Direct measurement of polyethylene glycol induced depletion attraction between lipid bilayers
Direct measurement of polyethylene glycol induced depletion attraction between lipid bilayers
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DOI：
10.1021/la950802l
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发表时间：
1996-06-12
期刊：
影响因子：
3.9
通讯作者：
Hui, SW
中科院分区：
文献类型：
--
作者：
Kuhl, T;Guo, YQ;Hui, SW
尽管聚乙二醇（PEG）被广泛用于聚集或融合细胞，但负责这些相互作用的力仍然难以捉摸。通过各种技术，包括准弹性光散射、表面力测量和P-31-NMR，我们已经确定，分子量为8000-10000的PEG可以有效地引起囊泡的聚集，而分子量较低或较高的PEG（分别为1000和18500）则无效。在8000-10000分子量的溶液中，脂质双分子层之间的直接力测量首次揭示了由于双分子层表面附近的聚合物耗尽层而存在的吸引渗透力。低分子量的PEG没有足够大的尺寸（Flory半径，RF）来产生明显的耗竭力，而高分子量的PEG在双分子层表面充分吸附以消除耗竭吸引力，并产生聚集的排斥性位阻屏障。所测得的力可以用目前胶体和聚合物相互作用的理论来定量描述。这些发现表明，由耗尽层产生的差渗透压是囊泡聚集的原因，当耗尽压力足够大时，通过可能在最接近的点上使两层膜变薄，从而局部破坏两层膜的稳定，从而促进融合。该结果为使用一定分子量的聚乙二醇作为细胞、脂质体和囊泡的融合原提供了物理化学基础。
Although polyethylene glycol (PEG) is widely used for aggregating or fusing cells, the forces responsible for these interactions have remained elusive. Through a variety of techniques including quasi-elastic light scattering, surface force measurements, and P-31-NMR, we have established that while PEG of molecular weight 8000-10000 is effective in causing the aggregation of vesicles, PEG of lower or higher molecular weight (1000 and 18500, respectively)is ineffective. For the first time, direct force measurements between lipid bilayers in solutions of 8000-10000 molecular weight reveal the existence of an attractive osmotic force due to a polymer depleted layer near the bilayer surface. Lower molecular weight PEG does not have a large enough size (Flory radius, RF) to generate a significant depletion force, while higher molecular weight PEG adsorbs sufficiently on the bilayer surfaces to eliminate the depletion attraction and produces a repulsive steric barrier to aggregation. The measured forces can be quantitatively described in terms of current theories of colloidal and polymer interactions. These findings suggest that the differential osmotic pressure produced by the depletion layer is responsible for vesicle aggregation and that fusion is promoted when the depletion pressure is strong enough to locally destabilize two membranes by possibly thinning them at their point of closest approach. The results provide a physicochemical basis for using PEG of certain molecular weights as fusogens for cells, liposomes, and vesicles.