Understanding the Hydrophobic Effect In Confined Water

Understanding the Hydrophobic Effect in Confined Water

Tamaghna Chakraborti and  K. G. Ayappa

Department of Chemical Engineering, Indian Institute of Science Bangalore, 560012, India

The influence of confined water on the hydrophobic effect is investigated using all atom molecular dynamics simulations. It is now recognized that protein folding in a confined environment is considerably different from that observed in bulk solution. Thus confinement can prevent protein aggregation and induce folding toward the native state. Since protein folding is intrinsically associated with the hydrophobic effect we have investigated the potential of mean force (PMF) between two methane molecules confined within a reverse micelle. In contrast to the studies of protein conformation in hydrophobic cavities, the reverse micelle provides an interior which is hydrophilic in nature. Using umbrella sampling with the weighted histogram method, our results reveal a single minimum associated with the solvent separated pair in the PMF, for reverse micelles whose radii are 1.4 and 1.9 nm. The solvent separated minimum is absent and the depth of the PMF associated with the contact pair is about three times stronger than the value observed in bulk water. This study clearly reveals the enhancement in the hydrophobic effect associated with confined water and offers insight into the role of chaperones in driving in-vivo protein folding events.