THE STRUCTURE OF SODIUM THYMONUCLEATE FIBRES .2. THE CYLINDRICALLY SYMMETRICAL PATTERSON FUNCTION
THE STRUCTURE OF SODIUM THYMONUCLEATE FIBRES .2. THE CYLINDRICALLY SYMMETRICAL PATTERSON FUNCTION
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DOI：
10.1107/s0365110x53001940
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发表时间：
1953-01-01
期刊：
影响因子：
--
通讯作者：
GOSLING, RG
中科院分区：
文献类型：
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作者：
FRANKLIN, RE;GOSLING, RG
在高度结晶的胸腺核酸钠纤维的X射线显微照片上测量了反射的位置和最大照相强度。一个程序描述从这些测量推导出的反射的积分强度。这些已被用来计算圆柱对称帕特森函数。从这个帕特森函数，它是可能的，以获得单位细胞，从而分配指数的所有66个观察到的反射。从显示微晶双取向的单纤维的照片中获得了索引的正确性的确认。测量的密度的湿和干的~ qa DNA的描述，和可能的形状的基本结构units.Introduction在前面的文件中，它表明，通过改变水含量的高度定向纤维的脱氧核糖核酸钠（NaDNA）不同的结构修改可以得到。最高度有序的结构是在约75/a rh下操作时获得的结构（结构A）。因此，选择了这一点进行系统的定量研究。这种晶体结构的纤维图（Fra~ l-liu & Gosling，1953 a，图1）显示了66个独立的反射，分布在9条定义明确的层线上。在尝试索引反射的过程中，很明显，单位晶胞是单斜C面为中心的，c轴平行于纤维轴。然而，由于不可避免的测量误差，以及在大衍射角下分度反射的模糊性，发现不可能通过直接检查确定所有的单元参数。因此决定计算MacGillavry和Bruins（1948）描述的圆柱对称帕特森函数。这个函数包含了所有可以从纤维图中获得的信息，而不需要给反射分配除层线数以外的任何指数，因此只在c方向上是周期性的。它是这样一种函数，取真正的三维P~ tter ~ n函数，使它绕一个通过原点并平行于纤维轴的轴旋转，然后取一个通过旋转轴的截面，从而使它具有圆柱对称性。的主要周期性，或晶格平移，而不是对应于层平面间距，将揭示在这个非周期帕特森函数的重要峰。他们一般都在英国伦敦WC 1伯克贝克学院物理系.
The positions and maximum photographic intensities of reflexions have been measured on X-ray microphotographs of highly crystalline sodium thymonucleate fibres. A procedure is described for deducing from these measurements the integrated intensities of the reflexions. These have been used to calculate the cylindrically symmetrical Patterson function. From this Patterson function it was possible to obtain the unit cell and hence to allot indices to all the 66 observed reflexions. Confirmation of the correctness of the indexing was obtained from photographs of a single fibre which showed double orientation of the crystallites. Measurements of the density of wet and dry~ qa DNA are described, and the possible shape of the fundamental structural unit is discussed.Introduction In the preceding paper it was shown that by varying the water content of highly orientated fibres of sodium desoxyribonucleate (NaDNA) different structural modifications could be obtained. The most highly ordered structure was that obtained when operating at about 75/a rh (structure A). This has therefore been selected for a systematic quantitative study. The fibre diagram of this crystalline structure (Fra~ l~ liu & Gosling, 1953a, Fig. 1) shows 66 inde-pendent reflexions distributed on nine well defined layer lines. During the course of attempts to index the reflexions it became fairly clear that the unit cell was monoclinic C-face-centred, with the c axis parallel to the fibre axis. However, owing to the inevitable errors of measurement, and to the ambiguities of indexing reflexions at large angles of diffraction, it was not found possible, by direct inspection, to establish all the cell parameters with certainty. It was therefore decided to calculate the cylindrically symmetrical Patterson function described by MacGillavry & Bruins (1948). This function contains all the information which can be obtained from the fibre diagram without allot-ring to the reflexions any indices other than their layer-line numbers, and is therefore periodic in the c direction only. It is the function which would result from taking the true three-dimen~ ion~ l P~ tter~ 0n func-tion, giving it cylindrical symmetry by rotating it about an axis through the origin and parallel to the fibre axis, and then taking a section through the axis of rotation. The principal periodicities, or lattice translations, other than that corresponding to the layer-plane spacing, will be revealed as important peaks in this aperiodic Patterson function. They will, in general, be* Present aadre~ s: Department of Physics, Birkbeck College, London WC 1, England.