title: [Study of the spatial structure of des-Gly9-[Arg8]vasopressin by two-dimensional NMR spectroscopy and theoretical conformation analysis].
abstract: 2D 1H-NMR spectra of des-Gly9-[Arg8]vasopressin in dimethylsulfoxide have been taken and the 1H resonances have been assigned. The coupling constants and amide proton temperature coefficients (delta delta/delta T) have been measured and the NOE cross-peaks in the NOESY spectrum have been analyzed. The most essential information on the spatial structure of des-Gly9-[Arg8]vasopressin is extracted from the low delta delta/delta T value for Asn5 amide proton and from the NOE between the Cys1 and Cys6 alpha-protons. A diminished accessibility of the Asn5 NH proton for the solvent is ascribed to the presence of a beta-turn in the fragment 2-5. The distance between the Cys1 and Cys6 C alpha H protons seems to be less than 4 A. These constraints were taken into account in the conformational analysis of the title peptide. The derived set of the low-energy backbone conformations was analyzed against the background of the all available NMR data. The most probable conformation of the cyclic moiety in des-Gly9-[Arg8]vasopressin was found to be the type III beta-turn. The corner positions are occupied by the residues 3, 4, while the residues 1-2 and 5-6 are at the extended sites. Some NMR data indicate that this structure is in a dynamic equilibrium with other minor conformers.
mesh_terms: D000595:Amino Acid Sequence; D001127:Arginine Vasopressin / Q000031:analogs & derivatives*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D011487:Protein Conformation
chemical_list: D001127:Arginine Vasopressin; C015119:argipressin, des-GlyNH2(9)-
vernacular_title: Issledovanie prostranstvennoĭ struktury des-Gly9-[Arg8]vazopressina metodami dvumernoĭ spektroskopii IaMR i teoreticheskogo konformatsionnogo analiza.