Hydroxyl group interactions in polysaccharides: a deuterium-induced differential isotope shift 13C-NMR investigation

The secondary isotope shift in (13)C-nmr spectra in water was used to obtain information on the interactions of hydroxyl groups with their environment in polysaccharides. Specifically, the possibility of detecting the preference of intramolecular hydrogen bonding with respect to solvation was investigated. Different aliphatic alcohols were studied in both protic and aprotic solvents in order to obtain reference systems. The polysaccharides investigated were selected so as to include both different types of glycosidic linkages and different conformational properties of the polymeric chain. In addition to polysaccharides, beta-cyclodextrin and inulin were also investigated. The experiments demonstrated that isotope shift data can advantageously contribute to the understanding of the conformational properties of polysaccharides and in particular, in setting up of constraints in molecular modeling calculations.