Hydrophilic/Hydrophobic Balance Determines Morphology of Glycolipids with Oligolactose Headgroups

Abstract

The morphology of synthetic glycolipids with lactose oligomers (Lac N, the number of lactose units, N = 1, 2, 3) was studied in lamellar phase. By a systematic combination of differential scanning calorimetry and small- and wide-angle x-ray scattering experiments, the effects of hydrophilic/hydrophobic balance on their thermotropic phase behaviors were discussed. The dispersion of Lac 1 exhibited a crystalline-fluid phase transition, dominated by the strong van der Waals interaction between dihexadecyl chains. In the case of Lac 2, the hydrophilic/hydrophobic balance between the headgroup and the alkyl chains is shifted to the hydrophilic side, resulting in a gel-fluid phase transition with a decreased transition temperature and phase transition enthalpy. Different from the first two systems, the differential scanning calorimetry trace of Lac 3 showed much less remarkable peaks. The small- and wide-angle x-ray diffraction patterns did not reveal any transition in the chain ordering, suggesting that the correlation between the hexasaccharide headgroups is so strong that the melting of the alkyl chains was not allowed. Such dominant effects of the hydrophilic/hydrophobic balance on the morphology of Lac N lipids can be attributed to the small sterical mismatch between the alkyl chains and the linear, cylindrical oligolactose groups.

Influence of length and conformation of saccharide head groups on the mechanics of glycolipid membranes: Unraveled by off-specular neutron scattering

“…The multiple endothermic peaks observed in heating scans suggest polymorphic behavior of lipids, as in other reported glycosphingolipid systems. 44 This enthalpy value is significantly suppressed compared to that of H-Lac1 lipid (∆H H-Lac1 = 30 kcal/mol), 3 which can be attributed to the shift of the hydrophilic/hydrophobic balance and the entropic contribution caused by the additional α-galactose attached to the 4th position.…”

“…difference between κ D−Gent and κ D−Lac1 = 32 k B T can instead be interpreted in terms of the decrease in intra-membrane interactions between the head groups caused by the entropic contribution derived from less ordered lateral packing due to their "bent" structure, which could be identified from a clear difference in T m ; T m Lac1 = 74 • C and T m Gent = 45 • C. 3,19 Second, the mechanical parameters of D-Gb3 membranes were compared with DPPC membranes measured under identical conditions (60 • C, h rel ∼ 95%). 21 The compression modulus of D-DPPC B D−DPPC = 48 MPa is more than 5-fold that of D-Gb3.…”

“…The beam width was 2 mm horizontally and 25 mm vertically. The scattered beam was detected at exit angle Γ by a position sensitive 3 He 2D detector with 128 × 128 channels. The sample was rotated stepwise with respect to the incident beam.…”

“…X-ray and neutron scattering [1][2][3][4][5] from isotropic lipid suspensions have been widely used to gain insight into structural features of biological membranes over multiple length scales as a function of temperature, 6,7 osmotic pressure, 8,9 and the molar ratios of substitutional additives (cholesterol, proteins, etc.). 1,10 However, powder diffraction experiments do not allow for the discrimination of momentum transfers parallel and perpendicular to the membrane planes.…”

Oligomer‐to‐Polymer Transition in Short Ethylene Glycol Chains Connected to Mobile Hydrophobic Anchors

“…Such a symmetric WAXS peak has also been found for glycolipids with the same ether junctions, where the alkyl chains have almost no tilt. [29] When the alkyl chains assume an all-trans conformation with only a little tilt, the chains prefer to assume hexagonal packing and, therefore, the area per molecule A can be calculated by the wide-angle diffraction line w, using Equation (3): [25,26] A…”