title: Conformational study of two substance P hexapeptides by two-dimensional NMR.
abstract: The conformation of two substance P (SP) related hexapeptides. Glp-Phe-Phe-(L-Pro)-Leu-Met.NH2 (I) and Glp-Phe-Phe-(D-Pro)-Leu-Met.NH2 (II), in two solvents, chloroform-d and trifluoroethanol(TFE)-d3/H2O, was studied by two-dimensional NMR methods, including COSY, TOCSY, ROESY and HMQC. The study shows that these two peptides exist predominantly in the extended form in TFE/H2O, but in general exhibit a reverse-turn structure in chloroform. I is clearly less ordered than II in both solvents. Furthermore, extensive Phe3-Pro4 cis<==>trans isomerization was found in I but not in II. The differences in the conformational behavior of these two peptides, which are selective agonists for neurokinin NK1 and NK2 receptors, respectively, are discussed.
authors.affiliation: Department of Chemistry, University of Missouri, Columbia.
authors.forename: T C
authors.initials: TC
authors.lastname: Wong
authors.forename: C M
authors.initials: CM
authors.lastname: Lee
authors.forename: W
authors.initials: W
authors.lastname: Guo
authors.forename: D K
authors.initials: DK
authors.lastname: Chang
mesh_terms: D000595:Amino Acid Sequence; D002725:Chloroform; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry*; D011487:Protein Conformation; D017510:Protein Folding; D011761:Pyrrolidonecarboxylic Acid / Q000031:analogs & derivatives; D012997:Solvents; D013237:Stereoisomerism; D013373:Substance P / Q000031:analogs & derivatives* / Q000737:chemistry; D014270:Trifluoroethanol; D014867:Water
chemical_list: D010446:Peptide Fragments; D012997:Solvents; D014867:Water; D013373:Substance P; D014270:Trifluoroethanol; C054725:septide; D002725:Chloroform; D011761:Pyrrolidonecarboxylic Acid