Electron crystallography of crotoxin complex thin crystals

1983 ◽  
Vol 41 ◽  
pp. 430-431
Author(s):  
T.W. Jeng ◽  
W. Chiu
Keyword(s):  
Electron Diffraction ◽  
Diffraction Pattern ◽  
Electron Diffraction Pattern ◽  
Unit Cell ◽  
Electron Crystallography ◽  
Electron Microscopic ◽  
Complex Molecules ◽  
Complex Crystal ◽  
Thin Crystal ◽  
Microscopic Techniques

Crotoxin complex is a neurotoxin isolated from the venom of the South America rattlesnake, Crotalus durrissus terrificus. It consists of two dissimilar subunits, one very acidic and the other very basic. Both acidic and basic subunits are required to show its neurotoxicity. The toxin attacks novally on both the pre-synaptic and the post-synaptic sites of the neuro-muscular junction.This protein has been crystallized in thin platelet forms suitable for electron crystallographic studies and an electron diffraction pattern of a glucose embedded crotoxin complex crystal has been recorded to an atomic resolution. The space group of this thin crystal was determined to be P4222 by a combination of electron microscopic techniques. In each unit cell, there are 8 crotoxin complex molecules arranged in a 4 layer configuration along the c axis. Different crystals have been found to have different thicknesses. We have been able to determine whether the diffraction data is obtained from a crystal with a half or a full unit cell by calculating the crystallographic reliability factors from the digitized electron diffraction pattern and by measuring optical density of a low magnification image recorded immediately after each electron diffractign pattern.

scholarly journals UnitCell Tools, a package to determine unit-cell parameters from a single electron diffraction pattern

IUCrJ ◽  
2021 ◽  
Vol 8 (5) ◽  
Author(s):  
Hong-Long Shi ◽  
Zi-An Li
Keyword(s):  
Electron Diffraction ◽  
Diffraction Pattern ◽  
Electron Diffraction Pattern ◽  
Zone Axis ◽  
Unit Cell ◽  
Single Electron ◽  
Primitive Cell ◽  
Unit Cell Parameters ◽  
Experimental Conditions ◽  
Cell Parameters

Electron diffraction techniques in transmission electron microscopy (TEM) have been successfully employed for determining the unit-cell parameters of crystal phases, albeit they exhibit a limited accuracy compared with X-ray or neutron diffraction, and they often involve a tedious measurement procedure. Here, a new package for determining unit-cell parameters from a single electron diffraction pattern has been developed. The essence of the package is to reconstruct a 3D reciprocal primitive cell from a single electron diffraction pattern containing both zero-order Laue zone and high-order Laue zone reflections. Subsequently, the primitive cell can be reduced to the Niggli cell which, in turn, can be converted into the unit cell. Using both simulated and experimental patterns, we detail the working procedure and address some effects of experimental conditions (diffraction distortions, misorientation of the zone axis and the use of high-index zone axis) on the robustness and accuracy of the software developed. The feasibility of unit-cell determination of the TiO2 nanorod using this package is also demonstrated. Should the parallel-beam, nano-beam and convergent-beam modes of the TEM be used flexibly, the software can determine unit-cell parameters of unknown-structure crystallites (typically >50 nm).

Quantitative Analysis of Electron Diffraction Pattern and Image of Crotoxin Complex Thin Crystal

1981 ◽  
Vol 39 ◽  
pp. 40-41
Author(s):  
T.W. Jeng ◽  
W. Chiu
Keyword(s):  
Quantitative Analysis ◽  
Electron Diffraction ◽  
Diffraction Pattern ◽  
Electron Diffraction Pattern ◽  
Group Symmetry ◽  
Protein Crystal ◽  
Synaptic Membrane ◽  
South American ◽  
Crotalus Durissus ◽  
Thin Crystal

Crotoxin complex is the toxic principle in the venom of the South American rattlesnake, Crotalus durissus terrificus. This protein has two non-identical subunits and expresses its neurotoxicity via synergistic interaction. Unlike most of the neurotoxins isolated from snake venoms, this protein can have binding affinity to both post- and pre-synaptic membrane. We have reported earlier preliminary results of forming a thin crystal from this complex and of an electron diffraction pattern recorded to atomic resolution. The present paper is to discuss the space group symmetry of this protein crystal from the quantitative analysis of the electron diffraction intensities as well as of the low dose images.The crotoxin complex crystal was embedded in 1% glucose. The electron diffraction pattern and image were recorded on Kokak Industrex AA x-ray film with 0.1 e/Å2 and 2.5 e/Å2, respectively, at room temperature. These data were scanned with a Perkin-Elmer microdensitometer Model 1010. Figure 1 shows the original and the computer processed electron diffraction pattern.

