FIGURE 2.
H-bond acceptors vastly exceed donors in RNA. Acceptors and donors are depicted in red and blue, respectively. Oxygens can accept two H-bonds, while unprotonated nitrogens can accept a single H-bond. The exocyclic amine, which cannot accept an H-bond due to donation of its lone electron pair into the ring system, can donate two H-bonds. In contrast, all other nitrogen and oxygen donors can donate only a single H-bond. This counting of H-bonds does not consider multifurcated interactions (e.g., a bifurcated H-bond), which are mentioned in Figure 1. Labels to the key atoms are provided.
