Figure 4.

(a) Melting curves for sequences Br-9 (upward triangle solid line), containing a single syn substitution; Br-22 (downward triangle solid line), containing a single anti substitution; and Br-9-22 (diamonds with dotted line), containing both syn and anti substitutions. The curve for the unmodified sequence (gray solid line) serves as a reference. The additive effect of multiple substitutions on the T_m can be seen. (b) Modification-dependence stability (^BrG > ^OmetG > ^AmG) was observed for substitutions to syn guanines, as illustrated by the melting curves of Br-9 (circles), Omet-9 (squares), and Am-9 (diamonds). The melting curve of the unmodified sequence is shown for reference. Melting curves presented are normalized UV cooling curves monitored at 295 nm. (c) Comparison of the change in T_m values for each guanine derivative over substitutions to various syn residues. Modifications are shown as circles (^BrG), squares (^OmetG), and diamonds (^AmG).