Fiber Diffraction from Macromolecular Assemblies

9630787 Makowski该项目的长期目标是开发从纤维衍射数据中提取结构信息的可靠方法，并使用这些方法来表征分子组装的结构和活性。纤维衍射的数据参数与模型参数的比率大大低于X射线结晶学，即使当有许多同构的衍生物可用时，也不可能从纤维衍射数据中获得唯一的结构解。因此，在若干年后，关于丝状噬菌体M13和PF1的结构的文献中仍然存在实质性的争议。病毒分子模型之间的差异对于我们理解它们的膜介导的组装以及它们在噬菌体展示技术中的应用具有重要的意义。最近的发展为在不久的将来解决这些争议提供了很大的希望：(I)现在可以从丝状噬菌体的结构变体中获得纤维衍射数据，这可以为竞争结构模型提供严格的测试。(2)最近开发了一些计算测试，以评估构建晶体蛋白质分子模型的准确性。这些测试已经被证明是针对球状蛋白质的，现在可以用于分析大分子组装的结构。这个项目的主要目标是利用这些策略来解决关于丝状噬菌体结构的争议，并建立这些技术用于其他系统的光纤衍射研究。构成任何生命系统的大部分的大分子组件远不像可溶性大分子那样易于结构表征，但关于它们的三维结构的信息对于在分子水平上理解许多生物过程是核心的。很少有膜蛋白、丝状蛋白或大分子组装体被解析到原子分辨率。结构信息的获取是我们努力回答许多关于生命系统的基本问题的限速步骤：生命结构是如何组装的，组成分子是如何运动来执行其重要功能的？要回答这些问题，需要详细描述大分子组装在细胞系统的组织和活动中的作用。到目前为止，还没有确定这些系统的三维结构的常规程序。人类的想象力是如此之大，以至于一张三维图像对于理解复杂分子机器的功能真的是必不可少的。光纤衍射是为数不多的能够提供有关这些体系结构的原子或近原子分辨率信息的技术之一。目前在这个国家使用光纤衍射的科学家很少，未来的大部分进展可能来自欧洲和日本。该项目致力于保持我国在光纤衍射方面最先进的研究，并改进技术，以促进这些系统的表征。***

9630787 Makowski The long term goal of this project is to develop reliable methods for extracting structural information from fiber diffraction data and to use these methods to characterized the structure and activity of maromolecular assemblies. The ratio of data-to-model parameters for fiber diffraction is substantially lower than for x-ray crystallography, and even when a number of isomorphous derivatives are available, it may not be possible to obtain a unique structural solution from fiber diffraction data. Consequently, after a number of years, there continues to be substantial controversy in the literature about the structure of the filamentous bacteriophages M13 and Pf1. Differences among the molecular models for the viruses have substantial implications for our understanding of their membrane-mediated assembly, and for their use in phage display technology. Recent developments provide substantial hope that these controversies can be resolved in the near future: (i) It is now possible to obtain fiber diffraction data from structural variants of filamentous bacteriophages that can provide rigorous tests of competing structural models. (ii) A number of computational tests have recently been developed to assess the accuracy with which a molecular model of a crystalline protein has been constructed. These tests have been demonstrated for globular proteins and can now be utilized for analysis of structures of macromolecular assemblies. The principle goal of this project is to utilize these strategies to resolve the controversies about the structure of filamentous bacteriophages and to establish the use of these techniques for other systems to be studies by fiber diffraction. %%% The macromolecular assemblies that constitute a large part of any living system are far less amenable to structural characterization than soluble macromolecules, but information about their three-dimensional structure is central to understanding many biological processes at the molecular level. Few membran e proteins, filamentous proteins or large macromolecular assemblies have been solved to atomic resolution. Acquisition of structural information is the rate limiting step in our efforts to answer many fundamental questions about living systems: How are living structures assembled and how do the constituent molecules move in carrying out their vital functions? Answers to these questions require a detailed characterization of the role of macromolecule assemblies in the organization and activities of cellular systems. There are, as of yet, no routine procedures for determining the three-dimensional structures of these systems. The human imagination is such that a three-dimensional picture is really essential for an understanding of the function of a complex molecular machine. Fiber diffraction is one of the few techniques that can provide atomic or near-atomic resolution information about the structure of these systems. There are currently very few scientists using fiber diffraction in this country, and much of the future progress is likely to come from Europe and Japan. This program seeks to maintain state-of-the-art research in fiber diffraction in this country, and to improve the techniques in order to facilitate in the characterization of these system. ***