TEMP DEPEND OF AVERAGE & SITE-SPECIFIC RADIATION DAMAGE IN PROTEIN CRYSTALS

温度取决于平均值

• 批准号: 8171497
• 负责人: Robert E. Thorne
• 金额: $ 2.41万
• 依托单位: CORNELL UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-07-01 至 2011-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8171497
• 关键词: Address; Belief; Computer Retrieval of Information on Scientific Projects Database; Data; Data Collection; Data Set; Diffusion; Dose; Electron Transport; Electrons; Funding; Gases; Glass; Grant; Growth; Helium; Humulus; Institution; Methods; Molecular; Motion; Nail plate; Nature; Nitrogen; Proteins; Protocols documentation; Radiation; Research; Research Personnel; Resources; Series; Site; Source; Spottings; Temperature; Transition Temperature; United States National Institutes of Health; Water; base; disulfide bond; professor; research study

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. We will try to address two questions: 1. Is there any difference in damage versus dose to protein crystals when data is collected at T=100 K (nitrogen gas) and T=20 K (helium gas)? Several experiments have seen little or no effect, but the effects may be too small to be reliably quantified using standard methods. Postdoctoral Associate (now Assistant Professor) Jan Kmetko developed a data collection and analysis protocol that should give the accuracy to reliably resolve differences. In this part of the experiment, we will dose crystals and collect data in a narrow angular wedge (5 degrees), which will not be sufficient for a full structural refinement, out to doses of 20 MGray or more. 2. Does site-specific radiation damage depend on temperature at temperatures well below water's glass transition temperature? There is a belief among those currently studying radiation damage to protein crystals that the observation of site-specific damage (e.g., breakage of disulfide bonds) at relatively low doses is evidence for secondary radiation damage. However, we believe (based on old ESR experiments and basic considerations) that this damage occurs via electron transfer, not by thermal diffusion of atomic and molecular radicals, and therefore is primary damage. Even if site specific damage is due entirely to electron motion, this motion may occur via tunneling or thermal hopping. By comparing site-specific damage to protein crystals at T=100 K and T=20 K, we hope to be able to nail down the nature of site-specific damage. These experiments will involve taking a series of data sets (each with enough information to evalate the status of disulfide bonds) from the same spot on the same crystal , and watching the growth of site specific damage with total absorbed dose. Comparison of data collected at T=100 K and T=20 K will reveal any differences in the rate and extent of site specific damage.

该副本是利用众多研究子项目之一 由NIH/NCRR资助的中心赠款提供的资源。子弹和 调查员（PI）可能已经从其他NIH来源获得了主要资金， 因此可以在其他清晰的条目中代表。列出的机构是 对于中心，这不一定是调查员的机构。 我们将尝试解决两个问题： 1。当在T = 100 K（氮气）和T = 20 K（氦气）收集数据时，损伤与蛋白质晶体有任何差异？ 几个实验几乎没有效果，但是效果可能太小，无法使用标准方法可靠地量化。 博士后助理（现任助理教授）Jan Kmetko开发了一个数据收集和分析协议，该协议应具有可靠解决差异的准确性。 在实验的这一部分中，我们将在狭窄的角楔（5度）中剂量晶体并收集数据，这对于完整的结构细化不足以达到20 mgray或更多的剂量。 2。特定于位点的辐射损伤是否取决于温度远低于水的玻璃过渡温度的温度？ 当前正在研究蛋白质晶体辐射损害的人中，人们认为在相对较低的剂量下观察到位点特异性损伤（例如，二硫键断裂）是继发辐射损害的证据。 但是，我们认为（基于旧的ESR实验和基本考虑），这种损害是通过电子转移而不是通过原子和分子自由基的热扩散而发生的，因此是主要损害。 即使特定于位点的损害完全归因于电子运动，这种运动也可能通过隧道或热跳。 通过比较T = 100 K和T = 20 K的蛋白质晶体特异性损伤，我们希望能够降低特定地点损伤的性质。 这些实验将涉及从同一晶体上同一地点进行一系列数据集（每个数据集（每个数据都有足够的信息以评估二硫键键的状态），并观察特定损害的增长，并使用总吸收剂量。 在T = 100 K和T = 20 K时收集的数据的比较将揭示特定损坏的速率和程度的任何差异。