Small- And Wide-angle X-ray Scattering Research Articles

Layer formations in the bacteria membrane mimetic DPPE-DPPG/water system induced by sulfadiazine

The effect of the frequently used antibiotic sulfadiazine (SD) was studied on a bacteria membrane mimetic model system by using differential scanning calorimetric (DSC), small- and wide-angle X-ray scattering (SWAXS) and freeze-fracture methods. The membrane model system consisted of dipalmitoylphosphatidylethanolamine (DPPE, 0.8 molar ratio) and dipalmitoylphosphatidylglycerol (DPPG, 0.2 molar ratio). The SD molar ratio (relative to the lipids) was varied between 10 − 3 and 1. In the presence of SD, two transitions between the gel and liquid crystalline phases appear at 60.5 °C and about at 65 °C. In the temperature domain of the gel phase, the subcell of the chain packing is strongly temperature dependent indicating the increased dominance of the hydration forces during the first transition and the location of SD molecules in the neighbourhood of the polar lipid head groups. The second transition is accompanied by the changes in the nanometer-scale layer arrangements observed by SAXS and in the μm-scale morphology observed by freeze-fracture. Above the temperature of the second transition, the SD-induced metastable structures undergo further formations to produce a more homogeneous state favoured by the geometrical packing of the cylindrical-shaped lipid molecules.

Small-and Wide Angle X-ray Scattering of Oriented Lecithin Multilayers

Abstract It is the aim of this paper to demonstrate that much information is to be obtained about lameller systems when diffraction work is performed on well aligned samples and paracrystal methods are applied. There is no need to examine “crytallized” monohydrates in order to get more diffractio spots. Contrary to this, a water cotent above 20% is of higherbiological relevance. The water content of 23 wt.% wasd introduced by swelling in the gel-phase, giving a bigger stackign period than usually reported, when swelling is performed in the Lα-phase. At various temperatures oriented “multi-sandwiches” of dipalmitoyl lecithin (DPL) multilayers were analyzed by small-and wide angle X-ray diffraction as party reported before. Thus, in the gel-phase the tilt angle θ of the hydrocarbon chains can directly be measured, and moreover it is proved that the chains are tilted by 7° to 15° in b-direction of the orthorhombic and the hexagonal lattice. 012-[paraffine netplanes sablize a well-defined membrane surface lik...