Attachment of a single fluorescent label to peptides for determination by capillary zone electrophoresis

Complicated electropherograms are produced in the separation of fluorescently labeled peptides. Incomplete labeling of epsilon-amino groups on lysine residues results in the production of 2n-1 reaction products, where n is the number of alpha and epsilon amino groups in the peptide. A single label is attached to the peptide by first taking the peptide through one cycle of the Edman degradation reaction. All epsilon-amino groups are converted to the phenyl thiocarbamyl and the cleavage step exposes one alpha-amino group at the N-terminus of the peptide; the fluorescent label is attached to the N-terminus.