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

Abstract

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.