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

Abstract

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.

Molecular Aspects of the Interaction of Iminium and Alkanolamine Forms of the Anticancer Alkaloid Chelerythrine with Plasma Protein Bovine Serum Albumin

“…For the present case, K 2 = 0.67, N = 1.336, and φ = 0.15. , The other parameters obtained using eqs –) are presented in Table . It was observed that the average distance between the protein donor and the alkaloid acceptor after the interaction was <8 nm for both forms of the alkaloid and 0.5 R 0 < r < 1.5 R 0 , which in turn establishes the fact that the energy transfer from BSA to CHL occurred with high probability . These data are in good agreement with the state of affairs associated with the Förster’s nonradiative resonance energy transfer theory and again indicate the occurrence of static quenching between BSA and CHL .…”

“…It was observed that the average distance between the protein donor and the alkaloid acceptor after the interaction was <8 nm for both forms of the alkaloid and 0.5R 0 < r < 1.5R 0 , which in turn establishes the fact that the energy transfer from BSA to CHL occurred with high probability. 48 These data are in good agreement with the state of affairs associated with the Forster's nonradiative resonance energy transfer theory and again indicate the occurrence of static quenching between BSA and CHL. 66 These results also suggest that both the forms of bound CHL are found to be present in subdomain II of BSA which is also the residing area of Trp 212 residue.…”

“…In the case of static quenching that explains the formation of a ground state complex, K q value exceeds 2.0 × 10 10 L·mol –1 ·s –1 . The values of K q obtained from three different temperatures are presented in Table .…”

“…Combining the results obtained from fluorescence quenching and site selective binding, we have come to a conclusion that Trp 212 residue resides near or within the binding site of CHL. Several small molecules are found to bind preferably to this location in BSA, making the site favorable for small molecule–protein interaction. ,,− …”

“…43 In the case of static quenching that explains the formation of a ground state complex, K q value exceeds 2.0 × 10 10 L•mol −1 • s −1 . 48 The values of K q obtained from three different temperatures are presented in Table 2. The values are of 3 orders of magnitude larger than the maximum diffusion collision quenching rate constant in dynamic quenching.…”