5CMX:
reference: Different duplex/quadruplex junctions determine the properties of anti-thrombin aptamers with mixed folding., Russo Krauss I, Spiridonova V, Pica A, Napolitano V, Sica F, Nucleic Acids Res. 2015 Dec 15. pii: gkv1384. PMID: 26673709

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