An application of a new phase determination procedure to the structure of cyclo(hexaglycyl)demihydrate
An application of a new phase determination procedure to the structure of cyclo(hexaglycyl)demihydrate
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新相测定程序在环（六甘氨酰）二水合物结构中的应用
DOI：
10.1107/s0365110x63002607
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发表时间：
1963
期刊：
影响因子：
--
通讯作者：
J. Karle
中科院分区：
文献类型：
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作者：
I. Karle;J. Karle
（接收于1962年12月1日）合成多肽环（hcxaglycyl）半水合物（CH~ CONH）~的晶体结构。1/2 H2O的浓度已经通过简单的直接相确定方法确定，其中字母符号被分配给初始相。所有的最后阶段都可以用最初指定的几个字母来表达。这个过程的优点是它非常简单，可以通过手工计算来执行，并且对所有中心对称空间群是完全通用的。环（六环丙基）晶体属三斜晶系，空间群PY，晶胞尺寸a= 12.31，B= 15-50，c= 19”04/~; a= 94 58”，fl= 121 09 '，~，= 88 05'，Z= 8。有一个很强的伪细胞与c/4。分子是18元环的形式，在晶胞中具有四种明显不同的构型。氢键使结构稳定。水分子仅与环（六环基）分子的一半结合。简介环（六环基）是由Ballard，Bamford & Weymouth（1955）合成的环状多肽。该化合物对酸和碱的高度稳定性阻碍了纸色谱法对部分水解产物的检测。然而，Bamford & Weymouth（1955）倾向于形成18元环。在先前的晶体学检查（Cant，1956）中，确定了空间群和晶胞尺寸，并显示该材料是分子式为（CH~ CONH）6的半水合物。1/2 H2O。本研究是在D.皱，通过谁的晶体获得。我们特别感兴趣的是在多肽的配置和应用程序的相决定的解决方案的结构。这项研究提供了一个机会，说明一个新的一般计划，在中心对称晶体的相位测定。实验测量（CH 2CONH）6的晶体。半汞。0是无色，小，针状;他们在三斜晶系结晶。衍射结果显示出具有以下参数的明显的伪晶胞：
(Received 1 December 1962) The crystal structure of the synthetic polypeptide cyclo (hcxaglycyl) hemihydrate,(CH~ CONH)~. ½H20, has been determined by a simple, direct phase determination method in which letter symbols are assigned to initial phases. All the final phases are expressible in terms of a few of the initially assigned letters. The virtue of this procedure is that it is very simple, may be performed by hand computation, and is completely general for all centrosymmetric space groups. The crystals of cyclo (hexaglycyl) are triclinic in space group PY with cell dimensions a= 12.31, b= 15-50, c= 19" 04/~; a= 94 58", fl= 121 09',~,= 88 05'and Z= 8. There is a strong pseudo-cell with c/4. The molecules are in the form of 18-membered rings with four distinctly different configurations in the unit cell. Hydrogen bonding stabilizes the structure. The water molecule is associated with only one-half of the cyclo (hexaglycyl) molecules.Introduction Cyclo (hexaglycyl) is a cyclic polypeptide which was synthesized by Ballard, Bamford & Weymouth (1955). The great stability of this compound to both acids and alkalis hindered the examination of partial hydrolysates by paper chromatography. Bamford & Weymouth (1955), however, favored the formation of an 18-membered ring. In a previous crystallographic examination (Cant, 1956), the space group and cell dimensions were determined and the material was shown to be a hemihydrate with the molecular formula (CH~ CONH) 6. ½H20. The present investigation was undertaken at the suggestion of Prof. D. Wrinch, through whom the crystals were obtained. Our particular interest was both in the configuration of the polypeptide and in the application of phase determining procedures for the solution of the structure. This investigation affords the opportunity to illustrate a new general scheme for phase determination in centrosymmetric crystals. Experimental measurements Crystals of (CH2CONH) 6. ½Hg. 0 are colorless, small, and needle-shaped; they crystallize in the triclinic system. The diffraction results show a pronounced pseudo-cell with the following parameters: