Nigeran chain

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 with a DP of 300-350 is also soluble in hot water but is insoluble in cold water. The irregularities in the chain produced by combining 1 4 and 1 - 3 linkages is expected to reduce intermolecular fit... 

The "dry" and "hydrate" forms of nigeran correspond to specific crystallographic states with and without water of hydration in the crystal lattice, respectively.(13,14) X-ray and electron diffraction studies have established the unit cell and chain conformation of these two polymorphs.(13,14)... 

Figure 5. Schematic of chain organization in lamellar single crystals. The chain folds are shown as regular with adjacent reentry although larger loops at the folds are also a possibility. Based on the known degree of polymerization of the nigeran (ca. 1000—2000 anhydroglu-cose units), the chain orientation in the crystals and crystals dimensions, chain folding must occur (14).

Figure 11. Conformation of a single chain of nigeran in the dry state. It is a two-fold helix with an advance per monomer of 7.31 A (71).

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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