3D9B:
reference: There is a baby in the bath water: AcrB contamination is a major problem in membrane-protein crystallization., Veesler D, Blangy S, Cambillau C, Sciara G, Acta Crystallogr Sect F Struct Biol Cryst Commun. 2008 Oct 1;64(Pt 10):880-5., Epub 2008 Sep 30. PMID: 18931428

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