FLinT Center, Institute of Physics and Chemistry, University of Southern Denmark, 5230 Odense, Denmark.
Astrobiology. 2009 Dec;9(10):979-87. doi: 10.1089/ast.2009.0384.
The self-assembly of simple amphiphiles like fatty acids into cell-like membranous structures suggests that such structures were available on prebiotic Earth to support the origin of cellular life. However, the composition of primitive membranes remains unclear because the physical properties of the aqueous environment in which they assembled are relatively unconstrained in terms of temperature, pH, and ionic concentrations. It seems likely that early membranes were composed of mixtures of various amphiphiles in an aqueous medium warmed by geothermal activity prevalent in the Archean era. To better understand the properties of mixed bilayers formed by binary mixtures of single-chain amphiphiles under these conditions, we conducted stability experiments, using membranes composed of various fatty acids having hydrocarbon chain length between 8 and 18 carbons, in mixtures with their glycerol monoacyl amphiphile derivatives (GMAs). The parameters investigated were critical vesicle concentration (CVC), encapsulation, and temperature-dependent stability. We found that hydrocarbon chain length and the presence of GMAs were major factors related to membrane stability. As chain length increased, GMA additions decreased the CVC of the mixtures 4- to 9-fold. Encapsulation ability also increased significantly as a function of chain length, which reduced permeation of small marker molecules. However, long exposures to temperatures in excess of 60 degrees C resulted in a total release of encapsulated solutes and extensive mixing of the membrane components between vesicles. We conclude that GMAs can significantly increase the stability of mixed amphiphile membranes, but further studies are required to establish model membranes that are stable at elevated temperatures.
简单的两亲分子（如脂肪酸）自组装成类似细胞的膜状结构表明，在原始地球上存在这样的结构，可以支持细胞生命的起源。然而，原始膜的组成仍不清楚，因为它们组装的水相环境的物理性质在温度、pH 值和离子浓度方面相对不受限制。早期的膜很可能由各种两亲分子在由太古宙时期普遍存在的地热活动加热的水介质中组成的混合物构成。为了更好地了解在这些条件下由单链两亲物的二元混合物形成的混合双层的性质，我们进行了稳定性实验，使用的膜由具有 8 至 18 个碳原子的烃链长度的各种脂肪酸组成，与它们的甘油单酰基两亲物衍生物（GMAs）的混合物。研究的参数是临界囊泡浓度（CVC）、包封和温度依赖性稳定性。我们发现烃链长度和 GMAs 的存在是与膜稳定性相关的主要因素。随着链长的增加，GMA 的添加将混合物的 CVC 降低了 4 至 9 倍。包封能力也随着链长的增加而显著增加，这降低了小分子标记物的渗透。然而，长时间暴露在超过 60 摄氏度的温度下会导致包封溶质的完全释放和囊泡之间膜成分的广泛混合。我们得出结论，GMAs 可以显著提高混合两亲物膜的稳定性，但需要进一步的研究来建立在高温下稳定的模型膜。
