6-Amino-5-nitropyridin-2-one, a pyridine derivative, serves as a nucleobase within hachimoji DNA, where it is specifically paired with 5-aza-7-deazaguanine.
2-Thiouridine (s2U) is a modified nucleobase found in tRNAs that is known to stabilize U:A pairs and modestly destabilize U:G wobble pairs. Modified nucleobases, including 2-thiouridine, are used to study nucleic acid structure and function as well as to engineer novel RNA-based biomolecules.