Lunina Natalia, Lunin Vladimir Y, Urzhumtsev Alexandre
Institute of Mathematical Problems of Biology, Russian Academy of Sciences, Pushchino, Moscow Region 142290, Russia.
Acta Crystallogr D Biol Crystallogr. 2003 Oct;59(Pt 10):1702-15. doi: 10.1107/s0907444903015154. Epub 2003 Sep 19.
The connectivity-based phasing method currently allows ab initio determination of phases for several hundred reflections. In the case of large macromolecular crystals, these reflections correspond to a very low resolution and the structural information deduced essentially consists of the molecular packing and an approximate molecular envelope. However, when the unit cell is relatively small, such a phasing procedure can produce phases such that secondary-structure elements can be identified in the corresponding maps. In the case of the pheromone Er-1, all three alpha-helices present are seen in the ab initio phased maps. In the case of protein G, not only the alpha-helix but also some individual beta-strands are distinguishable.
基于连通性的定相方法目前能够从头确定数百个反射的相位。对于大型大分子晶体而言，这些反射对应于非常低的分辨率，所推导的结构信息基本上仅包括分子堆积和一个近似的分子轮廓。然而，当晶胞相对较小时，这样的定相过程能够产生可在相应图谱中识别二级结构元件的相位。在信息素Er-1的情况下，从头定相图谱中可以看到所有三个存在的α螺旋。在蛋白质G的情况下，不仅α螺旋，而且一些单独的β链也清晰可辨。
