title: Structure effects of double D-amino acid replacements: a nuclear magnetic resonance and circular dichroism study using amphipathic model helices.
abstract: D-Amino acid replacements and the determination of resulting structural changes are a useful tool to recognize amphipathic helices in biologically active peptides such as neuropeptide Y and corticotropin-releasing factor. In this paper the secondary structures of one amphipathic alpha-helical peptide and its double D-amino acid analog have been determined by means of 1H NMR and CD spectroscopies under equivalent conditions. The chemical shifts (NH and C alpha H) and the analysis of nuclear Overhauser effects show a split of the continuous helix for the all-L peptide into two helices at the position of double D-amino acid replacement. Hydrogen exchange rates correlate with water accessibilities in the hydrophobic/hydrophilic face and confirm the amphipathic helical structure in the all-L peptide as well as in its double D-amino acid analog. A significantly accelerated hydrogen isotope exchange rate is observed for the D-Ala9 backbone proton, implying an increased flexibility at that position. These results show that the incorporation of an adjacent pair of D-amino acids only causes a local change in structure and flexibility, which makes the double D replacement interesting as a tool for specific helix-disturbing modifications to search for helical conformations in biologically active peptides.
authors.affiliation: Institute of Molecular Pharmacology, Berlin, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Rothemund
authors.forename: M
authors.initials: M
authors.lastname: Beyermann
authors.forename: E
authors.initials: E
authors.lastname: Krause
authors.forename: G
authors.initials: G
authors.lastname: Krause
authors.forename: M
authors.initials: M
authors.lastname: Bienert
authors.forename: R S
authors.initials: RS
authors.lastname: Hodges
authors.forename: B D
authors.initials: BD
authors.lastname: Sykes
authors.forename: F D
authors.initials: FD
authors.lastname: Sönnichsen
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry*; D002942:Circular Dichroism; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013237:Stereoisomerism; D013329:Structure-Activity Relationship
chemical_list: D000596:Amino Acids; D010455:Peptides