Huebner S, Battersby B J, Grimm R, Cevc G
Medizinische Biophysik, Technische Universität München, D-81675 München, Germany.
Biophys J. 1999 Jun;76(6):3158-66. doi: 10.1016/S0006-3495(99)77467-9.
Cryoelectron microscopy has been used to study the reorganization of unilamellar cationic lipid vesicles upon the addition of DNA. Unilamellar DNA-coated vesicles, as well as multilamellar DNA lipid complexes, could be observed. Also, DNA induced fusion of unilamellar vesicles was found. DNA appears to adsorb to the oppositely charged lipid bilayer in a monolayer of parallel helices and can act as a molecular "glue" enforcing close apposition of neighboring vesicle membranes. In samples with relatively high DNA content, there is evidence for DNA-induced aggregation and flattening of unilamellar vesicles. In these samples, multilamellar complexes are rare and contain only a small number of lamellae. At lower DNA contents, large multilamellar CL-DNA complexes, often with >10 bilayers, are formed. The multilamellar complexes in both types of sample frequently exhibit partially open bilayer segments on their outside surfaces. DNA seems to accumulate or coil near the edges of such unusually terminated membranes. Multilamellar lipid-DNA complexes appear to form by a mechanism that involves the rupture of an approaching vesicle and subsequent adsorption of its membrane to a "template" vesicle or a lipid-DNA complex.
冷冻电子显微镜已被用于研究添加DNA后单层阳离子脂质体的重组情况。可以观察到单层DNA包被的囊泡以及多层DNA脂质复合物。此外，还发现DNA诱导单层囊泡融合。DNA似乎以平行螺旋单层的形式吸附到带相反电荷的脂质双层上，并可作为分子“胶水”促使相邻囊泡膜紧密贴附。在DNA含量相对较高的样品中，有证据表明DNA诱导单层囊泡聚集和扁平化。在这些样品中，多层复合物很少见，且仅包含少量片层。在DNA含量较低时，会形成大型多层CL-DNA复合物，通常具有超过10个双层。这两种类型样品中的多层复合物在外表面经常呈现部分开放的双层片段。DNA似乎在这种异常终止的膜边缘附近积累或盘绕。多层脂质-DNA复合物似乎通过一种机制形成，该机制涉及接近的囊泡破裂以及其膜随后吸附到“模板”囊泡或脂质-DNA复合物上。
