Phase Transition in Glycolipid Monolayers Induced by Attractions between Oligosaccharide Head Groups

Abstract

The surface property of two kinds of synthetic glyceroglycolipids was investigated to confirm the stereoeffect of sugar residues on the phase behavior in monolayers: one is the maltooligosaccharide-containing lipids [Mal N (C12)2] and the other is cellooligosaccharide-containing lipids [Cel N (C12)2]. The two kinds of glycolipids exhibit the opposite dependence of the surface pressure−area (Π−A) isotherm on the number of glucose residues (N), in that Mal N (C12)2 tends to be more expanded as N increases, while Cel N (C12)2 tends to be more condensed. The liquid-expanded/liquid-condensed phase transition in Cel4(C12)2 was evaluated by the Brewster angle microscopy and the latent heat analysis with the Clausius−Clapeyron equation, as a model of film condensation induced by the attraction between oligosaccharide head groups. The film morphology of Cel4(C12)2 was unique in that it exhibits the optically isotropic and flexible fluid type of the LC phase, while Glc(C16)2 forms a two-dimensional tilted crystalline phase in the same way as fatty acids and phospholipids. The heat of transition (ΔH) of Cel4(C12)2 does not converge toward zero even at high temperature. In other words, the main transition of Cel4(C12)2 does not become second order in contrast to the behavior usually encountered in monolayers. The refractive index of the oligosaccharide head groups in water as well as the alkyl chains in air must be properly taken into account to interpret the reflectivity.

Synthesis, surface properties, and biocompatibility of 1,2,3-triazole-containing alkyl β-d-xylopyranoside surfactants

“…This phenomenon has been reported for different types of monolayers. 55-57 In all cases the kinetics of monolayer formation appear to be the driving force behind the unique shape of the compression isotherm. Further experiments are necessary to determine the nature of this phase transition of 5e and 5f .…”

Reversible collapse of the Langmuir films of a series of triphenylsilyl ether-terminated amphiphiles

“…Bommarito et al attribute the negative entropy changes as due to the first-order crystallization of a less-ordered phase to a well-ordered, crystalline phase. In contrast, amphiphiles with a larger cross-section, including glycolipids and phospholipids, have shown an increase in entropy as the Langmuir film is compressed from the liquid-expanded to the liquidcondensed phase [19].…”

Effect of the side chain of N-acyl amino acid surfactants on micelle formation: An isothermal titration calorimetry study

“…According to the packing parameter theory, a single-tailed surfactant tends to form spherical micelles, while a double-tailed surfactant leads to a bilayer structure in aqueous solution. Generally, a systematical examination of the effect of the surfactant head group on the molecular aggregates has some difficulties compared with that of the hydrophobic tail group, except for some nonionic surfactants with polyethylene or polysaccharide units [3][4][5][6][7][8][9][10][11][12][13][14]. Another exception is the amino acid-type surfactant system [15][16][17][18][19].…”