Globule to Helix Transition in Sodiated Polyalanines

Jonathan K. Martens (1, 2) , Isabelle Compagnon (3) , Edith Nicol (1) , Terry B. Mcmahon (2) , Carine Clavaguera (1) , Gilles Ohanessian (1)

1 DCMR - Laboratoire des mécanismes réactionnels
2 Department of Chemistry [Waterloo]
3 LASIM - Laboratoire de Spectrométrie Ionique et Moléculaire

The structures of sodiated poly-alanine peptides containing 8-12 residues are investigated using infrared multiple photon dissociation (IRMPD) spectroscopy and classical and quantum modeling. Calculations indicate that the a-helical structure is the most stable conformation for the peptides whatever their size. The IRMPD spectra provide evidence for the coexistence of helical and globular shapes for Ala(8)Na(+), and possibly for Ala(9)Na(+) The turning point from globule to helix is thus found at Ala(8-9)Na(+). The N-H and O-H stretching region allows identifying a new spectroscopic pattern typical for alpha-helical structures of polyalanines.

Domaines: Chimie théorique et/ou physique

Jonathan K. Martens, Isabelle Compagnon, Edith Nicol, Terry B. Mcmahon, Carine Clavaguera, et al.. Globule to Helix Transition in Sodiated Polyalanines. Journal of Physical Chemistry Letters, 2012, 3 (22), pp.3320-3324. ⟨10.1021/jz301326w⟩. ⟨hal-00904399⟩