Rationalization of the effects of compatible solutes on protein stability in terms of thermodynamic nonideality

Inhibition by compatible solutes such as proline and glycine betaine of the rate of coagulation, at 60 degrees C, of bovine serum albumin in 0.1 M acetate buffer, pH 5, is used as a model system to substantiate the concept that the production of high concentrations of osmolytes by plants and other organisms in response to stress (e.g., drought) results in stabilization of native enzyme structures via nonspecific excluded volume effects. The paradoxical situation whereby this effect of compatible solutes counters to some extent the protein-precipitating effect of poly(ethylene glycol) is also seemingly resolved.