Unusually large magnetite (Fe3O4) crystals inside a magnetotatic bacterium

1990 ◽  
Vol 48 (4) ◽  
pp. 1084-1085
Author(s):  
Marcos Farina ◽  
Henrique G.P. Lins ◽  
Darci M.S. Esquivel
Keyword(s):  
Electron Microscope ◽  
Electron Diffraction ◽  
Southern Hemisphere ◽  
Rio De Janeiro ◽  
Magnetotactic Bacterium ◽  
Previous Communication ◽  
Linear Chains ◽  
Magnetite Fe3o4 ◽  
Wide Range ◽  
Almost All

Magnetite crystals inside magnetotactic microorganisms have been shown to cover a wide range of dimensions and shapes. However in almost all cases reported until now, crystals width and length remain under the magnetic monodomai dimensions when using Butler and Banerjee theoretical curves. We report here one type of magnetotactic bacterium which produces very large magnetite crystals as compared with those described in the literature. In previous communication we had notified this fact, but without detail. Samples were collected from brakish water from ITAIPU lagoon near Rio de Janeiro (24º Southern hemisphere). In the same sample it was possible to find different magnetotactic microorganisms.After standard isolation treatments we obtained different groups of crystals identifyed as magnetite (Fe3O4) by electron diffraction. It was observed that larger crystals(> 1000 Aº in length) stayed always closely attached in linear chains differently from smaller ones appearing as rolled chains under the electron microscope (Fig.l).

Unusually large magnetite (Fe3O4) crystals inside a magnetotactic bacterium

1990 ◽  
Vol 48 (3) ◽  
pp. 588-589
Author(s):  
Marcos Farina ◽  
Henrique G.P. Lins de Barros ◽  
Darci M.S. Esquivel
Keyword(s):  
Electron Diffraction ◽  
Southern Hemisphere ◽  
Rio De Janeiro ◽  
Magnetotactic Bacterium ◽  
Previous Communication ◽  
Magnetite Fe3o4 ◽  
Wide Range ◽  
Almost All

Magnetite crystals inside magnetotactic microorganisms have been shown to cover a wide range of dimensions and shapes. However in almost all cases reported until now, crystals width and length remain under the magnetite monodomain dimensions when using Butler and Banerjee theoretical curves. We report here one type of magnetotactic bacterium which produces very large magnetite crystals as compared with those described in the literature. In a previous communication we had notified this fact, but without detail.Samples were collected from brakish water from ITAIPU lagoon near Rio de Janeiro (24° Southern hemisphere). In the same sample it was possible to find different magnetotactic microorganisms. After standard isolation treatments we obtained different groups of crystals identifyed as magnetite (Fe3O4) by electron diffraction.

The Application of Electron Diffraction in the Study of Biocrystals

1982 ◽  
Vol 40 ◽  
pp. 570-571
Author(s):  
DoSuk D. Lee
Keyword(s):  
Electron Microscope ◽  
Electron Diffraction ◽  
Transmission Electron Microscope ◽  
Interdisciplinary Studies ◽  
Atomic Configuration ◽  
Naturally Occurring ◽  
Transmission Electron ◽  
Wide Range ◽  
Potential Applications

The transmission electron microscope (TEM) is employed in a wide range of interdisciplinary studies related to the ultrastructure of the synthetic and naturally occurring calcified crystals. However, the use of electron diffraction in studying the orientation, atomic configuration and defects of these crystals has been given little attention. This paper will examine the potential applications of electron diffraction in the study of these biominerals.

Simple Identification of Electron Diffraction Ring Patterns

1969 ◽  
Vol 27 ◽  
pp. 160-161
Author(s):  
Carolyn Nohr ◽  
Ann Ayres
Keyword(s):  
Electron Microscope ◽  
Electron Diffraction ◽  
Diffraction Ring ◽  
Image Position

Texts on electron diffraction recommend that the camera constant of the electron microscope be determine d by calibration with a standard crystalline specimen, using the equation

Vacuum System to Minimize the Specimen Contamination of High-Performance EM

1977 ◽  
Vol 35 ◽  
pp. 68-69
Author(s):  
N. Yoshimura ◽  
K. Shirota ◽  
T. Etoh
Keyword(s):  
Electron Microscope ◽  
High Speed ◽  
High Performance ◽  
High Vacuum ◽  
Vacuum System ◽  
Pump System ◽  
Pumping System ◽  
Diffusion Pump ◽  
Almost All ◽  
Cascade Type

One of the most important requirements for a high-performance EM, especially an analytical EM using a fine beam probe, is to prevent specimen contamination by providing a clean high vacuum in the vicinity of the specimen. However, in almost all commercial EMs, the pressure in the vicinity of the specimen under observation is usually more than ten times higher than the pressure measured at the punping line. The EM column inevitably requires the use of greased Viton O-rings for fine movement, and specimens and films need to be exchanged frequently and several attachments may also be exchanged. For these reasons, a high speed pumping system, as well as a clean vacuum system, is now required. A newly developed electron microscope, the JEM-100CX features clean high vacuum in the vicinity of the specimen, realized by the use of a CASCADE type diffusion pump system which has been essentially improved over its predeces- sorD employed on the JEM-100C.

