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On the Role of Nonspherical Cavities in Short Length-Scale Density Fluctuations in Water

Sosso, GC; Caravati, S; Rotskoff, G; Vaikuntanathan, S; Hassanali, A; (2016) On the Role of Nonspherical Cavities in Short Length-Scale Density Fluctuations in Water. J. Phys. Chem. A, , 121 (1) pp. 370-380. 10.1021/acs.jpca.6b11168. Green open access

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Abstract

Density fluctuations in liquid water are at the heart of numerous phenomena associated with hydrophobic effects such as protein folding and the interaction between biomolecules. One of the most fundamental processes in this regard is the solvation of hydrophobic solutes in water. The vast majority of theoretical and numerical studies examine density fluctuations at the short length scale focusing exclusively on spherical cavities. In this work, we use both first-principles and classical molecular dynamics simulations to demonstrate that density fluctuations in liquid water can deviate significantly from the canonical spherical shapes. We show that regions of empty space are frequently characterized by exotic, highly asymmetric shapes that can be quite delocalized over the hydrogen bond network. Interestingly, density fluctuations of these shapes are characterized by Gaussian statistics with larger fluctuations. An important consequence of this is that the work required to create non spherical cavities can be substantially smaller than that of spheres. This feature is also qualitatively captured by the Lum–Chandler–Weeks theory. The scaling behavior of the free energy as a function of the volume at short length scales is qualitatively different for the nonspherical entities. We also demonstrate that nonspherical density fluctuations are important for accommodating the hydrophobic amino acid alanine and are thus likely to have significant implications when it comes to solvating highly asymmetrical species such as alkanes, polymers, or biomolecules.

Type: Article
Title: On the Role of Nonspherical Cavities in Short Length-Scale Density Fluctuations in Water
Open access status: An open access version is available from UCL Discovery
DOI: 10.1021/acs.jpca.6b11168
Publisher version: http://dx.doi.org/ 10.1021/acs.jpca.6b11168
Language: English
Additional information: Copyright © 2016 American Chemical Society
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
URI: https://discovery.ucl.ac.uk/id/eprint/1533253
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