3AL4:
reference: Crystal structure of the swine-origin A (H1N1)-2009 influenza A virus hemagglutinin (HA) reveals similar antigenicity to that of the 1918 pandemic virus., Zhang W, Qi J, Shi Y, Li Q, Gao F, Sun Y, Lu X, Lu Q, Vavricka CJ, Liu D, Yan J, Gao GF, Protein Cell. 2010 May;1(5):459-67. Epub 2010 Jun 4. PMID: 21203961

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