Water structure and dynamics play an important in protein structure, dynamics, and function. Water packing, orientations, and dynamics in the vicinity of proteins are affected by protein surface roughness as well as the chemically heterogeneous nature of protein surface, which ranges from hydrophilic to hydrophobic in character. We use molecular dynamics simulations of model solutes with varying sizes and charge densities to understand how they affect the vicinal water structure and dynamics. Water-mediated interactions between solutes of varying charge densities yields (for the first time) "molecular volcano" relationships observed in experimental data on salt pairs in solution. We make connections of fundamental understanding of charge-density-dependent hydration obtained for model solutes with hydration of proteins through complementary simulations of several proteins in explicit water. Together, these studies are beginning to provide molecular level insights into protein-X interactions (where X = ligands, chromatographic displacers, and interfaces).