Acquisition of a New-Generation, Variable Pressure, Digital Scanning Electron Microscope for Multi-Disciplinary Studies in Biological Sciences and Biotechnology

该提案要求为爱荷华州州立大学的中央贝西显微镜设施（BMF）提供新一代可变真空（压力）扫描电子显微镜（SEM），该显微镜具有数字图像增强系统，可通过使用自动化功能的简单操作更清楚地观察细节，并能够提供高分辨率（30 kV时为3.5 nm）。 该仪器可以改装有冷冻保存系统和已经在BMF中使用的X射线能量色散检测器。某些现代SEM能够在高真空下在KV和放大率范围内提供高分辨率，明亮的图像，以及在低真空和KV下提供高分辨率，明亮的图像，以减少样品辐射损伤和充电，但也具有良好的分辨率。对高性能、高分辨率SEM的需求已成为生物科学和其他不同科学研究领域的基本要求。此外，在低于SkV的kV下使用SEM的兴趣也在诸如研究细胞内超微结构、用背散射检测器检测和鉴定用于免疫细胞化学标记的5-10 nm胶体金标记物、特别是观察光束敏感和/或或不稳定的样品，例如食品和其他脆弱的生物样品，它们不能承受高加速电压和束流。这些后一种标本可以通过使用快速冷冻能力来保存，例如使用BMF中已有的低温保存单元和丙烷喷射冷冻机。同样重要的是，要观察样品的表面结构和断裂面，同时提供这些表面内局部物质的X射线元素分析。成分信息和相应的表面超微结构也可以用背散射电子检测器测定和分析。爱荷华州州立大学校园已经确定了六个具体的研究项目，这些项目将直接受益于具有上述功能的新一代高分辨率可变真空SEM。 还有许多其他项目也将受益于BMF的各种其他用户的新一代SEM。

This proposal requests a new-generation, variable-vacuum (pressure) scanning electron microscope (SEM), for the central Bessey Microscopy Facility (BMF) at Iowa State University, with a digital image enhancement system for observing details more clearly with simple operation using automated functions, and capable of providing high resolution (@ 3.5nm at 30 kV). This instrument can be retrofitted with a cryopreservation system and a x-ray energy dispersive detector already in use in the BMF. Certain modern-day SEMs are able to provide both high-resolution, bright images at high vacuum over a range of kVs and magnifications, and at low vacuums and kVs to reduce specimen radiation damage and charging, but also with good resolution. Need for a high performance, high resolution SEM has become a basic requirement in biological sciences, and in other diverse areas of scientific research. In addition, interest of using SEM at a kV below SkV is also recognized in such applications as studying intracellular ultrastructure, detection and identification of 5-10 nm colloidal gold markers for immunocytochemical labeling with a backscattered detector, and particularly viewing beam sensitive and/or unstable specimens such as food products and other delicate biological samples which cannot withstand high accelerating voltages and beam currents. These latter specimens can be preserved by using quick freezing capabilities such as with a cryopreservation unit and a propane jet freezer already available in the BMF. It is also important to observe with increased resolution surface structures and fracture faces of specimens and, at the same time, to provide x-ray elemental analysis of localized substances within these surfaces. Compositional information and corresponding surface ultrastructure can also be determined and analyzed with a backscattered electron detector. Six specific research projects have been identified on the Iowa State University campus which would directly benefit from a new-generation, high-resolution, and variable-vacuum SEM with the above capabilities. There are a number of other projects that would also benefit from this new-generation SEM by a wide variety of other users of the BMF.