Amylopectin molecular weight

Our initial objective was to evaluate the amylose component of different genetic varieties of starch. The exclusion volume of the particular column system was selected to end at 13 to 14 minutes the early peak in the chromatogram is actually excluded material. This peak represents higher molecular weight materials and probably contains amylopectin Molecular weight approximations were limited to the highest pullulan molecular weight of 853 000 at a retention time of about 18 minutes. 

Some of the true solution properties of starch appear to be related to the molecular weight of the amylose or amylopectin fractions. For example, the viscosity of jelly gums probably depends on the amylopectin molecular weight. The literature has tended to show increased... 

Cellulose is a high molecular weight polymer of D-glucose with fi( 1 -4)-glycosidic bonds, found in plant fibres it is the major component of most plant tissues. Starch is another common polysaccharide, containing two polymers of glucose, amylose and amylopectin. It was used in some paint preparations and in the production of paper. Acid treatment of starch produces dextrins, which are used as adhesives and additives in water colour paintings. 

The labile nature of the components necessitates that, for fundamental investigations, the starch should preferably be extracted from its botanical source, in the laboratory, under the mildest possible conditions.26 Industrial samples of unknown origin and treatment should not be used. The characterization of the starch would appear to entail (1) dissolution of the granule without degradation, (2) fractionation without degradation, (3) complete analysis of the finer details of structure of the separated components (including the possibilities of intermediate structures between the extremes of amylose and amylopectin), and (4) the estimation of the size, shape, and molecular-weight distribution of these fractions. 

The Results of Molecular-Weight Determinations on Amylopectin and its Derivaiives... 

Further measurements appear necessary before the molecular weights of the amylopectin component of starches can be adequately characterized, and it may well be that light-scattering is the only method which can be satisfactorily applied to these polysaccharides of very high molecular weight. Certainly, it is the only method which enables studies of very dilute solutions to be made with high accuracy, particularly in the case of aqueous solutions. 

These synthetic linear and branched molecules may be important as type polymers, particularly if the interconversion of amylose to amylopectin is intramolecular, in which case the initial molecular weight and molecular-weight distribution would be retained. There is the possibility that the in vitro synthesis may even result in a truly three-dimensional structure, as distinct from that of the natural component. 

Amylose has a lower molecular weight than amylopectin but forms linear chains while amylopectin has a higher molecular weight but forms more compact molecules. While both molecules have a structure mainly based on a-(l - 4)-D-glucose units, the amylopectin structure is branched at the a-(l - 6)-D-glucose units. 

In comparison with a pullulanase, the purified amylopullulanase displayed 3-fold higher specificity towards soluble starch and amylopectin and 7-fold higher specificity towards glycogen (12). The amylopullulanase hydrolyzed various high molecular weight starch substrates (Table II). Even the mammalian glycogen which... 

Glycogen, animal starch, is similar to amylopectin, but it features more branching and tends to have a higher molecular weight. Glycogen occurs in the liver and muscle tissue. It interacts with iodine to produce a red color. 

Most potato starches are composed of a mixture of two polysaccharides, a linear fraction, amylose, and a highly branched fraction, amylopectin. The content of amylose is between 15 and 25% for most starches. The ratio of amylose to amylopectin varies from one starch to another. The two polysaccharides are homoglucans with only two types of chain linkage, a-(l 4) in the main chain and a-(l 6)-linked branch chains. Physicochemical properties of potato and its starch are believed to be influenced by amylose and amylopectin content, molecular weight, and molecular weight distribution, chain length and its distribution, and phosphorus content (Jane and Chen, 1992). 

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