4AFH:
reference: Molecular actions of smoking cessation drugs at alpha4beta2 nicotinic receptors defined in crystal structures of a homologous binding protein., Billen B, Spurny R, Brams M, van Elk R, Valera-Kummer S, Yakel JL, Voets T, Bertrand D, Smit AB, Ulens C, Proc Natl Acad Sci U S A. 2012 Jun 5;109(23):9173-8. Epub 2012 May 22. PMID: 22619328

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