Komatsu H, Guy P T, Rowe E S
Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City 66103.
Chem Phys Lipids. 1993 Apr;65(1):11-21. doi: 10.1016/0009-3084(93)90077-g.
Unilamellar liposomes are widely used as model membranes to represent and study the properties of biological membranes and as potential drug delivery systems. It is well established that ethanol and other amphiphiles induce the interdigitated L beta I phase in multilamellar vesicles of dipalmitoylphosphatidylcholine (DPPC). However, all of the work on this phase has been performed using the hand shaken multilamellar preparations. In the present report, we have studied the induction of interdigitation in a series of unilamellar vesicles prepared by sonication and by extrusion. The methods used to characterize the vesicles were freeze fracture electron microscopy and quasielastic light scattering (QELS). Two fluorescence methods were used to detect interdigitation, the DPH fluorescence quenching method (Nambi, P., Rowe, E.S. and McIntosh, T.J. (1988) Biochemistry 27, 9175-9182) and the pyrene-PC fluorescence method (Komatsu, H. and Rowe, E.S. (1991) Biochemistry 30: 2463-2470). It was found that sonicated vesicles are not stable in the presence of interdigitating concentrations of ethanol; they form higher aggregates at all temperatures examined. The behavior of the extruded vesicles was different from that of the SUV; each size studied was stable in the presence of ethanol, although they exhibited an increase in size. It was shown that extruded vesicles having a 200-nm or greater diameter become interdigitated in the presence of ethanol. The threshold concentration for interdigitation in vesicles is greater than that for MLVs and it decreases with increasing vesicle size, approaching the MLV value for the largest vesicles.
单层脂质体被广泛用作模型膜，以表征和研究生物膜的特性，并作为潜在的药物递送系统。众所周知，乙醇和其他两亲性物质可诱导二棕榈酰磷脂酰胆碱（DPPC）多层囊泡形成叉指状的LβI相。然而，关于这个相的所有研究都是使用手摇多层制剂进行的。在本报告中，我们研究了通过超声处理和挤压制备的一系列单层囊泡中叉指化的诱导情况。用于表征囊泡的方法是冷冻断裂电子显微镜和准弹性光散射（QELS）。使用两种荧光方法检测叉指化，即DPH荧光猝灭法（Nambi, P., Rowe, E.S.和McIntosh, T.J. (1988) Biochemistry 27, 9175 - 9182）和芘 - PC荧光法（Komatsu, H.和Rowe, E.S. (1991) Biochemistry 30: 2463 - 2470）。结果发现，在存在叉指化浓度的乙醇时，超声处理的囊泡不稳定；在所有检测温度下它们都会形成更大的聚集体。挤压囊泡的行为与小单层囊泡（SUV）不同；所研究的每种尺寸的挤压囊泡在乙醇存在下都是稳定的，尽管它们的尺寸有所增加。结果表明，直径为200纳米或更大的挤压囊泡在乙醇存在下会发生叉指化。囊泡中叉指化的阈值浓度高于多层囊泡的阈值浓度，并且随着囊泡尺寸的增加而降低，对于最大的囊泡接近多层囊泡的值。
