Spectroscopy characterization of the interaction between brevifolin carboxylic acid and bovine serum albumin.

Themechanism of binding of the antivirus drug, brevifolin carboxylic acid (BCA) with bovine serum albumin (BSA) was investigated by steady-state and time-resolved fluorescence, circular dichroism (CD), Fourier transform infrared (FT-IR) and Raman spectroscopy under pseudo-physiological conditions for the first time. A strong fluorescence quenching was observed and the quenching mechanism was considered as static quenching. Various binding parameters were evaluated. The quantitative analysis of CD spectral data revealed that the a-helical content of BSA increased from 48.91% (in free BSA) to 52.46% (in bound form) in the presence of BCA. Based on the Förster's theory of non-radiation energy transfer, the relation of the binding average distance r between the donor (BSA) and acceptor (BCA) and acceptor concentration was determined. The changes in association constants of BCA-BSA in the presence of the common ions are also discussed. From the CD, FT-IR, time-resolved fluorescence and Raman spectroscopic results, it is apparent that the interaction of BCA with BSA causes a conformational change in the protein, and the Trp and Tyr residues are buried in more hydrophobic surroundings. BCA mainly binds to residue Trp 212 located in domain II of BSA by hydrophobic interaction and hydrogen bond.