Studies on electrostatic interactions within model nano-confined aqueous environments of different chemical nature

Abstract

We study the potential of mean force for pairs of parallel flat surfaces with attractive electrostatic interactions by employing model systems functionalized with different charged, hydrophobic and hydrophilic groups. We study the way in which the local environment (hydrophobic or hydrophilic moieties) modulates the interaction between the attractive charged groups on the plates by removing or attracting nearby water and thus screening or not the electrostatic interaction. To explicitly account for the role of the solvent and the local hydrophobicity, we also perform studies in vacuo. Additionally, the results are compared to that for non-charged plates in order to single out and rationalize the non-additivity of the different non-covalent interactions. Our simulations demonstrate that the presence of neighboring hydrophobic groups promote water removal in the vicinity of the charged groups, thus enhancing charge attraction upon self-assembly. This role of the local hydrophobicity modulating electrostatic interactions is consistent with recent qualitative descriptions in the protein binding context.

Ionic Transport in Electrostatic Janus Membranes. An Explicit Solvent Molecular Dynamic Simulation

“…The strength of the electrostatic interactions and, therefore, the dynamics of ionic motion, could be significantly affected by the distinctive orientation of water at the entrance of the smaller section of the pore. 30 Importantly, although the dipole moment is altered in these regions, the average number of HB per molecule remains at 3.47, which almost exactly matches the average all across the system, including the reservoir, of 3.44. The results in Figure 7 allow us to make two additional, important observations.…”

“…There is some precedent for the dipole behavior found here in the literature. − Past studies also proposed a reduction of the dielectric constant in the direction perpendicular to the confinement, and an increase in the parallel direction. The strength of the electrostatic interactions and, therefore, the dynamics of ionic motion, could be significantly affected by the distinctive orientation of water at the entrance of the smaller section of the pore . Importantly, although the dipole moment is altered in these regions, the average number of HB per molecule remains at 3.47, which almost exactly matches the average all across the system, including the reservoir, of 3.44.…”

Comparing the performance of two structural indicators for different water models while seeking for connections between structure and dynamics in the glassy regime

“…The comprehension of the structural and dynamical behavior of water is not only a matter of great intrinsic interest but it also becomes essential for several central fields of science and technology [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. But contrary to what its simple molecular structure might suggest, water represents in fact a quite complex system, with several anomalies that get more pronounced as the liquid is cooled down [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32].…”

Size dependence of dynamic fluctuations in liquid and supercooled water

“…Slow dynamics in liquid water has also received a significant attention. Water is central for main fields ranging from biology to materials science [30][31][32][33][34][35][36][37][38][39][40][41][42][43]. Within such contexts, being usually at interfaces or subject to nanoconfinement, water usually shows certain reminiscences of glassy behavior at low or even at room temperature [34][35][36][37][38][39][40][41].…”