Figure 6.

Inhibition of SARS-CoV-2 ExoN activity by fisetin. A mixture of 500 nM RNA (sequence shown at the top of the figure) and 50 nM SARS-CoV-2 pre-assembled exonuclease complex (nsp14/nsp10) was incubated in buffer solution at 37 °C for 15 min (B) in the absence and (C,D) presence of 50 μM and 150 μM fisetin. The (A) RNA and the (B–D) products of the ExoN reaction were analyzed by MALDI-TOF MS. The signal intensity was normalized to the highest peak. The peak at 8164 Da corresponds to the intact RNA (8157 Da expected).