Photogenerated radical intermediates of vitamin K-1: a time-resolved resonance Raman study

Quinones play a vital role in the process of electron transfer in bacterial photosynthetic reaction centers. It is of interest to investigate the phot ochemical reactions involving quinones with a view to elucidating the struc ture-function relationships in the biological processes. Resonance Raman sp ectra of radical anions and the time-resolved resonance Raman spectra of vi tamin K-1 (model compound for Q(A) in Rhodopseudomonas viridis, a bacterial photosynthetic reception center) are presented. The photochemical intermed iates of vitamin K-1, viz. radical anion, ketyl radical and o-quinone methi de have been identified. The vibrational assignments of all these intermedi ates are made on the basis of comparison with our earlier TR3 studies on ra dical anions of naphthoquinone and menaquinone. (C) 1999 Elsevier Science B .V. All rights reserved.