| 1IZ5: reference: Intermolecular ion pairs maintain the toroidal structure of Pyrococcus furiosus PCNA., Matsumiya S, Ishino S, Ishino Y, Morikawa K, Protein Sci 2003 Apr;12(4):823-31. PMID: 12649440 |
This OCA 
Structure page
uses Jmol,
developed by the Jmol Development Team
(documentation).