Phase Plate Holder for Transmission Electron Microscopy

描述（由申请人提供）：在生物电子显微镜的前沿，有一个很强的强调成像细胞，细胞器和大分子的“天然”状态的三维结构。这是通过使用没有经过化学固定、脱水或染色的冷冻水合标本来实现的。目前由于电子辐照损伤，分辨率限制在4nm左右。在透射电子显微镜（TEM）中使用焦内相衬成像-通过在物镜的后焦平面中加入相位板来完成-可以提高电子断层扫描的分辨率，也增加了吞吐量。虽然这些改进最近已经通过初步实验得到证实，并且相板的好处已经知道了几十年，但技术上的困难一直阻碍着它们的使用。三个主要困难是：保持相板在电子光轴上的中心，避免污染，并允许在显微镜中容易更换相板。在第一阶段，我们已经开发和测试了一个具有精确定位系统的相板支架的工作原型，一个加热器和一个用于静电相板的电馈线。将TEM的原始物镜孔径支架与相板支架交换，几乎可以使任何冷冻电镜都配备相板。这种支架的成本大大低于任何其他技术，可以在冷冻水合标本成像方面产生类似的改进。在第二阶段，我们将把这个概念完善为商业产品，并在支架上添加自动定心软件和负载锁，允许在不破坏显微镜柱真空的情况下更换相板。后一项添加将消除打破真空插入相板的需要，并使该产品成为传统上阻止科学家更常规地使用该表征技术的所有技术问题的完整解决方案。

DESCRIPTION (provided by applicant): At the frontier of biological electron microscopy, there is a strong emphasis on imaging the 3-D structure of cells, organelles, and macromolecules in their "native" state. This is facilitated by the use of frozen-hydrated specimens which have not been subjected to chemical fixation, dehydration or stains. The resolution is currently limited to about 4 nm by electron irradiation damage. The use of in-focus phase contrast imaging in the transmission electron microscope (TEM) - accomplished by incorporating a phase plate in the back focal plane of the objective lens - can increase resolution in electron tomography, and also increase throughput. Although these improvements have recently been confirmed by preliminary experiments, and the benefits of phase plates have been known for decades, technical difficulties have always inhibited their use. The three main difficulties are: keeping the phase plate centered on the electron optical axis, avoiding contamination and allowing easy phase plate replacement in the microscope. In Phase I we have developed and tested a working prototype of a phase plate holder with precision positioning system, a heater and an electrical feed-through for use with electrostatic phase plates. Exchanging the original objective aperture holder of the TEM with the phase plate holder allows nearly any cryo-EM to be equipped with a phase plate. The cost of this holder is substantially lower than any other technology that can yield a similar improvement in imaging of frozen- hydrated specimens. In Phase II we will refine this concept into a commercial product and add auto-centering software as well as a load-lock to the holder, allowing replacement of the phase plates without breaking the vacuum in the microscope column. This latter addition will eliminate the need to break the vacuum to insert the phase plate, and makes this product into a complete solution to all technical issues that have traditionally prevented scientists from more routinely using this characterization technique. PUBLIC HEALTH RELEVANCE: Phase plate holder for transmission electron microscopy Relevance The phase plate holder that will be developed and commercialized in this project allows routine transmission electron microscopy characterization of biological structures at unprecedented resolution and contrast levels. The routine use of phase plates will allow the acquisition of levels of details in 3D tomographic images of non-crystalline materials to increase by a large leap. This TEM imaging ability is used to gain a comprehensive understanding of cellular structures and allows direct correlation between structure and function.