| 3TGA: reference: Guanidine-Ferroheme Coordination in the Mutant Protein Nitrophorin 4(L130R)., He C, Fuchs MR, Ogata H, Knipp M, Angew Chem Int Ed Engl. 2012 Apr 27;51(18):4470-3. doi: 10.1002/anie.201108691., Epub 2012 Feb 14. PMID: 22334402 |
This OCA 
Structure page
uses Jmol,
developed by the Jmol Development Team
(documentation).