Comparison of a nonlocal dielectric model with a discontinuous model

We compare local and nonlocal dielectric models for the electric potential around a solute. We choose a water molecule as solute so that the comparisons can be related to the behavior of bulk water. We see that, near the solute, the two models give predictions that differ by an order of magnitude, although the difference diminishes away from the solute. We also compare the two models for the prediction of the electric potential around the protein BPTI. Discontinuous (local) dielectric models are widely used to approximate the electrostatic field surrounding proteins, small molecules, and other systems involving a dielectric material [18]. In some cases, one uses the dielectric solvent model together with a quantum mechanics model [25]. More commonly, the discontinuous dielectric model is used as an implicit solvent model in molecular dynamics simulations [16, 23, 2, 3]. Recently, nonlocal models [9, 10, 4, 5] have been of interest. Here we compare the predictions of the two models of the electrostatic potential around solutes of different sizes. In one case, we choose the solute to be a water molecule in order to compare with bulk water properties. In the other, we take the solute to be a small protein, BPTI. In both cases, we see drammatic differences between the predictions of the two models near the solute.