2-DIMENSIONAL H-1-NMR EXPERIMENTS SHOW THAT THE 23-RESIDUE MAGAININ ANTIBIOTIC PEPTIDE IS AN ALPHA-HELIX IN DODECYLPHOSPHOCHOLINE MICELLES,SODIUM DODECYL-SULFATE MICELLES, AND TRIFLUOROETHANOL WATER SOLUTION/

Magainin2 is a 23-residue antibiotic peptide that disrupts the ionic g radient across certain cell membranes. Two-dimensional H-1 NMR spectro scopy was used to investigate the structure of the peptide in three of the membrane environments most commonly employed in biophysical studi es. Sequence-specific resonance assignments were determined for the pe ptide in perdeuterated dodecylphosphocholine (DPC) and sodium dodecyls ulfate micelles and confirmed for the peptide in 2,2,2-trifluoroethano l solution. The secondary structure is shown to be helical in all of t he solvent systems. The NMR data were used as a set of restraints for a simulated annealing protocol that generated a family of three-dimens ional structures of the peptide in DPC micelles, which superimposed be st between residues 4 and 20. For these residues, the mean pairwise rm s difference for the backbone atoms is 0.47 +/- 0.10 Angstrom from the average structure. The calculated peptide structures appear to be cur ved, with the bend centered at residues Phe(12) and Gly(13).