Dynamic nuclear polarization / solid-state NMR of membrane polypeptides. Free radical optimization for matrix-free lipid bilayer samples.

Fiche publication

Date publication

août 2017

Journal

Chemphyschem : a European journal of chemical physics and physical chemistry

Auteurs

Membres identifiés du Cancéropôle Est :
Pr BECHINGER Burkhard

Tous les auteurs :
Ouari O, Salnikov ES, Abel S, Karthikeyan G, Karoui H, Aussenac F, Tordo P, Bechinger B

Lien Pubmed

https://www.ncbi.nlm.nih.gov/pubmed/28574169

Résumé

Dynamic Nuclear Polarization boosts the sensitivity of NMR spectroscopy by orders of magnitude making possible investigations previously out of scope. For MAS solid-state NMR studies the samples are typically mixed with biradicals dissolved in glass forming solvent and investigated at 100K. Here we present new biradical polarizing agents developed for matrix-free samples such as supported lipid bilayers, which are systems widely used for the investigation of membrane proteins of high biomedical importance. A series of 11 biradicals with different structure, geometry and physico-chemical properties was comprehensively tested for DNP performance in lipid bilayers, some of them developed specifically for membranes investigations. The membrane-anchored biradicals PyPol-C16, AMUPOL-cholesterol and bTurea-C16 exhibit improved g-tensor alignment, inter-radical distance and dispersion, and the highest signal enhancement factors so far obtained for matrix-free membranes or other matrix-free samples, potentially shortening NMR acquisition times by three orders of magnitude. Furthermore, optimal biradical-to-lipid ratio, sample deuteration and membrane lipid composition were determined under static and MAS conditions. In order to better rationalize biradical performance DNP enhancement was measured using the 13C and 15N signals of lipids and peptide, as a function of biradical concentration, DNP build-up time, resonance line width, quenching effect, microwave power and MAS frequency.