title: New insights into the ultrafast photophysics of oxidized and reduced FAD in solution.
abstract: The ultrafast photophysics of oxidized and reduced flavin adenine dinucleotide (FAD) in aqueous solution was studied by broadband UV-vis femtosecond transient absorption spectroscopy. We observed that oxidized FAD (FAD(ox)) in solution readily aggregates at submillimolar concentration. Upon excitation of FAD(ox), three excited-state lifetimes were found and assigned to three different species: the closed (stacked) conformation of the monomer (∼5.4 ps), the open (extended) conformation of the monomer (∼2.8 ns), and the dimer (∼27 ps). In the case of the stacked conformation of the monomer, we show that intramolecular electron transfer from the adenine to the isoalloxazine ring occurs with a time constant of 5.4 ps and is followed by charge recombination on a faster time scale, namely, 390 fs. We additionally demonstrate that deprotonated reduced flavin (FADH(-)) undergoes biphotonic ionization under high excitation fluence and dissociates into a hydrated electron and the neutral semiquinone radical FADH(•).
authors: Département de Chimie, École Normale Supérieure, Paris, France.
authors: Johanna
authors: J
authors: Brazard
authors: Anwar
authors: A
authors: Usman
authors: Fabien
authors: F
authors: Lacombat
authors: Christian
authors: C
authors: Ley
authors: Monique M
authors: MM
authors: Martin
authors: Pascal
authors: P
authors: Plaza
mesh_terms: D005182:Flavin-Adenine Dinucleotide / Q000138:chemical synthesis / Q000737:chemistry*; D015394:Molecular Structure; D010084:Oxidation-Reduction; D055668:Photochemical Processes; D012996:Solutions
chemical_list: D012996:Solutions; D005182:Flavin-Adenine Dinucleotide