CRYSTAL AND MOLECULAR-STRUCTURE AND ABSOLUTE-CONFIGURATION OF ETHYL CHLOROPHYLLIDE ALPHA DIHYDRATE - MODEL FOR DIFFERENT SPECTRAL FORMS OF CHLOROPHYLL-ALPHA
CRYSTAL AND MOLECULAR-STRUCTURE AND ABSOLUTE-CONFIGURATION OF ETHYL CHLOROPHYLLIDE ALPHA DIHYDRATE - MODEL FOR DIFFERENT SPECTRAL FORMS OF CHLOROPHYLL-ALPHA
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DOI：
10.1021/ja00858a006
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发表时间：
1975-01-01
影响因子：
15
通讯作者：
STROUSE, CE
中科院分区：
文献类型：
--
作者：
CHOW, HC;SERLIN, R;STROUSE, CE
叶绿酸乙酯a的单晶x-射线结构测定首次提供了含镁叶绿素衍生物的详细结构数据。它也提供了一个模型，叶绿素聚集在体内。由叶绿素酶催化的叶绿素a转晶反应制备的叶绿素a乙酯，在丙酮-水混合物中以二水合物形式结晶。晶体属三方晶系，空间群P2\，晶胞参数a= 8.859（1），c= 38.119（5）μ，Z= 3，ifu，icd= 1.31，<$/，μ= 1.28（3）.通过标准方法测定晶体结构，并将其精修至0.053的常规R。完善的完整数据集，包括dccl对，在空间群P31和Pii提供了一个绝对的配置与化学确定forchlorophylla一致。该结构中的镁原子是五配位的，水分子位于第五配位位点。第二个水分子与配位水分子、一个氯苯内酯分子的甲酯羰基氧原子和另一个氯苯内酯分子的乙酯羰基氧原子形成氢键。形成了层状晶体结构，其中构成每一层的二维聚集体由交联的一维聚合物组成。这些一维聚合物为光合循环生物中的叶绿素聚集模型提供了基础。短一维聚合物的红色吸收最大值位置的估计与活体叶绿素的观测结果有着惊人的一致性。叶绿素a是藻类和高等植物的主要光合色素。在光合作用过程中，这种色素既是光激发的收集者，又是初级光合反应中的电子供体。要了解光合机构的分子结构，就必须详细阐明这种色素在细胞中的分布和结构。
A single crystal x-ray structural determination of ethyl chlorophyllide a has provided the first detailed structural data for a magnesium-containing chlorophyll derivative. It has also furnished a model for chlorophyll aggregation in vivo. Ethyl chlorophyllide a, prepared by the chlorophyllasc catalyzed transcstcrification of chlorophyll a, crystallizes from acc-tonc-water mixtures in theform of the dihydrate. The crystals arc trigonal with space group P2\and unit cell parameters a= 8.859 (1), c= 38.1 19 (5) Á, Z= 3, ífu, icd= 1.31, í/,, µ= 1.28 (3). The crystal structure was determined by standard methods and refined to a conventional R of 0.053. Refinement of the complete data set, including Fricdcl pairs, in space groups P31 and Pii provided an absolute configuration consistent with that determined chemically forchlorophyll a. The magnesium atom in this structure is five coordinate with a water molecule in the fifth coordination site. The second water molecule is hydrogen bonded to the coordinated water molecule and to the methyl ester carbonyl oxygen atom of one chloro-phyllide molecule and to thecarbonyl oxygen atom of the ethyl ester of another. Alayered crystal structure is formed in which the two-dimensional aggregate that makes up each layer is composed of cross-linked one-dimensionalpolymers. These one-dimensional polymers provide the basis for a model of chlorophy ll aggregation in photosynthclic organisms. Estimates of the positions of the red absorption maxima of short one-dimensional polymers show a striking correspondence to those ob-served for chlorophyll in vivo.Chlorophyll a is the principal photosynthetic pigment in algae and higher plants. In the process of photosynthesis this pigment serves both as a collector of photoexcitation and as the electron donor in the primary photosynthetic re-action. A knowledge of the molecular structure of the pho-tosynthetic apparatus depends upon the detailedelucidation of the distribution and organization of this pigment in the cell.