Capillary Electrophoresis Using Concentrated Solution of Oligomeric Saccharides as the Medium : Elucidation of the Mechanism of the Size-dependent Separation and Its Development

本项目源于一位博士，M.R.Karim和Takagi偶然观察到，在约0.1%的十二烷基硫酸钠和约10%的高浓度低聚葡聚糖(约1000)存在下，蛋白质的大小依赖分离。分离方式明显类似于十二烷基硫酸钠-聚丙烯酰胺。作为低聚葡聚糖浓度的函数的流动性和粘度的测定清楚地表明，观察到的尺寸依赖的分离不是由于分子筛分，因为没有观察到网络结构的存在的迹象。在十二烷基硫酸钠-聚丙烯酰胺凝胶电泳法条件下，蛋白质在自由溶液中展开成卷曲的链，其多肽链带电较大，表现出自由渗漏行为。在分子筛存在的情况下，这种链可以自然地依大小分开。我们观察到的新的分离模式可以解释为，如果链由于浓缩的低聚糖的存在而松动自由排水行为，变成不能穿透其中的溶剂和离子的卷曲。这一工作假设的确认有待检验，我将继续努力这样做。

The present project originated serendipically from the accidental observation of size-dependent separation of proteins in the presence of SDS of about 0.1% and oligomeric dextran (molecular weight of about 1,000) in a high concentration around 10% by a PhD stident, M.R.Karim and Takagi. The mode of separation was apparently like that in SDS-polyacrylamide. Mobility and viscosity determinations as a function of concentration of the oligomeric dextran clearly showed that the observed size-dependent separation is not due to molecular-sieving, because no sign of the presence of network structure was observed. Under the condition of SDS-polyacrylamide gel electrophoresis, proteins are unfolded to become coiled chains and their polypeptide chains are heavily charged to show free-drainage behavior in free-solution electrophoresis. Such a chains can be naturally size-dependently separated in the presence of molecular-sieve. The new mode of separation we have observed can be interpreted, if the chains loose the free-drainage behavior as the result of the presence of concentrated oligomeric saccharide to become coils not penetrable to solvent and ions contained therein. Confirmation of this working hypothesis is left to be examined, and I will continue making efforts to do so.