Spectroscopic study on the interaction of bovine serum albumin with zinc(II) phthalocyanine.

The interaction between the photosensitive antitumour drug, 2(3),9(10),16(17),23(24)-tetra-(((2-aminoethylamino)methyl)phenoxy)phthalocyaninato-zinc(II) (ZnPc) and bovine serum albumin (BSA) has been investigated using various spectroscopic methods. This work may provide some useful information for understanding the interaction mechanism of anticancer drug-albumin binding and gain insight into the biological activity and metabolism of the drug in blood. Based on analysis of the fluorescence spectra, ZnPc could quench the intrinsic fluorescence of BSA and the quenching mechanism was static by forming a ground state complex. Meanwhile, the Stern-Volmer quenching constant (KSV), binding constant (Kb), number of binding sites (n) and thermodynamic parameters were obtained. Results showed that the interaction of ZnPc with BSA occurred spontaneously via hydrogen bond and van der Waal's force. According to Foster's non-radioactive energy transfer theory, the energy transfer from BSA to ZnPc occurred with high possibility. Synchronous fluorescence and circular dichroism (CD) spectra also demonstrated that ZnPc induced the secondary structure of and conformation changes in BSA, especially α helix.