Membrane protein hydration bridges polymer physics and biology.

Understanding the role of water in membrane protein structure and function is crucial for elucidating the mechanisms that govern cellular processes. Recent experiments with the G-protein-coupled receptor (GPCR) archetype rhodopsin have shed light on polymer osmotic effects as an important metric for studying hydration in membrane protein activation. Still, to gain mechanistic insights into the multifaceted problem of membrane protein hydration involving lipids, membranes, and polymers, one needs information at atomistic resolution. Recent advances in molecular dynamics simulations have made capturing such information possible. Here we review membrane protein hydration as a multidisciplinary research topic at the intersection of polymer physics and biology through a computational lens using rhodopsin as an example. Recent advances and challenges in spectroscopic and structural approaches to study hydration in proteins are discussed generally, and for membrane proteins specifically. We explore the synergy between polymer physical chemistry and membrane protein hydration by reviewing the contributions of lattice models, polymer osmolytes, and crowding to motivate the need for computational methods in studying membrane protein hydration. Finally, we discuss recent advances in understanding hydration in membrane proteins, using rhodopsin as an example, through hybrid Monte Carlo/molecular dynamics simulations.