Nigeran crystallinity

With the exception of cellulose and chitin, plant polysaccharides are usually hydrated. Hydration often occurs in the crystalline regions as well as in the amorphous areas. When water of hydration is found in the crystallites, it may or may not affect the conformation of the polysaccharide backbone and in most cases, it affects the unit-cell dimensions, while in a few cases, the water appears to have no effect on unit-cell dimensions. The structures of six hydrated neutral polysaccharides will be examined with regards to the state of water of hydration in the structure. It wi 11 be seen that water may occur as columns or as sheets in these structures. The structures that will be discussed are (1 4)-3-p-xylan, nigeran, amylose, galactomannan, (1 3)-3-p-gTucan and (1 3)-s-P-xy1 an. The chemical structures of these polysaccharides are shown in Figure 1. 

Studies on the Synthesis, Organization, and Conformation of Crystalline Nigeran in Hyphal Walls... 

This fact is confirmed by the kinetics of enzymatic hydrolysis of the complex at 20°C which are intermediate in rate between the "quench precipitate" and that of a lamellar crystalline preparation of pure nigeran (Table III). SDS polyacrylamide gel electrophoresis of the solubilized protein fraction indicates it is composed of four components. The major one constituting probably 80% or more of the staining material has an apparent molecular weight of approximately 12,000 the 3 minor species present have molecular weights of 16,000 ... 

Nigeran extracted with hot water represents about 5% of the wall s dry weight(, ) but studies by Bobbitt et. (3), have shown that this treatment fails to extract all the nigeran. They conclude that nigeran chains occupy at least three distinct domains in the hyphal wall and that the polymer s organization in situ is highly crystalline. While it cannot be ruled out that a certain proportion of non-crystalline nigeran may be present in the wall, all three domains contain the crystalline polymer. The first fraction is directly... 

Nigeran is a space filling polysaccharide since it is not a suitable structural material due to its warm-water solubility. Although its role is now known, its high level of crystallinity at room temperature could confer a protective property especially when it is the outer layer of the cel 1.(70)... 

D-glucan and D-galactans than those of the parent strain. Examination of the cell walls of A. niger and A. awamori by X-ray methods, electron microscopy, and enzymic techniques showed that chains of nigeran occupy, at least, three domains or configurations in the hyphal walls and that they form a highly crystalline arrangement in situ. ... 

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