Figure 1.

SAMDI-MS assay of NSP14 ExoN activity. (A) RNA substrates utilized in this study. Asterisk represents a PO bond. (B) Scheme of the NSP14/NSP10 ExoN assay on dsRNA substrates, where B represents the biotin moiety. (C) Scheme of SAMDI-MS assay where quenched homogenous reactions are transferred to neutravidin-presenting self-assembled monolayers to specifically immobilize the biotinylated substrate, products, and internal standard. (D) Representative SAMDI-MS spectrum showing the internal standard (m/z 2844.9) and major nuclease product using the Exo control substrate (m/z 2080.6). (E) NSP14/NSP10 exhibits ExoN activity on three substrates measured by SAMDI-MS. All measurements are from triplicate data.