6ASF:
reference: First Structure of a Designed Minor Groove Binding Heterocyclic Cation that Specifically Recognizes Mixed DNA Base Pair Sequences., Harika NK, Germann MW, Wilson WD, Chemistry. 2017 Dec 11;23(69):17612-17620. doi: 10.1002/chem.201704563. Epub 2017, Nov 16. PMID: 29044822

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