19F NMR detection of the complex between amantadine and the receptor portion of the influenza A M2 ion channel in DPC micelles

19F NMR probes were used to follow interactions between ligands in the aminoadamantane series, amantadine (Am) 1 and 3-F-Am 2, and the 5-F-Trp20 transmembrane fragment of the influenza A M2 proton channel (F-M2TM 3) in dodecylphosphocholine micelles over the pH range 5–8. Above pH 7, when the peptide adopts a tetrameric state that is able to bind channel blocking ligands, 19F-Trp signals from both the free and bound states of the M2TM tetramer are resolved. This differentiation of bound and unbound states of the M2TM receptor by 19F NMR may provide a system for SAR studies.