7-deaza-dG (Figure 1) can be inserted in an oligonucleotide to create an asymmetric base pair.
The Tm of the 7-deaza-dG: C binding is 1 °C lower, compared to the natural G: C binding. Therefore, replacing native Gs with 7-deaza-dG in GC-rich sequences can partially solve problems arising from G or GC-rich regions, such as formation of secondary structure.
Figure 1. Structure of 7-deaza-dG at the 5'-end (R = sequence).
metabion offers 7-deaza-dG as a modification in its RNA portfolio: