6EGY:
reference: Noncovalent PEGylation via Sulfonatocalix[4]arene-A Crystallographic Proof., Mummidivarapu VVS, Rennie ML, Doolan AM, Crowley PB, Bioconjug Chem. 2018 Nov 20. doi: 10.1021/acs.bioconjchem.8b00769. PMID: 30445810

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