Microsolvation of dimethylphosphate: a molecular model for the interaction of cell membranes with water

Abstract

We present an exhaustive stochastic search of the quantum conformational spaces of the (CH(3)O)(2)PO(2)(-) + nH(2)O (n = 1,2,3) systems. We uncover structural, conformational and energetic features of the problem. As in the isolated species, clusters containing the gauche-gauche (gg) conformation of dimethylphosphate (DMP(-)) are energetically preferred, however, contributions from hydrated gauche-anti (ga) and anti-anti (aa) monomers cannot be neglected because such structures are quite common and because they are close in energy to those containing the gg monomer. At least seven distinct types of O∙∙∙H-O-H contacts lead to DMP(-) ↔ water interactions that are always stabilizing, but not strong enough to induce significant changes in the geometries of either DMP(-) or water units. Our results lead us to postulate DMP(-) to be a suitable model to study explicit and detailed aspects of microsolvation of cell membranes.

Infrared signature of micro-hydration in the organophosphate Sarin: an ab initio study

“…Details of the H 2 O-phosphate hydrogen bond formation can be probed by calculating and comparing induced IR shifts for a wide range of hydrated clusters. Previous ab initio studies have predicted a reduction (red shift) in the P=O vibrational frequency of 30 cm −1 for the monohydrated DMP anion, a red shift of 32 cm −1 for the trihydrated DMP cluster [14,15], while the mono-hydrated DMMP cluster experienced a 21 cm −1 red shift [23]. The impact on other IR vibrations has also been discussed, including Lee and co-worker's simulation of the water complexation with DMMP, DIFP, Sarin, and Soman (GD).…”

“…Ab initio computational methods have previously proven to be useful in investigating OP micro-hydration and include studies of the dihydrogen phosphate (DHP) and dimethyl phosphate (DMP) anion [14][15][16], bisphosphonates [17][18][19], phosphate [20], polyphosphate anions [21], DMMP [22,23], the G-agent simulant diisopropyl fluorophosphate (DIFP), and Sarin [22]. Recently we reported ab initio studies of adsorption energetics for the micro-hydrated Sarin•nH 2 O (n=1-4) clusters, confirming that the primary interaction was hydrogen bonding between the Sarin P=O group and water [24].…”

Microsolvation of small cations and anions

“…We rigorously comply and use as weighting factors the Boltzmann derived populations. This practice has allowed us to explain several puzzling observations, from the shifts in vibrational frequencies due to microsolvation of ibuprofen and of model cell membranes, to the symmetry breaking upon microsolvation of and the number of water molecules needed to dissociate HCl …”

Vibrational spectroscopy of water in hydrated lipid multi-bilayers. III. Water clustering and vibrational energy transfer

“…1, 2 The local structure and dynamics of water surrounding biological molecules including lipids, [3][4][5] DNA, [6][7][8][9] and proteins [10][11][12] have been extensively studied through a variety of experimental [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] and computational [28][29][30][31][32][33][34][35][36][37][38][39][40] techniques, and in general the behavior of such "biological" water is quite distinct from bulk water. 41,42 For example, in phosphatidylcholine (PC) lipid bilayers, water preferentially forms strong hydrogen bonds to phosphate oxygens, 43 and molecular dynamics simulations have suggested a clathrate-like water cage around the PC choline.…”