[Investigation of interaction between catechin and bovine serum albumin by spectroscopic methods].

In the present work, the interaction of catechin with bovine serum albumin (BSA) under physiological condition was studied by fluorescence quenching spectra in combination with Fourier transform infrared (FTIR) spectroscopy. The binding constants, the drug-binding mode, the binding site between catechin and BSA in aqueous solution at pH 7.40, and the effect of common ions were studied. The results show that catechin has the ability to quench the intrinsic fluorescence of BSA because of a complex formed, and the quenching mechanism is static quenching. The binding constants K under 296, 303 and 310 K were 2.368, 2.249 and 2.152 x 10(6) L x mol(-1) respectively. The thermodynamic parameters showed that the interaction between catechin and BSA was driven mainly by hydrophobic force and electrostatic interaction. The displacement experiment shows that catechin can bind to the site I of BSA. The distance between the 214 tryptophan residues in BSA and catechin was estimated to be 1.46 nm using Foster's equation on the basis of fluorescence energy transfer. According to FTIR, the secondary structure of BSA changed when catechin was added.

[Research on the interaction of aristolochic acid and bovine serum albumin].

The interaction between aristolochic acid and bovine serum albumin (BSA) under physiological conditions was investigated by fluorescence quenching methods. The results indicate that there is a strong interaction between aristolochic acid and BSA, and the distances between the binding location and tryptophan residue is 2.8 nm. The binding location of aristolochic acid in BSA is in subdomain III A. In addition, the effects of aristolochic acid on the protein second structure were studied using CD and FTIR techniques. The results of CD proved that the alpha-helix contents of BSA decreased from 43.5% to 36.7% after binding with aristolochic acid.

Interaction of magnolol with bovine serum albumin: a fluorescence-quenching study.

The interaction of magnolol with bovine serum albumin(BSA) was studied using fluorescence spectroscopy under physiological conditions. The binding constants, K, and the ratio of quantum yields of protein fluorescence for complex and free protein, f, at 298 K, 304 K, and 310 K were obtained; the values were 6.799x10(5) L mol(-1), 5.541x10(5) L mol(-1), and 4.344x10(5) L mol(-1) and 0.17, 0.30, and 0.34, respectively. The standard enthalpy change (delta H degrees ) and the standard entropy change (delta S degrees ) were calculated to be -28.53 kJ mol(-1) and 15.88 J mol(-1) K(-1), which indicated that hydrophobic forces played major role in the interaction of magnolol and BSA. The binding average distance between magnolol and BSA (4.32 nm) was obtained on the basis of the theory of Förster energy transfer.