Protein hydration and volumetric properties

Pressure effects on proteins stem from volumetric differences between their conformational states. These differences implicate rigid structure-based solvent excluded void volumes, although hydration and thermal expansivity differences between states may also play a role. Defining quantitatively the contributions of hydration and solvent excluded voids to protein volumetric properties and thermal expansivities remains a major challenge. Experimental information concerning thermal expansivity can be gained from pressure perturbation calorimetric studies (PPC). We review here recent results from PPC that suggest that while hydration plays a significant role in the volumetric properties of unfolded states of proteins, the volumetric properties of folded states are defined by structural and energetic properties of the folded chain.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (56 K)Download as PowerPoint slideResearch Highlights► Protein volume includes atoms, voids and hydration; the latter two change on unfolding. ► Thermal expansivity, α, is a key determinant of ΔVu. ► PPC measurements of α revealed opposite behavior for polar and apolar moieties. ► PPC of proteins suggests complex contributions to expansivity.