We present four new HA-tagged activity-based probes for deubiquitinating enzymes (DUBs).

• UbiQ-216: HA-Ahx-Ahx-Ub-VAE (VAE= vinyl azido ester)
• UbiQ-217: HA-Ahx-Ahx-Ub-VAA (VAA= vinyl azido amide)
• UbiQ-218: HA-Ahx-Ahx-Ub-VPE (VPE= vinyl pentynyl ester)
• UbiQ-219: HA-Ahx-Ahx-Ub-VPA (VPA= vinyl pentynyl amide)

The HA peptide sequence (YPYDVPDYA) allows for the sensitive identification or purification of DUBs by anti-HA antibodies and/or anti-HA-agarose. The HA tag is separated from the N-terminus by two 6-aminohexanoic acid (Ahx) linkers for efficient recognition. The alkyne group (UbiQ-218 or UbiQ-219, Figure 1) and the azide group (UbiQ-216 or UbiQ-217) in the C-terminal warhead, allow for further modification by click chemistry. 

Figure 1.