Explicit vs Implicit Water Simulations of Charged Dendrimers

Charged dendrimers with terminal or full charge of the nodes, single- or double-spacer, are simulated and a comparison is made between implicit and explicit water results. The main conclusion is that modeling the solvent with a continuum (dielectric constant er = 80) and ignoring its discrete nature results into a surprisingly accurate description of their properties. Sizes, density profiles and spacer dependence are reproduced within 10% at most. The counterion intake is overestimated by the implicit water model because in reality water intrudes all the way to the center and locally expels some counterions. The amount of water absorbed increases rapidly with charging the dendrimer.