Micro-segregation induced by bulky-head lipids : formation of characteristic patterns in a giant vesicle
Micro-segregation induced by bulky-head lipids : formation of characteristic patterns in a giant vesicle
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大头脂质诱导的微分离：巨型囊泡中特征模式的形成
DOI：
10.1039/c1sm06381b
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发表时间：
2012
期刊：
影响因子：
3.4
通讯作者：
K.Yoshikawa
中科院分区：
文献类型：
--
作者：
M.Yanagisawa;N.Shimokawa;M.Ichikawa;K.Yoshikawa
糖脂等大头脂质在细胞膜中起着不可或缺的作用。然而，鲜为人知的是，大块头脂质的膜上的物理化学性质的影响。在这项研究中，我们研究了含有聚乙二醇缀合胆固醇（PEG-Chol）的巨大囊泡（作为天然大头脂质的模型）对膜中相分离的影响。我们使用包括饱和磷脂DPPC、不饱和磷脂DOPC和Chol的脂质组合，已知其导致相分离成两个液相。这种相分离在朗道的标准下被分类为一级相变，因此微畴倾向于显示粗粒化，直到全局畴对，即，单畴，以使界面不稳定性最小化。在这种粗化的三元系统相比，我们在这里展示了稳定的微域的产生在存在的PEG-胆固醇以上的临界组合物。从整体偏析到微观偏析的转变从理论上解释为两种物理效应之间的竞争，即，PEG-胆固醇的大头部基团之间的空间排斥相互作用和沿着域边界的线能量的消耗。有趣的是，在微畴结构中，畴的网络图案作为小畴彼此连接的中间状态出现。我们研究了使用聚焦激光局部加热下的网络图案的稳定性，并证实了图案的自恢复。基于这些观察，细胞中的天然大头脂质也可以稳定结构域结构，如脂筏。
Bulky-head lipids, such as glycolipids, play indispensable roles in cellular membranes. However, little is known about the effects that bulky-head lipids have on the physicochemical properties of the membrane. In this study, we examined the effects of a giant vesicle containing poly(ethylene glycol)-conjugated cholesterol (PEG-Chol), as a model of natural bulky-head lipids, on phase separation in the membrane. We used a lipid combination that included the saturated phospholipid DPPC, the unsaturated phospholipid DOPC and Chol, which is known to cause phase separation into two liquid phases. This phase separation is classified as a first-order phase transition under the criterion of Landau, and thus micro-domains tend to show coarse-graining up to a global pair of domains, i.e., mono-domains, so as to minimize interfacial instability. In contrast to such coarsening in the ternary system, we show here the generation of stable micro-domains in the presence of PEG-Chol above a critical composition. The transition from global- to micro-segregation is interpreted theoretically in terms of the competition between two physical effects, i.e., steric repulsive interaction between the bulky-head groups of PEG-Chol and the cost in line energy along the domain boundaries. Interestingly, among the micro-domain structures, a network pattern of domains appears as an intermediate state in which small domains are connected to each other. We examined the stability of the network pattern under local heating using a focused laser, and confirmed self-recovery of the pattern. Based on these observations, natural bulky-head lipids in cells may also stabilize the domain structure like a lipid raft.