This products is a fluorescence polarization (FP) assay reagent, which is based on a 5-carboxytetramethylrhodamine (TAMRA) modified Lys-Gly sequence that is linked to ubiquitine via a native isopeptide bond with the lysine side-chain. Typical substrate concentrations range from 10−100 nM. DUB concentrations can range from 0.01-10 nM but depend on specific assay conditions and method of detection. FP assays can be performed with any fluorescence polarization reader with a 530 nm excitation filter and two 580 nm emission filters.