title: Picosecond fluorescence lifetime of the coenzyme of D-amino acid oxidase.
abstract: Conformational difference surrounding the coenzyme, FAD, of D-amino acid oxidase (D-amino-acid:O2 oxidoreductase (deaminating), EC 1.4.3.3) between its monomeric and dimeric forms were examined by observing fluorescence of FAD. The fluorescence lifetimes of the coenzyme was measured directly with a mode-locked Nd:YAG laser and a streak camera in picosecond region. The values of lifetime of FAD fluorescence in the monomer and dimer were 130 +/- 20 ps and 40 +/- 10 ps, respectively. The relative quantum yield of the fluorescence of FAD combined with the protein to that of free FAD depended on the concentration of the enzyme; it was higher at lower concentration. Comparing the lifetime with relative quantum yield of FAD combined with the protein, it is concluded that the fluorescence is quenched mostly by a dynamic process. These results indicate that the distance between the isoalloxazine nucleus and a quencher is nearer in the dimer than in the monomer.
mesh_terms: D003605:D-Amino-Acid Oxidase / Q000378:metabolism*; D005182:Flavin-Adenine Dinucleotide / Q000032:analysis*; D007700:Kinetics; D008433:Mathematics; D011789:Quantum Theory; D013050:Spectrometry, Fluorescence; D013997:Time Factors
chemical_list: D005182:Flavin-Adenine Dinucleotide; D003605:D-Amino-Acid Oxidase