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. Author manuscript; available in PMC: 2009 Oct 19.
Published in final edited form as: Chem Commun (Camb). 2008 Sep 26;(41):5128–5130. doi: 10.1039/b811159f

Fig. 2.

Fig. 2

One example of an “artificially expanded genetic information system” (Aegis). Nucleobase pairs in this system have a Watson–Crick geometry, with large purines or purine analogs (indicated by “pu”) pairing with small pyrimidines or pyrimidine analogs (indicated by “py”) joined by hydrogen bonds. The hydrogen-bonding acceptor (A) and donor (D) groups are listed from the major to the minor groove as indicated. Lobes represent electron density in the minor groove. The nucleotides implementing the pyDDA:puAAD hydrogen bonding pattern (dZ:dP), the topic of this paper, are at the right.