title: Dynamics of intramolecular electron transfer reaction of FAD studied by magnetic field effects on transient absorption spectra.
abstract: The kinetics of intermediates generated from intramolecular electron-transfer reaction by photo irradiation of the flavin adenine dinucleotide (FAD) molecule was studied by a magnetic field effect (MFE) on transient absorption (TA) spectra. Existence time of MFE and MFE action spectra have a strong dependence on the pH of solutions. The MFE action spectra have indicated the existence of interconversion between the radical pair and the cation form of the triplet excited state of flavin part. All rate constants of the triplet and the radical pair were determined by analysis of the MFE action spectra and decay kinetics of TA. The obtained values for the interconversion indicate that the formation of cation radical promotes the back electron-transfer reaction to the triplet excited state. Further, rate constants of spin relaxation and recombination have been studied by the time profiles of MFE at various pH. The drastic change of those two factors has been obtained and can be explained by SOC (spin-orbit coupling) induced back electron-transfer promoted by the formation of a stacking conformation at pH > 2.5.
authors.affiliation: Department of Chemistry, University of Tsukuba, 1-1-1 Tenno-dai, Tsukuba City, Ibaraki Pref, 305-8571, Japan.
authors.forename: Masaaki
authors.initials: M
authors.lastname: Murakami
authors.forename: Kiminori
authors.initials: K
authors.lastname: Maeda
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Arai
mesh_terms: D004563:Electrochemistry; D004583:Electrons; D005182:Flavin-Adenine Dinucleotide / Q000737:chemistry*; D005609:Free Radicals / Q000737:chemistry; D007700:Kinetics; D008280:Magnetics; D015394:Molecular Structure; D010777:Photochemistry; D013053:Spectrophotometry; D013057:Spectrum Analysis
chemical_list: D005609:Free Radicals; D005182:Flavin-Adenine Dinucleotide