2BSG:
reference: The tail structure of bacteriophage T4 and its mechanism of contraction., Kostyuchenko VA, Chipman PR, Leiman PG, Arisaka F, Mesyanzhinov VV, Rossmann MG, Nat Struct Mol Biol. 2005 Sep;12(9):810-3. Epub 2005 Aug 14. PMID: 16116440

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