Silvius J R, Zuckermann M J
Department of Biochemistry, McGill University, Montréal, Québec, Canada.
Biochemistry. 1993 Mar 30;32(12):3153-61. doi: 10.1021/bi00063a030.
A series of conjugates has been prepared by linking various hydrophilic macromolecules [poly-(ethylene glycols), polylysine, aminodextrans, or apotransferrin] to synthetic phosphatidylethanolamines via linker moieties incorporating a fluorescent bimane group. Using a fluorescence energy transfer-based assay, the rate of transfer of these species between phospholipid vesicles has been monitored as a function of the nature and size of the coupled macromolecule and of the acyl chain composition of the lipid anchor. Conjugates in which the phospholipid anchor is linked to a small hydrophilic terminal residue (e.g., ethanolamine or ethylenediamine) transfer between large unilamellar vesicles of egg phosphatidylcholine with half-times ranging from tens of minutes (for dimyristoyl lipid conjugates) to a few tens of hours (for dipalmitoyl and 1-palmitoyl-2-oleoyl lipid conjugates), in agreement with previous results for unlabeled phospholipids. Conjugation of these same lipid anchors to larger hydrophilic molecules markedly accelerates their rates of intermembrane transfer, by factors ranging from 5-7-fold (for conjugates with apotransferrin and aminodextrans of molecular weight 10,000-70,000) to over 25-fold [for conjugates with poly(ethylene glycol)-5000]. In all cases the observed transfer appears to reflect the diffusion of lipid monomers through the aqueous phase. Our results suggest that substantial intermembrane transfer can occur, on a time scale of several hours or less, for hydrophilic macromolecules conjugated to diacyl(/alkyl) lipids with 14- to 18-carbon chains unless portions of the conjugate other than the lipid anchor also interact strongly with the membrane.
通过连接基团将各种亲水性大分子（聚乙二醇、聚赖氨酸、氨基葡聚糖或脱铁转铁蛋白）与合成磷脂酰乙醇胺相连，制备了一系列共轭物，连接基团中含有荧光双硫腙基团。使用基于荧光能量转移的分析方法，监测了这些物质在磷脂囊泡之间的转移速率，该速率是偶联大分子的性质和大小以及脂质锚定物的酰基链组成的函数。磷脂锚定物与小的亲水性末端残基（如乙醇胺或乙二胺）相连的共轭物在卵磷脂大单层囊泡之间转移，半衰期从几十分钟（对于二肉豆蔻酰脂质共轭物）到几十小时（对于二棕榈酰和1-棕榈酰-2-油酰脂质共轭物）不等，这与未标记磷脂的先前结果一致。将这些相同的脂质锚定物与更大的亲水性分子共轭，显著加快了它们的膜间转移速率，加快倍数从5 - 7倍（对于与分子量为10,000 - 70,000的脱铁转铁蛋白和氨基葡聚糖的共轭物）到超过25倍[对于与聚（乙二醇）-5000的共轭物]。在所有情况下，观察到的转移似乎反映了脂质单体在水相中的扩散。我们的结果表明，对于与具有14至18个碳链的二酰基（/烷基）脂质共轭的亲水性大分子，除非脂质锚定物以外的共轭物部分也与膜强烈相互作用，否则在几小时或更短的时间尺度上可以发生大量的膜间转移。
