CAREER: Imaging dynamic macromolecules in solution with x-ray lasers

美国亚利桑那州立大学（ASU）因开发利用超亮x射线源独特能力的新型生物分子成像技术而获奖。该研究旨在为在生理温度下观察溶液中蛋白质和其他生物分子的动态运动提供广泛适用的方法。该教育计划将本科生和博士生纳入具体的研究项目，以及在亚利桑那州立大学发展超快x射线科学的更广泛的倡议。亚利桑那州立大学为第一代社区学院转校生提供了在亚利桑那州立大学从事有指导的独立研究的机会。一个由本科生和博士生组成的团队将朝着互补的研究目标共同努力，并将前往大型实验室设施，如SLAC国家实验室的直线加速器相干光源，以了解不同的科学家团队如何协同工作。学生的职业发展将通过合作机构的交叉培训机会、参与国际会议、协助个人发展计划以及其他形式的指导来支持。我们将开发一套新的免费开源软件，作为教学工具，帮助更多的学生掌握x射线数据分析方法，探索新的成像概念。一个互补的光学衍射成像实验室设备将开发，以教实验技术。这些硬件和软件工具将整合到亚利桑那州立大学的本科物理课程中，并将为在亚利桑那州立大学的公共宣传活动中展示的交互式衍射x射线成像显示器提供基础。该教育计划与现有的NSF BioXFEL科学技术中心和亚利桑那州立大学生物设计研究所的紧凑型x射线光源设施高度协同。科学研究的目标是测量技术的普遍需要，可以揭示详细的三维结构和功能动力学的生物分子，如蛋白质。它开发了x射线散射方法来确定结构，而不需要培养宏观蛋白质晶体或低温冷冻样品，这两者都是现有技术的要求，可以限制它们对动态分子的有效性。x射线自由电子激光器被用于产生快照散射模式，通过使用仅10飞秒（10-14秒）的强超短x射线脉冲来超越原子运动。与传统的x射线溶液散射不同，快照散射模式之间的两点强度相关性分析可以直接产生三维结构，并且在有利的情况下，可以对嵌入复杂环境中的原子子结构进行化学选择性成像。结构变化可以通过延迟快照来及时排序，形成“分子电影”，直到反应被闪光、温度跳跃或其他机制触发后不久。这些方法适用于各种各样的生物分子系统，其中包括参与光合作用、视觉、病毒感染和调节活细胞和生物体中几乎所有重要过程的信号过程的蛋白质。在本研究过程中所研究的模型蛋白质系统将阐明光激活蛋白质运动的超快动力学。除了在同行评议的期刊上发表结果和在科学会议上发表报告外，x射线散射数据和分析软件将向公众开放，这将有助于超快x射线成像科学的总体发展。同样，在研究过程中开发的创新硬件技术，如用于生产液体纳米液滴的微喷嘴设计，将向公众开放。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

An award is made to Arizona State University (ASU) for the development of new biomolecular imaging techniques that exploit the unique capabilities of ultrabright x-ray sources. The research aims to enable broadly applicable methods of visualizing dynamic motions of proteins and other biomolecules in solution at physiological temperature. The education plan integrates undergraduate and PhD students into the specific research project, as well as the broader initiative to develop ultrafast x-ray science at ASU. Opportunities are tailored to undergraduate first-generation community college transfer students to engage in mentored independent research at ASU. A team of undergraduate and PhD students will work together toward complementary research goals and will travel to large-scale laboratory facilities, such as the Linac Coherent Light Source at SLAC National lab, to learn how diverse teams of scientists work together. Student career development will be supported through cross-training opportunities at collaborator institutes, participation in international conferences, assistance with individual development plans, and other forms of mentorship. A new freely available open-source software suite will be developed as a pedagogical tool to help a broader audience of students master x-ray data analysis methods and explore new imaging concepts. A complementary optical diffractive imaging laboratory apparatus will be developed to teach experimental techniques. These hardware and software tools will be integrated into undergraduate physics curriculum at ASU and will also provide a foundation for an interactive diffractive x-ray imaging display to be showcased at public outreach events at ASU. The educational plans are highly synergistic with the existing NSF BioXFEL Science and Technology Center and the Compact X-Ray Light Source facility at ASU’s Biodesign Institute.The scientific research targets the general need for measurement techniques that can reveal detailed three- dimensional structures and functional dynamics of biomolecules such as proteins. It develops x-ray scattering methods to determine structures without the need to grow macroscopic protein crystals or to cryogenically freeze samples, both of which are requirements of existing techniques that can limit their effectiveness for dynamic molecules. X-ray free-electron lasers are used to produce snapshot scattering patterns by outrunning atomic motions with intense ultrashort x-ray pulses of just 10 femtoseconds (10-14 seconds). Unlike conventional x-ray solution scattering, the analysis of two-point intensity correlations amongst snapshot scattering patterns can directly yield three-dimensional structures, and in favorable cases allows for chemically selective imaging of atomic sub-structures embedded in complex environments. Structural changes may be sequenced in time to form “molecular movies” by delaying snapshots until shortly after reactions are triggered with light flashes, temperature jumps, or by other mechanisms. These methods are applicable to a broad variety of biomolecular systems which includes, among numerous examples, proteins that are involved in photosynthesis, vision, viral infection, and signaling processes that regulate nearly all vital processes in living cells and organisms. Model protein systems studied in the course of this research will elucidate ultrafast dynamics of light-activated protein motions. In addition to the publication of results in peer-reviewed journals and presentations at scientific conferences, x-ray scattering data and analysis software will be made publicly available and will contribute to the general development of ultrafast x-ray imaging science. Similarly, innovative hardware technologies developed in the course of the research, such as micro-nozzle designs for the production of liquid nanodroplets, will be made publicly available.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.