Highly efficient and chemoselective blocking of free amino group by ortho-phthalaldehyde (OPA) for comprehensive analysis of protein terminome

Herein, we introduced ortho-phthalaldehyde (OPA) for blocking free amino groups and established a simple and robust method for comprehensive profiling of protein terminome based on strong cation exchange chromatography (SCX) fractionation. With the highly efficient and chemoseletive amine-group blocking, we identified 2271 canonical human protein N-termini, 1650 canonical human protein C-termini, as well as 645 protein neo-Ntermini from HeLa cells.