The unit cells of four proteins
The unit cells of four proteins
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四种蛋白质的单位细胞
DOI：
10.1107/s0365110x5300065x
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发表时间：
1953
期刊：
影响因子：
--
通讯作者：
F. Crick
中科院分区：
文献类型：
--
作者：
F. Crick
在寻找更适合于X射线晶体学的蛋白质晶体时，人们粗略地检查了一些晶体，看看它们是否有希望。本文所描述的所有这些化合物在不对称单元中都有一个以上的分子，因此没有对它们进行进一步的研究。在这里公布结果主要是为了防止其他人花时间在没有希望的材料上。所研究的蛋白质晶体是牛胰胰蛋白酶抑制剂的常见形式，它与牛胰蛋白酶的复合物，以及鸡溶菌酶的两种盐，硝酸盐和碘化物。前两种蛋白质晶体的制备细节和照片一起收集在Northrop，Kunitz和Herriott（1948）中，在此称为NKH 1948。所有使用的晶体都以通常的方式安装在密封的毛细管中。X射线照片用过滤的铜辐射拍摄。在某些情况下，如果晶体相当小，则使用与晶体直径大致相同的铅针孔。这是安装在晶体和X射线源之间，尽可能靠近晶体。此外，还使用了一个悬挂式后挡，安装在胶片前面一厘米左右，以捕捉直射光束。这两个预防措施的效果是大大减少了背景散射，这在晶体小而晶胞大时特别理想。在选择空间群时，那些具有镜像或滑动平面的空间群被排除在外，理由是因为蛋白质仅由低级氨基酸组成，这些对称元素不会出现。
In the search for more favourable protein crystals for X-ray crystallography a number have been examined roughly to see if they appear promising. All those described in this paper have more than one molecule in the asymmetric unit, so that no further work has been done on them. The results are published here mainly to prevent others spending time on unpromising material. The protein crystals studied are the common forms of bovine pancreatic trypsin inhibitor, its compound with bovine trypsin, and two salts of chick lysozyme, the nitrate and the iodide. Details of preparation, and photographs of the first two of these protein crystals are collected together in Northrop, Kunitz & Herriott (1948), which will be referred to here as NKH 1948. All the crystals used were mounted'wet'in sealed capillary tubes in the usual way. The X-ray photographs were taken with filtered copper radiation. In some cases, where the crystal was rather small, a lead pinhole of about the same diameter as the crystal was used. This was mounted between the crystal and the X-ray source, and as near to the crystal as possible. In addition, a hanging back-stop was used, mounted a centimetre or so in front of the film, to catch the direct beam. The effect of these two precautions was to reduce the background scattering considerably, which is especially desirable when the crystal is small and the unit cell large. In choosing space groups, those with mirror or glide planes have been excluded, on the grounds that since proteins are made up of laevo amino acids only, these symmetry elements will not occur.