title: Triplet-singlet energy transfer in the complex of auramine O with horse liver alcohol dehydrogenase.
abstract: Triplet-singlet energy transfer has been studied in the complex formed between auramine O (AO) and horse liver alcohol dehydrogenase with optically detected magnetic resonance (ODMR) spectroscopy. The results show that Trp-15 and Tyr residues transfer triplet energy mainly by a trivial process, whereas Trp-314 transfers triplet energy by a Förster process with two observed lifetimes at 77 K of 170 and 50 ms. The different Förster energy-transfer lifetimes are ascribed either to quenching of the two Trp-314 residues of the dimer by a single asymmetrically bound AO or to two distinct conformations of the enzyme-dye complex with differing separations and/or orientations of donor and acceptor. Individual spin sublevel transfer rate constants are reported for the major decay component with the 170-ms Trp triplet-state lifetime; these are found to be highly selective with kxtr much greater than kytr and kztr.
mesh_terms: D000426:Alcohol Dehydrogenase; D000429:Alcohol Oxidoreductases / Q000378:metabolism*; D000814:Aniline Compounds / Q000378:metabolism*; D000818:Animals; D001576:Benzophenoneidum / Q000378:metabolism*; D004735:Energy Transfer; D006736:Horses; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008163:Luminescent Measurements; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008433:Mathematics; D011485:Protein Binding
chemical_list: D000814:Aniline Compounds; D001576:Benzophenoneidum; D000429:Alcohol Oxidoreductases; D000426:Alcohol Dehydrogenase