Amylose and Other a-D-Linked Polysaccharides

In contrast to the fibrous and well-oriented polysaccharides (such as cellulose and chitin), amylose in its natural state is found only in more-or-less spherical starch granules. Amylose is the minor constituent of most starches, and is a linear polymer of a-D-(l— 4)-linked D-glucose residues. The birefringence of starch grains was already well known at the turn of the century, and the cross of isocline pattern between crossed Nicols was interpreted in terms of radially arranged crystallites. Later, 

Unit-cell Size, in A., for Guar Galactomannan at Different Contents of Moisture 

When starch is fractionated into its two components, usually by precipitating the amylose from solution by means of an organic solvent (such as an alcohol), a third type of structure is found this survives drying, and ultimately reverts to the B structure upon rehydration. This structure has been termed the V form, and it yields an x-ray pattern that is distinctly different from the other two types. Essentially the same pattern was observed for the amylose-iodine complex. Bundle and coworkers studied the various V amyloses obtained by complexing with alcohols or iodine, and, on the basis of powder diagrams, suggested unit-cell parameters for both the wet and dry (hydrated and anhydrous) states, as shown in Table I (seep. 422). From these data, Bear had suggested earlier that the V structure of amylose is helical. (Historically, it is of 

Other than the early studies on the determination of unit-cell parameters, little work has been done on the determination of structure of the different crystal forms of amylose. The major reason for this is the nature of the material itself namely, its powdery character. Following additional developments in the preparation of amylose, the discovery of its film-forming ability, and the synthesis of film-forming derivatives of amylose (such as the triacetate), some new structural studies were attempted, on which some comments will now be made. 

In a subsequent study by Kreger, a micro-diffraction technique was 

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