Multi-spectral characterization & effect of metal ions on the binding of bovine serum albumin upon interaction with a lincosamide antibiotic drug, clindamycin phosphate

• Interaction of CP with BSA was studied by different spectroscopic methods.
• CD, SFS and 3D fluorescence data revealed conformational changes in the protein.
• The fluorescence quenching of BSA by CP was dynamic which was also confirmed by lifetime measurements.
• CP can bind to BSA with stoichiometric ratio of 1:1.
• Binding constant, binding site and binding force were determined.

The interaction of clindamycin phosphate (CP) with bovine serum albumin (BSA) is studied by using fluorescence spectra, UV–visible absorption, synchronous fluorescence spectra (SFS), CD, 3D fluorescence spectra and lifetime measurements under simulated physiological conditions. CP effectively quenched intrinsic fluorescence of BSA. The binding constants KA values are 2.540 × 105, 4.960 × 105, 7.207 × 105 L mol−1, the number of binding sites n and corresponding thermodynamic parameters ΔGo, ΔHo and ΔSo between CP and BSA were calculated at different temperatures. The interaction between CP and BSA occurs through dynamic quenching and the effect of CP on the conformation of BSA was also analyzed using SFS. The average binding distance r between the donor (BSA) and acceptor (CP) was determined based on Förster’s theory. The results of fluorescence spectra, UV–vis absorption spectra and SFS show that the secondary structure of the protein has been changed in the presence of CP.

It is a dynamic quenching mechanism. CP bound to site I of BSA, located in the hydrophobic pocket of subdomain IIA. Hydrophobic interaction forces are important in stabilizing the complex.Figure optionsDownload as PowerPoint slide