4KI1:
reference: A range of C3-C4 interdomain angles in IgE Fc accommodate binding to its receptor CD23., Dhaliwal B, Pang MO, Yuan D, Beavil AJ, Sutton BJ, Acta Crystallogr F Struct Biol Commun. 2014 Mar;70(Pt 3):305-9. doi:, 10.1107/S2053230X14003355. Epub 2014 Feb 20. PMID: 24598915

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