence.

Ultrafast photophysics of “non-fluorescent” flavoproteins, as D-amino acid oxidase-benzoate complex, glucose oxidase, medium-chain acyl CoA dehydrogenase, riboflavin binding protein and flavodoxins, wild type and its mutants, is described in femtoseconds-picoseconds time region by means of an up-conversion method. Tryptophan(es) and/or tyrosine(s) locate near isoalloxazine ring in all of these flavoproteins. Fluorescence lifetimes of riboflavin binding protein were shortest, 94 fs (95%) and 1.02 ps (5%),  among  these flavoproteins. The rate constants of the photoinduced electron transfer from Trp-60 and from Tyr-98 to the excited isoalloxazine in flavodoxin were determined with its mutants to be 3.5 ps^-1 and 2.6 ps^-1 , respectively, The rate constant of flavodoxin wild type, where both of Trp-60 and Tyr-98 exist, was 6.3 ps^-1 , which is almost identical with sum of 3.5 and 2.6 ps^-1 .