Water-like solvation thermodynamics in a spherically symmetric solvent model with two characteristic lengths

doi:10.1073/pnas.0708427104

Water-like solvation thermodynamics in a spherically symmetric solvent model with two characteristic lengths

*Department of Physics, Yeshiva University, 500 West 185th Street, New York, NY 10033;
^‡Center for Polymer Studies and Department of Physics, Boston University, Boston, MA 02215;
^§Department of Chemical Engineering, Princeton University, Princeton, NJ 08544-5263; and
^¶Department of Chemistry and Biochemistry, University of Texas, Austin, TX 78712-1167

Contributed by H. Eugene Stanley, September 6, 2007 (received for review August 22, 2007)

Abstract

We examine by molecular dynamics simulation the solubility of small apolar solutes in a solvent whose particles interact via the Jagla potential, a spherically symmetric ramp potential with two characteristic lengths: an impenetrable hard core and a penetrable soft core. The Jagla fluid has been recently shown to possess water-like structural, dynamic, and thermodynamic anomalies. We find that the solubility exhibits a minimum with respect to temperature at fixed pressure and thereby show that the Jagla fluid also displays water-like solvation thermodynamics. We further find low-temperature swelling of a hard-sphere chain dissolved in the Jagla fluid and relate this phenomenon to cold unfolding of globular proteins. Our results are consistent with the possibility that the presence of two characteristic lengths in the Jagla potential is a key feature of water-like solvation thermodynamics. The penetrable core becomes increasingly important at low temperatures, which favors the formation of low-density, open structures in the Jagla solvent.

Footnotes

^†To whom correspondence should be addressed. E-mail: buldyrev{at}yu.edu
Author contributions: S.V.B., P.K., P.G.D., P.J.R., and H.E.S. designed research; S.V.B. and P.K. performed research; S.V.B., P.K., P.G.D., P.J.R., and H.E.S. analyzed data; and S.V.B., P.K., P.G.D., P.J.R., and H.E.S. wrote the paper.
The authors declare no conflict of interest.
This article contains supporting information online at www.pnas.org/cgi/content/full/0708427104/DC1.