Investigation of water-mediated intermolecular interactions with the adaptive resolution simulation technique.

We use the adaptive resolution simulation technique (AdResS) to estimate the region in space where water-mediated effects in molecule-molecule interactions are relevant. AdResS is employed to identify the region around the solute (solvation shell) where the atomistic details of the hydrogen bonding network are relevant while outside water plays the role of a thermodynamic bath that can be described at simplified macroscopic level. The consequence is that for the interaction of two solutes the intermolecular distance at which water mediated effects start to be relevant is represented by the sum of the radii of the two respective solvation shells identified via AdResS. The hypothesis formulated above will be proven by calculating the solute-solute potential of mean force (PMF) for different solutes. As test molecules we use amino acids derived from fragments of the FCHo2-F-BAR domain protein; this choice stems from the fact that the current results, beside proving the technical capability of AdResS in this context, may provide data for future actual coarse-grained models.