2INX:
reference: Testing geometrical discrimination within an enzyme active site: constrained hydrogen bonding in the ketosteroid isomerase oxyanion hole., Sigala PA, Kraut DA, Caaveiro JM, Pybus B, Ruben EA, Ringe D, Petsko GA, Herschlag D, J Am Chem Soc. 2008 Oct 15;130(41):13696-708. Epub 2008 Sep 23. PMID: 18808119

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