text: The success and implications of xDNA prompted research to examine other factors which could alter B-DNAs chemical properties and create a new system for information storage with broader applications. yDNA also uses a benzene ring, similar to xDNA, with the only difference being the site of addition of the aromatic ring. The location of the benzene ring changes the preferred structure of the expanded helix. The altered conformation makes yDNA more similar to B-DNA in its orientation by changing the interstrand hydrogen bonds. Stability is highly dependent on the bases rotation about the link between the base and the sugar of the backbone. yDNAs altered preference for this orientation makes it more stable overall than xDNA. The location of the benzene spacer also affects the bases groove geometry, altering neighbour interactions. The base pairs between y-nucleotides and natural nucleotides is planar, rather than slightly twisted as with xDNA. This decreases the rise of the helix even further than achieved by xDNA. 
  While xDNA and yDNA are quite similar in most properties, including their increased stacking interactions, yDNA shows superior mismatch recognition. y-pyrimidines display slightly stronger stacking interactions than x-pyrimidines as a result of the distance between the two anomeric carbons, which is slightly larger in yDNA. xDNA still has stronger stacking interactions in model helices, but adding either x- or y-pyrimidines to a natural double helix strengthens the intra- and interstrand interactions, increasing overall helix stability. In the end, which of the two has the strongest overall stacking interactions is dependent on the sequence; xT and yT bind A with similar strength, but the stacking energy of yC bound to G is stronger than xC by 4kJ/mol. yDNA and other expanded bases are part of a very young field which is highly understudied. Research suggest that the ideal conformation still remains to be discovered, but knowing that the benzene location affects the orientation and structure of expanded nucleobases adds information to their future design.