Detectors for Serial Nanocrystal Electron Diffraction

原子分辨结构是化学、结构生物学和材料科学的核心。有一种新的范式正在出现，以提供这一关键信息。多伦多大学开发的系列纳米晶体电子衍射仪(Serial NED)已被证明能够在室内进行高分辨率结构测定，与国际上主要的X射线设备不相上下。通过采用连续采样和剂量分级相结合的方法，已被证明消除了辐射损伤对结构分辨率的限制。电子对X射线的散射截面高达105-106倍，这意味着只需要纳米晶体就可以解决结构问题。此外，考虑到从合成的放大到足够材料生长更大的微晶体以用于X射线分析、样品提纯、访问光束线的潜在延迟等确定结构的全部时间预算，这种新方法在结构确定的流水线上最多可以加快10倍。 已经开发了两种最先进的透射电子显微镜(TEM)来促进系列化NED的发展。一个电子显微镜专门用于小分子结构测定，另一个专门针对结构生物学进行优化，两个都将设在化学系，以便于监督和维护。这项提议要求这两个TE M使用两个基于电子计数的直接电子探测器来消除噪声，并允许极短的有效帧读出剂量分数，以确保收集的数据没有辐射损害。这些探测器对执行Serial NED是必不可少的，并且在基本零噪声、连续读出格式的亚毫秒有效快门速度和接近单位的量子效率方面具有独特的性能。考虑到材料需求的减少和结构测定相关的更高产量，也因为不需要去遥远的国际设施，Serial NED承诺改变化学和结构生物学中结构测定的方式。 化学、生物化学、物理和材料科学系的几个小组将联合起来推动这一新概念。该设施将培养一个高度跨学科的学生培训环境，直接影响到75名学生和受训人员，为此将举办专门的讲习班，使学生能够亲身接触结构确定的所有方面，从数据收集、大数据分析到结构改进的最新方法。这一级别的培训超越了在使用主要国际设施期间通常获得的培训，因为学生将成为实验的所有方面的专家。他们将是下一代学生，他们将推动采用Serial NED，以帮助它充分发挥其改变结构生物学和化学的潜力。

Atomically resolved structures are at the core of chemistry, structural biology, and material science. There is a new paradigm emerging to provide this critical information. Serial Nanocrystal Electron Diffraction (Serial NED) developed at the University of Toronto has been demonstrated to be capable of high resolution structure determination in house on par with major international x-ray facilities. By adopting serial sampling in combination with dose fractionation, it has been shown to eliminate radiation damage limits to structural resolution. The factor of 105 - 106 higher scattering cross section of electrons over x-rays means that only nanocrystals are needed to solve structures. Further, in considering the full time budget in determining structures from the scale up in synthesis for enough material to grow larger microcrystals for x-ray analysis, sample purification, potential delays in accessing beam lines etc, this new approach represents an up to 10-fold speed up in the pipeline for structure determination. Two state of the art Transmission Electron Microscopes (TEMs) have been developed to advance Serial NED. One TEM is dedicated to small molecule structure determination and the other is optimized for structural biology and both will be co-located in the Department of Chemistry for ease of oversight and maintenance. This proposal requests two direct electron detectors based on electron counting for these two TEMs to eliminate noise and allow extremely short effective frame readouts for dose fraction to ensure the collected data is free of radiation damage. These detectors are essential to the execution of Serial NED and are unique in performance with respect to essentially zero noise, sub-millisecond effective shutter speeds in continuous readout formats, and near unity quantum efficiency. Given the reduction in material requirements and associated much higher throughput in structure determination, also because there is no need to go to remote international facilities, Serial NED holds the promise to change how structure determination in chemistry and structural biology are done. Several groups spanning the departments of chemistry, biochemistry, physics, and material science will join forces to advance this new concept. This facility will foster a highly interdisciplinary environment for student training, directly impacting over 75 students and trainees, for which specialized workshops will be offered that will give students hands on access to all aspects of structure determination from data collection, big data analysis, to latest methods in structure refinement. This level of training goes beyond that typically acquired during the use of major international facilities in that the students will become expert in all aspects of the experiment. They will be the next generation of students who will drive the adoption of Serial NED to help it reach its full potential to transform structural biology and chemistry.