Abstract
The absorption and fluorescence spectra of 7, 8-dihydroxy-4-methylcoumarin (DHMC) in ethanol–water (1:9v/v) solution at varying pH values were investigated . The interaction between DHMC and bovine serum albumin (BSA) was investigated by fluorescence, FT-IR, and circular dichroism (CD) spectroscopy. The Stern–Volmer quenching constant (KSV), the quenching rate constant of the bimolecular reaction (Kq), the binding constant, and number of binding sites (n) of DHMC with BSA were evaluated. The results showed that DHMC quenches the fluorescence intensity of BSA through a static quenching process. Positive value of entropy change (ΔS) and negative value of enthalpy change (ΔH) of the BSA–DHMC interaction were obtained according to the van't Hoff equation. The interaction between DHMC and BSA was driven mainly by hydrophobic forces. The binding process was spontaneous and exothermic. The binding distance between the tryptophan residue in BSA and the DHMC was found to be about 2.6nm based on the Förster theory of non-radiation energy transfer.
► 7,8-dihydroxy-4-methylcoumarin (DHMC) quenched the bovine serum albumin (BSA) fluorescence. ► The formation of the DHMC-BSA complex was spontaneous through a static quenching process. ► The polarity around the tryptophan residues decreased with the increase of DHMC concentration.