The assay was measured by adding 2-fold dilutions of testing peptides (final concentration from 2666.7 nM to 0.17 nM) to premixed N-Terminal 6×His-tagged KEAP1 (final concentration 20 nM), Sulfo-Cy5-N3-labeled peptide probe (final concentration 40nM) and Europium-labeled anti-6×His antibody (final concentration 0.5 nM) in HEPES buffer (10 mM HEPES, 150 mM NaCl, 0.005% (w/v) Tween-20, 0.05% (w/v) BSA, pH 7.4). The reagents were added to wells of a 384-microwell plate (ThermoFischer NUNC™ 384 shallow well std height plates non-sterile, black) to reach a total assay volume of 15 μl. The plate was sealed and centrifuged at 800 g for 1 minute to eliminate bubbles in the wells. After 30 min incubation at RT, the TR-FRET signal was measured using a plate reader (PHERAstar FSX, BMG) exciting at 337 nm and measuring with a delay of 60 μs the emission at both, 620 nm (from europium) and 665 nm (from Cy5) with a measurement window of 400 μs. Ratio of fluorescent emission intensity at 665-620 nm was calculated for each reaction (equation 1). Percent inhibition was calculated based upon Min (control compound -KI696) vs. Max (DMSO) according to equation 2 & 3. Sigmoidal curves were fitted to the data using Graphpad Prism 5 software.