Free energy changes in .alpha.-lactalbumin denaturation

Abstract

Previous work has shown that native [bovine] .alpha.-lactalbumin (N) is completely denatured by the addition of guanidine hydrochloride (conformation D) but that partially denatured conformations appear in other denaturants. Conformation I appears when the pH is lowered from 5.5-2.2 (I2.2) or when LiClO4 is added at pH 5.5 (I5.5). The free energy changes were presently determined for the processes N .fwdarw. I5.5, N .fwdarw. D5.5, and I2.2 .fwdarw. D2.2. The maximum value of the free energy change was also estimated for the process N .fwdarw. I2.2, and this allows the changes for all conformational changes between any 2 of these 5 conformations to be estimated.