Meyuhas D, Nir S, Lichtenberg D
Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Ramat-Aviv, Israel.
Biophys J. 1996 Nov;71(5):2602-12. doi: 10.1016/S0006-3495(96)79452-3.
Water-soluble polymers such as dextran and polyethylene glycol are known to induce aggregation and size growth of phospholipid vesicles. The present study addresses the dependence of these processes on vesicle size and concentration, polymer molecular weight, temperature, and compartmentalization of the vesicles and polymers, using static and dynamic light scattering. Increasing the molecular weight of the polymers resulted in a reduction of the concentration of polymer needed for induction of aggregation of small unilamellar vesicles. The aggregation was fully reversible (by dilution), within a few seconds, up to a polymer concentration of at least 20 wt %. At relatively low phosphatidylcholine (PC) concentrations (up to approximately 1 mM), increasing the PC concentration resulted in faster kinetics of aggregation and reduced the threshold concentration of polymer required for rapid aggregation (CA). At higher PC concentrations, CA was only slightly dependent on the concentration of PC and was approximately equal to the overlapping concentration of the polymer (C*). The extent of aggregation was similar at 37 and 4 degrees C. Aggregation of large unilamellar vesicles required a lower polymer concentration, probably because aggregation occurs in a secondary minimum (without surface contact). In contrast to experiments in which the polymers were added directly to the vesicles, dialysis of the vesicles against polymer-containing solutions did not induce aggregation. Based on this result, it appears that exclusion of polymer from the hydration sphere of vesicles and the consequent depletion of polymer molecules from clusters of aggregated vesicles play the central role in the induction of reversible vesicle aggregation. The results of all the other experiments are consistent with this conclusion.
已知水溶性聚合物（如葡聚糖和聚乙二醇）可诱导磷脂囊泡的聚集和尺寸增长。本研究使用静态和动态光散射，探讨了这些过程对囊泡大小、浓度、聚合物分子量、温度以及囊泡与聚合物分隔的依赖性。增加聚合物的分子量会导致诱导小单层囊泡聚集所需的聚合物浓度降低。在几秒钟内，聚集是完全可逆的（通过稀释），直至聚合物浓度至少达到20 wt%。在相对较低的磷脂酰胆碱（PC）浓度（高达约1 mM）下，增加PC浓度会导致聚集动力学加快，并降低快速聚集所需的聚合物阈值浓度（CA）。在较高的PC浓度下，CA仅略微依赖于PC浓度，且大致等于聚合物的重叠浓度（C*）。在37℃和4℃时，聚集程度相似。大单层囊泡的聚集需要较低的聚合物浓度，这可能是因为聚集发生在二级极小值处（无表面接触）。与将聚合物直接添加到囊泡中的实验不同，将囊泡与含聚合物的溶液进行透析不会诱导聚集。基于这一结果，似乎从囊泡的水合层中排除聚合物以及随之而来的聚集囊泡簇中聚合物分子的耗尽在诱导可逆囊泡聚集中起核心作用。所有其他实验的结果均与这一结论一致。
