4H3M:
reference: Recovery of Red Fluorescent Protein Chromophore Maturation Deficiency through Rational Design., Moore MM, Oteng-Pabi SK, Pandelieva AT, Mayo SL, Chica RA, PLoS One. 2012;7(12):e52463. doi: 10.1371/journal.pone.0052463. Epub 2012 Dec 20. PMID: 23285050

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