Figure 3.

Treatment of the RNA products with exonuclease and analysis by MALDI-TOF MS to determine relative excision of Sofosbuvir, UMP and Remdesivir. Untreated products (0 min) are shown in (a) for SOF extended RNA, (d) for UMP extended RNA and (g) for UMP plus RDV extended RNA. Exonuclease reactions were performed by incubating the purified RNA products, generated using the same procedure as in Fig. 2, with pre-assembled SARS-CoV-2 exonuclease complex (nsp14 and nsp10) for 5 min (b,e,h) or 30 min (c,f,i), followed by detection of reaction products by MALDI-TOF MS. The signal intensities were normalized to the highest peak within each time series. The accuracy for m/z determination is approximately ± 10 Da.