BIOLOGICAL APPLICATIONS OF A COMPUTED CONTROLLED ANALYTICAL ELECTRON MICROSCOPE

计算机的性能有了进一步的提高 控制分析电子显微镜，由北京工业大学和 DCRT，该仪器已被应用于几个生物 去年的问题。 其中两项研究涉及广泛的 电子能量损失谱 新安装的Gatan 607磁 扇形能量损失谱仪已被证明是完全校正， 二阶畸变 这使得在以下方面有了重大改进： 收集效率和能量分辨率，同时 能量色散X射线（EDXS）和电子能量损失的采集 光谱（EELS）以及同时弹性暗场成像 扫描传输模式。 进行了一项基础研究， 表征X射线探测器的峰值形状，这导致了 对Tracor北方探测器进行了改进， 性能 从胰腺中获得了EELS和EDXS元素图谱和光谱 通过快速冷冻、冷冻干燥（或 冷冻置换），然后进行包埋，以研究 分泌颗粒的组成。 光谱已被定量， 测定含胰岛素颗粒芯中元素的比例。 一 已进行了可行性研究，以获得低剂量EELS地图， 在膜的周期性晶体阵列中的平均程序。 数据具有 从重组孔蛋白膜的薄样品中获得， 脂质和蛋白质亚单位以及跨膜通道。 两者 实验数据和理论信号/噪声估计表明，低 剂量元素映射应该是可能的。

Further advances have been made in the capabilities of the computer controlled analytical electron microscope, developed jointly by BEIB and DCRT, and the instrumentation has been applied to several biological problems in the past year. Two of these studies involved extensive electron energy loss spectroscopy. The newly installed Gatan 607 magnetic sector energy loss spectrometer has been shown to be fully corrected for second order aberations. This has permitted a significant improvement in collection efficiency and energy resolution while allowing concurrent acquisition of energy dispersive x-ray (EDXS) and electron energy loss spectra (EELS) as well as simultaneous elastic dark field imaging in the scanning transmission mode. A basic study has been carried out to characterize the peak shapes of the x-ray detectors, and this has led to modifications to the Tracor Northern detector in order to improve performance. EELS and EDXS elemental maps and spectra have been obtained from pancreas beta cells prepared by rapid freezing, freeze-drying (or freeze-substitution) followed by embedding in order to investigate the composition of the secretory granules. Spectra have been quantitated to determine ratios of elements in the insulin-containing granule cores. A feasibility study has been made for obtaining low dose EELS maps using averaging procedures in periodic crytalline arrays of membranes. Data have been obtained from thin samples of reconstituted porin membrane containing lipid and protein sub-units and transmembrane channels. Both the experimental data and theoretical signal/noise estimations suggest that low dose elemental mapping should be possible.