Interactions of β-lactoglobulin with Cationic Surfactants: Spectroscopy Study

The interactions of β-lactoglobulin AB in the presence of cationic surfactants such as Cetyltrimethylammonium bromide and Cetyltrimethylammonium p-Toluenesulfonate have been investigated using a variety of experimental techniques such as conductivity, UV-Vis spectrophotometry and fluorimetry. The conductivity of surfactants aqueous solutions with β-lactoglobulin shows that the cmc of cationic surfactants decreases with increasing of counterion size. The results of UV-Vis and fluorescence studies show a red shift in wavelength and an increase in absorbance and intensity of the emission maximum of protein during the interactions of surfactants with β-lactoglobulin. The results of UV-Vis also show two distinct conformational changes at pHs 6.7 and 8.0 and the cooperative character of binding at pH 2.0. The results of fluorescence studies show that the binding strength of β-lactoglobulin / surfactant complex decreases with increasing of the pH.