Solving the phase problem in fiber diffraction. Application to tobacco mosaic virus at 3.6 Å resolution
Solving the phase problem in fiber diffraction. Application to tobacco mosaic virus at 3.6 Å resolution
复制标题
解决纤维衍射中的相位问题，应用于烟草花叶病毒，分辨率为 3.6 Å。
DOI：
10.1107/s010876738500054x
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发表时间：
1985
期刊：
影响因子：
--
通讯作者：
G. Stubbs
中科院分区：
文献类型：
--
作者：
K. Namba;G. Stubbs
产生光纤衍射图的衍射粒子围绕纤维轴随机取向，因此，衍射图是柱面平均的。光纤衍射中的位相问题不仅在于确定通常晶体意义上的位相，而且在于克服这种平均法所带来的信息损失。这是通过蛋白质晶体同构替换的多维模拟，结合使用当螺旋结构在给定的轮次中大约但不完全重复时发生的层线精细分裂的信息来完成的。所测定的相已通过溶剂展平程序进行了精制。通过假设柱面平均贝塞尔阶项的分离(从早期的多维同构替换和后期的模型)，并应用传统的同构替换(二维同构替换)来确定项的相位，对它们进行了进一步的改进。在烟草花叶病毒的情况下，发现了建模和二维同构替换的循环，极大地提高了电子密度图的质量，并使基于3.6A分辨率的高可解释性图建立的病毒原子模型能够分开5个贝塞尔阶数(由于柱面平均而重叠的项)。
The diffracting particles that give rise to a fiber diffraction pattern are randomly oriented about the fiber axis and, in consequence, the diffraction pattern is cylindrically averaged. The phase problem in fiber diffraction is not only to determine the phase in the usual crystallographic sense, but to overcome the loss of information from this averaging. This has been done by a multi-dimensional analog of protein crystallographic isomorphous replacement, combined with the use of information from the fine splitting of layer lines that occurs when a helical structure repeats approximately, but not exactly, in a given number of turns. The phases thus determined have been refined by a solvent-flattening procedure. They have been further refined by assuming the separation of cylindrically averaged Bessel-order terms (from multi-dimensional isomorphous replacement at an early stage and from a model at a later stage) and applying conventional isomorphous replacement (two-dimensional isomorphous replacement) to determine the phases of the terms. Cycles of model building and two-dimensional isomorphous replacement were found in the case of tobacco mosaic virus to improve greatly the quality of the electron density map, and enabled an atomic model of the virus to be built based on a highly interpretable map at 3.6 A resolution with five Bessel orders (terms overlapping because of cylindrical averaging) separated.