Attractions, Water Structure, and Thermodynamics of Hydrophobic Polymer Collapse

Abstract

We explore the prospects of a perturbation approach for predicting how weak attractive interactions affect collapse thermodynamics of hydrophobic polymers in water. Specifically, using molecular dynamics simulations of model polymers in explicit water, we show that the hydration structure is sensitive to the strength of the van der Waals attractions but that the hydration contribution to the potential of mean force for collapse is not. We discuss how perturbation theory ideas developed for small spherical apolar solutes need to be modified in order to account for the effect of attractions on the conformational equilibria of polymers.

Water density fluctuations relevant to hydrophobic hydration are unaltered by attractions

“…Because water molecules have strong hydrogen bond interactions, it is the penalty for this disruption of the water structure that dominates hydrophobic hydration free energies. Hard sphere solutes that simply exclude water molecules from the region they occupy have thus served as idealized hydrophobic solutes, and their hydration and assembly have been extensively studied using both molecular simulations [2,[19][20][21][22][23][24][25][26][27][28][29] and theory [3,17,20,[30][31][32][33][34][35][36].…”

Potential of mean force between hydrophobic solutes in the Jagla model of water and implications for cold denaturation of proteins

“…molecules in water has also been studied computationally [14][15][16][17][18] by many investigators. The nature of hydrophobic hydration and its role in cold denaturation is less well understood, but it has recently been addressed [19][20][21][22][23][24] using simplified models displaying properties analogous to water, e.g., anomalous thermodynamics.…”

Characterizing Solvent Density Fluctuations in Dynamical Observation Volumes

“…Interestingly, we find that the transition between right-and left-handed turns has the lowest barrier when the peptide is partially dehydrated. Although the free energetic landscapes of many conformationally flexible molecules have been extensively characterized using enhanced sampling methods, previous studies have averaged over the solvent degrees of freedom to obtain free energy as a function of conformational order parameters, such as R g or dihedral angles [74,75,80,81]. The resulting loss of information makes it challenging to anticipate how the solute conformational landscape will respond to perturbations, such as proximity to interfaces or the addition of co-solutes.…”