Periodic Extension in Optical Diffraction Analysis

1982 ◽  
Vol 40 ◽  
pp. 428-429
Author(s):  
R. Gronsky ◽  
C.S. Murty
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Considerable Increase ◽  
High Resolution Electron Microscopy ◽  
Optical Diffraction ◽  
Diffraction Spectrum ◽  
Optical Bench ◽  
Instrumental Performance ◽  
Resolution Electron ◽  
Diffraction Effects

Although the more traditional applications of optical diffractograms in high resolution electron microscopy are related to determining instrumental performance, a significant advantage can also be achieved with this technique in the analysis of fine microstructural detail. Optical microdiffraction utilizes a field-limiting aperture in the optical bench system to selectively obtain the diffraction spectrum of specific segments of high resolution negatives, with a considerable increase in spatial resolution. Unfortunately the diffraction effects from the sampling aperture itself often interfere with the interpretation of results

Structural analysis of the surface-layer protein of spirillum serpens by high-resolution electron microscopy

1983 ◽  
Vol 41 ◽  
pp. 738-739
Author(s):  
W. H. Wu ◽  
R. M. Glaeser
Keyword(s):  
Electron Microscopy ◽  
Surface Layer ◽  
Structural Analysis ◽  
High Resolution ◽  
Low Dose ◽  
High Resolution Electron Microscopy ◽  
Optical Diffraction ◽  
Surface Layer Protein ◽  
Morphological Unit ◽  
Resolution Electron

Spirillum serpens possesses a surface layer protein which exhibits a regular hexagonal packing of the morphological subunits. A morphological model of the structure of the protein has been proposed at a resolution of about 25 Å, in which the morphological unit might be described as having the appearance of a flared-out, hollow cylinder with six ÅspokesÅ at the flared end. In order to understand the detailed association of the macromolecules, it is necessary to do a high resolution structural analysis. Large, single layered arrays of the surface layer protein have been obtained for this purpose by means of extensive heating in high CaCl2, a procedure derived from that of Buckmire and Murray. Low dose, low temperature electron microscopy has been applied to the large arrays.As a first step, the samples were negatively stained with neutralized phosphotungstic acid, and the specimens were imaged at 40,000 magnification by use of a high resolution cold stage on a JE0L 100B. Low dose images were recorded with exposures of 7-9 electrons/Å2. The micrographs obtained (Fig. 1) were examined by use of optical diffraction (Fig. 2) to tell what areas were especially well ordered.

On the interpretation of electron diffraction patterns from materials containing planar boundaries: the intergrowth tungsten bronzes

1990 ◽  
Vol 429 (1876) ◽  
pp. 91-117 ◽  
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Electron Diffraction ◽  
High Resolution Electron Microscopy ◽  
Optical Diffraction ◽  
General Interest ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Resolution Imaging ◽  
Diffraction Patterns

Materials containing planar boundaries are of general interest and complete understanding of their structures is important. When direct imaging of the boundaries by, for instance, high-resolution electron microscopy, is impracticable, details of their structure and arrangement may be obtained from electron diffraction patterns. Such patterns are discussed in terms of those from intergrowth tungsten bronzes as specific examples. Fourier-transform calculations for proposed structures have been made to establish, in conjunction with optical-diffraction analogues, the features of the far-field diffraction patterns. These results have been compared with diffraction patterns obtained experimentally by transmission electron microscopy. The aim of the study, to show that the arrangement of the boundaries in these complicated phases can be deduced from their diffraction patterns without the need for high-resolution imaging, has been achieved. The steps to be taken to make these deductions are set out.

High-resolution electron microscopy of disordered LiFeO2

1984 ◽  
Vol 42 ◽  
pp. 430-431
Author(s):  
Nobuo Tanaka ◽  
J.M. Cowley
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Electron Diffraction ◽  
Diffuse Scattering ◽  
Fine Powder ◽  
High Resolution Electron Microscopy ◽  
Optical Diffraction ◽  
Lithium Ferrite ◽  
Clustering Model ◽  
Resolution Electron

The disordered structure of lithium ferrite (α-LiFeO2) has been investigated in X-ray and electron diffraction techniques. The characteristic short range order (SRO) diffuse scattering was commonly interpreted by the clustering model. The SRO state can be described by interconnecting two kinds of clusters (Fig. 1). Alternatively, it may be interpreted in terms of microdomains of some ordered structures.In the present study, the specimen was investigated with high resolution electron microscopy and optical diffraction technique. The techniquescould give the information about the SRO state in a direct way. The material investigated was α-LiFeO2 in the form of a fine powder dispersed on a holey carbon grid.Fig. 2 shows electron diffraction patterns of the specimen in the <001> and <110> observing directions. The locus of the diffuse scattering does not exactly fit with the formula, cosπh + cosπk + cosπℓ = 0, which was derived from SRO arrangement of Li and Fe ions inside the clusters. This fact suggests the existance of “inter-cluster” ordering.

Computer Experiments for High Resolution Electron Microscopy at 100 and 500 kV

1977 ◽  
Vol 35 ◽  
pp. 74-75
Author(s):  
William Krakow
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Spherical Aberration ◽  
Computer Experiments ◽  
High Resolution Electron Microscopy ◽  
Computer Programs ◽  
Optical Diffraction ◽  
Objective Lens ◽  
Bright Field ◽  
Resolution Electron

A system of computer programs has been written to simulate both bright-field and dark-field micrographs of a variety of materials of interest in both metallurgical and biomolecular applications of high resolution electron microscopy. Selected area diffraction has also been incorporated into this system of programs as well as the ability to orient the object of interest relative to the microscope coordinate system by specifying the Eulers angles between the microscope and object coordinate systems. For bright-field imaging both elastic and inelastic scattering can be included for the tilted beam or axial imaging modes. Optical diffraction programs yield the power spectra of these micrographs and filtering programs have also been designed for high pass filtering and correction of the microscope transfer function. Some of the variables which are input into this system of computer programs are: objective lens defocus, spherical aberration, chromatic aberration, beam tilt, objective aperture size and electron wave length.

Recent Applications of High Resolution Electron Microscopy to Crystalline Arrays of Virus Particles

1978 ◽  
Vol 36 (3) ◽  
pp. 470-482 ◽  
Author(s):  
R.W. Horne
Keyword(s):  
Electron Microscopy ◽  
Image Processing ◽  
Analytical Techniques ◽  
Staining Technique ◽  
High Resolution Electron Microscopy ◽  
Optical Diffraction ◽  
Full Potential ◽  
Virus Particles ◽  
Resolution Electron ◽  
Wide Range

The technique of surrounding virus particles with a neutralised electron dense stain was described at the Fourth International Congress on Electron Microscopy, Berlin 1958 (see Home & Brenner, 1960, p. 625). For many years the negative staining technique in one form or another, has been applied to a wide range of biological materials. However, the full potential of the method has only recently been explored following the development and applications of optical diffraction and computer image analytical techniques to electron micrographs (cf. De Hosier & Klug, 1968; Markham 1968; Crowther et al., 1970; Home & Markham, 1973; Klug & Berger, 1974; Crowther & Klug, 1975). These image processing procedures have allowed a more precise and quantitative approach to be made concerning the interpretation, measurement and reconstruction of repeating features in certain biological systems.

Electron microscopy of rabbit FC crystals

1983 ◽  
Vol 41 ◽  
pp. 730-731
Author(s):  
Robert A. Grant ◽  
Laura L. Degn ◽  
Wah Chiu ◽  
John Robinson
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
High Resolution Electron Microscopy ◽  
Molecular Replacement ◽  
X Ray ◽  
X Ray Crystallography ◽  
Resolution Electron ◽  
Replacement Technique ◽  
Hydrated Crystal ◽  
Molecular Structure Analysis

Proteolytic digestion of the immunoglobulin IgG with papain cleaves the molecule into an antigen binding fragment, Fab, and a compliment binding fragment, Fc. Structures of intact immunoglobulin, Fab and Fc from various sources have been solved by X-ray crystallography. Rabbit Fc can be crystallized as thin platelets suitable for high resolution electron microscopy. The structure of rabbit Fc can be expected to be similar to the known structure of human Fc, making it an ideal specimen for comparing the X-ray and electron crystallographic techniques and for the application of the molecular replacement technique to electron crystallography. Thin protein crystals embedded in ice diffract to high resolution. A low resolution image of a frozen, hydrated crystal can be expected to have a better contrast than a glucose embedded crystal due to the larger density difference between protein and ice compared to protein and glucose. For these reasons we are using an ice embedding technique to prepare the rabbit Fc crystals for molecular structure analysis by electron microscopy.

High resolution electron microscopy of lanthanum phosphate crystals

1978 ◽  
Vol 36 (1) ◽  
pp. 274-275
Author(s):  
J. C. Wheatley ◽  
J. M. Cowley
Keyword(s):  
Electron Microscopy ◽  
Catalytic Activity ◽  
High Resolution ◽  
Petroleum Industry ◽  
High Resolution Electron Microscopy ◽  
Lanthanum Phosphate ◽  
Good Catalyst ◽  
Resolution Electron ◽  
Good Catalytic Activity ◽  
Physical And Chemical

Rare-earth phosphates are of particular interest because of their catalytic properties associated with the hydrolysis of many aromatic chlorides in the petroleum industry. Lanthanum phosphates (LaPO4) which have been doped with small amounts of copper have shown increased catalytic activity (1). However the physical and chemical characteristics of the samples leading to good catalytic activity are not known.Many catalysts are amorphous and thus do not easily lend themselves to methods of investigation which would include electron microscopy. However, the LaPO4, crystals are quite suitable samples for high resolution techniques.The samples used were obtained from William L. Kehl of Gulf Research and Development Company. The electron microscopy was carried out on a JEOL JEM-100B which had been modified for high resolution microscopy (2). Standard high resolution techniques were employed. Three different sample types were observed: 669A-1-5-7 (poor catalyst), H-L-2 (good catalyst) and 27-011 (good catalyst).

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