A Simple Model of Water and the Hydrophobic Effect

Silverstein, Kevin A.T.; Haymet, A. D. J.; Dill, Ken A.

doi:10.1021/ja973029k

Cited by 330 publications

(406 citation statements)

References 77 publications

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“…However, while the Monte Carlo simulations of the MB water show a minimum in the isothermal compressibility versus temperature, it is not as pronounced as in experiments. 55 The present theory also reproduces a minimum in T ‫ء‬ ͑Fig. 6͒, consistent with scattering experiments.…”

Section: Resultssupporting

confidence: 83%

“…The present theory gives much better agreement with both experiments and with the Monte Carlo MB simulation results. 55 Even so, the agreement is not perfect. The theory still underpredicts hydrogen bonding compared to the MB simulations.…”

Section: Resultsmentioning

confidence: 99%

“…It is a variant of the so-called Mercedes-Benz ͑MB͒ model, so named because each water is a disk with three hydrogen-bonding arms, resembling the MB logo. The MB model, originally proposed by Ben-Naim 52,53 in 1971, has been studied extensively by ͑N , p , T͒ Monte Carlo simulations [54][55][56][57][58][59] and by integral equation methods [60][61][62][63][64][65] based on Wertheim's theory for associating fluids. 66,67 The MB model of water was recently extended to three dimensions ͑3D͒ by our group 68,69 and Dias et al 70 In particular, our treatment here is most directly descendant from a treatment of Truskett and Dill, [71][72][73] who developed a nearly analytical version of the MB model.…”

Section: Introductionmentioning

confidence: 99%

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A statistical mechanical theory for a two-dimensional model of water

Urbič

Dill²

2010

The Journal of Chemical Physics

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We develop a statistical mechanical model for the thermal and volumetric properties of waterlike fluids. Each water molecule is a two-dimensional disk with three hydrogen-bonding arms. Each water interacts with neighboring waters through a van der Waals interaction and an orientation-dependent hydrogen-bonding interaction. This model, which is largely analytical, is a variant of the Truskett and Dill ͑TD͒ treatment of the "Mercedes-Benz" ͑MB͒ model. The present model gives better predictions than TD for hydrogen-bond populations in liquid water by distinguishing strong cooperative hydrogen bonds from weaker ones. We explore properties versus temperature T and pressure p. We find that the volumetric and thermal properties follow the same trends with T as real water and are in good general agreement with Monte Carlo simulations of MB water, including the density anomaly, the minimum in the isothermal compressibility, and the decreased number of hydrogen bonds for increasing temperature. The model reproduces that pressure squeezes out water's heat capacity and leads to a negative thermal expansion coefficient at low temperatures. In terms of water structuring, the variance in hydrogen-bonding angles increases with both T and p, while the variance in water density increases with T but decreases with p. Hydrogen bonding is an energy storage mechanism that leads to water's large heat capacity ͑for its size͒ and to the fragility in its cagelike structures, which are easily melted by temperature and pressure to a more van der Waals-like liquid state.

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Section: Resultssupporting

confidence: 83%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A statistical mechanical theory for a two-dimensional model of water

Urbič

Dill²

2010

The Journal of Chemical Physics

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“…IT models of the solvation thermodynamics can easily be generalized to various aqueous and non-aqueous solvents and mixtures, combined with other approaches, or extended to "unusual" models of water, such as a recently proposed two dimensional model of water 106 or an isotropic water model without directional hydrogen-bond interactions. 83 We have successfully adapted the method to study the solubility of small molecules in polymeric fluids.…”

Section: Discussionmentioning

confidence: 99%

Hydrophobic Effects on a Molecular Scale

et al. 1998

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A theoretical approach is developed to quantify hydrophobic hydration and interactions on a molecular scale, with the goal of insight into the molecular origins of hydrophobic effects. The model is based on the fundamental relation between the probability for cavity formation in bulk water resulting from molecular-scale density fluctuations, and the hydration free energy of the simplest hydrophobic solutes, hard particles. This probability is estimated using an information theory (IT) approach, incorporating experimentally available properties of bulk water -the density and radial distribution function. The IT approach reproduces the simplest hydrophobic effects: hydration of spherical nonpolar solutes, the potential of mean force (PMF) between methane molecules, and solvent contributions to the torsional equilibrium of butane. Applications of this approach to study temperature and pressure effects provide new insights into the thermodynamics and kinetics of protein folding. The IT model relates the hydrophobic-entropy convergence observed in protein unfolding experiments to the macroscopic isothermal compressibility of water. A novel explanation for pressure denaturation of proteins follows from an analysis of the pressure stability of hydrophobic aggregates, suggesting that water penetrates the hydrophobic core of proteins at high pressures. This resolves a long-standing puzzle, whether pressure denaturation contradicts the hydrophobic-core model of protein stability. Finally, issues of "dewetting" of molecularly large nonpolar solutes are discussed in the context of a recently developed perturbation theory approach.

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“…Interactions between water molecules were described using the 3D Mercedes-Benz (MB) potential, a geometric water model designed to accurately reproduce the thermodynamic and structural properties of water, including freezing and pressure-induced melting, while being computationally more efficient than, e.g., the TIPnP models [20,21]. Although the extension of the MB model to 3D is relatively new [20], in 2D the MB model has been successful in describing the correct physics of phenomena such as cold denaturation of proteins [22], water's anomalous thermodynamic properties [23], and solute hydration [24]. The parameters of the potential were scaled so as to yield a melting temperature of approximately 270 K. The temperature range of 240-280 K was probed in the simulations, the presented results being obtained at 260 K. The wire was described in a coarse grained fashion as a rigid string of beads, where the beads interact with water molecules via hard-sphere pair potentials.…”

mentioning

confidence: 99%

Cutting Ice: Nanowire Regelation

et al. 2010

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Even below its normal melting temperature, ice melts when subjected to high pressure and refreezes once the pressure is lifted. A classic demonstration of this regelation phenomenon is the passing of a thin wire through a block of ice when sufficient force is exerted. Here we present a molecular-dynamics study of a nanowire cutting through ice to unravel the molecular level mechanisms responsible for regelation. In particular, we show that the transition from a stationary to a moving wire due to increased driving force changes from symmetric and continuous to asymmetric and discontinuous as a hydrophilic wire is replaced by a hydrophobic one. This is explained at the molecular level in terms of the wetting properties of the wire.

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A Simple Model of Water and the Hydrophobic Effect

Cited by 330 publications

References 77 publications

A statistical mechanical theory for a two-dimensional model of water

A statistical mechanical theory for a two-dimensional model of water

Hydrophobic Effects on a Molecular Scale

Cutting Ice: Nanowire Regelation

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