Abstract:

The interaction between bovine serum albumi （BSA） and three N-acyl amino acid surfactants, including sodium lauroyl sarcosinate （SLS）, sodium lauroyl glutamate （SLGLU） and sodium lauroyl glycine （SLG） was studied by fluorescence spectrum and UV spectrum in this paper. The fluorescence peak wavelength of tryptophan residue in BSA showed a blue-shift with the increase of the concentration of the three surfactants, and the polarity of microenvironment around the tryptophan residue was decreased. The critical aggregation concentrations （cac） of the three surfactants on protein surface of BSA by fluorescence spectrum are: cac_SLS=0.4 mmol/L, cac_SLG=0.1 mmol/L, and cac_SLGLU=0.09 mmol/L, respectively. The binding isotherms of BSA interacted with the three surfactants can be divided into four feature regions: specific binding, non-cooperative binding, cooperative binding and saturation. With the increase of surfactant concentration, the characteristic UV absorption wavelength of tryptophan residue in BSA is red shifted, and the polarity of amino acid residues in the microenvironment is decreased; while the characteristic UV absorption wavelengths of tyrosine and phenylalanine residues in BSA are blue-shift, and the polarity of amino acid residues in BSA is enhanced. The binding site of BSA with the three surfactants was confirmed at the vicinity of Trp-213 of BSA domain II A by probe molecules, such as phenylbutazone, ibuprofen and heme chloride. The interaction modes between AAS and BSA at different surfactant concentrations were analyzed.

Key words: surfactant, bovine serum albumi, amino acid, interaction, fluorescence spectrum