Gliozzi A, Rolandi R, De Rosa M, Gambacorta A
J Membr Biol. 1983;75(1):45-56. doi: 10.1007/BF01870798.
The membrane of Caldariella acidophila, an extreme thermophilic archaebacterium, is characterized by unusual bipolar complex lipids. They consist of two nonequivalent polar heads, linked by a C40 alkylic component. The molecular organization of these lipids in the plasma membrane is still a matter of study. In this paper, we present current-voltage measurements on artificial bipolar lipid membranes, indicating that molecules are indeed organized as a covalently bound bilayer, in which each molecule is completely stretched and spans its entire thickness. Furthermore, conformational transitions of these artificial membranes (which could be formed only above 70 degrees C from a lipid/squalene dispersion) are analyzed in the 80 to 15 degrees C temperature range. Abrupt variations in capacitance and valinomycin-induced conductance seem to indicate the occurrence of at least two structural changes. Measurements are also extended to different solvent systems. Results are consistent with the picture of a monolayer bipolar lipid membrane in which few solvent molecules align themselves parallel to the lipophilic chains. The amount of solvent as well as the temperature at which conformational transitions occur, depend on the solvent system in which the lipid is dispersed.
嗜酸栖热嗜酸菌（一种极端嗜热古细菌）的膜以异常的双极复合脂质为特征。它们由两个不等价的极性头部组成，通过一个C40烷基成分相连。这些脂质在质膜中的分子组织仍然是一个研究课题。在本文中，我们展示了对人工双极脂质膜的电流-电压测量结果，表明分子确实以共价结合的双层形式排列，其中每个分子完全伸展并跨越其整个厚度。此外，在80至15摄氏度的温度范围内分析了这些人工膜（仅在70摄氏度以上由脂质/角鲨烯分散体制备而成）的构象转变。电容的突然变化和缬氨霉素诱导的电导似乎表明至少发生了两种结构变化。测量还扩展到不同的溶剂体系。结果与单层双极脂质膜的情况一致，其中很少有溶剂分子与亲脂性链平行排列。溶剂的量以及发生构象转变的温度取决于脂质分散其中的溶剂体系。
