Models for hydrogen exchange from folded proteins. II.

The kinetics of hydrogen exchange from folded proteins can be molded as a function of two continuous distributions of rate constants, kcx and kn, representing exchange from the folded and unfolded conformations, respectively. This model can account for the temperature dependence of soybean trypsin inhibitor at pH 3 and pH 6.5. The physical significance of this model, especially the shape and breadth of the kn distribution, are discussed.