A facility for electron microscopy of specimens in controlled environments

Ward, P.; Rupert, Mitchell,

doi:10.1088/0022-3735/5/2/021

Cited by 20 publications

(12 citation statements)

References 8 publications

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“…Unit-cell dimensions, calibrated with a Au ° powder diffraction standard are a= 69.7 A, c= 177 A, with an orthorhombic unit cell assumed (Labaw, 1967), and are in good agreement with previous measurements of diffraction patterns from both wet and negatively stained catalase crystals of this habit (Ferrier, 1969;Wrigley, 1968;Matricardi, 1972;Unwin, 1972;Labaw, 1967;Moretz, 1973;Ward & Mitchell, 1972;Matricardi, Moretz & Parsons, 1972).…”

Section: Unit-cell Parameters and Symmetrysupporting

confidence: 87%

Electron diffraction from single, fully-hydrated, ox-liver catalase microcrystals

Dorset¹,

Parsons²

1975

Acta Cryst A

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Section: Unit-cell Parameters and Symmetrysupporting

confidence: 87%

Electron diffraction from single, fully-hydrated, ox-liver catalase microcrystals

Dorset¹,

Parsons²

1975

Acta Cryst A

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“…There are, for instance, studies in progress to reduce beam damage using HVEM, low-temperature specimen stages, image intensification and minimum radiation dosage devices, etc. (Williams & Fisher, 1970;Cosslett, 1971Cosslett, , 1974Ward & Mitchell, 1972;Glaeser, 1974;Hart & Yoshiyama, 1975;and others).…”

Section: R W H O M Ementioning

confidence: 99%

Special Specimen Preparation Methods For Image Processing in Transmission Electron Microscopy: A Review*

1978

Journal of Microscopy

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One of the important developments in quantitative electron microscopy has been the application of optical and computer imaging methods to electron micrographs. In general these techniques of image analysis have been applied to electron micrographs from isolated biological structures prepared in the presence of various negative stains. To make full use of image processing techniques there are obvious advantages in preparing suitable specimens containing large areas of repeating features. However, the number of naturally occurring biological specimens exhibiting crystalline or paracrystalline features suitable for high resolution electron microscopy and subsequent image analysis is relatively small.Some recent experiments on the in vitro formation of crystalline and paracrystalline arrays from highly concentrated and purified isometric, filamentous and rod-like viruses is reviewed. The problems associated with the preparative procedures for producing two-dimensional and three-dimensional crystalline arrays are discussed together with the possibility of extending the negative staining-carbon film method for studying the gradual dissociation or assembly of viral components.

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“…Swann has constructed an environmental chamber for the pole piece gap of the AEI EM7 1.0-Mev electron microscope (30) and used it extensively for metallurgical and gas reaction studies. A single-stage differentially pumped unit was constructed for the Cavendish Laboratory high-voltage microscope (36) for use in the examination of wet biological specimens.…”

Section: Principle Of the Thin Film Window Chambermentioning

confidence: 99%

Structure of Wet Specimens in Electron Microscopy

Parsons

1974

Science

142

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Several recent technological advances have increased the practicality and usefulness of the technique of electron microscopy of wet objects. (i) There have been gains in the effective penetration of high-voltage microscopes, scanning transmission microscopes, and high-voltage scanning microscopes. The extra effective penetration gives more scope for obtaining good images through film windows, gas, and liquid layers. (ii) Improved methods of obtaining contrast are available (especially dark field and inelastic filtering) that often make it possible to obtain sufficient contrast with wet unstained objects. (iii) Improved environmental chamber design makes it possible to insert and examine wet specimens as easily as dry specimens. The ultimate achievable resolution for wet objects in an environmental chamber will gradually become clear experimentally. Resolution is mainly a function of gas path, liquid and wet specimen thickness, specimen stage stability, acceleration voltage, and image mode (fixed or scanning beam) (13). Much depends on the development of the technique for controlling the thickness of extraneous water film around wet objects or the technique for depositing wet objects onto dry, hydrophobic support films. Although some loss of resolution due to water or gas scattering will always occur, an effective gain is anticipated in preserving the shape of individual molecules and preventing the partial collapse that usually occurs on drying or negative staining. The most basic question for biological electron microscopy is probably whether any living functions of cells can be observed so that the capabilities of the phase contrast and interference light microscopes can be extended. Investigators are now rapidly approaching a final answer to this question. The two limiting factors are (i) maintaining cell motility in spread cells immersed in thin layers of media and (ii) reducing beam radiation damage to an acceptable level. The use of sensitive emulsions and image intensifiers can bring the observation dose below that required to stop cell motility. Use of a timed, pulsed deflector system enables sufficiently short exposures to be obtained to eliminate blurring due to Brownian motion. Environmental chambers have enhanced the possibilities of electron diffraction analysis of minute crystals and ordered biological structures. High-resolution electron diffraction patterns (especially kinematic) of protein crystals can only be obtained in a wet environment. Hence, it may now be possible to obtain undistorted images of protein molecules. Moreover, by subjecting diffraction patterns to image-iterative techniques (56), it will be possible to phase the electron diffraction patterns to give a calculated image with a higher resolution than that which can be produced by electron microscope objective lenses. Environmental chambers offer exciting prospects for the determination of water structure and water and ice nucleation (atmospheric science). Nucleation data near the molecular level have been badly needed for some ti...

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A facility for electron microscopy of specimens in controlled environments

Cited by 20 publications

References 8 publications

Electron diffraction from single, fully-hydrated, ox-liver catalase microcrystals

Electron diffraction from single, fully-hydrated, ox-liver catalase microcrystals

Special Specimen Preparation Methods For Image Processing in Transmission Electron Microscopy: A Review*

Structure of Wet Specimens in Electron Microscopy

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