Live cell off-target identification of lapatinib using ligand-directed tosyl chemistryDedicated to Professor Seiji Shinkai on the occasion of his 70th birthday.Electronic supplementary information (ESI) available: Experimental details, figures (Fig. S1-S11), schemes (Schemes S1 and S2), and a table (Table S1). See DOI: 10.1039/c4cc05885b

We demonstrate that ligand-directed tosyl (LDT) chemistry is applicable to off-target identification in live cells. Lapatinib (Lap)-based LDT reagents not only labeled a receptor tyrosine kinase, HER2, target protein, but also the protein disulfide isomerase (PDI) that should be an off-target protein for Lap. We demonstrate that ligand-directed tosyl (LDT) chemistry is applicable to off-target identification in live cells.