Fig. 3.

Faster and more accurate copying of a 3′-NP-DNA template using 2-thio-T in place of T monomer. (A) Scheme for self-copying of a 3′-NP-DNA template using C and T (or 2-thio-T) monomers. The primer is a 5′-Cy3-DNA-3′-NH₂ and the template is a chimeric DNA/3′-NP-DNA (underlined) 5′-CAGAGGACTATCGGC-3′. (B) PAGE analysis of primer extension products. Primer extension reactions were carried out as in Fig. 1. The reaction was initiated by addition of 5.0 mM 3′-NH₂-2-MeImpddC and 5.0 mM 3′-NH₂-2-MeImpddT/sT as indicated. Arrows indicate primer and full-length product. (C) Scheme for self-copying AGAG 3′-NP-DNA template with an entirely 3′-NP-DNA primer. (D) High-resolution MS analysis of the full-length extension products from a reaction initiated by the addition of 5.0 mM 3′-NH₂-2-MeImpddC and 5.0 mM 3′-NH₂-2-MeImpddT. There are three major isomeric families for three different 14-mer full-length N+4 products, corresponding to C₃T₁, C₂T₂, and C₁T₃ respectively. (E) High-resolution MS analysis of the full-length extension products from a reaction initiated by the addition of 5.0 mM 3′-NH₂-2-MeImpddC and 5.0 mM 3′-NH₂-2-MeImpddsT. The major peak corresponds to the 14-mer full-length N+4 product C₂sT₂.