Determination of the defocus value of micrographs of ice-embedded specimen without carbon support film

1993 ◽  
Vol 51 ◽  
pp. 560-561
Author(s):  
Z. Hong Zhou
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Transfer Function ◽  
Carbon Support ◽  
Objective Lens ◽  
Contrast Transfer Function ◽  
X Ray ◽  
Spatial Frequencies ◽  
High Resolution Reconstruction

It is well recognized that the contrast transfer function (CTF) of an electron microscope modulates the image contrast The effects of this CTF are to reverse the sign of the phases and to alter the amplitudes at different spatial frequencies. These changes are dependent on the defocus of the objective lens in a given microscope setting. Therefore, it is necessary to determine the defocus experimentally in order to correct the phase reversal and the amplitudes due to the CTF for attaining a high resolution reconstruction. The most straightforward way of determining the defocus value is to determine the positions of the Thon rings in the CTF by optical or computed transforms. In a crystalline specimen, the defocus value of an image can be refined against the electron diffraction amplitude. For specimen of which the x-ray structure is known, one can also use the x-ray structure factor to determine the CTF parameters.

Correlation of cryo-electron microscopic and x-ray data and compensation of the contrast transfer function

1992 ◽  
Vol 50 (2) ◽  
pp. 996-997
Author(s):  
R. Holland Cheng
Keyword(s):  
Transfer Function ◽  
Phase Contrast ◽  
Objective Lens ◽  
Biological Macromolecules ◽  
Electron Microscopic ◽  
Contrast Transfer Function ◽  
Image Reconstruction Techniques ◽  
X Ray ◽  
Mass Distributions ◽  
Spatial Frequencies

Cryo-electron microscopy (cryoEM) along with image reconstruction techniques can produce vivid images of biological macromolecules in their “native” state, although objective interpretation of these images is influenced by the fact that the contribution of phase contrast greatly exceeds that of amplitude contrast in such weakly scattering objects. The microscope contrast transfer function (CTF), which is strongly dependent on the defocus level of objective lens, modulates images of the object density distribution as a function of spatial frequency. Compensation for the effects of phase contrast transfer is important because underweighting of the low spatial frequencies usually causes difficulties in evaluating absolute mass distributions in objects.Correct compensation for the CTF is difficult to achieve. This is due, in part, to ambiguities in measuring the exact defocus level in noisy micrographs, and in knowing the relative contributions of amplitude and phase contrast, beam coherence, and inelastic scattering. The availability of atomic resolution determinations for a few viruses allows one to determine empirically how to correct the cryoEM images to best fit the x-ray data.

Sideband imaging for sub-Å image resolution with an intermediate voltage conventional TEM

1991 ◽  
Vol 49 ◽  
pp. 412-413
Author(s):  
William Krakow
Keyword(s):  
Electron Microscope ◽  
Transfer Function ◽  
Amorphous Materials ◽  
Image Features ◽  
Image Resolution ◽  
Objective Lens ◽  
Contrast Transfer Function ◽  
Image Artifact ◽  
Cornell University ◽  
The Many

The impetus for achieving sub-angstrom resolution in a CTEM was put in place several years ago at Cornell University in the laboratory of Professor Benjamin Siegel. Amongst the many activities in his laboratory was the mission to retrieve and restore the information contained in HREM images by correcting the deleterious effects of the objective lens contrast transfer function. At this time, micrographs of amorphous materials such as Ge were being studied elsewhere with the premise that tilting the illumination would lead to improved resolution. This in fact led to the observation of fringe-like image features which could not be explained in terms of an amorphous material's microstructure. At this time we were able to demonstrate in Professor Siegel's laboratory that the appearance of pseudo fringe structures was an image artifact produced by spatial filtering in the electron microscope of elastically and inelastically scattered electrons.

Spot Scan Imaging and the Future of High Resolution

1990 ◽  
Vol 48 (1) ◽  
pp. 88-89
Author(s):  
K.H. Downing
Keyword(s):  
High Resolution ◽  
Transfer Function ◽  
Good Deal ◽  
Photographic Film ◽  
Modulation Transfer ◽  
Contrast Transfer Function ◽  
Electron Dose ◽  
High Resolution Data ◽  
Resolution Data

Electron crystallographers who have been working on determination of protein structure have set a goal of obtaining image information to a resolution of about 3.5 Å, from specimens tilted up to 60 degrees. This information would allow the construction of a three-dimensional density map within which the path of the peptide chain could be followed and locations of side chains defined. The recent determination of an atomic model of the membrane protein bacteriorhodopsin (bR) from EM data (1) which was not as complete as we would like, used a good deal of other biochemical and biophysical data to constrain the model. In cases where this type of information is not as extensive as with bR, isotropic high-resolution data would be required. Significant advances in several different areas have brought us tantalizingly close to reaching our goal, but there are still improvements to be made.The essential limitations in obtaining high resolution data from proteins arise from the radiation sensitivity of the specimen, which severely limits the electron exposure that can be used in recording an image and thus limits the signal-to-noise ratio (SNR). Increasing both the electron dose, which is possible with cold specimens, and the area processed, which required implementation of significant computer software, have each given about a factor of three improvement in SNR. Still, with conventional imaging, a study by Henderson and Glaeser (2) revealed that the best images contained only a small fraction of the signal that would be present in a perfect image. Factors such as the envelope of the contrast transfer function and the modulation transfer function of the photographic film account for some loss of contrast, but the factor causing the most loss was found to be beam-induced specimen motion. This motion results from the stress which is produced by changes in bond structure during the course of radiation damage.

