2H3O:
reference: Structure determination of a membrane protein with two trans-membrane helices in aligned phospholipid bicelles by solid-state NMR spectroscopy., De Angelis AA, Howell SC, Nevzorov AA, Opella SJ, J Am Chem Soc. 2006 Sep 20;128(37):12256-67. PMID: 16967977

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