ISOLATION & HOMOGENEITY OF PLANT CELL WALL PECTIC POLYSACCHARIDES

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The long-term goal of the research is to determine the structure, mode of attachment in the cell wall and pathway(s) of biosynthesis of the pectic polysaccharides of cell walls of representative higher plants, and use this information to develop plant varieties with altered pectic polysaccharide content that have improved characteristics in physiological processes of agricultural importance. Pectic polysaccharides will be purified through DEAE column chromatography. The pectic polysaccharide peaks from each column will be detected colorimetrically and will be tested for homogeneity by determining the Mw, glycosyl residue composition and degree of methyl esterfication of the pectic polysaccharide in individual fractions from the DEAE chromatography and comparing these properties across column fractions. The pectic polysaccharides from the above five plants and from Lemna minor (duckweed) that are not homogeneous will be further purified by other types of ion exchange chromatography and by size exclusion chromatography. The polysaccharide fractions that are homogeneous with respect to sugar composition and degree of methyl esterfication will be subjected to methylation analysis and to cleavage by specific enzymes. GC-MS has been used to confirm the identity of the alditol acetate derivatives of sugars and to determine the degree of methyl esterification and ratio of galactose to galacturonic acid.