1SSA:
reference: Structural investigation of catalytically modified F120L and F120Y semisynthetic ribonucleases., deMel VS, Doscher MS, Glinn MA, Martin PD, Ram ML, Edwards BF, Protein Sci 1994 Jan;3(1):39-50. PMID: 8142897

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