On the Mechanism of Hydrophobic Association of Nanoscopic Solutes

Abstract

The hydration behavior of two planar nanoscopic hydrophobic solutes in liquid water at normal temperature and pressure is investigated by calculating the potential of mean force between them at constant pressure as a function of the solute-solvent interaction potential. The importance of the effect of weak attractive interactions between the solute atoms and the solvent on the hydration behavior is clearly demonstrated. We focus on the underlying mechanism behind the contrasting results obtained in various recent experimental and computational studies on water near hydrophobic solutes. The length scale where crossover from a solvent separated state to the contact pair state occurs is shown to depend on the solute sizes as well as on details of the solute-solvent interaction. We find the mechanism for attractive mean forces between the plates is very different depending on the nature of the solute-solvent interaction which has implications for the mechanism of the hydrophobic effect for biomolecules.

Integral Equation Study of the Hydrophobic Interaction between Graphene Plates

“…This distance is ~0.1 Å less than the distance at which the minimum occurred in the PMF obtained from the MD simulation study [33]. Both distances are slightly less than the minimum shown in the direct potential.…”

“…Simulations of models having realistic solute-solvent attractive terms behave qualitatively differently than their purely repulsive models [33][34][35] . The state of hydration in the inter-solute regions in simulations has been shown to be highly dependent on a number of factors characterized by the solute properties such as shape and interaction strength.…”

Coupling nonpolar and polar solvation free energies in implicit solvent models

“…[15][16][17] Early evidence of confinement-induced dewetting was given only by explicit water simulations for smooth platelike solutes with a purely repulsive solute-solvent interaction. 18 More recently, however, it has been demonstrated in varying degrees in several systems with attractive solute-solvent interactions including smooth parallel platelike solutes, 19 atomistically resolved paraffin plates, 20 graphite plates, 21 carbon nanotubes, 22 and hydrophobic ion channels. [23][24][25] Several of these studies indicated that the magnitude of dewetting is sensitive to the nature of the solute-solvent attractive dispersion interactions.…”

Enthalpy−Entropy Contributions to the Potential of Mean Force of Nanoscopic Hydrophobic Solutes

“…In a series of recent studies 30,32,34,35 , the importance of attractive solute-solvent interaction on the wetting/dewetting behaviour of nanoscopically large solutes has been clearly demonstrated. It has been explicitly shown 30-32 that the cumulative effect of a large number of small solutesolvent attractive interactions can change large solute hydration behaviour.…”