A rapid isolation and identification method for blocked N-terminal peptides by isothiocyanate-coupled magnetic nanoparticles and MS.

A quick isolation and identification of N-blocked peptides from protein digest mixtures were achieved by diisothiocyanate or isothiocyanate-coupled magnetic nanoparticles and MS. After protein digests were guanidinated and then mixed with diisothiocyanate or isothiocyanate-coupled magnetic nanoparticles, unmodified N-terminal peptides were covalently bound to magnetic nanoparticles, and can be removed from the mixture under magnetic field. Therefore, N-blocked peptides could be isolated and analyzed by MALDI or ESI MS. This new strategy was demonstrated with model peptides, proteins, and the lysates of HepG2 cells.