Peptide heterogeneity in a preparation of synthetic fibrinopeptide B.
A commercially available preparation of synthetic human fibrinopeptide B (FpB) was shown by hplc to contain two chromatographically distinct peaks, one of which was identical to FpB. Our results suggest that the contaminant peptide (FpB-2), which represented approximately 43% of the total peptide composition, is FpB containing an alpha-aminosuccinimide (Asc) residue. This Asc residue probably arose as a result of the cyclization of 5Asp-6Asn during either the coupling or deprotection reactions. FpB-2 was rapidly hydrolysed by carboxypeptidase B to des-Arg-FpB-2. It was stable under acidic conditions but in dilute alkali was converted to equimolar amounts of FpB and FpB containing beta-Asp at residue 5. Since it has been suggested that 5Asp-6Asn is a major immunorecognition site in FpB, our observations emphasize the need to establish the purity of synthetic FpB preparations destined for use in the immunoassay of either FpB or des-Arg-FpB.
D000596:Amino Acids / Q000032:analysis; D043424:Carboxypeptidase B; D002268:Carboxypeptidases / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D005340:Fibrinogen / Q000032:analysis*; D005345:Fibrinopeptide B / Q000032:analysis*; D010455:Peptides / Q000032:analysis
D000596:Amino Acids; D010455:Peptides; D005345:Fibrinopeptide B; D005340:Fibrinogen; D002268:Carboxypeptidases; D043424:Carboxypeptidase B