title: The role of an L-leucine residue on the conformations of glycyl-L-leucine oligomers and its N- or C-terminal dependence: infrared absorption and Raman scattering studies.
abstract: The conformations of glycyl-L-leucine oligomers (GnL, residue number n = 3, 4, and 5) in the solid state were found to be similar to that of a polyglycine II (PGII). However, for L-leucyl-glycine oligomers (LGn; n = 3, 4, 5) in the solid state, LG3 and LG4 have already been confirmed to take a reverse-turn structure (LG3-type reverse-turn) while LG5 adopts a PGII-type helix. The present results provide evidence that the conformations of L-leucine-containing glycine oligomers depend strongly upon whether the L-leucine residue is placed in the N- or C-terminal position. For the aqueous G3L and G4L samples, we assumed that reverse-turn structures similar to the type II β-turn, rather than the LG3-type reverse-turn, are stabilized in concentrated solution, probably as the result of aggregation. Models to explain the mechanism of these phenomena are presented.
authors.affiliation: Department of Applied Chemistry, Nagoya Institute of Technology, Gokiso, Showa-ku, Nagoya, 466-8555, Japan. fwiw4348@mb.infoweb.ne.jp.
authors.forename: Hiro-Fumi
authors.initials: HF
authors.lastname: Okabayashi
authors.affiliation: Department of Applied Chemistry, Nagoya Institute of Technology, Gokiso, Showa-ku, Nagoya, 466-8555, Japan.
authors.forename: Hide-Hiro
authors.initials: HH
authors.lastname: Kanbe
authors.affiliation: Department of Chemistry, The University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand.
authors.forename: Charmian J
authors.initials: CJ
authors.lastname: O'Connor
mesh_terms: D065638:Absorption, Radiation; D005998:Glycine / Q000031:analogs & derivatives / Q000737:chemistry*; D007259:Infrared Rays; D007930:Leucine / Q000031:analogs & derivatives / Q000737:chemistry*; D009842:Oligopeptides / Q000737:chemistry*; D013059:Spectrum Analysis, Raman
chemical_list: D009842:Oligopeptides; D007930:Leucine; D005998:Glycine
keywords: Glycyl-L-leucine oligomers; Helical structure; L-leucine; LG3-type reverse-turn; N- or C-terminal-dependence