The Geometry Of Disorder: Theoretical Investigations Of Quasicrystals And Frustrated Magnets: Quasi-Crystals And Quasi-Equivalence: Symmetries And Energies In Alloys And Biological Materials

Electron microscopy and diffraction of biological materials in the hydrated state requires the construction of a chamber in which the water vapor pressure can be maintained at saturation for a given specimen temperature, while minimally affecting the normal vacuum of the remainder of the microscope column. Initial studies with chambers closed by thin membrane windows showed that at the film thicknesses required for electron diffraction at 100 KV the window failure rate was too high to give a reliable system. A single stage, differentially pumped specimen hydration chamber was constructed, consisting of two apertures (70-100μ), which eliminated the necessity of thin membrane windows. This system was used to obtain electron diffraction and electron microscopy of water droplets and thin water films. However, a period of dehydration occurred during initial pumping of the microscope column. Although rehydration occurred within five minutes, biological materials were irreversibly damaged. Another limitation of this system was that the specimen grid was clamped between the apertures, thus limiting the yield of view to the aperture opening.

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Evaluation of Freezing Methods by Low Temperature X-Ray Diffraction

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100079176 ◽

1977 ◽

Vol 35 ◽

pp. 330-333

Author(s):

T. Gulik-Krzywicki ◽

M.J. Costello

Keyword(s):

Biological Materials ◽

Molecular Organization ◽

X Ray Diffraction ◽

Glass Capillary ◽

X Ray ◽

Rate Dependent ◽

Before And After ◽

Freeze Etching ◽

Diffraction Patterns ◽

Set Up

Freeze-etching electron microscopy is currently one of the best methods for studying molecular organization of biological materials. Its application, however, is still limited by our imprecise knowledge about the perturbations of the original organization which may occur during quenching and fracturing of the samples and during the replication of fractured surfaces. Although it is well known that the preservation of the molecular organization of biological materials is critically dependent on the rate of freezing of the samples, little information is presently available concerning the nature and the extent of freezing-rate dependent perturbations of the original organizations. In order to obtain this information, we have developed a method based on the comparison of x-ray diffraction patterns of samples before and after freezing, prior to fracturing and replication.Our experimental set-up is shown in Fig. 1. The sample to be quenched is placed on its holder which is then mounted on a small metal holder (O) fixed on a glass capillary (p), whose position is controlled by a micromanipulator.

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Enhanced information from biological materials through technological improvements in cryo-electron microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100124343 ◽

1992 ◽

Vol 50 (1) ◽

pp. 788-789

Author(s):

Marc J.C. de Jong ◽

Wim M. Busing ◽

Max T. Otten

Keyword(s):

Electron Microscopy ◽

Electron Beam ◽

Biological Materials ◽

Electron Crystallography ◽

Cryo Electron Microscopy ◽

Transmission Electron ◽

The Many ◽

Technological Improvements ◽

Beam Damage

Biological materials damage rapidly in the electron beam, limiting the amount of information that can be obtained in the transmission electron microscope. The discovery that observation at cryo temperatures strongly reduces beam damage (in addition to making it unnecessaiy to use chemical fixatives, dehydration agents and stains, which introduce artefacts) has given an important step forward to preserving the ‘live’ situation and makes it possible to study the relation between function, chemical composition and morphology.Among the many cryo-applications, the most challenging is perhaps the determination of the atomic structure. Henderson and co-workers were able to determine the structure of the purple membrane by electron crystallography, providing an understanding of the membrane's working as a proton pump. As far as understood at present, the main stumbling block in achieving high resolution appears to be a random movement of atoms or molecules in the specimen within a fraction of a second after exposure to the electron beam, which destroys the highest-resolution detail sought.

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Application of ruthenium red/osmium tetroxide to bacteria, plant and animal tissue

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100141998 ◽

1986 ◽

Vol 44 ◽

pp. 54-55

Author(s):

R. L. Grayson ◽

N. A. Rechcigl

Keyword(s):

Electron Microscopy ◽

Electron Density ◽

Osmium Tetroxide ◽

Biological Materials ◽

Ruthenium Red ◽

Animal Tissue

Ruthenium red (RR), an inorganic dye was found to be useful in electron microscopy where it can combine with osmium tetroxide (OsO4) to form a complex with attraction toward anionic substances. Although Martinez-Palomo et al. (1969) were one of the first investigators to use RR together with OsO4, our computor search has shown few applications of this combination in the intervening years. The purpose of this paper is to report the results of our investigations utilizing the RR/OsO4 combination to add electron density to various biological materials. The possible mechanisms by which this may come about has been well reviewed by previous investigators (1,3a,3b,4).

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A Structural Model for a Quasi-Crystalline Material Derived from TEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100178999 ◽

1990 ◽

Vol 48 (1) ◽

pp. 48-49

Author(s):

Jan-Olov Bovin ◽

Osamu Terasaki ◽

Jan-Olle Malm ◽

Sven Lidin ◽

Sten Andersson

Keyword(s):

High Resolution ◽

Electron Diffraction ◽

Structural Model ◽

Image Intensifier ◽

Crystalline Materials ◽

Icosahedral Phases ◽

Transmission Electron ◽

Electron Microscopes ◽

Diffraction Patterns ◽

Quasi Crystals

High resolution transmission electron microscopy (HRTEM) is playing an important role in identifying the new icosahedral phases. The selected area diffraction patterns of quasi crystals, recorded with an aperture of the radius of many thousands of Ångströms, consist of dense arrays of well defined sharp spots with five fold dilatation symmetry which makes the interpretation of the diffraction process and the resulting images different from those invoked for usual crystals. The atomic structure of the quasi crystals is not established even if several models are proposed. The correct structure model must of course explain the electron diffraction patterns with 5-, 3- and 2-fold symmetry for the phases but it is also important that the HRTEM images of the alloys match the computer simulated images from the model. We have studied quasi crystals of the alloy Al65Cu20Fe15. The electron microscopes used to obtain high resolution electro micrographs and electron diffraction patterns (EDP) were a (S)TEM JEM-2000FX equipped with EDS and PEELS showing a structural resolution of 2.7 Å and a IVEM JEM-4000EX with a UHP40 high resolution pole piece operated at 400 kV and with a structural resolution of 1.6 Å. This microscope is used with a Gatan 622 TV system with an image intensifier, coupled to a YAG screen. It was found that the crystals of the quasi crystalline materials here investigated were more sensitive to beam damage using 400 kV as electron accelerating voltage than when using 200 kV. Low dose techniques were therefore applied to avoid damage of the structure.

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