3BC3:
reference: Exploring inhibitor binding at the s' subsites of cathepsin L., Chowdhury SF, Joseph L, Kumar S, Tulsidas SR, Bhat S, Ziomek E, Menard R, Sivaraman J, Purisima EO, J Med Chem. 2008 Mar 13;51(5):1361-8. Epub 2008 Feb 16. PMID: 18278855

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