6X79:
reference: Structure-guided covalent stabilization of coronavirus spike glycoprotein trimers in the closed conformation., McCallum M, Walls AC, Bowen JE, Corti D, Veesler D, Nat Struct Mol Biol. 2020 Aug 4. pii: 10.1038/s41594-020-0483-8. doi:, 10.1038/s41594-020-0483-8. PMID: 32753755

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