Fig. 6. Cleavable linkers for chemical proteomics. (a) Proteins enriched on resin e.g. by biotin–streptavidin, can be specifically released and then analysed by MS (bottom), or digested on bead and then the modified peptide selectively released (top). (b) The isotopically-encoded protease (TEV)-cleavable linker 1 for CuAAC and enrichment reported by Cravatt and co-workers.⁴⁰ .