There is no fully analogous method akin to Edman chemistry for determining the C-terminal sequencing of a biopharmaceutical. For an assessment of the C-termini, BioPharmaSpec scientists use carboxypeptidase digestion and/or mass-spectrometric mapping strategies.
In the latter approach, intactness of a protein C-terminus or the presence of ragged ends can be assessed using data obtained from a peptide map. This includes the generation of confirmatory peptide fragment ions to confirm the nature of the C-terminal peptide or peptides.
Intact molecular weight analysis of the product can also be used as an orthogonal procedure to support conclusions regarding the structures of the N- and C-termini. Monoclonal antibodies are an example of proteins where C-terminal variation is observed. In this case, the C-terminal Lysine residues of the heavy chains can be removed, resulting in variability of the C-terminus of the heavy chains.
Contact BioPharmaSpec to find out more about our terminal sequencing services.