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Electrostatic surface view representation of SARS-CoV-2 main protease (PDB ID: 6LU7) with bound xanthine derivatives: (A) caffeine, (B) chloroquine, (C) methylxanthine, (D) theobromine, (E) theophylline and (F) xanthine. The color coding is by electrostatic potential; negative, positive and neutral regions are shown in blue, red and white respectively (image generated using Pymol)
