Bilayer Properties of Totally Synthetic C16:0-Lactosyl-Ceramide

Abstract

Differential scanning calorimetry (DSC) and x-ray diffraction have been used to study the structural and thermal properties of totally synthetic D-erythro-N-palmitoyl-lactosyl-C(18)-sphingosine (C16:0-LacCer). Over the temperature range 0-90 degrees C, fully hydrated C16:0-LacCer shows complex thermal transitions characteristic of polymorphic behavior of exclusively bilayer phases. On heating at 5 degrees C/min, hydrated C16:0-LacCer undergoes a complex two-peak endothermic transition with maxima at 69 degrees C and 74 degrees C and a total enthalpy of 14.6 kcal/mol C16:0-LacCer. At a slower heating rate (1.5 degrees C/min), two endothermic transitions are observed at 66 degrees C and 78 degrees C. After cooling to 0 degrees C, the subsequent heating run shows three overlapping endothermic transitions at 66 degrees C, 69 degrees C, and 71.5 degrees C, followed by a chain-melting endothermic transition at 78 degrees C. Two thermal protocols were used to completely convert C16:0-LacCer to its stable, high melting temperature (78 degrees C) form. As revealed by x-ray diffraction, over the temperature range 20-78 degrees C this stable phase exhibits a bilayer structure, periodicity d approximately 65 A with an ordered chain packing mode. At the phase transition (78 degrees C) chain melting occurs, and C16:0-LacCer converts to a liquid crystalline bilayer (L(alpha)) phase of reduced periodicity d approximately 59 A. On cooling from the L(alpha) phase, C16:0-LacCer converts to metastable bilayer phases undergoing transitions at 66-72 degrees C. These studies allow comparisons to be made with the behavior of the corresponding C16:0-Cer (. J. Lipid Res. 36:1936-1944) and C16:0-GluCer and C16:0-GalCer (. J. Lipid Res. 40:839-849). Our systematic studies are aimed at understanding the role of oligosaccharide complexity in regulating glycosphingolipid structure and properties.

Thermal-history-dependent Phase Behavior of Ceramide Molecular Assembly in a UV-curable Acrylic Adhesive Resin

“…We concluded that the rapid cooling treatment induces the formation of a metastable amorphous-like phase in pure CER. For naturally occurring ceramides 14,29 and a synthetic pseudo-ceramide 30 , an exothermic peak has been distinctly observed. Hence, the appearance of the exothermic peak in the thermogram of the melt-quenched in-resin CER sample is not mainly caused by a specific interaction between the acResin ® and the CER, but it is due to the intrinsic nature of CER.…”

“…However, some drugs, such as diphenhydramine HCl 12 , undergo thermally induced degradation during the hotmelt process. Ceramides with saturated hydrocarbon chains exhibit greater thermal stability than diphenhydr-amine HCl; however, ceramides exhibit thermal-history-dependent phase behavior 14,15 , and the different phases of ceramides exhibit different physical properties. Obviously, these differences in physical properties may affect the release rate of ceramides from adhesive materials.…”

Structure of lipid bilayers

“…For example, there are many glycosphingolipids that have chain ordered phases. The thermodynamic behavior of these phases is characterized by hysteresis, so thermal protocols must be carefully considered when characterizing the three distinct phases that were recently seen in the ceramide lipid C16:0-LacCer [143].…”

Glycosphingolipids in microdomain formation and their spatial organization

“…It was observed that GalCer alone at 30 mol% concentration formed ordered domains which dissociated in a complex two step process upon temperature rise. On the other hand, GlcCer formed domains displaying a comparatively more cooperative dissociation behavior, but a relatively lower thermostability [29][30][31].…”