Plant and Algal Polysaccharides

Chromatographic and enzymic studies of the insoluble residues obtained by hydrolysis of various cereal starches with acid have suggested a new model for the structure of waxy maize amylopectin. A review dealing with the mechanism of action of a-amylases has discussed the compositions of the residual oligosaccharides. The results of a study of the catalytic activity of poly(acrylic acid-styrenesulphonic acid) towards amylose in aqueous solution at low pH indicated that interactions between the carboxy-groups of the copolymer and the hydroxy-groups of the substrate make no contribution to the rate of reaction.  

Lavintman, J. Tandecarz, M. Carceller, S. Mendiara, and C. E. Cardini, European J. 

The proposal that transverse sectioning of natural cellulose fibres can be used to test theories on the structure of microfibrils has been examined theoretically. It was concluded that fibre-sectioning experiments described in the literature do not disprove the folded-chain model, and it was suggested that clearly divided sections exist along the axis of the microfibril at intervals of 200 A. This cannot be explained in terms of a fringed micelle model. However, it is possible that cellulose II has a folded-chain conformation, since a single molecule of cellulose can be folded back and forth in the (101) plane to form a sheet-like structure that fits into the unit cell. A cellulose molecule can achieve a sharp U-tum in the 

Watanabe, J. Hayashi, and T. Akahori, J. Polymer ScL, Polymer Chem., 1974,12, 1065. 

Aspects of the structures and of the modes of biosynthesis of starch and glycogen have been reviewed. 

A Naegeli-type amylodextrin of DP 21 and containing one branch-point in each molecule has been prepared from waxy corn starch. The adsorption of monobasic fatty acids from n-hexane on to dry amylose has been found to follow Langmuir s adsorption isotherm. Changes in the physical properties of a potato starch with a high content of phosphate in the presence of cations have been described. Alkali-metal cations produced an increase in the viscosity of solutions of this potato starch, whereas alkaline-earth-metal cations initiated a two-step swelling process and lowered the viscosity. 

D-Glucose and malto-oligosaccharides (DP 9) in starch hydrolysates have been separated by h.p.l.c. Oxidized (sodium hypochlorite) starch has been degraded by the joint actions of amyloglucosidase and a- and 3-amylases. An unidentified, modified trisaccharide, which resisted further enzymic degradation, was isolated. 

Maltotriose, maltotetraose, and higher starch oligosaccharides are taken up by 

Agarose-gel filtration has been used to estimate the molecular-weight distribution of native wheat starch and some oxidation products thereof. Cations bound to the phosphate groups of potato starch have been extracted with mineral acids and then determined by atomic absorption spectroscopy.  

Changes in definition of the i.r. spectra of cellulose and related oligosaccharides with temperature have been attributed to the effect on the superstructure of changes in hydrogen-bonding. The marked effects that changes in temperature P. Meredith and L. D. Jenkins, Starke, 1976, 28, 189. 

The DP of y-irradiated cellulose, as measured by viscometry in cuprammonium solution, has been shown to be lower than that of the untreated cellulose. Irradiation not only induced direct scission of the polysaccharide chains but also the formation of alkali-labile groups, which subsequently underwent scission in the solvent used for viscometry. 

Buleon, H. Chanzy, and E. Roche, J. Polymer ScL, Part A-2, Polymer Phys., 1976,14,1913. J Schurz and K. John, Cellulose Chem. Technol., 1975, 9, 493. 

D-arabinose, and erythrose were also formed. Aldobionic acids through to aldo-octaonic acids composed of D-glucose and end-groups of erythronic, D-arabinonic, or o-gluconic acids comprised an appreciable proportion of the acidic material. 

Two cellulases isolated from culture filtrates of Trichoderma viride caused only a slight decrease in the DP of native cellulose, but a rapid decrease in that of reprecipitated cellulose. Both enzymes have the ability to release free fibres from filter paper. 

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The role of plant and algal polysaccharides as non-cytotoxic antitumour substances has been discussed. ... 

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