A REVISIT TO THE 3-DIMENSIONAL STRUCTURE OF B-TYPE STARCH
A REVISIT TO THE 3-DIMENSIONAL STRUCTURE OF B-TYPE STARCH
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DOI：
10.1002/bip.360270803
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发表时间：
1988-08-01
期刊：
影响因子：
2.9
通讯作者：
PEREZ, S
中科院分区：
文献类型：
--
作者：
IMBERTY, A;PEREZ, S
提出了一种新的b -淀粉的三维结构，其中单位细胞包含12个葡萄糖残基，它们位于两个左旋，平行链双螺旋中，排列在平行寄存器中；36个水分子位于这些螺旋之间。链在六方空间群P61中结晶，晶格参数a=b=1.85 nm, c=1.04 nm。空间群对称是从对迄今为止发表的大量结构研究的详尽分析中得出的。这项工作中使用的衍射数据来自先前报道的x射线纤维衍射图[H.C.Wu and A. Sarko(1978)，碳水化合物研究，61(7)-25。三维数据的最终R因子为0.145。重复单元由麦芽糖分子组成，其中葡萄糖残基具有4C1吡喃糖构象，并且是. α (1.fwdarw)。4)联系在一起。糖苷键的构象由扭转角（. phi）表征。（83.8°，-144.6°）和（84.3°，-144.1°），而糖苷桥的价角大小为115.8°。和116.5度。伯羟基以间扭式构象存在。没有分子内氢键。在双螺旋结构中，通过O(2)的出现，在没有任何空间冲突的情况下实现了链间的稳定。O(6)型氢键。本文给出的模型，水化率约为27% w/w。对应于有序的晶体样品，因为所有的水分子都可以定位，没有明显的混乱迹象。一半的水分子被紧紧地束缚在双螺旋结构上；其余的形成一个复杂的网络中心围绕六倍螺旋轴的单位细胞。分析了目前结构模型的一致性，从物理化学和生物化学的角度分析了块茎淀粉颗粒的结晶成分。
A new three-dimensional structure of B-starch is proposed in which the unit cell contains 12 glucose residues located in two left-handed, parallel-stranded double helices packed in a parallel register; 36 water molecules are located between these helices. Chains are crystallized in the hexagonal space group P61, with lattice parameters a=b=1.85 nm, c=1.04 nm. The space group symmetry was derived from an exhaustive analysis of the large body of structural studies published so far. Diffraction data used in this work were taken from the previously reported x-ray fiber diffractogram [H.C. Wu and A. Sarko (1978), Carbohydrate Research, 61, 7-25] after adequate reindexing. The final R factor is 0.145 for the three-dimensional data. The repeating unit consists of a maltose molecule where the glucose residues have the 4C1 pyranose conformation and are .alpha.(1.fwdarw.4) linked.THe conformation of the glycosidic linkage is characterized by torsion angles (.PHI., .PHI.) that take the values (83.8.degree., -144.6.degree.) and (84.3.degree., -144.1.degree.), whereas the valence angles at the glycosidic bridge have a magnitude of 115.8.degree. and 116.5.degree., respectively. The primary hydroxyl groups exist in a gauche-gauche conformation. There is no intramolecular hydrogen bond. Within the double helix, interstrand stabilization is achieved without any steric conflict and through the occurrence of O(2)...O(6) type of hydrogen bonds. The model presented here, with an hydration around 27% w/w. corresponds to a well-ordered crystalline sample, since all the water molecules could be located with no apparent sign of a disorder. Half of the water molecules are tightly bound to the double helices; the remainder forms a complex network centered around the sixfold screw axis of the unit cell. The consistency of the present structural model, with both physicochemical and biochemical aspects of the crystalline component of tuber starch granules, is analyzed.