Effect of solute size and solute - Water attractive interactions on hydration water structure around hydrophobic solutes

H. S. AshbaughAshbaugh, Michael Paulaitis

Research output: Contribution to journalArticle

Abstract

Using Monte Carlo simulations, we investigated the influence of solute size and solute - water attractive interactions on hydration water structure around spherical clusters of 1, 13, 57, 135, and 305 hexagonally close-packed methanes and the single hard-sphere (HS) solute analogues of these clusters. We obtain quantitative results on the density of water molecules in contact with the HS solutes as a function of solute size for HS radii between 3.25 and 16.45 Å. Analysis of these results based on scaled-particle theory yields a hydration free energy/surface area coefficient equal to 139 cal/(mol Å2), independent of solute size, when this coefficient is defined with respect to the van der Waals surface of the solute. The same coefficient defined with respect to the solvent-accessible surface decreases with decreasing solute size for HS radii less than ∼10 Å. We also find that solute - water attractive interactions play an important role in the hydration of the methane clusters. Water densities in the first hydration shell of the three largest clusters are greater than bulk water density and are insensitive to the cluster size. In contrast, contact water densities for the HS analogues of these clusters decrease with solute size, falling below the bulk density of water for the two largest solutes. Thus, the large HS solutes dewet, while methane clusters of the same size do not.

Original languageEnglish (US)
Pages (from-to)10721-10728
Number of pages8
JournalJournal of the American Chemical Society
Volume123
Issue number43
DOIs
StatePublished - Oct 31 2001
Externally publishedYes

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Hydration
Water
Methane
Free energy
Molecules

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

Cite this

Effect of solute size and solute - Water attractive interactions on hydration water structure around hydrophobic solutes. / AshbaughAshbaugh, H. S.; Paulaitis, Michael.

In: Journal of the American Chemical Society, Vol. 123, No. 43, 31.10.2001, p. 10721-10728.

Research output: Contribution to journalArticle

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