Protein (amino acids,precisely) sequences yield much information about the function of the protein more than its species diversity.

reductionism; systems biology

Repeat

Complete characterization of peptides/proteins, including post-translational modifications (PTMs), sequence mutations and variants, is very challenging. There are two approaches to determine the sequence of peptide/protein by mass spectrometry: database search and de novo sequencing. Database search approach compares acquired mass spectra to a database of known protein sequences to identify the protein sequences.

'Sequencing' is the next book in the series or sequel.