Figure 1:
(A) General isoTOP-ABPP workflow. Reactive cysteine residues on two proteome samples are labeled with IA-alkyne, followed by CuAAC with an isotopically heavy or light biotin-azide cleavable linker. The two lysates are combined, biotinylated proteins are enriched on streptavidin-agarose beads, and subjected to an on-bead trypsin digestion. The IA-labeled peptides are released and analyzed by LC/LC-MS/MS. Heavy and light peptide pairs are quantified by their extracted MS1 peaks. (B) IA-alkyne structure and cysteine-labeling scheme. (C) The tobacco-etch virus (TEV) protease cleavable biotin-azide tag for isoTOP-ABPP.