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. Author manuscript; available in PMC: 2009 Sep 16.
Published in final edited form as: J Phys Chem B. 2008 Feb 6;112(8):2405–2414. doi: 10.1021/jp709958f

Figure 3.

Figure 3

Illustration of the origin of the hydration free energy asymmetries. Shown are cartoons of hexagonal bracelets with a negative head bead (top) and positive head bead (bottom). A cartoon of a TIP3P water molecule is shown. The water van der Waals surface is shown as a transparent sphere, and charge sites are shown as filled spheres. Because the steric center of water is the oxygen charge site, the hydrogen charge sites can approach much closer to the negative head bead (top) than the oxygen charge site can approach the positive head bead (bottom). This, and associated differences in the water structure, results in hydration free energy asymmetries.