The origins of stability of spontaneous vesicles.
The origins of stability of spontaneous vesicles.
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DOI：
10.1073/pnas.98.4.1353
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发表时间：
2001-02
影响因子：
11.1
通讯作者：
H. T. Jung;B. Coldren;J. Zasadzinski;D. J. Iampietro;E. Kaler
中科院分区：
文献类型：
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作者：
H. T. Jung;B. Coldren;J. Zasadzinski;D. J. Iampietro;E. Kaler
根据弯曲常数的值，平衡单层囊泡通过两种不同机制之一来稳定。 Helfrich 起伏确保当弯曲常数 K 为 k(B)T 量级时，双层间电势始终是排斥的。当 K k(B)T 时，单层囊泡通过选择特定囊泡半径的自发曲率来稳定；其他半径在能量上是不利的。我们通过冷冻透射电子显微镜和小角度中子散射测定的囊泡尺寸分布分析，对三种不同的平衡囊泡系统的双层弹性常数和自发曲率 R(o) 进行了测量。对于十六烷基三甲基溴化铵 (CTAB)/辛基磺酸钠阴阳离子囊泡，K = 0.7 k(B)T，表明单层囊泡通过 Helfrich 波状排斥力得以稳定。然而，对于 CTAB 和全氟辛酸钠 (FC(7)) 囊泡，K = 6 k(B)T，表明通过偏离自发曲率的能量成本实现稳定。将电解质添加到全氟辛酸钠/CTAB囊泡中会产生具有两个双层的囊泡；双层之间的吸引相互作用可以克服自发曲率小偏差形成两层囊泡的成本，但禁止形成三层或更多层囊泡的较大偏差。只有具有大弯曲模量和自发曲率的双层才有可能形成具有离散数量的平衡双层的囊泡。
Equilibrium unilamellar vesicles are stabilized by one of two distinct mechanisms depending on the value of the bending constant. Helfrich undulations ensure that the interbilayer potential is always repulsive when the bending constant, K, is of order k(B)T. When K k(B)T, unilamellar vesicles are stabilized by the spontaneous curvature that picks out a particular vesicle radius; other radii are disfavored energetically. We present measurements of the bilayer elastic constant and the spontaneous curvature, R(o), for three different systems of equilibrium vesicles by an analysis of the vesicle size distribution determined by cryo-transmission electron microscopy and small-angle neutron scattering. For cetyltrimethylammonium bromide (CTAB)/sodium octyl sulfonate catanionic vesicles, K =.7 k(B)T, suggesting that the unilamellar vesicles are stabilized by Helfrich-undulation repulsions. However, for CTAB and sodium perfluorooctanoate (FC(7)) vesicles, K = 6 k(B)T, suggesting stabilization by the energetic costs of deviations from the spontaneous curvature. Adding electrolyte to the sodium perfluorooctanoate/CTAB vesicles leads to vesicles with two bilayers; the attractive interactions between the bilayers can overcome the cost of small deviations from the spontaneous curvature to form two-layer vesicles, but larger deviations to form three and more layer vesicles are prohibited. Vesicles with a discrete numbers of bilayers at equilibrium are possible only for bilayers with a large bending modulus coupled with a spontaneous curvature.