RESONANCE RAMAN AND INFRARED SPECTRAL STUDIES ON RADICAL-ANIONS OF MODEL PHOTOSYNTHETIC REACTION-CENTER QUINONES (NAPHTHOQUINONE DERIVATIVES)

Quinones play a vital role in the processes of electron transfer in ba cterial photosynthetic reaction centers. It is of interest to investig ate photochemical reactions involving quinones with a view to elucidat e structure-function relationships in biological processes. Resonance Raman and FTIR spectra of electrochemically generated radical anions o f 2-methyl-1,4-naphthoquinone, and 2-methyl-3-phytyl-1,4-naphthoquinon e, also known as Vitamin K-3 and Vitamin K-1, respectively, (model com pound for Q(A) in Rhodopseudomonas viridis, a bacterial photosynthetic reaction center) have been reported. The same study has also been ext ended to 1,4-naphthoquinone for comparison. The vibrational assignment s were carried out on the basis of comparison with our earlier time re solved resonance Raman studies on photochemically generated radical an ions of 1,4-naphthoquinone and 2-methyl-1,4-naphthoquinone (Balakrishn an er al., J. Phys. Chern., 100, (1996), 16472-16478). These in vitro results have been compared with the reported vibrational spectral data under in vivo conditions.