Determination of the protein sequence is as important today as it was a half century ago, even though the techniques and purposes have changed over time. Mass spectrometry has continued its recent rapid development to find notable application in the characterization of small amounts of protein, for example, in the field of proteomics. The traditional chemical N-terminal sequencing is still of great value in quality assurance of the increasing number of biopharmaceuticals that are to be found in the clinic, checking processing events of recombinant proteins, and so on. It is joined in the...