EXPERIMENTS WITH A HIGH RESOLUTION FIELD EMISSION STEM

高分辨率场发射干的实验

• 批准号: 6290683
• 负责人: Richard D Leapman
• 金额: --
• 依托单位: OFFICE OF THE DIRECTOR, NATIONAL INSTITUTES OF HEALTH
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6290683
• 关键词: image processing; phosphorus; plasmids; scanning transmission electron microscopy; technology /technique development; tobacco mosaic virus

Methods are being developed to map the distribution of elements in cells and macromolecular assemblies using the technique of electron- spectroscopic imaging in a scanning transmission electron microscope (STEM) equipped with a cold field-emission gun and a magnetic sector electron spectrometer coupled to a parallel detection system. Mapping single atoms in biological structures is now becoming within the reach of this instrumentation. Imaging can be performed at low dose with dark-field STEM prior to analysis at high dose, so that structures of macromolecular assemblies can be correlated with the numbers of specific atoms that they contain. Measurements confirm theoretical predictions that single atom detection of phosphorus can be realized by using a nanometer diameter probe. Although phosphorus atoms may have moved several nanometers from their original positions due to beam- induced structural degradation, damaged molecules are nevertheless stable enough to be analyzed at 1 or 2 nanometer resolution. Such analyses can only be achieved by means of spectrum-imaging with correction for specimen drift. Optimal strategies for mapping small numbers of phosphorus atoms have been investigated using well characterized specimens of DNA and viruses. Experiments are being designed to map single atoms of other biologically important elements like calcium and iron that also have favorable ionization cross sections. - STEM, scanning transmission electron microscopy, phosphorus, molecular weights, mass maps, microanalysis

正在开发方法来绘制使用具有冷场发射枪和磁性扇形电子光谱仪的扫描透射电子显微镜（STEM）中电子光谱成像技术在细胞和大分子组件中的分布。现在，生物结构中的单个原子映射到该仪器的范围内。在高剂量分析之前，可以在低剂量的情况下以低剂量进行成像，以便可以将大分子组件的结构与它们所含的特定原子的数量相关。测量值证实了理论上的预测，即可以使用纳米直径探针来实现磷的单个原子检测。尽管磷原子可能由于横梁诱导的结构降解而从原始位置移动了几种纳米，但损坏的分子仍然足够稳定，以便以1或2纳米分辨率分析。这样的分析只能通过频谱成像进行校正来实现样品漂移。已经使用了良好的DNA和病毒标本研究了绘制少量磷原子的最佳策略。实验的设计是为了绘制具有有利电离横截面的其他重要元素（例如钙和铁）的单个原子。 - 茎，扫描透射电子显微镜，磷，分子量，质量图，微分析