Binding of the scutellarin to albumin using tryptophan fluorescence quenching, CD and FT-IR spectra

The binding of scutellarin with bovine serum albumin (BSA) was investigated at three temperatures, 296k, 310K, and 318K, by the fluorescence, circular dichroism (CD) and fourier transform infrared spectroscopy (FT-IR) at pH 7.40. The binding parameters were determined by Stern-Volmer equation. The thermodynamic parameters were calculated according to the dependence of enthalpy change on the temperature as follows:ΔH0 and ΔS0 is negative value (-13.34 KJ/mol) and positive value (47.88J/mol⋅K), respectively. Quenching of the fluorescence BSA in the presence of scutellarin was observed. Data obtained by fluorescence spectroscopy and CD experiment, FT-IR experiment suggested that scutellarin can strongly bind to the BSA and it is considered that scutellarin binds to BSA mainly by hydrophobic interaction. The distance between the tryptophan residues in BSA and scutellarin was estimated to be 2.41 nm using Forster's equation on the basis of fluorescence energy transfer.