Hydration of denatured and molten globule proteins

The hydration of nonnative states is central to protein folding and stabili ty but has been probed mainly by indirect methods. Here we use water O-17 r elaxation dispersion to monitor directly the internal and external hydratio n of alpha-lactalbumin, lysozyme, ribonuclease A, apomyoglobin and carbonic anhydrase in native and nonnative states. The results show that nonnative proteins are more structured and less solvent exposed than commonly believe d. Molten globule proteins preserve most of the native internal hydration s ites and have native-like surface hydration, Proteins denatured by guanidin ium chloride are not fully solvent exposed but contain strongly perturbed o ccluded water. These findings shed new light on hydrophobic stabilization o f proteins.