Photochemistry of Physiologically Active Substances : Study by Time-Resolved Raman Spectroscopy

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Photochemistry of flavin mononucleotide (FMN) : Time-resolved absorption and time-resolved Raman spectra of the T_1 state, anion radical and semiquinone radical of FMN were measured. It was shown that semiquinone radical was generated from the T_1 state via the anion radical.Photochemistry of psoralen and its derivatives : Time-resolved Raman and absorption spectra of these compounds were measured. It was found that the yield of theT_1 state of 8-MOP is much too low compared to those of PS and 5-MOP. This is most probably related to the fact that the photoallergy and phototoxicity of 8-MOP is much smaller than those of PS and 5-MOP.Photochemistry of bilirubin : Transient absorption bands were observed at 450 and 415 nm by *adiation of bilirubin with 308 nm light. The transient band at 450 nm having the lifetime of 260 ns can be assigned to the T_1, state, because it is quenched by oxygen. The identity of the transient exhibiting 415 nm band and having the lifetime of 17μs is not clarified as yet.Photochemistry of nicotinamideadenine dinucleotide (NADH) : The photooxydation reaction of this compound proceeds with the following three steps : (1) generation of cation radical NADH^+ by ejection of an electron. (2) generation of neutral radical NAD by proton transfer. (3) generation of NAD^+ by an electron ejection.Photochemistry of ortho-nitrobenzyl compounds : This photoreaction is initiated with the abstraction of a hydrogen atom by the ortho-nitro group from the methylene group to generate aci-nitroacid. In polar solvents the acinitro acid dissociates into the acinitro anion and a proton which combines to the 2-pyridyl group or 4-nitro group to yield ortho-quinoid or para-acinitro acid.