CHEMBL5734610

IC50 Determination: The inhibitor library was first screened for inhibition of each 3CLpro at a concentration of 100 μM in duplicate assays containing the following assay buffer (50 mM HEPES, 0.1 mg/mL BSA, 0.01% TritonX-100, 1 mM DTT). The assays were carried out in Costar 3694 EIA/RIA 96-Well Half Area, Flat Bottom, Black Polystyrene plates from Corning Incorporated. 1 μL of 100× inhibitor stock in DMSO was added to 79 μL of enzyme in assay buffer and the enzyme-inhibitor mixture was incubated for 10 minutes. The reaction was initiated by the addition of 20 μL of 10 μM UIVT3 substrate, a custom synthesized Förster resonance energy transfer substrate peptide with the following sequence: HilyteFluor™488-ESARLQSGLRKAK-QXL520™-NH2, producing final concentrations of 100 nM and 100 μM for the 3CLpro enzyme and UIVT3 substrate, respectively. The fluorescence intensity of the reaction was then measured over time as relative fluorescence units (RFUt) for a period of 10 minutes, using an excitation wavelength of 485 and bandwidth of 20 nm and monitoring emission at 528 and bandwidth of 20 nm using a BioTek Synergy H1 multimode microplate reader.