Molecular dynamics approach to water structure of HII mesophase of monoolein

Abstract

The goal of the present work is to study theoretically the structure of water inside the water cylinder of the inverse hexagonal mesophase (H(II)) of glyceryl monooleate (monoolein, GMO), using the method of molecular dynamics. To simplify the computational model, a fixed structure of the GMO tube is maintained. The non-standard cylindrical geometry of the system required the development and application of a novel method for obtaining the starting distribution of water molecules. A predictor-corrector schema is employed for generation of the initial density of water. Molecular dynamics calculations are performed at constant volume and temperature (NVT ensemble) with 1D periodic boundary conditions applied. During the simulations the lipid structure is kept fixed, while the dynamics of water is unrestrained. Distribution of hydrogen bonds and density as well as radial distribution of water molecules across the water cylinder show the presence of water structure deep in the cylinder (about 6 Å below the GMO heads). The obtained results may help understanding the role of water structure in the processes of insertion of external molecules inside the GMO∕water system. The present work has a semi-quantitative character and it should be considered as the initial stage of more comprehensive future theoretical studies.

Role of counter-ion and helper lipid content in the design and properties of nanocarrier systems: a biophysical study in 2D and 3D lipid assemblies

“…MO monolayer ( Fig. 2A -blue line) agrees well with previously reported data 39 and has the typical shape of a LE phase of singlechain amphiphiles, but the molecular areas are smaller than expected. MO is highly hygroscopic.…”

Structural Properties of Inverted Hexagonal Phase: A Hybrid Computational and Experimental Approach

“…First, two GROMACS 34 modules, gmx editconf and gmx genconf, were used to build a single lipid cylinder for each lipid type. 35 Each lipid tubule was composed of 360 lipid molecules distributed on 15 rings (with a radius of ca. 2.5 nm).…”

Solvation Dynamics in Different Phases of the Lyotropic Liquid Crystalline System

“…However, with further enhancement of temperature (around 333–343 K) results in increase of critical packing parameter (CPP) value, which leads to the phase transition from H II mesophase to inverse micellar (L 2 ) phase . The structural properties of H II mesophases composed of GMO/TAG/PC/water were extensively studied by SAXS, FTIR, dielectric spectroscopy, DSC, etc. − The structure of H II mesophase is the two-dimensional arrays of infinitely long, densely packed, circular cylinders filled with water. − , Each cylinder is surrounded by a layer of amphiphilic molecules that are arranged perpendicular to the cylindrical interface with hydrophobic chains pointing outward and hydrophilic heads pointing inward toward a channel, where water molecules can diffuse. − These properties allow the H II mesophase to entrap water-soluble compounds inside the cylinder. They can also accommodate hydrophobic molecules by direct interactions with their lipid hydrophobic moieties oriented radially outward from the center of the water pool.…”

“…structure of H II mesophase is the two-dimensional arrays of infinitely long, densely packed, circular cylinders filled with water. [8][9][10]13 Each cylinder is surrounded by a layer of amphiphilic molecules that are arranged perpendicular to the cylindrical interface with hydrophobic chains pointing outward and hydrophilic heads pointing inward toward a channel, where water molecules can diffuse. 8−10 These properties allow the H II mesophase to entrap water-soluble compounds inside the cylinder.…”