Figure 3.

Imino proton NMR spectra for (a) the unmodified sequence, as well as modified sequences (b) Br-3, (c) Omet-3, (d) Am-3, and (e) Oxo-3 containing a single substitution to syn residue 3. The peaks in the unmodified spectrum are labeled with residue numbers, circled numbers representing guanines within the modified G3⋅G21⋅G17⋅G9 tetrad and the modified residue 3 shaded gray. Dotted lines identify the chemical shift of imino protons from the unmodified spectra for guanines located outside of the modified tetrad. Black dots indicate the presence of individual imino proton resonances.