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

本项目偶然起源于一位博士生M.R.Karim和Takagi在约0.1%的SDS和约10%的高浓度低聚葡聚糖（分子量约1，000）存在下意外观察到蛋白质的大小依赖性分离。分离模式与SDS-聚丙烯酰胺类似。作为低聚葡聚糖浓度的函数的迁移率和粘度测定清楚地表明，所观察到的尺寸依赖性分离不是由于分子筛分，因为没有观察到网络结构存在的迹象。在SDS-聚丙烯酰胺凝胶电泳条件下，蛋白质展开成卷曲链，其多肽链带重电荷，在自由溶液电泳中显示自由排水行为。在分子筛存在下，这种α链可以自然地以尺寸依赖性分离。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失去自由排水行为，成为溶剂和其中所含离子不可穿透的线圈。对这一工作假设的确认有待研究，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.