2QUS:
reference: Capturing hammerhead ribozyme structures in action by modulating general base catalysis., Chi YI, Martick M, Lares M, Kim R, Scott WG, Kim SH, PLoS Biol. 2008 Sep 30;6(9):e234. PMID: 18834200

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