Tenchov B G, Yanev T K, Tihova M G, Koynova R D
Biochim Biophys Acta. 1985 Jun 11;816(1):122-30. doi: 10.1016/0005-2736(85)90400-6.
The sonication procedure of preparation of small unilamellar vesicles is modelled as a process of uniform random fragmentation of the lipid aggregates. The vesicle size distribution evolving in this process is shown to be identical with the Weibull extremal probability distribution. Size histograms of sonicated small vesicles of various phospholipid composition were obtained by using electron microscopy (negative staining). Their successful simulation with Weibull curves shows that theory agrees with experiment. A similarly good agreement is found also with size histograms obtained by freeze-fracture of phosphatidylcholine-cholesterol vesicles (Van Venetië, R., Leunissen-Bijvelt, J., Verkleij, A.J. and Ververgaert, P.H.J.T. (1980) J. Microsc. 118, 401-408). This analysis allows a refinement of some earlier conclusions about the effect of cholesterol on the size of the sonicated vesicles. It follows from the theoretical model that the only intrinsic characteristic of the sonicated vesicles is the lower limit of their size. The other characteristics of the size distribution such as expectancy, dispersion, position and height of the maximum depend on the intensity of fragmentation. It is concluded that the size distribution of sonicated small vesicles is completely determined by the procedure of their preparation and, therefore, the condition of thermodynamic equilibrium between aggregated and monomeric lipid is irrelevant in this case.
小单层囊泡制备的超声处理过程被模拟为脂质聚集体均匀随机破碎的过程。在此过程中演变的囊泡大小分布被证明与威布尔极值概率分布相同。通过电子显微镜（负染色）获得了各种磷脂组成的超声处理小囊泡的大小直方图。用威布尔曲线对其进行成功模拟表明理论与实验相符。在通过磷脂酰胆碱 - 胆固醇囊泡的冷冻断裂获得的大小直方图中也发现了类似的良好一致性（Van Venetië, R., Leunissen - Bijvelt, J., Verkleij, A.J. 和 Ververgaert, P.H.J.T. (1980) J. Microsc. 118, 401 - 408）。这种分析有助于完善一些早期关于胆固醇对超声处理囊泡大小影响的结论。从理论模型可以得出，超声处理囊泡的唯一内在特征是其大小的下限。大小分布的其他特征，如期望值、离散度、最大值的位置和高度，取决于破碎强度。得出的结论是，超声处理小囊泡的大小分布完全由其制备过程决定，因此，在这种情况下，聚集态和单体态脂质之间的热力学平衡条件无关紧要。
