Singlet oxygen production by UV and visible photoexcited porphyrins under different states of aggregation

Tryptophan photosensitization was used to determine the quantum yield of singlet oxygen production by porphyrins irradiated with ultraviolet or visible light in phosphate buffer at pH 7.0. From a preliminary study of aggregation of these dyes, it was established that uroporphyrin, hematoporphyrin and deuteroporphyrin allowed to investigate the behaviour of monomers, dimers and higher aggregates, respectively. The photosensitization results show that monomers and polymers produce singlet oxygen with very similar yields. Inclusion of Zn2+ and Cu2+ metal ions on deuteroporphyrin inhibits partially (factor 3) and totally the singlet oxygen production.