3U8C:
reference: A Structural Basis for Reversible Photoswitching of Absorbance Spectra in Red Fluorescent Protein rsTagRFP., Pletnev S, Subach FV, Dauter Z, Wlodawer A, Verkhusha VV, J Mol Biol. 2012 Jan 30. PMID: 22310052

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