Amylose, periodate oxidation

Table I shows the results of periodate oxidation and methylation applied to amylopectins from various sources. If the percentage of amylose in a whole starch is known, the length of unit chain of the amylopectin component can be calculated from the results of periodate oxidation of the whole starch (see Table II). The length of unit chain appears to depend on the botanical species, but not the variety, from which the starch wras isolated. In the case of tapioca and corn amylopectins, sub-fractionation of these by precipitation with methanol, followed by periodate oxidation, showed the sub-fractions had the same degree of branching as the original amylopectins.71 The action of periodate on whole starches and amylopectins is now so well established and accurate, that it may well completely supersede the methylation technique for pure starches, in view of its many advantages.

Starch source Amylose, % Average (a) by metky-lation length of t b) by Periodate oxidation tnit chain (c) calc, for amylopectin from (6) References... 

Periodate oxidation has also been applied to this component.7 81 108 Theoretically, this method should be more satisfactory than methylation, as formation of derivatives is not necessary. However, recent work suggests that the chain length of amylose comprises several thousands of D-glucose units rather than hundreds (see Section V, 2), and the accuracy of such... 

Exhaustive studies on well-defined systems are rather scarce (4) nevertheless 3 systems thoroughly analyzed by independant research groups are of outstanding interest a) the quaternization of polyvinylpyridines by alkyl halogenides (20-25) b) the chlorination of polyethylene (13,26-28) c) the basic or acid hydrolysis of PMMA (29-31). On the other hand, neighbouring groups effects have been quantitatively taken into account for the kinetic analysis of periodate oxidation of amylose (32,33). 

Structural analysis of isolated amylose and amylopectin components has been carried out by standard methods based on methylation, periodate oxidation, and partial acid hydrolysis studies. Methylation and periodate oxidation studies established the linkage types and frequency of... 

Kooiman separated exocellular amylose formed in liquid media at pH < 5 by Cryptococcus albidus and Cryptococcus laurentii var. flavescens NRRL Y-1401 from a polysaccharide containing D-man-nose, D-xylose, and D-glucuronic acid. X-Ray diffraction patterns of the retrograded amyloses were identical with that of tuber starch (B modification). Periodate oxidation, optical rotational measurements, and hypoiodite oxidation data suggested a linear a-D-(l—>4)-linked structure having a chain length of about 44 units for the Cr. albidus amylose. Cryptococcus neoformans produces a crystalline amylose that was isolated by the method of Schoch. It has an iodine value and alpha- and hefa-amylase hydrolysis characteristics similar to those of corn amylose. 

This reaction scheme was elaborated after further work by Wolfrom and coworkers,in which pyrodextrins were prepared from amylose, in the presence and absence of acid catalysts. The copper-reducing power, the acidity, and the amount of periodate consumed and the amount of formic acid liberated on periodate oxidation were determined on samples heated at temperatures from 100-200°. 

Methods of assay (m) = methylation (p) = periodate oxidation (e) = enzymic. B.V. = Blue Value (compare Refs. 3 and 4). Xmax = wavelength of maximum absorption of polysaccharide-iodine complex. Priming activity toward P-enzyme soluble starch = 1.0. Priming activity toward muscle phosphorylase glycogen = 100, corn amylopectin = 63. Molecular weight, 64,000 (compared with about 100,000 for the parent amylose). 

Modified substrates may be used in testing the action patterns of purified enzymes. Thus, periodate-oxidized laminaran was used by Smith and coworkers to show the exo action of Basidiomycete (l- 3)-j8-n-glucanase. The oxidized-amylose substrate described earlier (see p. 266) has been used with alpha- and heta-amylases to illustrate how the method is completely general, and applicable to all classes of polysaccharides and poIysaccharidases. ° By use of oxidized pullulan, the endo nature of pullulanase action was confirmed. ... 

An alternative procedure for estimation of the number-average d.p. of (l- 4)-a-D-glucans has become apparent from work with partly periodate-oxidized amylose (see p. 266). This method depends on the fact that, when an average of one n-glucose residue per chain has been oxidized, the conversion into n-glucose by aZpba-amylase-free glucoamylase is only 50 . This is likely to become the preferred method for... 

The Michaelis constant and maximal velocity of a-amylase-free glucoamylase from Rhizopus delemar have been shown to decrease with increasing periodate oxidation of amylose.These kinetic features have been explained on the basis of competitive inhibition by the oxidized non-reducing end of the (1 4)-o -D-... 

Amyloses.—Various parameters and techniques have been used to define the morphology of amylose acetates. Chemical modification of maltotriose has been reported.Periodate-oxidized and reduced (sodium borohydride) amylose has been used as the substrate in an assay of a-amylase. The susceptibility of amylose-Cibachron Blue 3G-A to a-amylase and the use of this dyed amylose derivative in assays of a-amylase have been discussed. ... 

A /3-amylase isolated from culture filtrates of Bacillus polymyxa released maltose from amylose-like substrates, but it had only limited or no action on amylopectin, periodate-oxidized amylose, and cycloamyloses. ... 

The activity of j8-amylase towards dialdehydo(periodate-oxidized)-amylose distinguishes it from other D-glucanases. The benzylation of amylose and molecular parameters for dilute solutions of carboxymethylamylose (sodium salt) have been reported. 

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