LOW-DOSE ENERGY-SLECTED ELECTRON MICROSCOPY WITH AN OMEGA FILTER

我们已经研究了使用柱内omega过滤器的可能性 在元素的常规透射电子显微镜中 在低剂量下绘制生物结构图。数字图像被 通过1024×1024像素在100keV的束能量下收集， 蔡司912电子上的荧光粉耦合制冷慢扫描CCD相机 显微镜。单纯疱疹病毒冰冻水合标本 (通过插入液态乙烷进行玻璃化)被冷冻转移和 冷冻干燥前成像的区域的磷L-边缘在 能量损失约130 eV。这些数字显微照片是 从剂量小于1000的大量病毒中记录 每平方纳米的电子数。对产生的噪声图像进行了校正 对于在互相关之前的读出噪声和像素增益变化， 对非特征背景图像进行求和和去除 从鳗鱼光谱的前缘区域外推到 后边缘区域。这样，就有可能建立起一种 年平均预测的磷分布，即核酸 单纯疱疹病毒衣壳的核心。

We have investigated the potential of using an in-column omega filter in a conventional transmission electron microscope for elemental mapping of biological structures at low dose. Digital images were collected at a beam energy of 100 keV by means of a 1024 x 1024-pixel, phosphor-coupled, cooled slow-scan CCD camera on a Zeiss 912 electron microscope. Frozen-hydrated specimens of herpes simplex virus (vitrified by plunging into liquid ethane) were cryotransferred and freeze-dried before imaging in the region of the phosphorus L-edge at energy losses of around 130 eV. These digital micrographs were recorded from large numbers of viruses at a dose of less than 1000 electrons per square nanometer. Resulting noisy images were corrected for read-out noise and pixel-gain variations before cross-correlating, summing, and removing the noncharacteristic background image extrapolated from the pre-edge region of the EELS spectrum into the post-edge region. In this way, it was possible to build up an averaged projected distribution of phosphorus, i.e., nucleic acid, in the core of the herpes simplex capsid.