PHOTOCHEMICAL HYDROXYLATION OF 7,8-DIMETHYLALLOXAZINE (LUMICHROME)-A FLASH PHOTOLYSIS STUDY |
| |
| Authors: | R. R. Dü ren,,R. H. Dekker,,H. C. A. Van,Beek W. Berends |
| |
| Affiliation: | Biochemical and Biophysical Laboratory of the Technological University, Julianalaan 67, Delft, The Netherlands |
| |
| Abstract: | Abstract— Flash photolysis experiments on the hydroxylation of lumichrome (L) in aqueous 0.5 M H2SO4 solution in the presence of O2 or Ni2+ as triplet quenchers and quantum yield measurements confirm the assignment of the photoreactive species to the protonated form of the excited singlet state. A mechamism concerning the photochemical step is proposed, accounting for the formation of protonated 9-hydroxy-5,10-dihydrolumichrome (LOH3+). This primary stable photoproduct was characterized by spectral and kinetic data. The dark reactions originating from LOH3+ were investigated, and data regarding the successive steps are presented. The reaction LOH3+ L→ LO + LH3+ is demonstrated to be a two-electron reduction. The rate constant for the reaction of LH2+ with O2 is much larger than that for the oxidation of LH3+ by oxygen. |
| |
| Keywords: | |
|
|
