A ionic liquid in the hydration shell of a tripeptide: the case of Glutathione

Water-protein interactions play an important role in determining protein structure and function. Nevertheless, a complete microscopic description of the interactions between water atoms and specific sites of the peptide backbone and its side chains is still lacking. To shed light on this issue, we exploit the possibility of ionic liquids to act as water-replacer and as a solvent for biomolecules, when used as co-solvent in aqueous protein solutions, with particular relevance to protein stability, folding, and catalytic activity. Glutathione (GSH) is an important water-soluble peptide with a crucial role, as antioxidant, in living organisms. Results of this study will be compared with those obtained with GSH in water, indicating the ability of water to "identify" specific peptide sites, a critical step in the early stages of protein folding, and protein-ligand interactions.