Temperature dependence of the hydrophobic hydration and interaction of simple solutes: An examination of five popular water models

Abstract

We examine five different popular rigid water models (SPC, SPCE, TIP3P, TIP4P and TIP5P) using molecular dynamics simulations in order to investigate the hydrophobic hydration and interaction of apolar Lennard-Jones solutes as a function of temperature in the range between 275 K and 375 K along the 0.1 MPa isobar. For all investigated models and state points we calculate the excess chemical potential for the noble gases and Methane employing the Widom particle insertion technique. All water models exhibit too small hydration entropies, but show a clear hierarchy. TIP3P shows poorest agreement with experiment whereas TIP5P is closest to the experimental data at lower temperatures and SPCE is closest at higher temperatures. As a first approximation, this behaviour can be rationalised as a temperature-shift with respect to the solvation behaviour found in real water. A rescaling procedure inspired by information theory model of Hummer et al. (Chem.Phys. 258, 349-370 (2000)) suggests that the different solubility curves for the different models and real water can be largely explained on the basis of the different density curves at constant pressure. In addition, the models that give a good representation of the water structure at ambient conditions (TIP5P, SPCE and TIP4P) show considerably better agreement with the experimental data than the ones which exhibit less structured O-O correlation functions (SPC and TIP3P). In the second part of the paper we calculate the hydrophobic interaction between Xenon particles directly from a series of 60 ns simulation runs. We find that the temperature dependence of the association is to a large extent related to the strength of the solvation entropy. Nevertheless, differences between the models seem to require a more detailed molecular picture. The TIP5P model shows by far the strongest temperature dependence. The suggested density-rescaling is also applied to the chemical potential in the Xenon-Xenon contact-pair configuration, indicating the presence of a temperature where the hydrophobic interaction turns into purely repulsive. The predicted association for Xenon in real water suggest the presence a strong variation with temperature, comparable to the behaviour found for TIP5P water. Comparing different water models and experimental data we conclude that a proper description of density effects is an important requirement for a water model to account correctly for the correct description of the hydrophobic effects. A water model exhibiting a density maximum at the correct temperature is desirable.

Hydrophobic interactions in the formation of secondary structures in small peptides

“…This finding may help to assess prior studies that used effective ranges of cm attraction as large as 6.5Å [31,32]. db's arise from empty spaces created by water exclusion between hydrophobic groups [37][38][39][40]42] and are the hallmark of interactions between nonpolar groups [33,34,[36][37][38][39][40][41][42][43] that are partially exposed to water. As such, db's are pertinent to the α-β transition in amyloidogenesis [26,27], which can be affected by pressure [27,[74][75][76].…”

“…As such, db's are pertinent to the α-β transition in amyloidogenesis [26,27], which can be affected by pressure [27,[74][75][76]. Atomic PMF simulations indicated that temperature lowers both the cm and the db [34,37,38,42] whereas pressure raises them [77]. Inasmuch as a lower cm favors β (Fig.…”

“…Based on explicit-water simulations of a pair of methanes in water, we argue that a realistic range is ∼5.0Å and show that this favors β sheets. We also considered desolvation barrier (db) effects as they are critical in protein energetics [33][34][35][36][37][38][39][40][41][42][43]. db effects were neglected in many implicit-water potential functions [31,32] despite studies showing its importance for protein structure prediction [44].…”

Low-temperature and high-pressure induced swelling of a hydrophobic polymer-chain in aqueous solution

“…The water phase is represented by 1000 TIP5P water molecules [50]. The TIP5P model was chosen, since it represents the hydrophobic solvation behavior of water on the lowtemperature side probably most realistically among the simple point charge models [26]. Moreover, the temperature dependent strength of the hydrophobic interaction was found to be quite critically linked to the temperature dependence of waters expansivity [26].…”

“…The TIP5P model was chosen, since it represents the hydrophobic solvation behavior of water on the lowtemperature side probably most realistically among the simple point charge models [26]. Moreover, the temperature dependent strength of the hydrophobic interaction was found to be quite critically linked to the temperature dependence of waters expansivity [26]. The simulations discussed here were carried over a broad temperature range at pressures of 1 bar, 3000 bar, and 4500 bar.…”