Molecular structures of gum exudates from Hakea species.

Partial acid-hydrolysis of the gum exudates from Hakea sericea and H. gibbosa yields L-arabinose, D-galactose, D-xylose, D-mannose, D-glucuronic acid, the aldobiouronic acid GlcA (beta 1,2)Man, and a dimer of this acid alpha-linked from D-Man to O-4 of GlcA. Methylation analysis showed the modes of linkage of the sugar units to be typical of those present in plant polysaccharide exudates of the arabinogalactan type, while partial acid hydrolysis and Smith degradations established the position of linkage of the peripheral sugar assemblies at O-3 of D-Man in the interior core. Some minor differences were noted between the molecular structures of the gums from these two species of Hakea, the Gal:Ara ratio being higher for H. sericea gum.

The molecular structure of the capsular polysaccharide from Klebsiella type 27.

The capsular polysaccharide of Klebsiella serotype K27 had been investigated by techniques involving methylation analysis, autohydrolysis, and graded hydrolysis with acid. The anomeric configurations of the sugar constituents were determined, where possible, on the basis of p.m.r. spectroscopy and optical rotation data. The results of these studies are consistent with a primary structure in which the repeating-unit is the doubly branched hexasaccharide.