THERMODYNAMICS OF DENATURATION OF LYSOZYME BY GUANIDINE HYDROCHLORIDE .2. DEPENDENCE ON DENATURANT CONCENTRATION AT 25 DEGREES

The fact that guanidine hydrochloride shifts the equilibrium between native and denatured lysozyme toward the denatured form requires that more guanidinium and/or chloride ions are bound to the denatured form than to the native form; or that more water is bound to the native form than to the denatured form; or a combination of these effects. Various hypothetical equilibria are proposed, and it is found that all of them are consistent with the experimental data, so that no definite conclusions concerning the mode of action of guanidine hydrochloride can be reached. All of the hypothetical mechanisms, however, lead to the conclusion that the free energy of stabilization of native lysozyme, relative to the denatured state, under physiological conditions, in the absence of denaturant, is only 10-20 kcal/mole. © 1969, American Chemical Society. All rights reserved.