Investigations into the thermotrofic phase behaviour of natural membranes extracted from gram-negative bacteria and artificial membrane systems made from lipopolysaccharides and free lipid A

It is reported on investigations into the thermotropic phase behaviour of outer, cytoplasmic, and cell envelope preparations of Gram-negative bacteria, and their amphiphatic compounds - lipopolysaccherides and phospholipids - applying calorimetric, infrared spectroscopic, and 90°-light scattering techniques. Except for free lipid A, the lipid moiety of lipopolysaccharide, all investigated compounds exhibited gel-liquid crystalline phase transitions of the hydrocarbon chains in the temperature range 10 to 42 °C. The transition regions of the outer membrane end lipopolysaccharide preparations are narrower and appear at significantly higher temperatures (around 37 °C) as those from the cytoplasmic membrane and phospholipid preparations (around 26 °C). For both amphiphatic compounds the phase transitions are shifted to lower values at reduced growth temperature of the cells.