Role of Cosolvent in peptide hydration: The effect of ionic liquid in aqueous glutathione solution.

A major challenge in molecular biophysics lies in understanding biophysical processes such as peptide hydration. Techniques like Neutron Diffraction with Isotopic Substitution (NDIS) and UV-resonance Raman (UVRR) spectroscopy have proven to be powerful tools for probing the peptide hydration at atomic and vibrational levels, respectively. Water plays a crucial role as a basic solvent in many biological processes. The existence of biological water in the vicinity of the peptides has profound implications and is particularly important for the structural and biological functions of the peptides. The functional properties of peptides are governed by a sensitive interplay between their interactions with the surrounding aqueous environment. This balance can be modulated by the addition of various organic and inorganic small molecules known as cosolvents. Molecular-level understanding of how these cosolvents affect the hydration shell near the biomolecules is important for understanding the factors that affect the stability of peptides. In recent years, room-temperature ionic liquids have emerged as an excellent greener cosolvent for biomolecules such as proteins and peptides compared to conventional organic/inorganic solvents because of their biocompatibility, high tunability, low volatality, and high thermal stability. The presence of both cationic and anionic constituents of IL in the solution, the hydration property of peptide is modulated. In this context, the present research work focuses on investigating the effect of BMIM iodide IL on the hydration structure of the GSH peptide and any plausible interaction of BMIM iodide with GSH at the atomic and vibrational levels. These results will offer new insights on the hydration of peptides and the role of cosolvents in modulating biomolecular functionality.