Kinetic Equations for Consecutive Reversible Reactions with Special Reference to Protein Denaturations

Abstract

The interconversion of the native (N) and denatured (D) form of a protein sometimes exhibits simple exponential kinetic behaviour consistent with the mechanism N⇌D. Sometimes, however, logarithmic plots of the variation of a property y with time arc of a biphasic character, which requires that at least one additional species X is involved. Three alternative mechanisms are then possible: I N ⇌ X ⇌ D, II N ⇌ D ⇌ X, III X ⇌ N ⇌ D If a kinetic study is made of some change in a property y, the variation of y with time shows a number of patterns of behaviour. The present work is concerned with an analysis of these patterns, which are classified with respect to the three mechanisms. It is shown that some patterns are consistent only with mechanism I, and some only with II, but that certain patterns can occur with either II or III.