Spectroscopic evidence for gas-phase formation of successive beta-turns in a three-residue peptide chain.
We report the first gas-phase spectroscopic study of a three-residue model of a peptide chain, Ac-Phe-Gly-Gly-NH2 (Ac = acetyl), using the IR/UV double resonance technique. The existence of at least five different conformers under supersonic expansion conditions is established, most of them exhibiting rather strong intramolecular H-bonds. One of the most populated conformers, however, exhibits a different H-bonding network characterized by two weak H-bonds. Comparison of the amide A and I/II experimental data with density functional theory calculations carried out on a series of selected conformations enables us to assign this conformer to two successive beta-turns along the peptide chain, the two H-bonds being of C10 type, i.e., each of them closing a 10-atom ring in the molecule. The corresponding form is found to be more stable than the 310 helix secondary structure (not observed), presumably because of specific effects due to the glycine residues.
Chin
Wutharath
W
Laboratoire Francis Perrin (URA CEA CNRS 2453), Service des Photons, Atomes et Molécules, Centre d'Etudes de Saclay, Bât. 522, 91191 Gif-sur-Yvette Cedex, France.
Compagnon
Isabelle
I
Dognon
Jean-Pierre
JP
Canuel
Clélia
C
Piuzzi
François
F
Dimicoli
Iliana
I
von Helden
Gert
G
Meijer
Gerard
G
Mons
Michel
M
D000577:Amides / Q000737:chemistry; D005740:Gases; D006860:Hydrogen Bonding; D009842:Oligopeptides / Q000737:chemistry*; D017433:Protein Structure, Secondary; D011789:Quantum Theory; D013055:Spectrophotometry, Infrared; D013056:Spectrophotometry, Ultraviolet
D000577:Amides; D005740:Gases; D009842:Oligopeptides; C043963:phenylalanyl-glycyl-glycine