Structure and phase behavior of self-assembled DPPC-DNA-metal cation complexes.
Structure and phase behavior of self-assembled DPPC-DNA-metal cation complexes.
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自组装 DPPC-DNA-金属阳离子复合物的结构和相行为。
DOI：
10.1021/jp062713v
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发表时间：
2006
期刊：
影响因子：
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通讯作者：
O. Francescangeli
中科院分区：
文献类型：
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作者：
M. Pisani;P. Bruni;G. Caracciolo;R. Caminiti;O. Francescangeli
二棕榈酰磷脂酰胆碱（DPPC）多层脂质体与DNA和二价金属离子（Ca ~（2+）、Mn ~（2+）、Mg ~（2+））在溶液中自组装形成三元DPPC-DNA-Me ~（2+）复合物。复合物的超分子结构由有序的多层组装体组成，其中水合DNA螺旋夹在脂质双层之间，金属阳离子将DNA的磷酸基团结合到脂质极性头上。在探索的孵育时间范围内，复合物与未复合的DPPC在研究的整个温度范围内（20-55 ℃）共存。因此，观察到两种不同的共存层状相，一种对应于三元复合物，另一种对应于未复合的脂质。利用同步加速器X射线衍射研究了这两种化合物的结构和热致相行为，并从实验电子密度分布推导出相关结构数据。虽然未复合的脂质表现出与纯DPPC相同的相行为，即L β ′-P β ′-L α，但复合物中结合脂质的热致行为部分改变。这表现为主转变温度的升高和涟漪相的消失，导致单相转变。不同的金属阳离子在促进和稳定的DNA缩合成三元复合物的作用进行了讨论。
Multilamellar liposomes of dipalmitoylphosphatidylcholine (DPPC) in solution with DNA and bivalent metal cations (Ca2+, Mn2+, Mg2+) self-assemble into a ternary DPPC-DNA-Me2+ complex. The supramolecular structure of the complex consists of an ordered multilamellar assembly where hydrated DNA helices are sandwiched between the lipid bilayers and the metal cations bind the phosphate groups of DNA to the lipid polar heads. In the range of explored incubation times, the complex coexists with the uncomplexed DPPC over the whole temperature range investigated (20-55 degrees C). Accordingly, two distinct coexisting lamellar phases are observed, one corresponding to the ternary complex and the other to the uncomplexed lipid. The structure and thermotropic phase behavior of both of these have been investigated by means of synchrotron X-ray diffraction, and the relevant structural data are deduced from experimental electron density profiles. While the uncomplexed lipid exhibits the same phase behavior as pure DPPC, that is, L beta'-P beta'-L alpha, the thermotropic behavior of the bound lipid in the complex is partially altered. This is manifested as an increase in the main transition temperature and the disappearance of the ripple phase leading to the single -phase transition. The role of the different metal cations in promoting and stabilizing the DNA condensation into the ternary complex is also discussed.