Influence of acetic acid on the photocatalytic activity of photosensitiser-amphiphilic polymer complexes in the oxidation reaction of tryptophan.

The effect of acetic acid on the photosensitizing activity of dimegin (DMG), chlorin e6 (Ce6), and their complexes with amphiphilic polymers-Pluronic F-127 and poly-N-vinylpyrrolidone (PVP)-in the model reaction of tryptophan photo-oxidation has been established. It was shown that the photocatalytic activity of photosensitizers (PS), which is characterized by the effective constant of the tryptophan photo-oxidation rate (keff), increases by 1.4 times for DMG, while for Ce6, it decreases by 1.2 times in a weak acidic medium (pH ∼ 4). The influence of acetic acid on the effective constant keff of the tryptophan photo-oxidation rate in the presence of PS-amphiphilic polymer complexes is determined by the nature of the polymer. Thus, the photocatalytic activity of the PS-F127 system decreases at pH ∼ 4.0, and the photocatalytic activity of PS-PVP complexes is insensitive to the presence of acetic acid in the medium. It has been suggested that the observed effects in the PS-F127 system in a weak acidic medium (pH ∼ 4) are associated with the influence of acetic acid on the supramolecular structure of Pluronic F127.