Purification of cyanogen bromide fragments from beta-2-glycoprotein I by high-performance liquid chromatography.

Reversed-phase high-performance liquid chromatography (HPLC) with a linear elution gradient of 1-propanol in 0.1% aqueous trifluoroacetic acid was used to purify cyanogen bromide fragments from the human plasma protein beta-2-glycoprotein I. The fragments, ranging from 33 to 119 amino acids in length, were obtained in sufficient purity and yield for automated sequence analysis and enzymatic digestion. One fragment, which contained most of the carbohydrate, could be isolated as an aggregate or as two heterogeneous monomers. The elution of this fragment was much earlier than expected on the basis of its retention coefficient calculated from amino acid composition. Our results demonstrate the applicability of recently developed HPLC techniques to the separation of cyanogen bromide fragments from a carbohydrate-rich glycoprotein whose structure is not completely known.