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Abstract

The molecular interactions of three biologically important galactocerebrosides have been studied in monolayers formed at the soft air/water interface as 2D model membranes. Highly surface sensitive techniques as GIXD (grazing incidence X-ray diffraction), IRRAS (infrared reflection-absorption spectroscopy) and BAM (Brewster angle microscopy) have been used. The study reveals that small differences in the chemical structure have a relevant impact on the physical-chemical properties and intermolecular interactions. The presence of a 2-D-hydroxyl group in the fatty acid favored for GalCer C24:0 (2-OH) monolayers a higher hydration state of the head group at low lateral pressures (< 25 mN/m) and a higher condensation effect above 30 mN/m. An opposite behavior was recorded for GalCer C24:0 and GalCer C24:1 for which the intermolecular interactions are defined by the weakly hydrated but strong H-bonded interconnected head groups. Additionally, the 15-cis-double bond in the fatty acid chain (nervonic acid) of GalCer C24:1 stabilized the LE phase, but did not disturb the packing parameters of the LC phase as compared to the saturated compound GalCer C24:0.