2ADT:
reference: RNA Helical Packing in Solution: NMR Structure of a 30kDa GAAA Tetraloop-Receptor Complex., Davis JH, Tonelli M, Scott LG, Jaeger L, Williamson JR, Butcher SE, J Mol Biol 2005 Aug 12;351(2):371-82. PMID: 16002091

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