Figure 1.

Covalent cross-linking of a I^6S/U^4S or G^6S/U^4S base pair within duplex ODN 1∙2 (a) by bis-alkylation with 1,2-diiodoethane at pH 9.0 (b). The time course for the reaction of duplexes 1^I6S∙2^U4S (c) and 1^G6S∙2^U4S (d) is monitored by denaturing anion exchange HPLC. The non-cross-linked parent duplexes dissociate and elute as their respective single strands, while the covalently linked duplexes elute significantly later.