CHEMBL5736302

Endonuclease Activity Assay: Endonuclease activity assays were carried out in Black Costar 96-well plates. Each well contained a total volume of 100 μL comprised of: buffer (20 mM Tris, 150 mM NaCl, 2 mM MnCl2, 10 mM β-mercaptoethanol, 0.2% Triton-X100, pH=8.0), influenza PA endonuclease (25 nM) prepared from Example 1, inhibitor (various concentrations) in buffer, and fluorescent ssDNA-oligo substrate (200 nM). A single-stranded, 17-mer DNA substrate labeled with a 5′-FAM fluorophore and a 3′-TAMRA quencher ([6-FAM]AATCGCAGGCAGCACTC[TAM]) (SEQ ID NO:2) synthesized by Sigma-Aldrich was employed to measure endonucleic cleavage. Upon addition of the substrate, the change in fluorescence was measured over 45 minutes at 37° C. (excitation: 485 nm; emission 528 nm). The positive control wells contained no inhibitor for preliminary screens, and were set as an arbitrary 100% activity. Compounds that exhibited >80% inhibition at a concentration of 200 μM were re-evaluated at a concentration of 50 μM. Confirmation screens employed EGCG (Epigallocatechin 3-gallate), a previously validated inhibitor, as a positive control. The gain was set to 100 and the first 10 data points (the first 10 minutes) were excluded from the activity calculations. Dose-response curves were generated, fitted, and analyzed using Origin8 graphing software. Dose-response curves were compiled and IC50 values determined for compounds exhibiting >50% inhibition at 50 μM.