Rinia H A, Demel R A, van der Eerden J P, de Kruijff B
Department of Biochemistry of Membranes, Institute of Biomembranes, Centre for Biomembranes and Lipid Enzymology, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
Biophys J. 1999 Sep;77(3):1683-93. doi: 10.1016/S0006-3495(99)77015-3.
Asymmetric bilayers of different phospholipid compositions have been prepared by the Langmuir-Blodgett (L-B) method, and imaged by atomic force microscopy (AFM). Such bilayers can function as a model for biological membranes. The first leaflet consisted of zwitterionic phospholipids phosphatidylcholine (PC) or phosphatidylethanolamine (PE). The second leaflet consisted of the anionic phospholipid phosphatidylglycerol (PG), in either the condensed or liquid phase or, for comparison, of PC. Different bilayers showed different morphology. In all bilayers defects in the form of holes were present. In some bilayers with a first leaflet consisting of PC, polygonal line-shaped defects were observed, whereas when the first leaflet consisted of PE, mainly round defects were seen. Not only the shape, but also the amount of defects varied, depending on the condition and the composition of the second leaflet. In most of the PG-containing systems the defects were surrounded by elevations, which reversibly disappeared in the presence of divalent cations. This is the first time that such elevations have been observed on phospholipid bilayers. We propose that they are induced by phospholipid exchange between the two leaflets around the defects, leading to the presence of negatively charged phospholipids in the first leaflet. Because the substrate is also negatively charged, the bilayer around the edges is repelled and lifted up. Since it was found that the elevations are indeed detached from the substrate, we refer to this effect as bilayer blistering.
通过朗缪尔-布洛杰特（L-B）法制备了具有不同磷脂组成的不对称双层膜，并通过原子力显微镜（AFM）成像。这种双层膜可作为生物膜的模型。第一层由两性离子磷脂磷脂酰胆碱（PC）或磷脂酰乙醇胺（PE）组成。第二层由阴离子磷脂磷脂酰甘油（PG）组成，处于凝聚相或液相，或者为了比较，由PC组成。不同的双层膜呈现出不同的形态。在所有双层膜中都存在孔洞形式的缺陷。在一些第一层由PC组成的双层膜中，观察到多边形线状缺陷，而当第一层由PE组成时，主要看到圆形缺陷。不仅缺陷的形状不同，而且缺陷的数量也因第二层的条件和组成而异。在大多数含PG的体系中，缺陷被凸起包围，在二价阳离子存在下这些凸起可逆地消失。这是首次在磷脂双层膜上观察到这种凸起。我们认为它们是由缺陷周围两层之间的磷脂交换诱导产生的，导致第一层中存在带负电荷的磷脂。由于底物也带负电荷，边缘周围的双层膜被排斥并向上抬起。由于发现这些凸起确实与底物分离，我们将这种效应称为双层膜起泡。
