Low-Temperature and High-Pressure Induced Swelling of a Hydrophobic Polymer-Chain in Aqueous Solution

Abstract

We report molecular dynamics simulations of a hydrophobic polymer-chain in aqueous solution between $260K$ and $420K$ at pressures of $1bar$, $3000bar$, and $4500bar$. The simulations reveal a hydrophobically collapsed state at low pressures and high temperatures. At $3000bar$ and about $260K$ and at $4500bar$ and about $260K$, however, a transition to a swelled state is observed. The transition is driven by a smaller volume and a remarkably strong lower enthalpy of the swelled state, indicating a steep positive slope of the corresponding transition line. The swelling is stabilized almost completely by the energetically favorable state of water in the polymers hydrophobic first hydration shell at low temperatures. Although surprising, this finding is consistent with the observation of a positive heat capacity of hydrophobic solvation. Moreover, the slope and location of the observed swelling transition for the collapsed hydrophobic chain coincides remarkably well with the cold denaturation transition of proteins.

9 pages, 9 figures, twocolumn revtex

References in corpus (3)

• Temperature Dependence of the Hydrophobic Hydration and Interaction of Simple Solutes: An Examination of Five Popular Water Models
• A possible mechanism for cold denaturation of proteins at high pressure
• Heat Capacity Effects Associated with the Hydrophobic Hydration and Interaction of Simple Solutes: A Detailed Structural and Energetical Analysis Based on MD Simulations

Cited by in corpus (4)

• Microscopic mechanism for cold denaturation
• Effects of lengthscales and attractions on the collapse of hydrophobic polymers in water
• Contribution of Water to Pressure and Cold Denaturation of Proteins
• Test of cold denaturation mechanism for proteins as a function of water's structure