The fusion domain of the influenza coat protein hemagglutinin HA2, bound to dodecyl phosphocholine micelles, was recently shown to adopt a structure consisting of two antiparallel alpha-helices, packed in an exceptionally tight hairpin configuration. Four interhelical H-alpha to C=O aliphatic H-bonds were identified as factors stabilizing this fold. Here, we report evidence for an additional stabilizing force: a strong charge-dipole interaction between the N-terminal Gly(1) amino group and the dipole moment of helix 2. pH titration of the amino-terminal N-15 resonance, using a methylene-TROSY-based 3D NMR experiment, and observation of Gly(1) C-13' show a strongly elevated pK = 8.8, considerably higher than expected for an N-terminal amino group in a lipophilic environment Chemical shifts of three C-terminal carbonyl carbons of helix 2 titrate with the protonation state of Gly(1)-N, indicative of a dose proximity between the N-terminal amino group and the axis of helix 2, providing an optimal charge-dipole stabilization of the antiparallel hairpin fold, pK values of the side-chain carboxylate groups of Glu(11) and Asp(19) are higher by about 1 and 0.5 unit, respectively, than commonly seen for solvent-exposed side chains in water-soluble proteins, indicative of dielectric constants of epsilon = similar to 30 (Glu(11)) and similar to 60 (Asp(19)), placing these groups in the headgroup region of the phospholipid micelle.