3FCA:
reference: Genetic Incorporation of a Metal-Ion Chelating Amino Acid into Proteins as a Biophysical Probe., Lee HS, Spraggon G, Schultz PG, Wang F, J Am Chem Soc. 2009 Feb 4. PMID: 19193005

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