Investigation of the Effect of Sugar Stereochemistry on Biologically Relevant Lyotropic Phases from Branched-Chain Synthetic Glycolipids by Small-Angle X-ray Scattering

Abstract

Synthetic branched-chain glycolipids are suitable as model systems in understanding biological cell membranes, particularly because certain natural lipids possess chain branching. Herein, four branched-chain glycopyranosides, namely, 2-hexyl-decyl-α-D-glucopyranoside (α-Glc-OC10C6), 2-hexyl-decyl-β-D-glucopyranoside (β-Glc-OC10C6), 2-hexyl-decyl-α-D-galactopyranoside (α-Gal-OC10C6), and 2-hexyl-decyl-β-D-galactopyranoside (β-Gal-OC10C6), with a total alkyl chain length of 16 carbon atoms have been synthesized, and their phase behavior has been studied. The partial binary phase diagrams of these nonionic surfactants in water were investigated by optical polarizing microscopy (OPM) and small-angle X-ray scattering (SAXS). The introduction of chain branching in the hydrocarbon chain region is shown to result in the formation of inverse structures such as inverse hexagonal and inverse bicontinuous cubic phases. A comparison of the four compounds showed that they exhibited different polymorphism, especially in the thermotropic state, as a result of contributions from anomeric and epimeric effects according to their stereochemistry. The neat α-Glc-OC10C6 compound exhibited a lamellar (Lα) phase whereas dry α-Gal-OC10C6 formed an inverse bicontinuous cubic Ia3d (QII(G)) phase. Both β-anomers of glucoside and galactoside adopted the inverse hexagonal phase (HII) in the dry state. Generally, in the presence of water, all four glycolipids formed inverse bicontinuous cubic Ia3d (QII(G)) and Pn3m (QII(D)) phases over wide temperature and concentration ranges. The formation of inverse nonlamellar phases by these Guerbet branched-chain glycosides confirms their potential as materials for novel biotechnological applications such as drug delivery and crystallization of membrane proteins.

Butane-1,2,3,4-tetraol-based amphiphilic stereoisomers for membrane protein study: importance of chirality in the linker region

“…the same hydrophobicity and hydrophilicity), this result implies a different tendency to self-aggregate depending on the stereochemistry. 12 The M-isomers have the strongest self-aggregation tendency, followed by the A- and B-isomers. The sizes of micelles formed by the BTMs tend to increase with increasing alkyl chain length.…”

“…, glucose, maltose, or N -oxide). 7,12,25 In contrast, the FAs 6 and GDN 26 contain multiple chiral centers within the hydrophobic moiety, but in these cases the chirality is fixed and hard to vary. Because of the facile chiral induction in the linker region, in contrast, we could conveniently prepare three BTM stereoisomers for comparative evaluation with multiple membrane proteins.…”

Fluorescence characterization of water-driven self-assembled lipids and their temperature-induced phase transitions

“…40,41 The hexagonal phase of βMalOC 12 was obtained at 65% (w/w) (23 ºC) based on its published binary phase diagram 42 whereas the inverse bicontinuous cubic phase of βGlcOC 10 C 6 was observed at 20% (w/w) (23 ºC) according to its partial binary phase diagram. 43 Both samples were prepared with the same procedure above.…”

“…In our case, the βGlcOC 10 C 6 lipid forms an inverse cubic phase of the space group Ia3d with a lattice parameter of 7.6 nm. 43 Whereas for monoolein, the inverse cubic phase of the space group Pn3m has a lattice parameter of 9.7-10.1 nm, 53 while in the Ia3d symmetry this value is about 10.9 nm. 26 In addition to the difference in the lattice parameter, the size of the water nanochannels in the lipidic cubic phase is also important.…”

“…26 In addition to the difference in the lattice parameter, the size of the water nanochannels in the lipidic cubic phase is also important. At 20% (w/w) aqueous and 23°C, the chain length of βGlcOC 10 C 6 is d hc = 0.73 nm, 43 which produces an aqueous channel diameter of ~2.3 nm. This value seems to be close to the water channel diameter (~3.3 nm) of monoolein/Ia3d system at 20% (w/w) aqueous and 21 °C.…”