Photophysicochemical consequences of bovine serum albumin binding to non-transition metal phthalocyanine sulfonates

Abstract

The interactions between bovine serum albumin (BSA) and sulfonated metallophthalocyanine (MPc) complexes of aluminum (AlPcS_mix), zinc (ZnPcS_mix), silicon (SiPcS_mix), germanium (GePcS_mix) and tin (SnPcS_mix) are studied using fluorescence quenching of BSA by MPc complexes. The fluorescence quantum yields of the non-aggregated MPc complexes (AlPcS_mix, GePcS_mix and SiPcS_mix) decreased in the presence of BSA, but increased for the aggregated ZnPcS_mix and SnPcS_mix complexes. The BSA: MPc conjugates were less stable than the corresponding MPc complexes. The quenching constants were much higher for the non-aggregated complexes. The aggregated nature of the complexes also affected the rate constants (k_F, k_IC, k_ISC) for the deactivation of the excited singlet state.