Seguin C, Lewis R N, Mantsch H H, McElhaney R N
Department of Biochemistry, University of Alberta, Edmonton, Canada.
Isr J Med Sci. 1987 May;23(5):403-7.
We have investigated the comparative lipid thermotropic phase behavior of intact cells, isolated membranes and total membrane lipid dispersions from fatty acid-homogeneous Acholeplasma laidlawii B by high-sensitivity differential scanning calorimetry. We find that the gel to liquid-crystalline phase transition temperature, enthalpy and degree of cooperativity are essentially identical in viable cells and isolated membranes and that these parameters are not affected by the thermal denaturation of the cellular or membrane proteins. In contrast, the extracted lipid dispersions, although having the same phase transition temperature, exhibit a greater enthalpy and a reduced cooperativity than do the lipids in cells or membranes. These results imply that lipid organization is identical in cells and isolated membranes, but different in the derived model membrane, probably due to the influence of membrane proteins and/or the presence of lipid bilayer compositional asymmetry in cells and membranes. We also demonstrate for the first time the existence of gel state polymorphism in a biological membrane.
我们通过高灵敏度差示扫描量热法研究了来自脂肪酸均匀的莱氏无胆甾原体B的完整细胞、分离的膜和总膜脂分散体的脂质热致相行为比较。我们发现，活细胞和分离的膜中凝胶态到液晶态的相变温度、焓和协同程度基本相同，并且这些参数不受细胞或膜蛋白热变性的影响。相比之下，提取的脂质分散体虽然具有相同的相变温度，但与细胞或膜中的脂质相比，表现出更大的焓和更低的协同程度。这些结果表明，脂质在细胞和分离的膜中的组织方式相同，但在衍生的模型膜中不同，这可能是由于膜蛋白的影响和/或细胞和膜中脂质双层组成不对称的存在。我们还首次证明了生物膜中凝胶态多态性的存在。
