电镜与光镜光路图比较 回+回 Light microscope Electron microscope Figure 18.12 A comparison of the lens systems of a light and electron microscope(From w. Agar, Principles nd Practice of Electron Microscope Operat tion, Elsevier/ th-Holland, 1974)
电镜与光镜光路图比较
入=150V Work V:104-105Vat60,000,=0.05A theoretically D=0.61x 0.05/1x1=0.03 A Practically, resolution limit: 3-4 A, for Cellular structure 10-15 A
= 150/V Work V: 104—105 V at 60,000V, =0.05 Å theoretically D = 0.61x 0.05 / 1x1= ~0.03 Å Practically, resolution limit: 3-4 Å, for Cellular structure 10-15 Å
电镜与光镜的比较 电子显微镜与光学显微镜的基本区别 分辨本领光源透镜真空成像原理 0.2mm 可见光 光学显微镜 可见光 利用样本对光的吸收形成明暗 反差和颜色变化 100nm 紫外光 玻璃透镜不要求真空 (波长约200mm) 电子显微镜接近0.1mm电子束 电磁透镜 33×10 利用样品对电子的散射和透射形 (波长 1.33×10°Pa成明暗反差
电镜与光镜的比较 电子显微镜与光学显微镜的基本区别 分辨本领 光 源 透 镜 真 空 成像原理 人眼 0.2mm 可见光 光学显微镜 200nm 可见光 ( 波 长 400 ～ 700nm) 利用样本对光的吸收形成明暗 反差和颜色变化 100nm 紫外光 （波长约 200nm） 玻璃透镜 不要求真空 电子显微镜 接近 0.1nm 电子束 ( 波 长 0.01 ～ 0.9nm) 电磁透镜 1.33×1 0-3～ 1.33×1 0-5P a 利用样品对电子的散射和透射形 成明暗反差
s Specimen preparation for TEM Standard method: Fixation: Glutaraldehyde( proteins cross-linking),osmium tetroxide(lipid), Dehydration(in alcohol) and embedding within epoxy plastic called epon Section: 0.02-0.1 u m, cut by glass or diamond Section mounting on grids and stain by electron dyes, which provide the mass thickness required to scatter the electron beam: uranyl acetate and lead citrate or be treated with metal-tagged antibody ect. Or a number of cytochemical procedures to detect some ei enzymes as acid phosphatase
* Specimen preparation for TEM Standard method: Fixation: Glutaraldehyde ( proteins cross-linking), osmium tetroxide (lipid), Dehydration (in alcohol) and embedding within epoxy plastic called Epon Section: 0.02-0.1μm, cut by glass or diamond Section mounting on grids and stain by electron dyes, which provide the mass thickness required to scatter the electron beam: uranyl acetate and lead citrate, or be treated with metal-tagged antibody ect. Or a number of cytochemical procedures to detect some enzymes as acid phosphatase
Tissue dissected out After washing, the tissue is and placed in fixing Tissue is now placed in Specimen dehydrated by placing it dilute solution of plastic in higher and higher concentrations of acetone or alcohol Specimen holder for microtome When the plastic is hard. the block is trimmed and is ady Tissue is placed in final bedding mixture and the polymerized Sections are cut on an ultramicrotome with a glass or diamond knife The sections are floated off the edge of the knife onto the surface of a water trough The sections are picked off th After the sections dry, they surface with a copper grid in the electron microscope