UNUSUAL DEXTRANS .4. HIGH-TEMPERATURE ENHANCEMENT OF C-13-NMR CHEMICAL-SHIFTS OF UNUSUAL DEXTRANS, AND CORRELATION WITH METHYLATION STRUCTURAL-ANALYSIS

Dextran fractions from NRRL strains Leuconostoc mesenteroides B-742, B-1299, B-1355, and Streptobacterium dextranicum B-1254 were examined by 13C-n.m.r. spectroscopy at 34 and 90°, and by methylation structural analysis. The native, structurally homogeneous dextran from L. mesenteroides NRRL B-1402 was also examined. The data allow correlations to be made between the structure and physical properties of the S (soluble) and L (less-soluble) fraction pairs of dextrans B-742, B-1254, B-1299, and B-1355. For the dextrans under consideration here, increasing solubility of the dextran (both in water and in aqueous ethanol) was found to correlate with decreasing percentages of α-d-(1→6)-linked d-glucopyranosyl residues. Both the diagnostic nature of the 70-75-p.p.m. spectral region with regard to type of dextran branching, and the increase in resolution of the polysaccharide spectra at higher temperatures, have been further confirmed. © 1979.