1K8S:
reference: Solution conformation of a bulged adenosine base in an RNA duplex by relaxation matrix refinement., Thiviyanathan V, Guliaev AB, Leontis NB, Gorenstein DG, J Mol Biol 2000 Jul 28;300(5):1143-54. PMID: 10903860

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