title: Oligo(4-aminopiperidine-4-carboxylic acid): an unusual basic oligopeptide with an acid-induced helical conformation.
abstract: In sharp contrast with helical polypeptides carrying basic side chains, Api(8), a basic oligopeptide containing the non-natural achiral amino acid 4-aminopiperidine-4-carboxylic acid (Api), adopts a helical conformation only in acidic media. Alkaline titration of a protonated Api(8) oligomer appended with a leucine derivative at its N-terminus showed that disruption of its helical conformation occurs in a pH range of 7-10. NMR studies indicated that the piperidine groups in Api(8), when nonprotonated, possibly interact with the proximal amide protons in the peptide backbone and hamper the formation of the H-bonding network responsible for the helical conformation. The helical structure is induced not only by protonation but also by acylation of the piperidine groups.
authors.affiliation: Department of Chemistry and Biotechnology, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Joon-il
authors.initials: JI
authors.lastname: Cho
authors.forename: Masahiro
authors.initials: M
authors.lastname: Tanaka
authors.forename: Sota
authors.initials: S
authors.lastname: Sato
authors.forename: Kazushi
authors.initials: K
authors.lastname: Kinbara
authors.forename: Takuzo
authors.initials: T
authors.lastname: Aida
mesh_terms: D009682:Magnetic Resonance Spectroscopy; D009842:Oligopeptides / Q000737:chemistry*; D010880:Piperidines / Q000737:chemistry*; D011487:Protein Conformation
chemical_list: C481395:4-aminopiperidine; D009842:Oligopeptides; D010880:Piperidines