Figure 2.
Example for the cleavage of a natural tRNA by DNA enzymes. (a) Secondary structure of E. coli tRNAVal 1 and 10–23 DNA enzyme 2. The desired tRNA 5′-fragment 3 contains all modified nucleosides and possesses a 2′,3′-cyclophosphate terminus. (b) Anion-exchange HPLC analysis of the cleavage reaction (88% yield according to peak area integration) and the purified fragment; reaction conditions: cDNAzyme = 80 µM; ctRNA = 40 µM; 50 mM Tris–HCl (pH 7.5), 10 mM MgCl2, 10 mM DTT, temperature cycles (25–90°C); anion-exchange HPLC: for conditions see ‘Materials and Methods’ section. (c) LC-ESI MS analysis of 3: m.w. (calcd) = 19113, m.w. (found) = 19112 ± 10. For structures and abbreviations of modified nucleosides, see Supplementary Data.