Abstract
Several physicochemical experiments were done to obtain further information on the conformational changes occurring in β-conglycinin in acidic-ethanol solution, using a single molecular species of this protein, β3. By far-UV circular dichroism (CD), a transition from β-sheet to α-helical structure was observed upon addition of acidic-ethanol, and the α-helix content was found to reach 76% in 70% ethanol (pH 2). From analyses of near-UV CD and difference absorption spectra, it was found that the tertiary structure of the β3 species was significantly altered at ethanol concentrations between 10 and 20%. The profiles of binding of 1-anilinonaphthalene-8-sulfonic acid to the β3 species during acidic-ethanol denaturation were indicative of the existence of intermediate conformers in the molten globule-like denaturation state. By measuring Fourier transform infrared spectra and estimating the Stokes radius by dynamic light scattering, the β3 molecules were found to aggregate with an increase in ethanol concentration.