Loss of structural integrity and hydrophobic ligand binding capacity of acetylated and succinylated bovine β-lactoglobulin

The lysine residues of bovine β-lactoglobulin (β-lg) were acetylated and succinylated to investigate the effect of chemical modification on tertiary and secondary structures. Both derivatives showed higher electrophoretic mobility compared with native β-lg. The molar extinction coefficients of modified proteins were lower than native β-lg. A significant decrease in intrinsic tryptophan fluorescence intensities, and a red shift of emission maxima were observed. The structural stabilities of the derivatives were compared with the native form. Both modified β-lg structures were less stable against guanidine hydrochloride and urea denaturation. Hydrophobicities decreased, as measured by hydrophobic ligand binding of the modified β-lg. Circular dichroism spectra of modified forms were different. The beta structural content of modified β-lactoglobulins decreased substantially with an increase in random coil structure. These modifications changed the tertiary structure, and involved a significant loss of secondary structure of β-lg.