Studies on the skeletal cell wall of the cystocarpic stage of the red seaweed Iridaeaundulosa B. : Part II. Fractionation of the cell wall and methylation analysis of the inner core-fibrillar polysaccharides

Abstract

In order to determine the structure of the fibrillar cell wall, the material isolated from cystocarpic thalli of the red seaweed Iridaea undulosa was fractionated using different media. While classical methods produced a scarce solubilization of material, the use of lithium salts in polar aprotic solvents (dimethylsulfoxide or N, N-dimethylacetamide), had successfully extracted higher amounts of material. The final residue from the Li +/DMSO extraction contains cellulose and a mannan, while that from the Li +/DMAc extraction contains only cellulose and traces of a galactan. Methylation analyses of both residues confirm the presence of those polysaccharides, and shows that the mannan is (1→4)-linked. Treatment with proteases suggests that the protein is efficiently shielded from digestion. All the extracts and residues contain major amounts of (glyco)proteins and/or proteins, in agreement with a previous suggestion that they are of major importance in the structure of the cell wall.