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

正在开发使用扫描透射电子显微镜（STEM）中的电子能谱成像技术来绘制细胞和大分子组装体中元素分布的方法，该显微镜配备有冷场发射枪和与并联的扇形磁电子能谱仪。检测系统。绘制生物结构中的单个原子现在已成为这种仪器的能力范围。在进行高剂量分析之前，可以使用暗场 STEM 进行低剂量成像，以便将大分子组装体的结构与其所含的特定原子数量相关联。测量结果证实了使用纳米直径探针可以实现磷的单原子检测的理论预测。尽管由于光束引起的结构退化，磷原子可能已从其原始位置移动了几纳米，但受损的分子仍然足够稳定，可以在 1 或 2 纳米分辨率下进行分析。这种分析只能通过光谱成像并校正样本漂移来实现。使用特征明确的 DNA 和病毒样本研究了绘制少量磷原子图谱的最佳策略。正在设计实验来绘制其他生物学重要元素（例如钙和铁）的单个原子，这些元素也具有有利的电离截面。 - STEM、扫描透射电子显微镜、磷、分子量、质量图、微量分析