Atomistic simulation studies of the α/β-glucoside and galactoside in anhydrous bilayers: effect of the anomeric and epimeric configurations

Abstract

Fully atomistic molecular dynamics simulation studies of thermotropic bilayers were performed using a set of glycosides namely n-octyl-β-D-glucopyranoside (β-C8Glc), n-octyl-α-D-glucopyranoside (α-C8Glc), n-octyl-β-D-galactopyranoside (β-C8Gal), and n-octyl-α-D-galactopyranoside (α-C8Gal) to investigate the stereochemical relationship of the epimeric/anomeric quartet liner glycolipids with the same octyl chain group. The results showed that, the anomeric stereochemistry or the axial/equatorial orientation of C1-O1 (α/β) is an important factor controlling the area and d-spacing of glycolipid bilayer systems in the thermotropic phase. The head group tilt angle and the chain ordering properties are affected by the anomeric effect. In addition, the L(C) phase of β-C8Gal, is tilting less compared to those in the fluid L(α). The stereochemistry of the C4-epimeric (axial/equatorial) and anomeric (α/β) centers simultaneously influence the inter-molecular hydrogen bond. Thus, the trend in the values of the hydrogen bond for these glycosides is β-C8Gal > α-C8Glc > β-C8Glc > α-C8Gal. The four bilayer systems showed anomalous diffusion behavior with an observed trend for the diffusion coefficients; and this trend is β-C8Gal > β-C8Glc > α-C8Gal > α-C8Glc. The "bent" configuration of the α-anomer results in an increase of the hydrophobic area, chain vibration and chain disorganization. Since thermal energy is dispensed more entropically for the chain region, the overall molecular diffusion decreases.

Structural Insights into Solid‐to‐Solid Phase Transition and Modulated Crystal Formation in Octyl‐β‐d‐Galactoside Crystals

“…Despite these advances, studies of pure alkyl‐β‐ d ‐glycoside crystals and hydrates have been rare, possibly because of the difficulty of preparing single crystals with an adequate size for single‐crystal X‐ray structural analysis. In fact, to the best of our knowledge, there is no study that determines a single‐crystal structure of any alkyl‐β‐ d ‐glycoside . Moreover, while an anomalous initial hydration of anhydrous liquid crystals (LCs) was observed for octyl‐β‐ d ‐glucoside/water mixture, the influence of trace water amounts on the molecular assembly of alkyl‐β‐ d ‐glycoside is still unclear because of the lack of solid experimental evidence based on crystal analysis.…”

Dry Thermotropic Glycolipid Self-Assembly:A Review

“…For a dodecyl β-maltoside β-MalC 12 this total number i.e. both intra-and interlayer is 7.2 20 , while that for an octyl β-glucoside β-GlcC 8 is about halved or 4.18 HBs per headgroup 19 . For glucose and maltose headgroups the interlayer HBs per lipid have the same value of 3.1.…”

“…A simple monosaccharide glucolipid contains a glucose headgroup in which there are four OHs. Thus, in each glucose headgroup there are four polar hydrogens, and six oxygens able to make two HBs and ideally making the maximum number of HBs per headgroup is 16 19 . For a disaccharide e.g.…”

“…Generally a hydrogen bond can be classified into a weak, medium or strong HB depending on the distances 22 . In computational studies of self-assembly systems, a HB can also be classified into intra/interlayer or intra/intermolecular 19,20 , see Fig. 1 and Table 1 for clarity.…”

Self-Assemblies Behaviour of Palm Oil-Based Galactoside

“…Thermotropic properties are determined by studying phase transitions stimulated thermally using calorimetric and microscopic techniques. Lyotropic behavior is commonly observed in amphiphilic molecules where the molecules have at least two different solubility capacities towards a solvent (usually water) within itself [13]. The lyotropic properties are determined using microscopic technique and surface tension measurements to obtain the critical aggregation concentration (CAC).…”