Department of Food Science, Swedish University of Agricultural Sciences, Uppsala, Sweden.
Int J Biol Macromol. 2011 Nov 1;49(4):441-53. doi: 10.1016/j.ijbiomac.2011.04.014. Epub 2011 Jun 17.
The unit chains of amylopectin are organized into clusters. In this study, the cluster structure was analysed in detail in four different genotypes of barley, of which two possessed the amo1 genetic background. Amylose content of the barley starches differed from 0 to 32.6%. Isolated amylopectin was hydrolysed with α-amylase from Bacillus subtilis into domains, defined as groups of clusters, which were size-fractionated by methanol. The domain fractions were further treated with α-amylase to release single clusters. Amylopectin, domains and clusters were subsequently treated with phosphorylase and β-amylase to produce φ,β-limit dextrins and the detailed internal structures of these different structure levels were investigated. Analysis was performed with gel-permeation and anion-exchange chromatography. Equal amount of A-chains were detected in all barleys, but the distribution of B-chains differed. At least two types of domain structures were identified in all four barley varieties. Large domains were built up by large clusters and small domains by small clusters. In all four barley samples the number of long chains was small suggesting that shorter chains with a degree of polymerization of 25-35 also are involved in the interconnection of clusters. The cluster structure of the amylopectin correlated with the genetic background. The two barley samples with amo1 genetic background possessed a more dense structure. Internal chain lengths in these two barleys were shorter resulting in larger domains built up by larger clusters.
直链淀粉的单元链形成簇。在这项研究中，详细分析了四种不同基因型大麦中的簇结构，其中两种具有 amo1 遗传背景。大麦淀粉的直链淀粉含量从 0 到 32.6%不等。从枯草芽孢杆菌中分离出的直链淀粉用 α-淀粉酶水解成域，定义为簇的集合，用甲醇对其进行分级。将这些域级分进一步用 α-淀粉酶处理，以释放单个簇。然后用磷酸化酶和 β-淀粉酶处理直链淀粉、域和簇，产生 φ、β-极限糊精，并研究这些不同结构水平的详细内部结构。用凝胶渗透和阴离子交换色谱进行分析。在所有大麦中都检测到等量的 A-链，但 B-链的分布不同。在所有四种大麦品种中，至少鉴定出两种类型的域结构。大域由大簇构建，小域由小簇构建。在所有四种大麦样品中，长链的数量都很少，这表明聚合度为 25-35 的较短链也参与了簇的连接。直链淀粉的簇结构与遗传背景有关。具有 amo1 遗传背景的两种大麦样品具有更密集的结构。这些两种大麦中的内部链长度较短，导致由较大簇构建的较大域。