Domain structures in rapidly solidified Mn76Fe4Si20 alloys

1990 ◽  
Vol 48 (4) ◽  
pp. 1010-1011
Author(s):  
D. S. Zhou ◽  
W. Cao ◽  
Z.X. Jin ◽  
H.Q. Ye
Keyword(s):  
Electron Diffraction ◽  
Diffraction Pattern ◽  
Domain Structure ◽  
Electron Diffraction Pattern ◽  
Unit Cell ◽  
Domain Structures ◽  
Planar Fault ◽  
Rapidly Solidified ◽  
Form Domain ◽  
Similar Domain

In the study course of microstructures of the rapidly quenched Mn-Si alloy, 45° rotation twins showing striking eightfold symmetry in the electron diffraction pattern have been reported. These previous investigations interpreted the domain structures in terms of the β-Mn phase. The aim of this work is to show the similar domain structure having pseudo-eightfold symmetry in the reciprocal space in the Mn-Fe-Si system and to ascertain a new structure in the domain structure.The main phase in this alloy is the β-Mn phase with primitive cubic and a=0.63 nm. Fig.l gives the [001] HR image of the β-Mn phase where a square unit cell has been outlined. A planar fault showing projected rectangle network was also seen.The short edge of the rectangle remains to be the same as the a axis of the p-Mn phase, while its long side is equal to . The planar fault could appear repeatedly and form domain structure as shown in Fig.2.

Convergent Beam Electron Diffraction

1978 ◽  
Vol 36 (3) ◽  
pp. 304-315
Author(s):  
G. Lehmpfuhl
Keyword(s):  
Electron Diffraction ◽  
Diffraction Pattern ◽  
Crystal Surface ◽  
Diffraction Spot ◽  
Crystal Thickness ◽  
Large Area ◽  
Electron Microscopic ◽  
Additional Information ◽  
Microscopic Investigations

Introduction In electron microscopic investigations of crystalline specimens the direct observation of the electron diffraction pattern gives additional information about the specimen. The quality of this information depends on the quality of the crystals or the crystal area contributing to the diffraction pattern. By selected area diffraction in a conventional electron microscope, specimen areas as small as 1 µ in diameter can be investigated. It is well known that crystal areas of that size which must be thin enough (in the order of 1000 Å) for electron microscopic investigations are normally somewhat distorted by bending, or they are not homogeneous. Furthermore, the crystal surface is not well defined over such a large area. These are facts which cause reduction of information in the diffraction pattern. The intensity of a diffraction spot, for example, depends on the crystal thickness. If the thickness is not uniform over the investigated area, one observes an averaged intensity, so that the intensity distribution in the diffraction pattern cannot be used for an analysis unless additional information is available.

The structure of amorphous and polycrystalline materials using energy-filtered RDF analysis

1992 ◽  
Vol 50 (2) ◽  
pp. 1190-1191
Author(s):  
David Cockayne ◽  
David McKenzie
Keyword(s):  
Electron Diffraction ◽  
Diffraction Pattern ◽  
Density Function ◽  
Electron Diffraction Pattern ◽  
Polycrystalline Materials ◽  
Nearest Neighbour ◽  
X Ray ◽  
Selected Area Electron Diffraction ◽  
Reduced Density ◽  
System F

