4R0V:
reference: [FeFe]-hydrogenase oxygen inactivation is initiated at the H cluster 2Fe subcluster., Swanson KD, Ratzloff MW, Mulder DW, Artz JH, Ghose S, Hoffman A, White S, Zadvornyy OA, Broderick JB, Bothner B, King PW, Peters JW, J Am Chem Soc. 2015 Jan 12. PMID: 25579778

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