COLLECTIVE PROPERTIES OF HYDRATION - LONG-RANGE AND SPECIFICITY OF HYDROPHOBIC INTERACTIONS

We report results of molecular dynamics (MD) simulations of composite model solutes in explicit molecular water solvent, eliciting novel asp ects of the recently demonstrated, strong many-body character of hydra tion. Our solutes consist of identical apolar (hydrophobic) elements i n fixed configurations. Results show that the many-body character of P MF is sufficiently strong to cause 1) a remarkable extension of the ra nge of hydrophobic interactions between pairs of solute elements, up t o distances large enough to rule out pairwise interactions of any type , and 2) a SIF that drives one of the hydrophobic solute elements towa rd the solvent rather than away from it. These findings complement rec ent data concerning SIFs on a protein at single-residue resolution and on model systems. They illustrate new important consequences of the c ollective character of hydration and of PMF and reveal new aspects of hydrophobic interactions and, in general, of SIFs. Their relevance to protein recognition, conformation, function, and folding and to the ob served slight yet significant nonadditivity of functional effects of d istant point mutations in proteins is discussed. These results point o ut the functional role of the configurational and dynamical states (an d related statistical weights) corresponding to the complex configurat ional energy landscape of the two interacting systems: biomolecule + w ater.