THE DOUBLE-HELICAL NATURE OF THE CRYSTALLINE PART OF A-STARCH
THE DOUBLE-HELICAL NATURE OF THE CRYSTALLINE PART OF A-STARCH
复制标题
DOI：
10.1016/0022-2836(88)90144-1
复制
发表时间：
1988-05-20
影响因子：
5.6
通讯作者：
TRAN, V
中科院分区：
文献类型：
--
作者：
IMBERTY, A;CHANZY, H;TRAN, V
一个新的三维结构的A-淀粉的结晶部分的描述，其中单位细胞包含12个葡萄糖残基位于两个左手，平行双螺旋包装在平行的方式，四个水分子位于这些螺旋之间。链以a = 2.124 nm，B = 1.172 nm，c = 1.069 nm和γ的单斜晶格结晶。= 123.5 °，C轴平行于螺旋轴。系统性缺失与空间群B2一致。该结构来自单晶的电子衍射，分解成单个峰的X-射线粉末图案和先前报道的X-射线纤维衍射数据在充分重新索引后的联合使用。重复单元由麦芽三糖部分组成，其中葡萄糖残基具有4C 1吡喃糖构象并且是α-葡萄糖。（1）4)有联系糖苷键的构象由扭转角（Φ，. PSI）其取值为（91.8，sbd.153.2）、（85.7，sbd.145.3）和（91.8，sbd.151.3）;所有伯羟基均以gauche-gauche构象存在。分子内没有氢键。在双螺旋内，链间稳定化是在没有任何空间冲突的情况下通过O（2）…O（6）型氢键。本结构与谷物淀粉颗粒的结晶组分的物理化学和生物化学方面一致。
A new three-dimensional structure of the crystalline part of A-starch is described in which the unit cell contains 12 glucose residues located in two left-handed, parallel-stranded double helices packed in a parallel fashion; four water molecules are located between these helices. Chains are crystallized in a monoclinic lattice with a = 2.124 nm, b = 1.172 nm, c = 1.069 nm and .gamma. = 123.5.degree., the c axis being parallel to the helix axis. Systematic absences are consistent with the space group B2. The structure was derived from joint use of electron diffraction of single crystals, X-ray powder patterns decomposed into individual peaks and previously reported X-ray fibre diffraction data after adequate re-indexing. The repeating unit consists of a maltotriose moiety 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., .PSI.) which take the values (91.8,.sbd.153.2), (85.7,.sbd.145.3) and (91.8,.sbd.151.3); all the primary hydroxyl groups exist in a gauche-gauche conformation. There are no intramolecular hydrogen bonds. Within the double helix, interstrand stabilization is achieved without any steric conflict and through the occurrence of O(2)...O(6) type hydrogen bonds. The present structure is consistent with both physicochemical and biochemical aspects of the crystalline component of the cereal starch granules.