A Liquid Nitrogen Cooled Stage for STEM

1974 ◽  
Vol 32 ◽  
pp. 444-445
Author(s):  
Louis T. Germinario
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Liquid Nitrogen ◽  
Room Temperature ◽  
Objective Lens ◽  
Thermal Drift ◽  
Specimen Holder ◽  
Resolution Capability ◽  
Focal Position

A liquid nitrogen stage has been developed for the JEOL JEM-100B electron microscope equipped with a scanning attachment. The design is a modification of the standard JEM-100B SEM specimen holder with specimen cooling to any temperatures In the range ~ 55°K to room temperature. Since the specimen plane is maintained at the ‘high resolution’ focal position of the objective lens and ‘bumping’ and thermal drift la minimized by supercooling the liquid nitrogen, the high resolution capability of the microscope is maintained (Fig.4).

A New High Resolution Transmission Electron Microscope with Second-Zone Objective Lens

1969 ◽  
Vol 27 ◽  
pp. 176-177 ◽  
Author(s):  
H. Tochigi ◽  
H. Uchida ◽  
S. Shirai ◽  
K. Akashi ◽  
D. J. Evins ◽  
...  
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Transmission Electron Microscope ◽  
Objective Lens ◽  
High Excitation ◽  
Transmission Electron ◽  
New Instrument

A New High Excitation Objective Lens (Second-Zone Objective Lens) was discussed at Twenty-Sixth Annual EMSA Meeting. A new commercially available Transmission Electron Microscope incorporating this new lens has been completed.Major advantages of the new instrument allow an extremely small beam to be produced on the specimen plane which minimizes specimen beam damages, reduces contamination and drift.

Radiation Damage of Support Films

1981 ◽  
Vol 39 ◽  
pp. 28-29
Author(s):  
H.A. Cohen ◽  
W. Chiu
Keyword(s):  
Transfer Function ◽  
Low Temperatures ◽  
Carbon Support ◽  
Contrast Transfer Function ◽  
Electron Dose ◽  
Imaging Parameters ◽  
Negative Stain ◽  
Phase Corrections ◽  
Two Parameters ◽  
Medium Dose

The goal of imaging the finest detail possible in biological specimens leads to contradictory requirements for the choice of an electron dose. The dose should be as low as possible to minimize object damage, yet as high as possible to optimize image statistics. For specimens that are protected by low temperatures or for which the low resolution associated with negative stain is acceptable, the first condition may be partially relaxed, allowing the use of (for example) 6 to 10 e/Å2. However, this medium dose is marginal for obtaining the contrast transfer function (CTF) of the microscope, which is necessary to allow phase corrections to the image. We have explored two parameters that affect the CTF under medium dose conditions.Figure 1 displays the CTF for carbon (C, row 1) and triafol plus carbon (T+C, row 2). For any column, the images to which the CTF correspond were from a carbon covered hole (C) and the adjacent triafol plus carbon support film (T+C), both recorded on the same micrograph; therefore the imaging parameters of defocus, illumination angle, and electron statistics were identical.

Triosmium Clusters on a Support: Determination of Structure by X-ray Absorption Spectroscopy and High-Resolution Microscopy

2010 ◽  
Vol 17 (3) ◽  
pp. 1000-1008 ◽  
Author(s):  
Shareghe Mehraeen ◽  
Apoorva Kulkarni ◽  
Miaofang Chi ◽  
Bryan W. Reed ◽  
Norihiko L. Okamoto ◽  
...  
Keyword(s):  
High Resolution ◽  
Absorption Spectroscopy ◽  
Triosmium Clusters ◽  
X Ray ◽  
X Ray Absorption ◽  
High Resolution Microscopy

scholarly journals 3P-094 High resolution and precise X-ray crystal structure determination of Cyctochrome c Oxidase(The 46th Annual Meeting of the Biophysical Society of Japan)

2008 ◽  
Vol 48 (supplement) ◽  
pp. S142
Author(s):  
Michihiro Suga ◽  
Kyoko Ito-Shinzawa ◽  
Hiroshi Aoyama ◽  
Kazumasa Muramoto ◽  
Eiki Yamashita ◽  
...  
Keyword(s):  
Crystal Structure ◽  
High Resolution ◽  
Annual Meeting ◽  
Structure Determination ◽  
Crystal Structure Determination ◽  
X Ray ◽  
Biophysical Society

scholarly journals The use of scanning electron microscopy to the study of the painting from the Church in Radcze

2013 ◽  
Vol 12 (4) ◽  
pp. 095-105
Author(s):  
Beata Klimek
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Electron Microscope ◽  
Historic Buildings ◽  
X Ray ◽  
Composition And Structure ◽  
The Church ◽  
Diagnosis Technique ◽  
Scanning Electron

One of the main tasks in the study of historic buildings is the need to identify the original materials and extensions, which often have historic character. The next task concerns the determination of the composition and structure of the historical, diagnosis technique to develop original paint. The article presents the preliminary results of paintings. Methods were used with the scanning electron microscope was equipped with an energy dispersive X-ray spectrometer (SEM-EDS).

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