The technique of Electron Reduced Density Function (RDF) analysis has ben developed into a rapid analytical tool for the analysis of small volumes of amorphous or polycrystalline materials. The energy filtered electron diffraction pattern is collected to high scattering angles (currendy to s = 2 sinθ/λ = 6.5 Å-1) by scanning the selected area electron diffraction pattern across the entrance aperture to a GATAN parallel energy loss spectrometer. The diffraction pattern is then converted to a reduced density function, G(r), using mathematical procedures equivalent to those used in X-ray and neutron diffraction studies.Nearest neighbour distances accurate to 0.01 Å are obtained routinely, and bond distortions of molecules can be determined from the ratio of first to second nearest neighbour distances. The accuracy of coordination number determinations from polycrystalline monatomic materials (eg Pt) is high (5%). In amorphous systems (eg carbon, silicon) it is reasonable (10%), but in multi-element systems there are a number of problems to be overcome; to reduce the diffraction pattern to G(r), the approximation must be made that for all elements i,j in the system, fj(s) = Kji fi,(s) where Kji is independent of s.

Photographical Record of the Dispersion Surface in Rotating Crystal Electron Diffraction Pattern

1968 ◽  
Vol 23 (4) ◽  
pp. 544-549 ◽  
Author(s):  
G. Lehmpfuhl ◽  
A. Reissland
Keyword(s):  
Dynamical System ◽  
Electron Diffraction ◽  
Diffraction Pattern ◽  
Electron Diffraction Pattern ◽  
Plane Waves ◽  
Zone Axis ◽  
System Of Equations ◽  
Wave Fields ◽  
Dispersion Surface ◽  
Crystal Electron

Strong interacting wave fields in a wedge-shaped crystal are separated into different plane waves when leaving the crystal and reveal points on the dispersion surface. By rotating the crystal while moving the film one obtains a photographical record of a section through the dispersion surface which may be compared with theory. An experiment with a macroscopic MgO wedge is reported. The 002 interference with excitation error nearly zero was recorded near the [I10] zone axis while rotating the crystal about the [001] axis. The diagrams are compared with dynamical 17-beam calculations. The results show that a reduction of the infinite dynamical system of equations to 17 equations is correct under these special geometrical conditions.

In-Situ Transmission Electron Microscopy Investigation of Aluminum Induced Crystallization of Amorphous Silicon

2008 ◽  
Vol 1066 ◽  
Author(s):  
Ram Kishore ◽  
Renu Sharma ◽  
Satoshi Hata ◽  
Noriyuki Kuwano ◽  
Yoshitsuga Tomokiyo ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Amorphous Silicon ◽  
Diffraction Pattern ◽  
Electron Diffraction Pattern ◽  
Polycrystalline Silicon ◽  
Nanocrystalline Silicon ◽  
Transmission Electron ◽  
In Situ Heating ◽  
Induced Crystallization

ABSTRACTThe interaction of amorphous silicon and aluminum films to achieve polycrystalline silicon has been investigated using transmission electron microscope equipped with in-situ heating holder. Carbon coated nickel grids were used for TEM studies. An ultra high vacuum cluster tool was used for the deposition of a ∼50nm a-Si films and a vacuum deposition system was used to deposit a ∼50nm Al films on a-Si film. The microstructural features and electron diffraction in the plain view mode were observed with increase in temperature starting from room temperature to 275 °C. The specimen was loaded inside TEM heating holder. The temperature was measured and kept constant for 5 minutes during which the microstructure at fixed magnification of X63K was recorded and the electron diffraction pattern of the same area was also recorded. The temperature was then increase and fixed at desired value and microstructure and EDP were again recorded. The temperatures used in this experiment were 30, 100, 150, 200, 225, 275°C. A sequential change in microstructural features and electron diffraction pattern due to interfacial diffusion of boundary between Al and amorphous Si was investigated. Evolution of polycrystalline silicon with randomly oriented grains as a result of a-Si and Al interaction was revealed. After the in-situ heating experiment the specimen was subjected to high resolution TEM and EDS investigations after removing the excess Al. The EDS analysis of the crystallized specimen was performed to locate the Al distribution in the crystallized silicon. These studies show that the Al induced crystallization process can be used to prepare polycrystalline as well as nanocrystalline silicon by controlling the in-situ annealing parameters. The investigations are very useful as the nanocrystalline silicon is being investigated for its use in developing high efficiency silicon solar structures.

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