6N8H:
reference: Nuclear Magnetic Resonance Reveals That GU Base Pairs Flanking Internal Loops Can Adopt Diverse Structures., Berger KD, Kennedy SD, Turner DH, Biochemistry. 2019 Jan 31. doi: 10.1021/acs.biochem.8b01027. PMID: 30702283

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