2NYA:
reference: Spectropotentiometric and structural analysis of the periplasmic nitrate reductase from Escherichia coli., Jepson BJ, Mohan S, Clarke TA, Gates AJ, Cole JA, Butler CS, Butt JN, Hemmings AM, Richardson DJ, J Biol Chem. 2007 Mar 2;282(9):6425-37. Epub 2006 Nov 27. PMID: 17130127

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