1J8G:
reference: X-ray analysis of an RNA tetraplex (UGGGGU)(4) with divalent Sr(2+) ions at subatomic resolution (0.61 A)., Deng J, Xiong Y, Sundaralingam M, Proc Natl Acad Sci U S A 2001 Nov 20;98(24):13665-70. PMID: 11707581

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