2.

Characterization of c¹c³G-modified RNA using c¹c³G building block 12 for solid-phase synthesis and optimized deprotection conditions. Anion-exchange HPLC traces (top) of purified 9 nt RNA (A), 15 nt RNA (B), and 37 nt RNA (C), and corresponding LC-ESI mass spectra (bottom). HPLC conditions: Dionex DNAPac column (4 × 250 mm), 80 °C, 1 mL min^–1, 0–60% buffer B in 60 min; buffer A: Tris–HCl (25 mM), 10 mM NaClO₄, pH 8.0, 20% acetonitrile; buffer B: Tris–HCl (25 mM), 600 mM NaClO₄, pH 8.0, 20% acetonitrile. For LC-ESI MS conditions, see the Supporting Information.