Figure 3.

HPLC chromatograms of the enzymatic digestion of oligonucleotides 11, 12, 13 and 14 after two-step crosslinking reactions (315 nm). Oligonucleotides were reacted with DMC using optimized bifunctional activation conditions at 0° C (first step), purified, then crosslinked at 37°C with sodium dithionite (second step). Peaks labelled with an asterisk indicate bisulfite adducts. (a) 11, first alkylation step, 0°C; (b) 11, second alkylation step, 37°C; (c) 12, first alkylation step 0°C; (d) 12, second alkylation step, 37°C; (e) 13, first alkylation step, 0°C; (f) 13, second alkylation step, 37°C; (g) 14, first alkylation step, 0°C; (h) 14, second alkylation step, 37°C. Digestion and analysis were performed as described in Figure 2. More information is provided in the supporting information section (S-5-1 and S-4-2)