Extended Data Fig. 2: Design of TEprobes for discriminating SARS-CoV-2, SARS-CoV and MERS-CoV.
a, Target sequences on the N gene of SARS-CoV-2, SARS-CoV and MERS-CoV. Nucleotides in SARS-CoV and MERS-CoV differing from SARS-CoV-2 are marked in red. b, The TEprobe with a 7-nt reverse toehold and an 8-nt forward toehold cannot sufficiently respond to the target virus, SASR-CoV-2. c, TEprobes with extended forward toehold lengths up to 12 nt, 15 nt, 18 nt, 20 nt and 25 nt. d, Absorbance at 560 nm and visual result using TEprobes targeting SARS-CoV-2 in the presence of SARS-CoV-2, SARS-CoV or MERS-CoV. e, Discrimination factors to distinguish SARS-CoV-2 from SARS-CoV and MERS-CoV using TEprobes in c. Forward toehold up to 15 nt can support a sufficient color change response to the target virus, SARS-CoV-2. And a further increase of forward toehold reduced the discrimination factors due to the elevated color change induced by the non-target virus, SARS-CoV. f, Detection of SARS-CoV-2, SARS-CoV or MERS-CoV using its cognate TEprobe. g, Discrimination factor to distinguish SARS-CoV-2, SARS-CoV and MERS-CoV. Concentrations of urea, phenol red, urease and TEprobes were 500 mM, 250 μM, 1 nM and 3 nM, respectively. The measurement of absorbance was proceeded after 20-min urea cleavage reaction. The concentration of viruses was 30,000 copies/μl. Date in b and f are mean ± s.d. (n = 3).
