Dynamics of a methane hydrophobe in aqueous choline chloride solution: Insights from molecular dynamics simulations

Abstract

Motion of hydrophobic moieties in solvent plays a crucial role in biomolecular functioning and is strongly influenced by the properties of the surrounding environment. To have a molecular-level picture of the dynamics of tiny hydrophobes, we simulate a methane molecule in different concentrations of aqueous choline chloride (ChCl) solution. Our analyses reveal slower translational dynamics of methane and the emergence of spatiotemporal heterogeneity at the timescales across which methane shows cage and jump motion. This results non-Gaussianity in the dynamics and it becomes increasingly pronounced with higher ChCl concentration. This illustrates more confined motion of methane inside the smaller and closely spaced cages. Hence, the jump percentage increases, and the jump length decreases. However, the maximum contribution to total diffusion comes from residual diffusion, which accounts for caging and small step displacements.