2ICZ:
reference: Toward a Designed, Functioning Genetic System with Expanded-Size Base Pairs: Solution Structure of the Eight-Base xDNA Double Helix., Lynch SR, Liu H, Gao J, Kool ET, J Am Chem Soc. 2006 Nov 15;128(45):14704-11. PMID: 17090058

This OCA Structure page
uses Jmol, developed by the Jmol Development Team (documentation).