Conformational equilibria of polar and charged flexible polymer chains in water

Continuum model predictions of the conformational equilibria of idealized polar and charged linear polymers in water are compared to complementary simulations in explicit water. The continuum model of hydration predicts with reasonable accuracy the conformational dependence of the hydration free energy of these solutes observed in the simulations. However, a prerequisite for accurate predictions is the optimization of the phenomenological parameters inherent to the continuum model using the simulation results for a subset of the solutes, in this case the uncharged polymer and two amphiphilic polymer chains with a single positive or negative charge on one terminal group. Our results demonstrate that the continuum model can be used to discriminate among the conformational preferences for different sequences of backbone charges. Finally, an unexpected finding of this study is the stabilization in water of the more compact conformations of the polymer chains with a fixed dipole moment. The driving force for this behavior is greater than the hydrophobic driving force and is electrostatic in nature.