4NFV:
reference: Weak protein-cationic co-ion interactions addressed by X-ray crystallography and mass spectrometry., Benas P, Auzeil N, Legrand L, Brachet F, Regazzetti A, Ries-Kautt M, Acta Crystallogr D Biol Crystallogr. 2014 Aug 1;70(Pt 8):2217-31. doi:, 10.1107/S1399004714011304. Epub 2014 Jul 25. PMID: 25084340

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