title: Left-handed helical preference in an achiral peptide chain is induced by an L-amino acid in an N-terminal type II β-turn.
abstract: Oligomers of the achiral amino acid Aib adopt helical conformations in which the screw-sense may be controlled by a single N-terminal residue. Using crystallographic and NMR techniques, we show that the left- or right-handed sense of helical induction arises from the nature of the β-turn at the N terminus: the tertiary amino acid L-Val induces a left-handed type II β-turn in both the solid state and in solution, while the corresponding quaternary amino acid L-α-methylvaline induces a right-handed type III β-turn.
authors: School of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, UK.
authors: Matteo
authors: M
authors: De Poli
authors: Marta
authors: M
authors: De Zotti
authors: James
authors: J
authors: Raftery
authors: Juan A
authors: JA
authors: Aguilar
authors: Gareth A
authors: GA
authors: Morris
authors: Jonathan
authors: J
authors: Clayden
mesh_terms: D000596:Amino Acids / Q000737:chemistry*; D000621:Aminoisobutyric Acids / Q000737:chemistry*; D002942:Circular Dichroism; D018360:Crystallography, X-Ray; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D009842:Oligopeptides / Q000737:chemistry; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D013237:Stereoisomerism; D014633:Valine / Q000737:chemistry*
chemical_list: D000596:Amino Acids; D000621:Aminoisobutyric Acids; D009842:Oligopeptides; C100049:2-aminoisobutyric acid; D014633:Valine