1JGR:
reference: Locating monovalent cations in the grooves of B-DNA., Howerton SB, Sines CC, VanDerveer D, Williams LD, Biochemistry 2001 Aug 28;40(34):10023-31. PMID: 11513580

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