Energy filter with fast-counting direct electron detector

维尔茨堡朱利叶斯-马克西米利安大学的研究人员研究了生物组装支持多种功能的结构决定因素。2018年，他们建立了电子冷冻显微镜设施，用于高分辨率结构测定。这一设施被维尔茨堡内外的研究人员使用。该平台的核心是一台带有肖特基XFEG发射器和直接电子探测器的300千伏电子显微镜。该探测器允许在线性模式和计数模式下进行数据采集。后者给出了接近理论极限的探测量子效率。然而，由于其低帧速率，它将吞吐量限制为每天仅约700部电影。相比之下，线性模式允许每天采集多达7000部电影的数据，但探测量子效率只有计数模式的大约一半。由于在该设施获得的数据取得成功，JMU的研究人员的雄心已转向更具挑战性的项目，如更小、更具活力的络合物和用于药物发现的配体定位。这些项目的成功依赖于大量的数据集，其中约有5000部电影是通过计数模式获得的。在目前的设备下，获取这样的数据集可能需要一周甚至更长时间。更糟糕的是，对于较小的动态复合体(&lt；150 kDa)，24小时内获得的侦察数据往往不足以判断如果获得更大的数据集，结构是否可能得到解决。因此，目前带有缓慢计数相机的检测系统不能满足JMU研究人员在24小时内获得的图像数据的质量和数量方面的需求和雄心。为了确定不同的检测系统是否更适合需求，研究人员比较了维尔茨堡和其他地方同一样本的数据。这些比较表明，除了计数，能量过滤和零损失成像是其他重要的资产，使小型动态复合体能够更稳健地分类，并显著提高整体分辨率。为了使该平台达到当前图像采集的领先标准，我们申请用具有快速计数能力的能量过滤器和直接电子探测器取代现有的检测系统。

Researchers at the Julius-Maximilians-Universität Würzburg investigate the structural determinants by which biological assemblies support a diverse set of functionalities. In 2018 they established an electron cryo microscopy facility for high-resolution structure determination. This facility is used by researchers in and beyond Würzburg. At the heart of the platform is a 300 kV electron microscope with a Schottky type XFEG emitter and a direct electron detector. The detector enables data acquisition in linear mode and in counting mode. The latter gives a detective quantum efficiency, which is close to the theoretical limit. However, due to its low frame rate it limits the throughput to only about 700 movies per day. In contrast, linear mode allows data acquisition of up to 7,000 movies a day but with only about half of the detective quantum efficiency of the counting mode. Sparked by the success with data obtained at the facility, the ambitions of the researchers at the JMU have shifted towards more challenging projects such as smaller, and more dynamic complexes and ligand localization for drug discovery. The success of these projects depends on large data sets with some 5000 movies obtained in counting-mode. With the current equipment, acquisition of such data sets can take a week and more. Even worse, for smaller dynamic complexes (< 150 kDa), the scouting data obtained within 24 hours are often insufficient for judging whether a structure would likely be solved if a larger data set were obtained. Therefore, the current detection system with a slowly counting camera does not fulfill the needs and ambitions of the researchers at the JMU with respect to quality and quantity of image data obtained within a 24-hour slot. To establish whether a different detection system will be more suitable for the needs, researchers compared data obtained for the same sample in Würzburg and elsewhere. These comparisons showed that in addition to counting, energy filtration and zero-loss imaging are other important assets which enable more robust classification of small dynamic complexes and drastically improve the overall resolution. To bring the platform to the current leading standards in image acquisition, we apply for replacing the current detection system with an energy filter and a direct electron detector with fast counting capabilities.