Olaparib target ID with a cleavable linker. a Structure of Olaparib-TCO and a tetrazine-biotin cleavable linker. b Pull-down assay for Olaparib-TCO binding proteins. A2780 proteome were incubated with Olaparib-TCO and conjugated with Tz-biotin cleavable linker. After target protein enrichment using streptavidin beads, bead binding proteins were eluted by adding dithionite (DT). Eluted proteins were resolved in SDS gel electrophoresis and silver-stained. Lane 1 : marker, Lane 2 : Olaparib-TCO, cleaved with 25 mM DT, Lane 3 : protein left in beads from lane 2, Lane 4 : Olaparib-TCO, cleaved without DT, Lane 5 : protein left in beads from lane 4, Lane 6 : DMSO, cleaved with 25 mM DT, Lane 7 : protein left in beads from lane 6. Protein sizes on the right indicate bands for LC/MS-MS protein analysis. c List of identified target proteins. Beyond target protein PARP1, unknown target protein candidates are discovered. Reprinted with permission from ref 69. Copyright 2013 John Wiley & Sons, Inc.