Neu B, Armstrong J K, Fisher T C, Bäumler H, Meiselman H J
Department of Physiology and Biophysics, Keck School of Medicine, University of Southern California, 1333 San Pablo Street, Los Angeles, CA 90033, USA.
Biorheology. 2001;38(5-6):389-403.
Poly(ethylene glycol), abbreviated as PEG, was covalently attached to the surface of human red blood cells (RBC) and the effects of such coating on the regions near the cell's glycocalyx were explored by means of cell electrophoresis. RBC electrophoretic mobilities were measured, in polymer-free buffers of various ionic strengths, as functions of PEG molecular mass (3.35, 18.5, 35.0, 35.9 kDa), geometry, (linear or 8-arm branched) and polymer/RBC ratio during attachment. The results indicate marked decreases of the mobility (up to 85%) which were affected by polymer molecular mass and geometry. Since PEG is neutral and its covalent attachment only removes positively-charged amino groups on the cell membrane, such decreases of mobility likely reflect structural changes near and within the RBC glycocalyx. Experimental results were analyzed using an extended "hairy sphere" model to consider friction and thickness of the polymer layer. Calculated polymer layer thickness increased with molecular mass for linear PEGs and was less extended for a branched PEG of similar molecular mass. Friction within the polymer layer increased with polymer/RBC ratio and for the linear PEGs was inversely related to molecular mass; friction was greatest for the branched PEG. Our results are consistent with the effects of attached PEGs on RBC aggregation and surface antigenic site masking, and suggest the usefulness of electrophoretic mobility techniques for studies of bound neutral polymers.
聚乙二醇，简称为PEG，被共价连接到人红细胞（RBC）表面，并通过细胞电泳研究了这种包被对细胞糖萼附近区域的影响。在各种离子强度的无聚合物缓冲液中，测量了RBC的电泳迁移率，它是PEG分子量（3.35、18.5、35.0、35.9 kDa）、几何形状（线性或8臂分支）以及连接过程中聚合物/RBC比例的函数。结果表明迁移率显著降低（高达85%），这受到聚合物分子量和几何形状的影响。由于PEG是中性的，其共价连接仅去除细胞膜上带正电荷的氨基，因此迁移率的降低可能反映了RBC糖萼附近及内部的结构变化。使用扩展的“毛球”模型分析实验结果，以考虑聚合物层的摩擦和厚度。对于线性PEG，计算出的聚合物层厚度随分子量增加，而对于分子量相似的支化PEG，聚合物层扩展较小。聚合物层内的摩擦随聚合物/RBC比例增加，对于线性PEG，摩擦与分子量成反比；支化PEG的摩擦最大。我们的结果与连接的PEG对RBC聚集和表面抗原位点掩盖的影响一致，并表明电泳迁移率技术在研究结合的中性聚合物方面的有用性。
