Biological Structure, Nature of Matter Are Topics of Nobel Prizes

Structural investigations of biological macromolecules commonly employ CTEM with negative staining techniques. Difficulties in valid image interpretation arise, however, due to problems such as variability in thickness and degree of penetration of the staining agent, noise from the supporting film, and artifacts from defocus phase contrast effects. In order to determine the effects of these variables on biological structure, as seen by the electron microscope, negative stained macromolecules of high density lipoprotein-3 (HDL3) from human serum were analyzed with both CTEM and STEM, and results were then compared with CTEM micrographs of freeze-etched HDL3. In addition, we altered the structure of this molecule by digesting away its phospholipid component with phospholipase A2 and look for consistent changes in structure.

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Scanning Electron Microscopic Study of the Cell Surface

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100062087 ◽

1969 ◽

Vol 27 ◽

pp. 36-37 ◽

Cited By ~ 1

Author(s):

Toichiro Kuwabara

Keyword(s):

Tissue Fluid ◽

Biological Application ◽

Biological Structure ◽

Electron Microscopic ◽

Surface Appearance ◽

Minute Amount ◽

Scanning Electron Microscopic Study ◽

Scanning Electron Microscopic ◽

True Structure ◽

Scanning Electron

Although scanning electron microscopy has a great potential in biological application, there are certain limitations in visualization of the biological structure. Satisfactory techniques to demonstrate natural surfaces of the tissue and the cell have been reported by several investigators. However, it is commonly found that the surface cell membrane is covered with a minute amount of mucin, secretory substance or tissue fluid as physiological, pathological or artefactual condition. These substances give a false surface appearance, especially when the tissue is fixed with strong fixatives. It seems important to remove these coating substances from the surface of the cell for demonstration of the true structure.

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The High Resolution Appearance of Biological Substrates

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100063998 ◽

1969 ◽

Vol 27 ◽

pp. 416-417

Author(s):

Glen B. Haydon

Keyword(s):

High Resolution ◽

Phase Image ◽

Biological Structure ◽

Electron Microscopic ◽

Thin Sections ◽

Resolution Electron ◽

Discrete Structures ◽

Large Phase ◽

Biological Substrates ◽

High Resolution Electron Micrographs

High resolution electron microscopic study of negatively stained macromolecules and thin sections of tissue embedded in a variety of media are difficult to interpret because of the superimposed phase image granularity. Although all of the information concerning the biological structure of interest may be present in a defocused electron micrograph, the high contrast of large phase image granules produced by the substrate makes it impossible to distinguish the phase ‘points’ from discrete structures of the same dimensions. Theory predicts the findings; however, it does not allow an appreciation of the actual appearance of the image under various conditions. Therefore, though perhaps trivial, training of the cheapest computer produced by mass labor has been undertaken in order to learn to appreciate the factors which affect the appearance of the background in high resolution electron micrographs.

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Removal of inelastically scattered electrons substantially increases phase contrast on frozen-hydrated molecules

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100127694 ◽

1987 ◽

Vol 45 ◽

pp. 652-653

Author(s):

John P. Langmore ◽

Brian D. Athey

Keyword(s):

Electron Diffraction ◽

Phase Contrast ◽

Low Dose ◽

Dark Field ◽

Biological Structure ◽

Bright Field ◽

Low Contrast ◽

Negative Stain ◽

The Difference ◽

Better Than

Although electron diffraction indicates better than 0.3nm preservation of biological structure in vitreous ice, the imaging of molecules in ice is limited by low contrast. Thus, low-dose images of frozen-hydrated molecules have significantly more noise than images of air-dried or negatively-stained molecules. We have addressed the question of the origins of this loss of contrast. One unavoidable effect is the reduction in scattering contrast between a molecule and the background. In effect, the difference in scattering power between a molecule and its background is 2-5 times less in a layer of ice than in vacuum or negative stain. A second, previously unrecognized, effect is the large, incoherent background of inelastic scattering from the ice. This background reduces both scattering and phase contrast by an additional factor of about 3, as shown in this paper. We have used energy filtration on the Zeiss EM902 in order to eliminate this second effect, and also increase scattering contrast in bright-field and dark-field.

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