Microscopy of whole cells in ice

1991 ◽  
Vol 49 ◽  
pp. 428-429
Author(s):  
E.T. O'Toole ◽  
J.R. Mcintosh
Keyword(s):  
Electron Beam ◽  
Critical Point ◽  
High Voltage ◽  
Biological Material ◽  
Comparative Method ◽  
Native State ◽  
Whole Cells ◽  
The Past ◽  
Voltage Electron ◽  
Electron Microscopes

Cryomicroscopy of frozen hydrated specimens makes it possible to visualize biological material in a condition that is close to its native state by avoiding chemical fixatives, dehydration or stain. In the past, cryoimaging using a conventional TEM has been limited to thin frozen suspensions of biological material or to thin cryosections of frozen cells and tissues. High voltage electron microscopes (HVEM) offer the advantage of improved penetration of thick samples by the electron beam and thus are suitable for imaging thick frozen samples. Here we describe a comparative method for studying the ultrastructure of freeze substituted, critical point dried cells and frozen hydratpd cells in the HVEM.

Electron Accelerators for High-Voltage Electron Microscopy (HVEM)

1972 ◽  
Vol 30 ◽  
pp. 462-463
Author(s):  
Günter O. Reinhold
Keyword(s):  
Electron Beam ◽  
High Voltage ◽  
High Energy ◽  
Electron Gun ◽  
Resolving Power ◽  
High Voltage Electron Microscopy ◽  
Voltage Electron ◽  
High Voltage Electron ◽  
Electron Microscopes ◽  
The Stability

High-voltage electron microscopes are characterized by accelerating voltages in the megavolt range (500 kV and above). Compared to conventional electron microscopes, with voltages up to 200 kV, the high-voltage instruments offer the advantage of improved resolving power (1 to 10 Å) and greater effective penetration of the electron beam. A basic difference between ordinary and high-voltage electron microscopes is the use of an electron accelerator in place of the electron gun to accelerate the electron beam to the required high energy. The resolving power of an electron microscope is determined by the stability of the accelerating voltage, the mechanical precision of the lenses and specimen stages, the stability of the lens supply current and freedom from mechanical vibrations. The symmetrical cascade generator is the only high-voltage dc power supply to meet these requirements with regard to voltage stability and vibration-free performance.

The Reduction of Chromatic Aberrations Due to Instrumental Instabilities

1971 ◽  
Vol 29 ◽  
pp. 14-15
Author(s):  
J. S. Lally ◽  
R. Evans
Keyword(s):  
Electron Microscope ◽  
High Voltage ◽  
Focal Length ◽  
Chromatic Aberration ◽  
Objective Lens ◽  
Usual Practice ◽  
Voltage Electron ◽  
Short Focal Length ◽  
Chromatic Aberrations ◽  
Electron Microscopes

One of the instrumental factors often limiting the resolution of the electron microscope is image defocussing due to changes in accelerating voltage or objective lens current. This factor is particularly important in high voltage electron microscopes both because of the higher voltages and lens currents required but also because of the inherently longer focal lengths, i.e. 6 mm in contrast to 1.5-2.2 mm for modern short focal length objectives.The usual practice in commercial electron microscopes is to design separately stabilized accelerating voltage and lens supplies. In this case chromatic aberration in the image is caused by the random and independent fluctuations of both the high voltage and objective lens current.

A New High Intensity Grid Cap for RCA-EMU-3 Electron Microscopes

1968 ◽  
Vol 26 ◽  
pp. 316-317
Author(s):  
George Christov ◽  
Bolivar J. Lloyd
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
High Voltage ◽  
High Intensity ◽  
Electron Gun ◽  
Tungsten Filament ◽  
Fluorescent Screen ◽  
Electron Microscopes ◽  
Pass Through ◽  
Ground Potential

A new high intensity grid cap has been designed for the RCA-EMU-3 electron microscope. Various parameters of the new grid cap were investigated to determine its characteristics. The increase in illumination produced provides ease of focusing on the fluorescent screen at magnifications from 1500 to 50,000 times using an accelerating voltage of 50 KV.The EMU-3 type electron gun assembly consists of a V-shaped tungsten filament for a cathode with a thin metal threaded cathode shield and an anode with a central aperture to permit the beam to course the length of the column. The cathode shield is negatively biased at a potential of several hundred volts with respect to the filament. The electron beam is formed by electrons emitted from the tip of the filament which pass through an aperture of 0.1 inch diameter in the cap and then it is accelerated by the negative high voltage through a 0.625 inch diameter aperture in the anode which is at ground potential.

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