THE INFLUENCE OF TEMPERATURE ON PAIRWISE HYDROPHOBIC INTERACTIONS OF METHANE-LIKE PARTICLES - A MOLECULAR-DYNAMICS STUDY OF FREE-ENERGY

The association of a pair of hydrophobic solutes in water has been inv estigated by free energy molecular dynamics simulations of a system co ntaining 516 water molecules. Convergence of the calculations is guara nteed by the comparison of data obtained with two independent free ene rgy sampling techniques, which have been optimized for our system. Cou lomb interactions have been treated with the Ewald method. Using this computationally expensive approach many of the previously reported dis crepancies in the temperature, pressure and interaction parameter depe ndence of hydrophobic association are clarified. A temperature effect on both the free energy of association and the equilibrium between con tact and solvent-separated species is observed. Raising temperature fa vors association. The most pronounced temperature dependence occurs in the interval between 300 and 350K. (C) 1996 American Institute of Phy sics.