Probing n-Octyl α-d-Glycosides Using Deuterated Water in the Lyotropic Phase by Deuterium NMR

Abstract

The lyotropic phase behavior of four common and easily accessible glycosides, n-octyl α-D-glycosides, namely, α-Glc-OC 8 , α-Man-OC 8 , α-Gal-OC 8 , and α-Xyl-OC 8 , was investigated. The presence of normal hexagonal (H I ), bicontinuous cubic (V I ), and lamellar (L α ) phases in α-Glc-OC 8 and α-Man-OC 8 including their phase diagrams in water reported previously was verified by deuterium nuclear magnetic resonance ( 2 H NMR), via monitoring the D 2 O spectra. Additionally, the partial binary phase diagrams and the liquid crystal structures formed by α-Gal-OC 8 and α-Xyl-OC 8 in D 2 O were constructed and confirmed using small-and wide-angle X-ray scattering and 2 H NMR. The average number of bound water molecules (n b ) per headgroup in the L α phase was determined by the systematic measurement of the quadrupolar splitting of D 2 O over a wide range of molar ratio values (glycoside/ D 2 O), especially at high glucoside composition. The number of bound water molecules bound to the headgroup was found to be around 1.5−2.0 for glucoside, mannoside, and galactoside, all of which possesses four OH groups. In the case of xyloside, which has only three OH groups, the bound water content is ∼2.0. Our findings confirmed that the bound water content of all n-octyl α-Dglycosides studied is lower compared to the number of possible hydrogen bonding sites possibly due to the fact that most of the OH groups are involved in intralayer interaction that holds the lipid assembly together.

Surface Properties and Liquid Crystal Properties of Alkyltetra(oxyethyl) β-d-Glucopyranoside

“…Indeed, the addition of water would result in two isotropic phases, presumably a cubic phase and a normal micellar phase. Since both phases were black under crossed polarizers, but the former is more viscous than the latter, they could be distinguished from each other . Herein, the experimental results were consistent with the literature, and the nonbirefringent area (3) was considered as the bicontinuous cubic phase (C).…”

“…Since both phases were black under crossed polarizers, but the former is more viscous than the latter, they could be distinguished from each other. 54 Herein, the experimental results were consistent with the literature, and the nonbirefringent area (3) was considered as the bicontinuous cubic phase (C). Similar phase sequences were also found in other gradient samples 4c and 4d (GlcC10 and GlcC12, n = 10, 12).…”