4ZF3:
reference: Short Hydrogen Bonds and Proton Delocalization in Green Fluorescent Protein (GFP)., Oltrogge LM, Boxer SG, ACS Cent Sci. 2015 Jun 24;1(3):148-56. doi: 10.1021/acscentsci.5b00160. Epub 2015, Jun 5. PMID: 27162964

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