Solvent coarse-graining and the string method applied to the hydrophobic collapse of a hydrated chain

TL;DR

This study employs coarse-graining and the string method on extensive simulations to elucidate the hydrophobic collapse mechanism of a hydrated chain, confirming lengthscale-dependent dewetting as the rate-limiting step.

Contribution

It introduces a novel approach combining solvent coarse-graining and the string method to determine the minimum free energy pathway of hydrophobic collapse.

Findings

Lengthscale-dependent hydrophobic dewetting is the rate-limiting step.

The mechanism aligns with previous atomistic proposals by ten Wolde and Chandler.

Validation of the pathway using molecular dynamics trajectories.

Abstract

Using computer simulations of over 100,000 atoms, the mechanism for the hydrophobic collapse of an idealized hydrated chain is obtained. This is done by coarse-graining the atomistic water molecule positions over 129,000 collective variables that represent the water density field and then using the string method in these variables to compute the minimum free energy pathway (MFEP) for the collapsing chain. The dynamical relevance of the MFEP (i.e. its coincidence with the mechanism of collapse) is validated a posteriori using conventional molecular dynamics trajectories. Analysis of the MFEP provides atomistic confirmation for the mechanism of hydrophobic collapse proposed by ten Wolde and Chandler. In particular, it is shown that lengthscale-dependent hydrophobic dewetting is the rate-limiting step in the hydrophobic collapse of the considered chain.