Exploring conformational energy landscape of glassy disaccharides by cross polarization magic angle spinning 13C NMR and numerical simulations. I. Methodological aspects.
This article demonstrates the ability of chemical shift surfaces to provide information on distributions of various conformations of disaccharides in the glassy, solid state. The validity of the general method leading to a simulation of inhomogeneous (13)C chemical shift distributions is discussed in detail. In particular, a proper consideration of extrema and saddle points of the chemical shift map correctly accounts for the observed discontinuities in the experimental cross polarization magic angle spinning spectra. Provided that these basic requirements are met, density functional theory/gauge-independent atomic orbital chemical shift maps calculated on relaxed conformations lead to a very satisfactory description of the experimental line shapes. Using amorphous trehalose as a model disaccharide, the simulation unambiguously defines the range of most populated conformations in the glass.
Lefort
Ronan
R
Groupe Matière Condensée et Matériaux, Université de Rennes 1, Campus de Beaulieu, F-35042 Rennes Cedex, France.
Bordat
Patrice
P
Cesaro
Attilio
A
Descamps
Marc
M
D002250:Carbon Radioisotopes; D003198:Computer Simulation; D004187:Disaccharides / Q000737:chemistry*; D004735:Energy Transfer; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D044367:Phase Transition; D013113:Spin Labels
D002250:Carbon Radioisotopes; D004187:Disaccharides; D013113:Spin Labels