(127e) 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.