The origins of stability of spontaneous vesicles
The origins of stability of spontaneous vesicles
复制标题
DOI：
10.1073/pnas.041420998
复制
发表时间：
2001-02-13
影响因子：
11.1
通讯作者：
Kaler, EW
中科院分区：
文献类型：
--
作者：
Jung, HT;Coldren, B;Kaler, EW
平衡单层囊泡稳定的两个不同的机制取决于弯曲常数的值之一。当弯曲常数K为k（B）T阶时，Helfrich起伏保证了双层间势总是排斥的。当K远大于k（B）T时，单层囊泡通过挑选特定囊泡半径的自发曲率而稳定;其他半径在能量上是不利的。我们提出了测量的双层弹性常数和自发曲率，RO，为三个不同的系统的平衡囊泡通过冷冻透射电子显微镜和小角中子散射确定的囊泡尺寸分布的分析。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，这表明单层囊泡是稳定的Helfrich波动排斥。然而，对于十六烷基三甲基溴化铵和全氟辛酸钠（FC 7）囊泡，K = 6 k（B）T，这表明稳定的能量成本偏离自发曲率。向全氟辛酸钠/CTAB囊泡中添加电解质导致具有两个双层的囊泡;双层之间的吸引力相互作用可以克服形成两层囊泡的自发曲率的小偏差的成本，但是禁止形成三层或更多层囊泡的较大偏差。囊泡与离散数量的双层在平衡状态下是可能的，只有双层与一个大的弯曲模量加上自发曲率。
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 much greater than 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 (FC7) 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, hut 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.