title: Structure of an isolated gramicidin A double helical species by high-resolution nuclear magnetic resonance.
abstract: A conformational species of gramicidin A has been isolated in dioxane by high pressure liquid chromatography and characterized by circular dichroism and two-dimensional proton nuclear magnetic resonance. Double-quantum filtered two-dimensional correlation spectroscopy, two-dimensional homonuclear Hartman Hahn spectroscopy and two-dimensional nuclear Overhauser effect spectra at 500 MHz were used to obtain virtually complete proton assignments and produce 192 distance constraints. Protocols to determine the state of aggregation, monomer-specific assignment of nuclear Overhauser enhancement values, hydrogen bonding pattern and helix handedness are described. A distance geometry/simulated annealing routine was used to generate well-defined backbone and side-chain structures. The species isolated is a right-handed intertwined double helix, with approximately 5.7 residues per turn. Unique values for helical dimensions are also specified.
authors.affiliation: Institute of Molecular Biophysics, Florida State University, Tallahassee.
authors.forename: S M
authors.initials: SM
authors.lastname: Pascal
authors.forename: T A
authors.initials: TA
authors.lastname: Cross
mesh_terms: D000595:Amino Acid Sequence; D002942:Circular Dichroism; D004146:Dioxanes; D006096:Gramicidin / Q000737:chemistry* / Q000302:isolation & purification; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D012997:Solvents
chemical_list: D004146:Dioxanes; D012997:Solvents; D006096:Gramicidin; C025223:1,4-dioxane