title: Nuclear magnetic resonance studies of thyrotropin-releasing hormone (TRH) and analogues incorporating D-histidine and 4-hydroxy-L-proline.
abstract: NMR studies have been used to examine conformational effects in thyrotropin-releasing hormone (TRH), the epimer incorporating D-His, and their analogues where trans- and cis-4-hydroxy-L-proline replace L-proline (Pro). In all six compounds the observed overall conformation of the major conformer around the Pro-His amide bond, and the observed increase of the cis/trans ratio between the conformers when L-His is replaced by D-His, can be accommodated by assuming that a ten-membered ring is formed by hydrogen bonding between the N-H of the Pro carboxamide function and the N pi-atom of the His imidazole nucleus.
authors.affiliation: Department of Chemistry, University of Bergen, Norway.
authors.forename: D W
authors.initials: DW
authors.lastname: Aksnes
authors.forename: C
authors.initials: C
authors.lastname: Athanassopoulos
authors.forename: V
authors.initials: V
authors.lastname: Magafa
authors.forename: A
authors.initials: A
authors.lastname: Aaberg
authors.forename: G W
authors.initials: GW
authors.lastname: Francis
authors.forename: D
authors.initials: D
authors.lastname: Papaioannou
mesh_terms: D000595:Amino Acid Sequence; D006639:Histidine; D006909:Hydroxyproline; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D011487:Protein Conformation; D013973:Thyrotropin-Releasing Hormone / Q000737:chemistry*
chemical_list: D006639:Histidine; D013973:Thyrotropin-Releasing Hormone; D006909:Hydroxyproline