4X1H:
reference: The High-Resolution Structure of Activated Opsin Reveals a Conserved Solvent Network in the Transmembrane Region Essential for Activation., Blankenship E, Vahedi-Faridi A, Lodowski DT, Structure. 2015 Oct 27. pii: S0969-2126(15)00408-6. doi:, 10.1016/j.str.2015.09.015. PMID: 26526852

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