UbiQ-115 (Biotin-Ahx-K63 diUbiquitin VME) probe is a potent, irreversible and specific inhibitor of deubiquitylating enzymes (DUBs) based on K63 linked diUb. Here Lys63 has been replaced by a diaminobutyric acid residue equipped with a VME type warhead. The Dab(VME) type of structure is a DUB reactive mimic of the native isopeptidic linked Lys(Gly) residue. This DUB activity based probe can be used for activity profiling experiments and structural studies. Please note the native distance between the proximal and distal Ubiquitin is preserved as much as possible in UbiQ-115.