Ab Initio Phasing of Macromolecules

大分子从头开始定相

• 批准号: 7034099
• 负责人: ZBYSZEK OTWINOWSKI
• 金额: $ 22.13万
• 依托单位: UT SOUTHWESTERN MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-03-01 至 2008-02-29
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7034099
• 关键词: X ray crystallography; chemical structure; crystallization; electron density; macromolecule; method development; molecular asymmetry; structural biology

DESCRIPTION (provided by applicant): This grant is to solve ab initio the phase problem, a classic high risk/high impact challenge in structural biology. The macromolecular structure determination will be improved by novel approaches to identifying non-crystallographic symmetry, to direct methods an to phase extension. The first target will be the most frequent, and often the most challenging, cases in macromolecular crystallography: those of the molecules in the crystal lattice having and additional, non-crystallographic symmetry. The proposal is to develop the initial implementation of: - Identification of the rotational component of non-crystallographic symmetry by improving the self-rotation function; - A novel method to identify the molecule's shape and position ab initio; - Efficient use of the a priori information about the electron density inside the mask; - Ab initio phasing up to the intermediate resolution by conjugated gradient method; - Phase extension by state-of-the art solvent-flattening and NCS-averaging methods. These methods will be validated with a representative range of samples. It is expected that the developed framework will form a basis for the generally valid subsequent application that will led the structural biologists skip laborious and uncertain stage of developing heavy atom derivatized crystals. In terms of understanding the molecular biology, the highest expected impact is in structure determination of complex molecular assemblies.

描述（由申请人提供）：该基金是为了解决从头算阶段的问题，在结构生物学的一个经典的高风险/高影响的挑战。大分子结构的测定将通过识别非晶体学对称性、指导方法和相延伸的新方法得到改进。第一个目标将是最常见的，往往是最具挑战性的，在大分子晶体学的情况下：那些在晶格中的分子具有额外的，非晶体对称性。该建议旨在初步实现：通过改进自旋转函数确定非晶体学对称性的旋转分量;一种从头确定分子形状和位置的新方法;有效利用关于掩模内部电子密度的先验信息;通过共轭梯度法将从头逐步提高到中间分辨率;- 通过最先进的溶剂平坦化和NCS平均方法进行相延伸。将使用代表性范围的样品对这些方法进行验证。预计开发的框架将形成普遍有效的后续应用的基础，这将导致结构生物学家跳过开发重原子衍生晶体的费力和不确定的阶段。在理解分子生物学方面，最高预期的影响是复杂分子组装体的结构确定。