The influence of temperature on pairwise hydrophobic interactions of methane-like particles: A molecular dynamics study of free energy

Abstract

The association of a pair of hydrophobic solutes in water has been investigated by free energy molecular dynamics simulations of a system containing 516 water molecules. Convergence of the calculations is guaranteed by the comparison of data obtained with two independent free energy sampling techniques, which have been optimized for our system. Coulomb interactions have been treated with the Ewald method. Using this computationally expensive approach many of the previously reported discrepancies in the temperature, pressure and interaction parameter dependence of hydrophobic association are clarified. A temperature effect on both the free energy of association and the equilibrium between contact and solvent-separated species is observed. Raising temperature favors association. The most pronounced temperature dependence occurs in the interval between 300 and 350K.

Nanoscale Hydrophobic Interaction and Nanobubble Nucleation

“…As a consequence, the hydrophobic force on the hydrophobes (measured by the negative gradient of the PMF) is also reduced by increasing the temperature. In contrast, it has been shown that the molecular hydrophobic interaction between two methane molecules becomes slightly stronger with increasing the temperature [16].…”

“…2 that to form a one water-layer size nanobubble, the work of formation amounts to about 65k B T (where k B is the Boltzmann constant). As a comparison, the barrier to dissociation for a methane pair (corresponding to intermolecular distance about 6 A) in water is on the order of 1k B T [4,15,16]. Moreover, the midrange hydrophobic interaction is more than twice longer in range than that of molecular hydrophobic interaction between the methane pair.…”

“…The classical theory of molecular hydrophobicity [1] assumed that an increased ordering of water occurs around hydrophobic molecular groups, namely, the hydrophobic attraction is mainly driven by the gain in entropy [12]. However, the molecular hydrophobic attraction (e.g., between a pair of methane molecules in water) has been proven short ranged 4-8 A with the barrier to dissociate comparable to the thermal energy [4,15,16] and is thus unlikely responsible for the thermal stability of protein assemblies [17].…”

“…Berne and co-workers [23,24] have demonstrated the formation of nanobubble (drying) between two model oblate ellipsolids (as large as 1.3 nm in diameter) via molecular dynamics (MD) simulations. To gain more insight into the midrange nanoscale hydrophobic interaction, we have performed large-scale MD simulations to show that the midrange hydrophobic interaction, manifested by the nucleation of nanobubble between nanometer-sized hydrophobes at constrained equilibrium, is about twice the range of typical molecular hydrophobic interaction (e.g., between methane-methane molecules in water [15,16]). Particular attention is placed to the dependence of the interaction on the size of hydrophobes as well as the potential of mean force versus distance curve.…”

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

“…In particular, they are seen as an important driving force with regard to the folding of proteins [4,5,6]. Consequently, a wealth of studies of hydrophobic interactions using molecular simulation techniques have been undertaken over the past three decades [7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27]. Simulation studies have revealed that the contact state of a pair of hydrophobic particles in aqueous solution is entropically stabilized at ambient conditions [10,11].…”