6WQF:
reference: Structural plasticity of SARS-CoV-2 3CL M(pro) active site cavity revealed by room temperature X-ray crystallography., Kneller DW, Phillips G, O'Neill HM, Jedrzejczak R, Stols L, Langan P, Joachimiak A, Coates L, Kovalevsky A, Nat Commun. 2020 Jun 24;11(1):3202. doi: 10.1038/s41467-020-16954-7. PMID: 32581217

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