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首页> 外文期刊>Acta crystallographica.Section D. Biological crystallography >Automatic alpha-helix identification in Patterson maps.
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Automatic alpha-helix identification in Patterson maps.

机译：阿尔法螺旋自动识别在帕特森地图。

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摘要

alpha-Helices are peculiar atomic arrangements characterizing protein structures. Their occurrence can be used within crystallographic methods as minimal a priori information to drive the phasing process towards solution. Recently, brute-force methods have been developed which search for all possible positions of alpha-helices in the crystal cell by molecular replacement and explore all of them systematically. Knowing the alpha-helix orientations in advance would be a great advantage for this kind of approach. For this purpose, a fully automatic procedure to find alpha-helix orientations within the Patterson map has been developed. The method is based on Fourier techniques specifically addressed to the identification of helical shapes and operating on Patterson maps described in spherical coordinates. It supplies a list of candidate orientations, which are then refined by using a figure of merit based on a rotation function calculated for a template polyalanine helix oriented along the current direction. The orientation search algorithm has been optimized to work at 3 A resolution, while the candidates are refined against all measured reflections. The procedure has been applied to a large number of protein test structures, showing an overall efficiency of 77% in finding alpha-helix orientations, which decreases to 48% on limiting the number of candidate solutions (to 13 on average). The information obtained may be used in many aspects in the framework of molecular-replacement phasing, as well as to constrain the generation of models in computational modelling programs. The procedure will be accessible through the next release of IL MILIONE and could be decisive in the solution of new unknown structures.
机译：阿尔法螺旋是特殊的原子安排蛋白质结构特征。发生在晶体可以使用作为最小的先验信息驱动的方法定相的过程解决方案。蛮力方法已经开发出来搜索所有可能的位置阿尔法螺旋的水晶细胞的分子更换和探索系统。提前取向将是一个伟大的这种方法的优势。目的,全自动程序阿尔法螺旋方向在帕特森地图已经被开发。傅里叶技术专门解决螺旋形状的识别和操作帕特森地图中描述球形坐标。方向,然后精制通过使用基于旋转功能的品质因数计算出一个模板polyalanine螺旋面向沿电流方向。定向搜索算法进行了优化在3工作一项决议,而候选人对所有测量反射得到细化。程序已被应用于大量的蛋白质测试结构,表现出一个整体在寻找阿尔法螺旋效率77%方向,减少48%的限制候选解决方案的数量(13平均)。在许多方面的框架molecular-replacement定相,以及限制的生成模型计算模拟程序。将在下一个版本可以通过ILMILIONE和可能的解决方案是决定性的新的未知的结构。

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