yDNA: A New Geometry for Size‐Expanded Base Pairs

Room for expansion: Insertion of a benzene ring into the natural adenine heterocycle to generate the analogue yA results in the formation of base pairs that are 2.4 Å wider than natural ones (see structure). Melting temperature and free energy data show that yA⋅T and T⋅yA pairs can self-assemble into cooperative helices that are considerably more stable than natural DNA. Thus, yDNA may be a candidate for a new genetic system.