An in situ combinatorial methodology to synthesize and screen chemical probesElectronic supplementary information (ESI) available: Supplementary figures and tables, experimental procedures and compound characterization. See DOI: 10.1039/c8cc06991c

Chemical probes that label proteins of interest in the context of complex biological samples are useful research tools. The reactive group that forms the covalent bond with the target protein has a large effect on the selectivity and selecting the appropriate group determines the success of a probe. We here report the development of a combinatorial methodology based on imine chemistry that enables straightforward in situ synthesis and screening of different reactive groups and thereby simplifies identification of probe leads. Using our methodology, we found chemical probes targeting BirA and chloramphenicol acetyl transferase, two proteins associated with antibacterial activity and resistance. Linking of reactive groups and ligands by imine chemistry provides chemical probes that label proteins of interest.