Capillary electrophoretic separation of recombinant granulocyte-colony-stimulating factor glycoforms

Free zone capillary electrophoresis separated recombinant human granulocyte-colony-stimulating factor, expressed in Chinese hamster ovary cells, into two well-resolved species. Following incubation with neuraminidase, these species comigrated, eluting earlier than either of the original two species. This indicated that the observed heterogeneity was caused by different amounts of sialic acid present on the carbohydrate portion of the protein. It was determined that optimum separation occurred in the buffer pH range 7–9. Evidence is also presented to show that these glycoforms migrate in order of increasing numbers of sialic acids present.