Purity testing of recombinant proteins by capillary electrophoresis

Purity testing of recombinant DNA (rDNA) proteins using slab gel electrophoresis in conjunction with scanning densitometry is time consuming and labor intensive and is difficult to reproduce because the dyes used for visualizing proteins do not bind in a stoichiometric fashion for all proteins. The present report describes a micellar capillary zone electrophoresis (MCZE) procedure that overcomes these difficulties. The MCZE method was evaluated to estimate protein purity of hydrophobic cytomegalovirus proteins, expressed E. coli, and highly glycosylated hepatitis C virus proteins, expressed in Chinese hamster ovary cells. The results obtained by the MCZE procedure correlated very well with the purity results quantitated by the conventional slab gel electrophoresis method using purified Coomassie Brilliant Blue dye to reduce anomalies. MCZE may serve as an alternative method for in-process and purity testing of rDNA proteins.