Anomalous Diffraction Analysis of Biomolecular Structure

描述(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反常衍射方法。我们在布鲁克海文国家同步加速器光源(NSLS)的纽约结构生物学中心(NYSBC)光束线上取得的最新成就以及世界各地的经验表明，多波长异常衍射(MAD)和MAD的单波长对应的SAD目前在从头测定生物大分子的三维结构方面占据主导地位。我们建议通过满足对当前具有生物学意义的问题的强制应用的要求来优化SAD和MAD分期程序。生物刺激问题促使适当工具的开发，而前沿方法加速了具有生物和医学意义的系统的结构的解决。总体目标体现在四个具体目标上：(1)我们建议加强SAD阶段程序，以解决具有挑战性的问题，如低分辨率和仅有轻原子的天然结构的硒蛋氨酸蛋白。重点是通过组合来自多个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。将制定数据收集战略，以减轻辐射损害并将系统误差降至最低。(3)提出了发展低能反常衍射实验的方法。我们将为低能(3-7keV)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反常信号。(4)我们建议开发自动化和改进的程序，以促进从许多晶体进行SAD和MAD分析。当务之急是用方便的软件对我们目前的多晶体SAD过程进行编码和传播。

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.