THERMAL-DENATURATION OF BETA-CONGLYCININ - KINETIC RESOLUTION OF REACTION-MECHANISM

Thermal denaturation of soybean beta-conglycinin has been studied kinetically at pH 7.5 and ionic strength zero in distilled water by difference spectroscopy measuring the exposure of tyrosyl residues. Progress curves of the difference absorbance changes at 287 nm measured at elevated temperature revealed that the beta-conglycinin molecule can assume many different denatured conformations depending on the temperature, so long as the sample solution is maintained at elevated temperature. The thermal denatured state at 87-degrees-C has a degree of unfolding of about 80% compared to a completely unfolded state by GuHCl. Once the heat-denatured beta-conglycinin was cooled, the extent of these various-DELTA-epsilon-values, which represent conformational changes, is lowered to a constant value of around -5600. Thus, cooling induces refolding of the unfolded internal structure of dissociated monomers while the quaternary structure is not regained. From the slope of progress curves, reaction rates and activation energies were calculated.