6GZN:
reference: Adenine-driven structural switch from two- to three-quartet DNA G-quadruplex., Plavec J, Lenarcic Zivkovic M, Rozman J, Angew Chem Int Ed Engl. 2018 Sep 17. doi: 10.1002/anie.201809328. PMID: 30222243

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