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

这项提案要求为爱荷华州立大学的中央贝西显微镜设施(BMF)配备新一代可变真空(压力)扫描电子显微镜(SEM)，配备数字图像增强系统，使用自动化功能通过简单的操作更清晰地观察细节，并能够提供高分辨率(在30千伏时为@3.5 nm)。该仪器可以改装成低温保存系统和已经在BMF中使用的X射线能量色散探测器。某些现代的扫描电子显微镜能够在高真空和低真空的KVS和放大倍数范围内提供高分辨率、明亮的图像，以减少样品的辐射损伤和充电，而且分辨率也很好。对高性能、高分辨率扫描电子显微镜的需求已经成为生物科学以及其他不同科学研究领域的基本要求。此外，在低于SKV的千伏下使用扫描电子显微镜也被认为是有兴趣的，例如研究细胞内的超微结构，用背散射检测器检测和鉴定5-10 nm胶体金标记用于免疫细胞化学标记，特别是观察光束敏感和/或不稳定的样品，如食品和其他无法承受高加速电压和束电流的精致生物样品。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中已有的冷冻保存装置和丙烷喷射式冷冻机。同样重要的是，以更高的分辨率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探测器来确定和分析。爱荷华州立大学校区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能力的新一代、高分辨率和可变真空扫描电子显微镜。还有许多其他项目也将受益于这种新一代扫描电子显微镜，由BMF的各种其他用户。

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.