Synthesis and conformational characterisation of hexameric β-peptide foldamers by using double POAC spin labelling and cw-EPR.
A selected set of terminally protected β-hexapeptides, each containing two nitroxide-based (3R,4R)-4-amino-1-oxyl-2,2,5,5-tetramethylpyrrolidine-3-carboxylic acid (POAC) residues combined with four (1S,2S)-2-aminocyclopentane-1-carboxylic acid (ACPC) residues, was synthesised by using solution methods and was fully characterised. The two POAC residues are separated in the sequences by different numbers of intervening ACPC residues. The conformational features of the doubly spin-labelled β-hexapeptides were examined in chloroform by FTIR absorption and continuous-wave electron paramagnetic resonance spectroscopic techniques. In particular, the biradical exchange coupling (J) between two POAC residues within each peptide indicates unambiguously that the secondary structure overwhelmingly adopted is the 12-helix. Taken together, these results support the view that POAC is an excellent β-amino acid for exploring this type of helical conformation in doubly labelled β-peptides.
Wright
Karen
K
ILV, UMR CNRS 8180, University of Versailles, 78035 Versailles, France. wright@chimie.uvsq.fr
Wakselman
Michel
M
Mazaleyrat
Jean-Paul
JP
Franco
Lorenzo
L
Toffoletti
Antonio
A
Formaggio
Fernando
F
Toniolo
Claudio
C
D003517:Cyclopentanes / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D008968:Molecular Conformation; D009842:Oligopeptides / Q000138:chemical synthesis* / Q000737:chemistry; D010455:Peptides / Q000138:chemical synthesis* / Q000737:chemistry; D011487:Protein Conformation; D011759:Pyrrolidines / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013113:Spin Labels / Q000138:chemical synthesis*
C554503:(1S,2S)-2-aminocyclopentane-1-carboxylic acid; C554502:(3R,4R)-4-amino-1-oxyl-2,2,5,5-tetramethylpyrrolidine-3-carboxylic acid; D003517:Cyclopentanes; D009842:Oligopeptides; D010455:Peptides; D011759:Pyrrolidines; D013113:Spin Labels