Compostional Imaging with Energy Filtered Scanning Transmission Electron Microscopy

该研究小组将开发在2nm-3nm分辨率下绘制细胞膜和细胞器组成的方法，使用200kV场发射枪ıFEG！-配备的电子显微镜与平行电子能量损失光谱仪（平行EELS）和x射线探测器接口。物理学家和生物学家将合作开发生物冷冻切片中低浓度元素（如Ca， P, Gd）定量成像所需的特殊技术。利用200kV激励，并通过理论和实验发展最佳的光谱收集和数据分析方法，克服了EELS的主要障碍，即低温切片厚度造成的大背景。在每个扫描像素处收集的EELS光谱将是多个最小二乘拟合算法，该算法考虑了多重等离子体散射的贡献，在高损耗区域，碳能量损失及其精细结构，以及l边（例如钾）对EELS背景的贡献。电子光学元件将被设计并添加到现有的并行EELS系统中，以纠正降低检测灵敏度的增益变化。钙结合膜或隔离在细胞器和磷酸化位点的高分辨率组成制图将具有广泛的生物学应用，并将被探索。

This research group will develop methods for mapping the composition of cell membranes and organelles at 2nm-3nm resolution, with a 200kV field emission gun ıFEG!-equipped electron microscope interfaced with a parallel electron energy loss spectrometer (parallel EELS) and an X-ray detector. Physicists and biologists will collaborate to develop the special techniques required for quantitative imaging of low-concentrations of elements (e.g., Ca, P, Gd) in biological cryosections. The major obstacle to EELS, the large background due to the thickness of cryosections, will be overcome by the use of 200kV excitation and through theoretical and experimental development of optimal methods of spectral collection and data analysis. EELS spectra collected at each scanned pixel will be multiple least squares fitted with algorithms that take into account the contributions of plural plasmon scattering and, in the higher loss region, the carbon energy loss and its fine structure, and L-edges (e.g. potassium)to the EELS background. Electron optical components will be designed and added to an existing parallel EELS system to correct the gain variations that reduce detection sensitivities. High resolution compositional mapping of Ca-bound to membranes or sequestered in organelles and of phosphorylation sites will have broad biological applications and will be explored.