Aqueous Solvation of Charged and Hydrophobic Groups: from Simple Ions to Proteins

Abstract

Much of biology depends on proteins interacting with each other – pairwise or in aggregates – all mediated by water and ions. Understanding the aqueous solvation of electrolytes, simple and complex, is therefore important for biology, as also for industry. Today's solvation models mostly apply to dilute solutions and, despite being supported by all-atom simulations, do not yield good results for thermodynamic properties. Statistical-mechanics was applied to such systems using Wertheim's integral equation and thermodynamic perturbation theories, which are well suited for systems of molecules with directional forces. Such an approach is able to treat mixtures of water molecules, ions and proteins with all species treated on equal level of approximation. Results are presented for aqueous solutions of alkali halides to show the effects of ionic sizes on osmotic properties, followed by discussion of how hydrophobic groups affect solution energetics, and concluding with discussion of globular protein and monoclonal antibody self-association, demonstrating that the free energy of hydration of interacting charges is one of the crucial parameters to understand these aqueous solutions.