Leupeptin hemisulfate is a protease inhibitor with cell membrane-permeable, reversible, competitive, and oral activities. Leupeptin hemisulfate inhibits the activity of Cathepsin B, Cathepsin H, and Cathepsin L, and blocks fusion of amphipathic lysosomes. Leupeptin hemisulfate also has anti-inflammatory activity.

Human coronavirus strain 229E:0.4 µg/mL, SARS-CoV-2 (Vero cells):42.34 µM (EC50), Huh7 cells (SARS-CoV-2):39.29 µM (EC50)

Determination of BET Protein Binding Affinities to I-BET726: For determination of binding affinities to BET protein bromodomains, I-BET726 is titrated against truncates containing both BD1 and BD2 of BRD2 (10 nM), BRD3 (10 nM), and BRD4 (10 nM) in 50 mM HEPES pH7.5, 150 mM NaCl, 5% Glycerol, 1 mM DTT and 1 mM CHAPS in the presence of an Alexa 647 derivative (50 nM) of fluorescent ligand. After equilibrating for 1 h, the bromodomain protein: ligand interaction is detected using Time Resolved Fluorescence Resonance Energy Transfer (TR-FRET) following the addition of 1.5 nM europium chelate labeled anti-6His antibody. Plates are read using an Envision Plate reader (λEX = 337 nm, λEM = 615 nm, λEM = 665 nm; dual dichroic = 400 nm & 630 nm). These data are fitted to a four parameter IC50 model using Graphit data analysis software.