Effect of sulfadiazine on biological model membranes

Summary The effect of sulfadiazine on dipalmitoylphosphatidylethanolamin-dipalmitoylphosphatidylglycerol-water (DPPE-DPPG/water, 20 mass/mass%, with 0.2 DPPG/DPPE+DPPG molar ratio) vesicles considered as a model system of the cytoplasmic bacterial membranes was studied using DSC and freeze-fracture methods. The sulfadiazine/lipid molar ratio was varied from 10 -3 up to 1. It was found that the DPPE-DPPG/water system is drastically affected by the sulfadiazine, but there is no concentration effect in a wide range of sulfadiazine/lipid molar ratios from 10 -2 up to 2·10 -1 . The DSC and freeze-fracture methods reveal that a homogeneous incorporation of the sulfadiazine molecules occurs in the liquid crystalline phase while in the gel phase separation appears. The different local structures can be classified into two different types: vesicle-like and block-type. Although the surface morphology of the domains of both types shows lamellar arrangement, the blocks are constituted from closely packed long units.