Photosensitized protein damage by water-soluble phthalocyanine zinc(II) and gallium(III) complexes through electron transfer and singlet oxygen production

Abstract

The cationic phthalocyanines (ZnPyPc and GaPyPc) photosensitized the oxidation of human serum albumin (HSA). The scavenger experiment using sodium azide suggested the contribution of 1O2. However, the HSA photodamage was observed in the presence of sodium azide. Because the redox potential of these phthalocyanines were relatively small and the Gibbs energy of the electron transfer from tryptophan to singlet excited states of these phthalocyanines is negative, electron-transfer oxidation is possible in terms of thermodynamics. Fluorescence lifetime measurement supported the electron-transfer mechanism. This study showed that electron transfer–supported oxidation plays an important role in the protein photodamage by cationic phthalocyanines.