Direct Observation of DNA at a Molecular Scale Level by Three-Dimensional Fourier Filtering Method

三维傅立叶滤波法在分子尺度直接观察DNA

基本信息

批准号：
13450036
负责人：
TAKAI Yoshizo
金额：
$ 6.53万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-13450036/
关键词：
Transmission Electron Microscope DNA Molecular structure Bio Medical Sample Aberration-Free observation Phase Electron Microscopy Spherical aberration Correction Low electron dose

项目摘要

High-resolution transmission electron microscopy (HRTEM), at present, enables atomic level observation. However, the resulting image do not always show atomic structures precisely. Because, the image of the atomic structure is often distorted by multiple scattering of electron waves in the crystal and by aberrations ill the image-forming lenses. To solve the latter requirement, we proposed a new method called three-dimensional Fourier filtering method (3D-FFM), which enables us to observe spherical aberration-free phase and amplitude images separately. In the processing, a filtering shape function extracts only the linear component that appears -on a so-called Ewald sphere and the function works well for improving the S/N ratio by excluding the non-linear components and, quantum noises of the image, which effectively works for the biological sample observation under au extremely law electron dose conditionIn this study, the three-dimensional Fourier filtering method (3D FFM) has been successfully applied to observe a deoxyribonucleic acid (DNA) in the molecular scale level. To avoid the deterioration of the image quality cased by the contrast of the supporting film, a holey nano-sized gold grid was used and the DNA that was bridged over on the holey grid by a freeze drying method was observed. The processing made it possible to observe a spherical aberration-free phase image of the DNA with high contrast at in-focus condition. In the phase image of the DNA, periodic fine structures with intervals of 3.4-4.0 A, which seem to correspond to the distance between adjacent base pairs, were partially observed, though it seems to be heavily damaged. If we can reconstruct the DNA image by smaller dose of the electron, more,detail structures of the DNA will be, resolved, which is now under investigation

当前，高分辨率透射电子显微镜（HRTEM）可实现原子水平观察。但是，所产生的图像并不总是完全显示原子结构。因为，原子结构的图像通常会因晶体中的电子波的多个散射和形成图像形成镜片而扭曲。为了解决后者的要求，我们提出了一种称为三维傅立叶滤波方法（3D-FFM）的新方法，这使我们能够分别观察到无球差相和振幅图像。在处理过程中，滤波形状函数仅提取出现的线性组件 - 在所谓的埃瓦尔德球体中，该功能可以通过排除图像的非线性组件和图像的量子噪声来改善S/N比，从而有效地适用于AU剂量的生物剂量调节（三型型号）（三型型号），该方法有效地适用于生物剂量的调节（三）。观察分子尺度水平的脱氧核糖核酸（DNA）。为了避免通过支撑膜的对比度构成的图像质量的恶化，使用了一个空洞的纳米大小的金网格，并观察到通过冻干方法在孔网上桥接的DNA。该处理使观察到具有高对焦的DNA的无球形相位图像是可能的。在DNA的相位图像中，虽然观察到严重损坏，但观察到了部分观察到的3.4-4.0 A间隔的周期性细胞结构，似乎对应于相邻的碱基对之间的距离。如果我们可以通过较小的电子剂量重建DNA图像，则可以解决DNA的更多细节结构，现在正在研究中