Page "Protein sequencing" Paragraph 32

Digestion into peptide fragments Peptides longer than about 50-70 amino acids long cannot be sequenced reliably by the Edman degradation.

Because of this, long protein chains need to be broken up into small fragments which can then be sequenced individually.

Digestion is done either by endopeptidases such as trypsin or pepsin or by chemical reagents such as cyanogen bromide.

Different enzymes give different cleavage patterns, and the overlap between fragments can be used to construct an overall sequence.