H. Tang, P. Belton, S. C. Davies
Feb 15, 2001
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Carbohydrate research
Abstract
Crystalline alpha-D-galacturonic acid monohydrate has been studied by 13C CPMAS NMR and X-ray crystallography. The molecular dynamics were investigated by evaluating 13C spin-lattice relaxation in the rotating frame (T1rho) and chemical-shift-anisotropy properties of each carbon. Only limited molecular motions can be detected in the low frequency (< 10(4) Hz) range by 13C relaxation time measurements (T1rho) and changes of chemical shift anisotropy properties as a function of temperature. X-ray analysis (at both ambient temperature and 150 K) shows that the acid has the usual chair-shaped, pyranose ring conformation, and that the acid and water molecules are linked, through all their O-H groups, in an extensively hydrogen-bonded lattice.