1GGD:
reference: Correlation of low-barrier hydrogen bonding and oxyanion binding in transition state analogue complexes of chymotrypsin., Neidhart D, Wei Y, Cassidy C, Lin J, Cleland WW, Frey PA, Biochemistry 2001 Feb 27;40(8):2439-47. PMID: 11327865

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