The influence of single-chain-anchored galactose on the polymorphism of resuspended lyophilized dipalmitoylphosphatidylcholine lipsomes

Abstract

Three glycolipids consisting on a hexadecyl chain and galactose headgroup without or with different ethylenoxide spacers (EO) were studied in 1:2 mixtures with DPPC by means of calorimetry (DSC) and X-ray diffraction. Despite the high content of the glycolipid in the system without spacer and with two EO-units, miscibility was found. Only the glycolipid with three EO-units in the headgroup shows a demixing in the sample. It occurs in subgel and gel phases, but in the liquid crystalline phase the glycolipid solves itself in the DPPC matrix. In dependence on the headgroup structure of the glycolipids two different polymorphisms were detected. The consequence of mixing glycolipids to DPPC is that an interdigitation of the molecules occurs in gel phases, but in the liquid crystalline phases the situation is more complicated. In the Lα phase a shortening of the bilayer distance was observed as well as its increase with respect to the gel phase.

Nevertheless, a predominate influence of glycolipids on DPPC is obvious in liquid crystalline phases which should be studied further with relevant methods.