Molecular interactions in the microsolvation of anionic dimethylphosphate (DMP-, a molecular model for the polar head in cell membranes), with up to three water molecules are studied. Charge assisted PO2-center dot center dot center dot H-O-H contacts are shown to be the stronger interactions. CH3O center dot center dot center dot H-O-H interactions are also stabilizing and characterized as closed shell. Secondary H2C-H center dot center dot center dot OH2 interactions are also at play. All dominant intermolecular interactions correspond to the general lone pair -> antibonding (n(o) -> sigma(X-H)*) (X=O, C) form. The formal charge in DMP- has a strengthening effect in hydrogen bonds between water molecules in outer solvation shells. (c) 2015 Elsevier B.V. All rights reserved.