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Synthesis and Conformational Characterisation of Hexameric β‐Peptide Foldamers by Using Double POAC Spin Labelling and cw‐EPR
Author(s) -
Wright Karen,
Wakselman Michel,
Mazaleyrat JeanPaul,
Franco Lorenzo,
Toffoletti Antonio,
Formaggio Fernando,
Toniolo Claudio
Publication year - 2010
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201000821
Subject(s) - chemistry , electron paramagnetic resonance , nitroxide mediated radical polymerization , peptide , site directed spin labeling , helix (gastropod) , stereochemistry , carboxylic acid , crystallography , amino acid residue , peptide sequence , nuclear magnetic resonance , organic chemistry , monomer , biochemistry , polymer , ecology , physics , radical polymerization , biology , snail , gene
A selected set of terminally protected β‐hexapeptides, each containing two nitroxide‐based (3 R ,4 R )‐4‐amino‐1‐oxyl‐2,2,5,5‐tetramethylpyrrolidine‐3‐carboxylic acid (POAC) residues combined with four (1 S ,2 S )‐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.