N-terminalomics is a high-throughput strategy for identifying proteins by selectively enriching for and sequencing their N-terminal peptides by mass spectrometry. In the November issue of Cold Spring Harbor Protocols, Samie Jaffrey and colleagues from Cornell University present a newly-developed N-terminalomic approach, N-CLAP (N-terminalomics by Chemical Labeling of the alpha-Amine of Proteins). N-CLAP: Global Profiling of N-Termini by Chemoselective Labeling of the alpha-Amine of Proteins describes the use of Edman chemistry to modify all of the amines in proteins, followed by the generation of a new unmodified amine at the N-terminus after the removal of the first amino acid by peptide bond cleavage. The alpha-amine at the protein N-terminus is labeled with a cleavable biotin affinity tag, which facilitates the downstream purification of the N-terminal peptides. Peptides are eluted by cleaving the biotin affinity tag and identified by tandem mass spectrometry (MS/MS). N-CLAP can be used for the identification of signaling peptides for mature proteins as well as for global profiling of cleavage events that occur during cell signaling, such as apoptosis.