| 5VQ3: reference: Reversible Protonated Resting State of the Nitrogenase Active Site., Morrison CN, Spatzal T, Rees DC, J Am Chem Soc. 2017 Aug 9;139(31):10856-10862. doi: 10.1021/jacs.7b05695. Epub, 2017 Jul 26. PMID: 28692802 |
This OCA 
Structure page
uses Jmol,
developed by the Jmol Development Team
(documentation).