A refinement of the crystal structure of 9-methyladenine
A refinement of the crystal structure of 9-methyladenine
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9-甲基腺嘌呤晶体结构的精修
DOI：
10.1107/s0567740877003252
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发表时间：
1977
期刊：
影响因子：
--
通讯作者：
M. Rossi
中科院分区：
文献类型：
--
作者：
T. Kistenmacher;M. Rossi
C_6N_5H_7，单斜晶系，空间群P_(Jc)，V=674.43，A_3，Z=4，Din=1.474(4)，De=1.469 g·cm~(-3)，a=7.682(2)，b=12.330(3)，c=8.501(2)A。全矩阵最小二乘细化导致最终的R值为0.061。C6NsH~的X射线晶体结构已由Stewart&Jensen[J.化学]研究过。Phys(1964)，40,2071-2075]使用了一组有限的三维数据(385个独立的Fo‘s)和对非氢原子的各向同性精炼。这里给出的结果是基于更广泛的一组数据(1882个独立的Fo‘s)，非氢原子的各向异性精化和在各向同性水平上的H原子的包含。9-甲基腺嘌呤的晶体结构(Stewart&Jensen，1964)首次被用来确定9-甲基腺嘌呤的第一个紫外峰的跃迁是短轴还是长轴极化的。由于这样的信息可以在没有高精度的原子参数的情况下推导出来，最初的结构研究仅基于在CuKa辐射的极限球面内可能达到的1572个反射中的385个最强反射(Stewart&Jensen，1964)。然而，最近，中性的9-甲基腺嘌呤(De Meester，GoodGame，Skapski&Warnke，1973；Sletten&Thorstensen，1974；Sletten&Ruud，1975；McCall&Taylor，1975；Szalda，Kistenmacher&Marzilli，1975；Kisten-macher，Marzilli&Szalda，1976)和N(1)质子化的9-甲基腺嘌呤阳离子(Terzis，1976)被用作腺嘌呤核苷和核苷酸与金属离子和金属络合物结合的模型。除了金属结合部位的位置外，这些研究的一个方面是金属离子或金属络合物的成键对杂环体系中键长和键角的影响。这种详细的信息需要更精确地确定9-甲基腺嘌呤的原子位置以及衍生的键长和角度。在pH=8的微碱性水溶液中加入KOH，生长出了9-甲基腺嘌呤晶体。在我们的衍射仪研究中使用的晶体是棱柱针，尺寸如下：(011)-(011)0.25，(01])-(0I1)0.20和(100)-(]00)0.25 mm，As
C6N5H7, monoclinic, space group P2Jc, with a= 7.682 (2), b= 12.330 (3), c= 8.501 (2) A,/~= 123.12 (2), V= 674.43 A3, Z= 4, Din= 1.474 (4), De= 1.469 g cm-3. Full-matrix least-squares refinement led to a final R value of 0.061. The X-ray crystal structure of C6NsH~ has been previously studied by Stewart & Jensen [J. Chem. Phys.(1964), 40, 2071-2075] employing a limited set of three-dimen-sional data (385 independent Fo's) and isotropic refine-ment of the nonhydrogen atoms. The results presented here are based on a more extensive set of data (1882 independent Fo's), with anisotropic refinement of the nonhydrogen atoms and inclusion of H atoms at the isotropic level.Introduction. The crystal structure of 9-methyladenine (Stewart & Jensen, 1964) was first undertaken to estab-lish whether the transition moment for the first UV band of 9-methyladenine was short-axis or long-axis polarized. Since such information can be deduced without high precision for the atomic parameters, the original structural investigation was based only on the 385 most intense reflections out of a possible 1572 ac-cessible within the limiting sphere for Cu Ka radiation (Stewart & Jensen, 1964). More recently, however, neutral 9-methyladenine (de Meester, Goodgame, Skapski & Warnke, 1973; Sletten & Thorstensen, 1974; Sletten & Ruud, 1975; McCall & Taylor, 1975; Szalda, Kistenmacher & Marzilli, 1975; Kisten-macher, Marzilli & Szalda, 1976) and the N (1)-protonated 9-methyladenine cation (Terzis, 1976) have been employed as models for the binding of adenine nucleosides and nucleotides to metal ions and metal complexes. One aspect of these studies, besides the position of the metal binding site, is the effect on the bond lengths and bond angles in the heterocyclic ring system due to the bonding of the metal ion or metal complex. Such detailed information requires a more precise determination of the atomic positions and derived bond lengths and angles for 9-methyladenine. Crystals of 9-methyladenine were grown from an aqueous solution which was made slightly basic, pH= 8, by the addition of KOH. The crystal used in our diffractometer study was a prismatic needle-_ with the following dimensions:(011)-(011) 0.25,(01])--(0i 1) 0.20 and (100)-(] 00) 0.25 mm, with a as