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Figure 2
(a) Chemical diagrams of possible oxidation states of a cysteine side chain. (b) The catalytic site of SARS-CoV-2 3CL Mpro structure I. Possible hydrogen bonds are shown as blue dashed lines; the distance between Cys145 and His41, which is too long for a hydrogen bond, is shown as a black dotted line. The 2Fo − Fc electron-density map contoured at the 1.5σ level is shown as a purple mesh. All distances are given in ångströms.

IUCrJ
Volume 7| Part 6| November 2020| Pages 1028-1035
ISSN: 2052-2525
https://doi.org/10.1107/S2052252520012634