  The aim of this article is to assess the ability of chemical shift surfaces
to provide structural information on conformational distributions of
disaccharides in glassy solid state. The validity of the general method leading
to a simulation of inhomogeneous 13C 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 CPMAS spectra. Provided that these basic requirements are
met, DFT/GIAO chemical shift maps calculated on relaxed conformations lead to a
very satisfactory description of the experimental lineshapes. On solid-state
trehalose as a model of amorphous disaccharide, this simulation approach
defines unambiguously the most populated sugar conformation in the glass, and
can help in discriminating the validity of different models of intramolecular
energy landscape. Application to other molecular systems with broad
conformational populations is foreseen to produce a larger dependence of the
calculated chemical shift distribution on the conformational map.

Materials Science