Sensitive pulse sequences were developed in order to determine geometry dependent 1H and 13C chemical shift anisotropy terms (CSAg) of simple carbohydrates and carbohydrate polymers in solution. The methods are capable of monitoring CSA/DD cross-correlated relaxation for ca. 1 M solutions at natural abundance. Measured spectral densities were quantitatively interpreted for sialic acid and its α-(2→8) linked homopolymer, colominic acid. Although the geometric factors could not be separated from anisotropy terms, this is the first report of CSA data on a carbohydrate polymer, and its values differ substantially from those of monomeric sialic acid. The most pronounced differences were observed at C5, C6, and C7 for both 1H- and 13C-shift anisotropies. The differences may be attributed to conformational changes around the C6/C7 and C7/C8 bonds, and possible changes in hydrogen bonding interactions, and in OH rotamer populations. Application of these combined NMR methods provide a new parameter which may be sensitive to structural changes not detected with conventional NMR techniques.
|Original language||English (US)|
|Number of pages||7|
|Journal||Journal of the American Chemical Society|
|State||Published - Jan 11 1995|
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