2AAS:
reference: High-resolution three-dimensional structure of ribonuclease A in solution by nuclear magnetic resonance spectroscopy., Santoro J, Gonzalez C, Bruix M, Neira JL, Nieto JL, Herranz J, Rico M, J Mol Biol 1993 Feb 5;229(3):722-34. PMID: 8381876

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