The Chemical Probes Portal now includes several PROTACs in the list of recommended chemical probes and even more are under review by the Scientific Advisory Board.

PROTACs are bifunctional molecules that bind to the target protein and an E3 ligase, the simultaneous PROTAC binding of two proteins brings the target protein in close enough proximity for polyubiquitination by the E2 enzyme associated to the E3 ligase, which flags the target protein for degradation through the proteasome.

They have also put together a really useful list of criteria to help define the best choice of Protac probe.