Anomalous Diffraction Analysis of Biomolecular Structure

描述（由申请人提供）：拟议研究的总体目标是开发用于分析生物大分子结构的增强异常衍射方法。我们建立在我们最近在纽约结构生物学中心（NYSBC）取得的成就的基础上，布鲁克海文国家同步加速器光源（NSLS）的光束线和世界范围内的经验表明，多波长异常衍射（MAD）和SAD， MAD的单波长对应物，现在在生物大分子三维结构的重新确定中占主导地位。我们建议通过满足当前具有生物学意义的问题的引人注目的应用需求来优化SAD和MAD的分阶段程序。生物学上令人兴奋的问题激发了适当工具的发展，前沿方法加速了生物和医学意义系统结构的解决方案。总体目标体现在四个具体目标中：(1)我们建议加强具有挑战性的问题的SAD分相程序，例如低分辨率和仅光原子天然结构的硒甲硫基蛋白。重点是通过结合许多晶体的数据来提高异常衍射的信噪比的改进方法。(2)我们建议加强MAD程序，以准确评估实验阶段。将设计数据收集策略，以减轻辐射损害并尽量减少系统错误。(3)提出了低能反常衍射实验规程。我们将为低能量（3 - 7 keV）实验开发实验程序和设计仪器，旨在增强来自光原子（如硫和磷）的异常信号。(4)我们建议开发自动化和增强程序，以方便对许多晶体进行SAD和MAD分析。当务之急是在方便的软件中对现有的多晶SAD工艺进行编码和传播。

DESCRIPTION (provided by applicant): The overall objective of the proposed research is to develop enhanced anomalous diffraction methods for analyzing structures of biological macromolecules. We build on our recent accomplishments at New York Structural Biology Center (NYSBC) beamlines at Brookhaven's National Synchrotron Light Source (NSLS) and worldwide experience showing that multiwavelength anomalous diffraction (MAD) and SAD, MAD's single-wavelength counterpart, now predominate for de novo determinations of three- dimensional structures for biological macromolecules. We propose to optimize SAD and MAD phasing procedures by meeting the demands of compelling applications to current problems of biological significance. Biologically exciting problems motivate the development of appropriate tools, and forefront methods accelerate the solution of structures for systems of biological and medical significance. The overall objective is embodied in four specific aims: (1) we propose to enhance SAD phasing procedures for challenging problems such as selenomethionyl proteins at low resolution and only-light-atom native structures. A focus is on improved methods for increasing signal-to-noise ratios for anomalous diffraction by combining data from many crystals. (2) We propose to enhance MAD procedures for accurate experimental phase evaluation. Data collection strategies will be devised to mitigate radiation damage and minimize systematic errors. (3) We propose to develop procedures for low-energy anomalous diffraction experiments. We will develop experimental procedures and design instrumentation for low-energy (3 - 7 keV) experiments aiming to enhance anomalous signal from light atoms such as sulfur and phosphorous. (4) We propose to develop automation and enhanced procedures to facilitate SAD and MAD analyses from many crystals. A first priority is to encode and disseminate our current multi-crystal SAD process in convenient software.