Molecular architecture of a galactoglucan from Rhizobium meliloti.

Rhizobium meliloti mutants produce a linear, acidic exopolysaccharide with alternating galactopyranosyl and glucopyranosyl units having (1-->3) linkages. It has a 4,6-O-pyruvic cyclic acetal group on the alpha-galactosyl and 6-O-acetyl ester group on the beta-glucosyl units. X-ray diffraction patterns from polycrystalline and well oriented specimens of its potassium salt indicate that the polymer forms a 2-fold helix of pitch 15.

Roles of potassium ions, acetyl and L-glyceryl groups in native gellan double helix: an X-ray study.

Native gellan, the natural form of the polysaccharide excreted by the bacterium Pseudomonas elodea, has a tetrasaccharide repeating unit that contains L-glycerol and acetate ester groups, and forms only weak and elastic gels. Based on X-ray diffraction data from well oriented and polycrystalline fibers of its potassium salt, the crystal structure of native gellan, including ions and water, has been determined and refined to a final R-value of 0.17.

Structure of methyl 5-phenyl-2-propionyl-3-pyrrolecarboxylate.

C15H15NO3, Mr = 257.4, monoclinic, P2(1)/n, a = 10.070 (2), b = 5.