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型异常衍射方法。我们建立在我们最近的成就在纽约结构生物学中心（NYSBC）光束线在布鲁克海文的国家同步加速器光源（NSLS）和世界各地的经验表明，多波长异常衍射（MAD）和SAD，MAD的单波长对应物，现在占主导地位的从头测定的三维结构的生物大分子。我们建议通过满足当前具有生物学意义的问题的迫切应用的需求来优化SAD和MAD定相程序。生物学上令人兴奋的问题激发了适当工具的开发，前沿方法加速了生物学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：（1）我们建议加强SAD定相程序的挑战性问题，如硒甲硫酰蛋白在低分辨率和只有轻原子的天然结构。一个重点是通过结合来自许多晶体的数据来提高异常衍射的信噪比的改进方法。(2)我们建议提高MAD程序准确的实验阶段评估。将制定数据收集战略，以减轻辐射损害并尽量减少系统误差。(3)我们建议开发低能量异常衍射实验的程序。我们将为低能（3 - 7 keV）实验开发实验程序和设计仪器，旨在增强硫和磷等轻原子的异常信号。(4)我们建议开发自动化和增强的程序，以方便SAD和MAD分析从许多晶体。第一优先事项是在方便的软件中编码和传播我们当前的多晶体SAD过程。

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.