Solvation of nanoscale interfaces
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A dehydrogen is an ‘under-wrapped’ hydrogen bond in a protein that is purported to be a hot spot for binding due to the favorable replacement of water with hydrocarbon upon binding of another protein. A model at the level of dielectric constants is used to test the validity of the claim that moving a hydrogen bond from high dielectric (i.e. a dehydron) to low dielectric (i.e. after binding of another protein) is actually a thermodynamically favorable process. In simulation, several proteins have been shown to undergo a dewetting transition when fixed components are separated a small distance. A new atomic-level hydrophobicity scale is combined with topographical information to characterize protein interfaces. The relationship between hydrophobicity and topography for protein surfaces known to be involved in binding is examined. This framework is then applied to identify surface characteristics likely to have an affect on the occurrence of a dewetting transition. Cadmium selenide (CdSe) nanoparticles form nanospheres or nanorods when grown in solutions of varying concentrations of the surfactants hexylphosphonic acid (HPA) and trioctylphosphine oxide (TOPO). Relative binding free energies are calculated for HPA and TOPO to the solvent-accessible faces of CdSe crystals. Binding free energies calculated with a Molecular Mechanics-Generalized Born model are used to identify a set of low free energy structures for which the solvation free energy is refined with the solution to the Poisson equation. These relative binding free energies provide information about the relative growth rates of these crystal faces in the presence of surfactants. Relative growth rates are then used to help understand why nanoparticles form certain shapes in the presence of specific surfactants.