Dynamical Scattering in Crystalline Biological Specimens. I. Criteria of Validity for Scattering Approximations

1975 ◽  
Vol 33 ◽  
pp. 192-193
Author(s):  
Robert M. Glaeser ◽  
Bing K. Jap
Keyword(s):  
Biological Sciences ◽  
Electron Microscopy ◽  
Electron Microscope ◽  
Electron Diffraction ◽  
Born Approximation ◽  
Materials Science ◽  
Image Data ◽  
Dynamical Effect ◽  
Crystallographic Structure ◽  
Electron Microscope Image

The dynamical scattering effect, which can be described as the failure of the first Born approximation, is perhaps the most important factor that has prevented the widespread use of electron diffraction intensities for crystallographic structure determination. It would seem to be quite certain that dynamical effects will also interfere with structure analysis based upon electron microscope image data, whenever the dynamical effect seriously perturbs the diffracted wave. While it is normally taken for granted that the dynamical effect must be taken into consideration in materials science applications of electron microscopy, very little attention has been given to this problem in the biological sciences.

In-situ electrical-resistivity measurements in the high-voltage electron microscope

1978 ◽  
Vol 36 (1) ◽  
pp. 68-69
Author(s):  
W. E. King
Keyword(s):  
Electrical Resistivity ◽  
Electron Microscope ◽  
High Voltage ◽  
Resistivity Measurements ◽  
Voltage Electron ◽  
High Voltage Electron Microscope ◽  
High Voltage Electron ◽  
Wide Range ◽  
Helium Gas

A side-entry type, helium-temperature specimen stage that has the capability of in-situ electrical-resistivity measurements has been designed and developed for use in the AEI-EM7 1200-kV electron microscope at Argonne National Laboratory. The electrical-resistivity measurements complement the high-voltage electron microscope (HVEM) to yield a unique opportunity to investigate defect production in metals by electron irradiation over a wide range of defect concentrations.A flow cryostat that uses helium gas as a coolant is employed to attain and maintain any specified temperature between 10 and 300 K. The helium gas coolant eliminates the vibrations that arise from boiling liquid helium and the temperature instabilities due to alternating heat-transfer mechanisms in the two-phase temperature regime (4.215 K). Figure 1 shows a schematic view of the liquid/gaseous helium transfer system. A liquid-gas mixture can be used for fast cooldown. The cold tip of the transfer tube is inserted coincident with the tilt axis of the specimen stage, and the end of the coolant flow tube is positioned without contact within the heat exchanger of the copper specimen block (Fig. 2).

Characterization of submicrometer fluid Inclusions in minerals by Analytical/Transmission Electron Microscopy and electron diffraction

1990 ◽  
Vol 48 (4) ◽  
pp. 424-424
Author(s):  
George Guthrie ◽  
David Veblen
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Microscope ◽  
Electron Diffraction ◽  
Light Microscopy ◽  
Fluid Inclusions ◽  
Energy Dispersive Spectrometer ◽  
Analytical Transmission Electron Microscopy ◽  
Transmission Electron

The nature of a geologic fluid can often be inferred from fluid-filled cavities (generally <100 μm in size) that are trapped during the growth of a mineral. A variety of techniques enables the fluids and daughter crystals (any solid precipitated from the trapped fluid) to be identified from cavities greater than a few micrometers. Many minerals, however, contain fluid inclusions smaller than a micrometer. Though inclusions this small are difficult or impossible to study by conventional techniques, they are ideally suited for study by analytical/ transmission electron microscopy (A/TEM) and electron diffraction. We have used this technique to study fluid inclusions and daughter crystals in diamond and feldspar.Inclusion-rich samples of diamond and feldspar were ion-thinned to electron transparency and examined with a Philips 420T electron microscope (120 keV) equipped with an EDAX beryllium-windowed energy dispersive spectrometer. Thin edges of the sample were perforated in areas that appeared in light microscopy to be populated densely with inclusions. In a few cases, the perforations were bound polygonal sides to which crystals (structurally and compositionally different from the host mineral) were attached (Figure 1).

An Electron Diffraction Study on Litnerized Potato Starch

1990 ◽  
Vol 48 (1) ◽  
pp. 580-581
Author(s):  
Jean-Claude Jésior ◽  
Roger Vuong ◽  
Henri Chanzy
Keyword(s):  
Electron Microscope ◽  
Electron Diffraction ◽  
Signal To Noise Ratio ◽  
Potato Starch ◽  
Image Intensifier ◽  
Electron Diffraction Study ◽  
Starch Granules ◽  
X Ray ◽  
Individual Grains ◽  
Diamond Knife

Starch is arranged in a crystalline manner within its storage granules and should thus give sharp X-ray diagrams. Unfortunately most of the common starch granules have sizes between 1 and 100μm, making them too small for an X-ray study on individual grains. There is only one instance where an oriented X-ray diagram could be obtained on one sector of an individual giant starch granule. Despite their small size, starch granules are still too thick to be studied by electron diffraction with a transmission electron microscope. The only reported study on starch ultrastructure using electron diffraction on frozen hydrated material was made on small fragments. The present study has been realized on thin sectioned granules previously litnerized to improve the signal to noise ratio.Potato starch was hydrolyzed for 10 days in 2.2N HCl at 35°C, dialyzed against water until neutrality and embedded in Nanoplast. Sectioning was achieved with a commercially available low-angle “35°” diamond knife (Diatome) after a very carefull trimming and a pre-sectioning with a classical “45°” diamond knife. Sections obtained at a final sectioning angle of 42.2° (compared with the usual 55-60°) and at a nominal thickness of 900Å were collected on a Formvar-carbon coated grid. The exact location of the starch granules in their sections was recorded by optical microscopy on a Zeiss Universal polarizing microscope (Fig. 1a). After rehydration at a relative humidity of 95% for 24 hours they were mounted on a Philips cryoholder and quench frozen in liquid nitrogen before being inserted under frozen conditions in a Philips EM 400T electron microscope equipped with a Gatan anticontaminator and a Lhesa image intensifier.

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