2O4Y:
reference: Solution structure and dynamics of DNA duplexes containing the universal base analogues 5-nitroindole and 5-nitroindole 3-carboxamide., Gallego J, Loakes D, Nucleic Acids Res. 2007;35(9):2904-12. Epub 2007 Apr 16. PMID: 17438041

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