Amylopectin structural analysis

Yusuph, M., Tester, R. F., Ansell, R., Snape, C. E. (2003). Composition and properties of starches extracted from tubers of different potato varieties grown under the same environmental conditions. Food Chem., 82,283-289. Zhu, Q., Bertoft, E. (1996). Composition and structural analysis of alpha-dextrins from potato amylopectin. Carbohydr. Res., 288, 155-174. 

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... 

In addition to its in vivo importance, R-enzyme is extremely useful for structural analysis. For example, the release of maltose and maltotriose from amylopectin jS-dextrin by R-enzyme provides good evidence of multiple branching, since the yield (12.8%) is near to that calculated (10.4%) for a tree-type structure having equal numbers of A- and B-chains. In addition, the simultaneous action of R-enzyme and 8-amylase can be used for the determination of CL (for details, see Ref. 144). 

Use of MALDI-TOF-MS allows relatively straightforward separation and identification of oligosaccharides with DPs up to 30. This feature makes it possible to identify products from enzymatic debranching of amylopectin. Richardsson et al. employed MALDI-TOF-MS and ESI-MS for enzyme-aided structure analysis of cationic potato amylopectin. " By MALDI-TOF-MS, identification of the oligosaccharides with DP 6-20 obtained from hydrolysis with pullulanase could be performed. Use of ESI-MS", on the other hand, provided detailed information on the chemical structure of oligosaccharides with DP <5. However, the lack of suitable standards prevented quantification by MALDI-TOF-MS and ESI-MS. 

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. 

In order to gain some information about the fundamentals of the hydrothermal carbonization process, the hydrothermal carbonization of different carbohydrates and carbohydrate products was examined [12, 13]. For instance, hydrothermal carbons synthesized from diverse biomass (glucose, xylose, maltose, sucrose, amylopectin, starch) and biomass derivatives (HMF and furfural) were treated under hydrothermal conditions at 180 °C and were analyzed with respect to their chemical and morphological structures by SEM,13 C solid-state NMR and elemental analysis. This was combined with GC-MS experiments on residual liquor solutions to analyze side products... 

Mutations of SSIIa have been observed in wheat and rice.208 In wheat, each of the three wheat genomes were mutated to entirely eliminate expression of the SSIIa gene product, Sgp-1 protein in one line 209 the result was reduced starch amounts and an altered starch structure. In rice, two classes of starch have been found. In Indica rices, the starch is of the long chain variety, while in Japonica, it is of the short chain variety.208 Genetic analysis showed that the mutation in Japonica rice led to a loss of starch synthase II.209 Thus, in higher plants, it seems that loss of SSII activity in dicots and SSIIa activity in monocots have the same results with respect to reduced starch content, due to a lowered amount of amylopectin and altered amylopectin chain size distribution. Thus, these genes may have the same function in starch biosynthesis. 

Specific optical rotation values, [a], for starch pastes range from 180 to 220° (5), but for pure amylose and amylopectin fractions [a] is 200°. The structure of amylose has been established by use of x-ray diffraction and infrared spectroscopy (23). The latter analysis shows that the proposed structure (23) is consistent with the proposed ground-state conformation of the monomer D-glucopyranosyl units. Intramolecular bonding in amylose has also been investigated with nuclear magnetic resonance (nmr) spectroscopy (24). 

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