Studies of low molecular weight samples of glucuronans with various acetylation degree.

Partially acetylated, high molecular weight glucuronans were produced by a Sinorhizobium meliloti mutant strain. Two native glucuronan samples with various degrees of acetylation were sonicated to obtain lower molecular weight samples and with low viscosity suitable for chemical modification and (13)C NMR experiments. The average degree of substitution (DS) of the polymer was estimated by Fourier transform infrared (FTIR) and NMR. (13)C NMR spectra were obtained and used to suggest a complete assignment of the signals. The nuclear Overhauser effect spectroscopy (NOESY) and heteronuclear multi-bond coherence (HMBC) experiments were used to elucidate connectivities between the various residues and deduce the linkage of these residues within the polysaccharide.