2Y5F:
reference: Molecular Recognition at the Active Site of Factor Xa: Cation-pi Interactions, Stacking on Planar Peptide Surfaces, and Replacement of Structural Water., Salonen LM, Holland MC, Kaib PS, Haap W, Benz J, Mary JL, Kuster O, Schweizer WB, Banner DW, Diederich F, Chemistry. 2011 Dec 9. doi: 10.1002/chem.201102571. PMID: 22162109

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