Monosaccharide composition modifications

In the present study we used transgenic plants to analyse the amount of control exerted by an additional vacuolar invertase on the allocation of carbohydrates to the plant cell wall. Since physical parameters indicated a significant modification in the thermodynamic state of these invertase plants, the monosaccharide composition, the pore size and the amount of free and bound acids present in the cell wall were measured. 

Carbohydrates exhibit enormous diversity because of variation in monosaccharide composition, glycosidic linkage positions, and chain branching [17], Further diversity is achieved by covalent modification of carbohydrates via acetylation, methyl-ation, phosphorylation, and sulfation [1]. Sulfation can be incorporated into the carbohydrates of glycolipids and glycoproteins. Modifications of both A-linked and 0-linked chains are found. 

Modifications of the amino-acid composition of pseudomurein could be induced by addition of glycine, threonine, ornithine, or aspartic acid in elevated concentrations to the culture medium [21]. The isolated sacculi from several species also contain varying amounts of monosaccharides (Table 2). They could be extracted with hot formamide, indicating that they belong to polysaccharides associated with but not covalently bound to pseudomurein. Teichoic acid or teichuronic acid-like polymers are, however, not present in gram-positive methanogens. 

It is the heteropoiysaccharides of plants that bestow cellulosic composites with the ability to absorb impact, the ability to absorb moisture, and the ability to create pores in the form of free volume in amorphous (disordered or para-crystalline) materials [58,59]. Modification by reducing molecular regularity has the additional benefit of creating a transition from a focus on mechanical (structural) functions to an emphasis on energy storage and gel formation. Reduction in order translates into ease of hydrolysis, enzyme accessibility, rate of nutrient release for decay organisms, water absorption and swelling. Reduction in order is achieved by the introduction of monosaccharide units, and of bond types, which differ from those of cellulose. The principal monosaccharides involved in the heteropoiysaccharides of plants are shown in O Fig. 12. 

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