title: Cis/trans conformational equilibrium across the N-methylphenylalanine- N-methylphenylalanine peptide bond of arginine vasopressin analogs.
abstract: Two cyclic analogs of vasopressin, -Pro-Arg-Gly-NH(2) (1) and -Pro-Arg-Gly-NH(2) (2) were synthesized by the solid phase method. Their structure was determined in aqueous solution by two-dimensional NMR techniques and simulated annealing algorithm from an extended template in X-PLOR. The total chemical shift correlation spectroscopy and rotating-frame Overhauser enhancement spectroscopy of the peptides displayed four distinct sets of residual proton resonances. This suggests that both analogs adopt four families of conformations in H(2)O/D(2)O (9 : 1) (one major and three minor species). In further analysis only signals of major species (M) and of one minor species (m(1)) were considered. The major species of both peptides include a trans peptide bond between the first and second residue, and a cis form between the second and third residue. In the minor species, all peptide bonds were found to exist in trans geometry.
authors.affiliation: Faculty of Chemistry, University of Gdańsk, Sobieskiego 18, 80-952, Gdańsk, Poland. milka@chemik.chem.univ.gda.pl
authors.forename: E
authors.initials: E
authors.lastname: Trzepałka
authors.forename: W
authors.initials: W
authors.lastname: Kowalczyk
authors.forename: B
authors.initials: B
authors.lastname: Lammek
mesh_terms: D001127:Arginine Vasopressin / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry*; D006860:Hydrogen Bonding; D007536:Isomerism; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D010456:Peptides, Cyclic / Q000138:chemical synthesis / Q000737:chemistry*; D010649:Phenylalanine / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: D010456:Peptides, Cyclic; D001127:Arginine Vasopressin; C034515:phenylalanine methyl ester; D010649:Phenylalanine