The ABC's (and XYZ's) of peptide sequencing.

Proteomics is an increasingly powerful and indispensable technology in molecular cell biology. It can be used to identify the components of small protein complexes and large organelles, to determine post-translational modifications and in sophisticated functional screens. The key - but little understood - technology in mass-spectrometry-based proteomics is peptide sequencing, which we describe and review here in an easily accessible format.