送交者: Godfather 于 2006-1-22, 10:52:08:
回答: 剩下一个非常具体的技术问题 由 桂铭 于 2006-1-22, 09:46:33:
Colicin's pI was reported to be approximately 10, and Streptomycin's pKa for the 2 amido groups should be around 10-11 ( did not check reference to get the accurate number). Therefore, their ionic strength is very similar and their binding affinity to the CM resin is also similar. It's highly possible for them to be coeluted from the column. Besides, the stepwise elution typically results in poor resolution, and the substances with slightly different ionic strength still are coeluted usually. I suspect Qiu was following the activity to collect the fractions, and the inconsistency of activity has been puzzling him for years. Please see my previous explanation posted earlier.