title: Excited state processes in 1-deazariboflavin studied by ultrafast fluorescence kinetics.
abstract: The photochemical reactions of the 1-deaza derivative of riboflavin (RF) have been studied by sub-ps time-resolved fluorescence spectroscopy. A potential effect of the solvent polarity and hydrogen bonding capability on the excited state (ES) dynamics was tested by measuring 1-deaza RF in water and, after acetylation of the sugar moiety, also in acetonitrile. Opposite to former reports, which indicated no fluorescence after laser excitation (Spencer et al. [1977] Biochemistry 16: 3586-3594), we find a significant fluorescence in either solvent. For both compounds, the fluorescence decays are biexponential with lifetimes in the ps time domain (1.8 and 12.5 ps for 1-deaza RF, and 3 and 87 ps for Ac(4)-1-deaza RF). In addition, a third, independent fluorescence decay was observed for both compounds. The remarkably slower second decay process for the measurements of the tetra-acetyl derivative in acetonitrile points to the involvement of hydrogen bonding or changes in the protonation/tautomerization state in the ES. In contrast to the parent compound (RF), no triplet state formation can be detected for 1-deaza RF, making the internal conversion and the fluorescence the only decay processes of the ES.
authors.affiliation: Max-Planck-Institut für Bioanorganische Chemie, Mülheim, Germany.
authors.forename: Chavdar
authors.initials: C
authors.lastname: Slavov
authors.forename: Madina
authors.initials: M
authors.lastname: Mansurova
authors.forename: Alfred R
authors.initials: AR
authors.lastname: Holzwarth
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Gärtner
mesh_terms: D000107:Acetylation; D005453:Fluorescence; D006860:Hydrogen Bonding; D007700:Kinetics; D012997:Solvents; D014372:Tubercidin / Q000031:analogs & derivatives* / Q000737:chemistry
chemical_list: D012997:Solvents; C036159:1-deazatubercidin; D014372:Tubercidin