6CSS:
reference: Entropy as a Driver of Selectivity for Inhibitor Binding to Histone Deacetylase 6., Porter NJ, Wagner FF, Christianson DW, Biochemistry. 2018 May 18. doi: 10.1021/acs.biochem.8b00367. PMID: 29775292

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