APPLICATION OF PHYSICAL ORGANIC-CHEMISTRY TO ENGINEERED MUTANTS OF PROTEINS - HAMMOND POSTULATE BEHAVIOR IN THE TRANSITION-STATE OF PROTEIN-FOLDING

Transition states in protein folding may be analyzed by linear free-en ergy relationships (LFERs) analogous to the Bronsted equation for chan ges in reactivity with changes in structure. There is an additional so urce of LFERs in protein folding: the perturbation of the equilibrium and rate constants by denaturants. These LFERs give a measure of the p osition of the transition state along the reaction coordinate. The tra nsition state for folding/unfolding of barnase has been analyzed by bo th types of LFERs: changing the structure by protein engineering and p erturbation by denaturants. The combination has allowed the direct mon itoring of Hammond postulate behavior of the transition state on the r eaction pathway. Movement of the transition state has been found and a nalyzed to give further details of the order of events in protein fold ing.