Monte Carlo simulation of the α -amylolysis of amylopectin potato starch
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Degree of polymerization
Branching (polymer chemistry)
Potato starch
Enzymatic Hydrolysis
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Potato starch
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Degree of polymerization
Molar mass
Molar mass distribution
Multiangle light scattering
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Abstract The composition and starch molecular structure of eight rice varieties were studied. Waxy and non‐waxy (long‐, medium‐, and short‐grain) rice varieties from California and Texas were used. The amylose contents were measured using the Concanavalin A method and were found to be related to the type of rice: waxy ≈ 1.0%, short and medium grain 8.7–15.4%, and long grain 17.1–19.9%. The weight‐average molar masses ( M w ) of the starches varied from 0.52 to 1.96×10 8 g/mol. As would be expected, a higher M w of rice starch correlated to lower amylose content. The range of M w of amylopectin was 0.82 to 2.50 ×10 8 g/mol, and there was also a negative correlation of amylopectin M w with amylose content. Amylose M w ranged from 2.20 to 8.31×10 5 g/mol. After debranching the amylopectin with isoamylase, the weight‐average degree of polymerization (DP w ) for the long‐chain fraction correlated positively with a higher amylose content. California and Texas varieties were significantly different in their amylose content, starch M w (short‐ and medium‐grain only), and amylopectin M w ( p < 0.05).
Isoamylase
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To our knowledge the present paper shows for the first time the kinetic parameters of all the three starch branching enzyme (BE) isozymes, BEI, BEIIa and BEIIb, from rice with both amylopectin and synthetic amylose as glucan substrate. The activities of these BE isozymes with a linear glucan amylose decreased with a decrease in the molar size of amylose, and no activities of BEIIa and BEIIb were found when the degree of polymerization (DP) of amylose was lower than at least 80, whereas BEI had an activity with amylose of a DP higher than approximately 50. Detailed analyses of debranched products from BE reactions revealed the distinct chain length preferences of the individual BE isozymes. BEIIb almost exclusively transferred chains of DP7 and DP6 while BEIIa formed a wide range of short chains of DP6 to around DP15 from outer chains of amylopectin and amylose. On the other hand, BEI formed a variety of short chains and intermediate chains of a DP ≤40 by attacking not only outer chains but also inner chains of branched glucan while BEIIa or BEIIb could only scarcely or could not attack inner chains, respectively. The comprehensive in vitro studies revealed different enzymatic characteristics of the three BE isozymes and give a new insight into the distinct roles of individual BE isozymes in amylopectin biosynthesis in the endosperm. Based on these results, the functional distinction and interaction of BE isozymes during amylopectin biosynthesis in cereal endosperm is discussed.
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A high amylose rice mutant Goamy2 and its wild type Ilpumbyeo were used to analyze starch pasting properties and structure. There were considerable differences in physico-chemical characters and pasting properties between the high amylose mutant Goamy2 and its wild type Ilpumbyeo,as well as their water soluble and insoluble starch structure according to the results of Size Exclusion Chromatography(SEC). The cold water soluble components of rice flour of the mutant Goamy2 were mainly smaller molecules with the degree of polymerization(DP) of DP141 to DP2. The cold water soluble components of the wild type Ilpumbyeo were bigger molecules and the proportion of branched chains with the degree of polymerization of DP4100 to DP64 was high(33.3%). The hot water soluble starch of Goamy2 were mainly amylose,and the ratio of amylose to amylopectin was 4∶1 approximately,whereas for the hot water soluble starch of Ilpumbyeo,amylose and amylopection were both nearly a half. The ratios of long chains to short chains in hot water soluble amylopectin of the mutant and the wild type varied,being 0.67 and 0.32,respectively. The hot water insoluble starch of both two varieties were mostly amylopectin,and the proportion of amylose were less than 5%. The chain of the hot water insoluble amylopectin in the wild type was mainly short chains,with a proportion of short chains of 72.5%,whereas for the mutant,the proportion of long chains was close to the proportion of short chains.
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ABSTRACT Structures and properties of starches isolated from different botanical sources were investigated. Apparent and absolute amylose contents of starches were determined by measuring the iodine affinity of defatted whole starch and of fractionated and purified amylopectin. Branch chain‐length distributions of amylopectins were analyzed quantitatively using a high‐performance anion‐exchange chromatography system equipped with a postcolumn enzyme reactor and a pulsed amperometric detector. Thermal and pasting properties were measured using differential scanning calorimetry and a rapid viscoanalyzer, respectively. Absolute amylose contents of most of the starches studied were lower than their apparent amylose contents. This difference correlated with the number of very long branch chains of amylopectin. Studies of amylopectin structures showed that each starch had a distinct branch chain‐length distribution profile. Average degrees of polymerization (dp) of amylopectin branch chain length ranged from 18.8 for waxy rice to 30.7 for high‐amylose maize VII. Compared with X‐ray A‐type starches, B‐type starches had longer chains. A shoulder of dp 18–21 (chain length of 6.3–7.4 nm) was found in many starches; the chain length of 6.3–7.4 nm was in the proximity of the length of the amylopectin crystalline region. Starches with short average amylopectin branch chain lengths (e.g., waxy rice and sweet rice starch), with large proportions of short branch chains (dp 11–16) relative to the shoulder of dp 18–21 (e.g., wheat and barley starch), and with high starch phosphate monoester content (e.g., potato starch) displayed low gelatinization temperatures. Amylose contents and amylopectin branch chain‐length distributions predominantly affected the pasting properties of starch.
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Potato starch
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Fine Structures of Amylose and Amylopectin from Large, Medium, and Small Waxy Barley Starch Granules
ABSTRACT Amylose and amylopectin were prepared from large, medium, and small granule starches of classified waxy barley flour, and their fine structures were investigated. The amylose content had a wide distribution range (≈1.4–9.4%). Number‐average degrees of polymerization (DP n ) of the amyloses were similar among the samples (≈1,200–1,300). But number of chains per molecule (NC) decreased from the surface to the center (≈6–10 chains). DP n of the amylopectins varied from 4,657 to 14,604; decreased in the order of large, medium, and small granules in same fractions of the grain; and increased from the surface layer to the center. Longest chains (LC) were not found in any of the amylopectin molecules. The large amylopectin molecule had more long chains and fewer A chains than the small molecule. The amylose content had definite effects on the transition temperature range and crystal formation of the starch granules. There were positive correlations between DP n of the amylopectin and relative crystallinity (γ = +0.69) and enthalpy value (γ = +0.80), respectively. These findings may help to elucidate biosynthesis mechanism of starch.
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Abstract Laboratory isolated mung bean starch was fractionated into its amylose and amylopectin components using a modified procedure. The resulting products were shown to be both homogeneous and more susceptible to the hydrolyzing enzymes commonly used for structural analysis. The fine structure of the fractions was investigated using hydrolytic enzymes, chemical analysis and gel filtration chromatography. Differences in amylose/amylopectin fractions isolated by the modified and conventional extraction procedures were apparent. The unit chain length of amylopectin, DP n and limiting viscosity number of amylose were all lower for samples isolated by the modified method. In contrast the enzymatic hydrolysis of both the amylose and amylopectin fractions was improved for the material extracted by the modified method, low levels of branching and a unit chain distribution by gel filtration chromatography of the two overlapping populations with average degree of polymerization of 42 and 14 was obtained.
Degree of polymerization
Branching (polymer chemistry)
Gel permeation chromatography
Enzymatic Hydrolysis
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