scholarly journals OPTICAL DIFFRACTION STUDIES OF CRYSTALLINE STRUCTURES IN ELECTRON MICROGRAPHS

1969 ◽  
Vol 43 (3) ◽  
pp. 442-447 ◽  
Author(s):  
Jacob E. Berger
Keyword(s):  
Molecular Weight ◽  
Diffraction Analysis ◽  
Electron Micrographs ◽  
Crystalline Material ◽  
Unit Cell ◽  
Optical Diffraction ◽  
Isolation And Purification ◽  
Crystalline Structures

Determination of the unit cell of crystalline particles by optical diffraction analysis of electron micrographs may establish the identity and help in approximating the molecular weight of the substances contained in the crystal. This technique may be particularly helpful when isolation and purification of the crystalline material cannot be accomplished.

Light Optical Diffraction Studies of Macromolecular Ultrastructure

1970 ◽  
Vol 28 ◽  
pp. 258-259
Author(s):  
Glen B. Haydon
Keyword(s):  
High Resolution ◽  
Diffraction Analysis ◽  
Diffraction Pattern ◽  
Electron Micrographs ◽  
Optical Diffraction ◽  
Electron Micrograph ◽  
Its Analysis ◽  
Resolution Electron ◽  
Diffraction Patterns

Analysis of light optical diffraction patterns produced by electron micrographs can easily lead to much nonsense. Such diffraction patterns are referred to as optical transforms and are compared with transforms produced by a variety of mathematical manipulations. In the use of light optical diffraction patterns to study periodicities in macromolecular ultrastructures, a number of potential pitfalls have been rediscovered. The limitations apply to the formation of the electron micrograph as well as its analysis.(1) The high resolution electron micrograph is itself a complex diffraction pattern resulting from the specimen, its stain, and its supporting substrate. Cowley and Moodie (Proc. Phys. Soc. B, LXX 497, 1957) demonstrated changing image patterns with changes in focus. Similar defocus images have been subjected to further light optical diffraction analysis.

scholarly journals An electron microscopic and optical diffraction analysis of the structure of Limulus telson muscle thick filaments.

1982 ◽  
Vol 92 (2) ◽  
pp. 443-451 ◽  
Author(s):  
R W Kensler ◽  
R J Levine
Keyword(s):  
Electron Microscopy ◽  
Diffraction Analysis ◽  
Electron Micrographs ◽  
Optical Diffraction ◽  
X Ray Diffraction ◽  
Electron Microscopic ◽  
X Ray ◽  
Thick Filaments ◽  
Diffraction Patterns ◽  
Cross Bridges

Long, thick filaments (greater than 4.0 micrometer) rapidly and gently isolated from fresh, unstimulated Limulus muscle by an improved procedure have been examined by electron microscopy and optical diffraction. Images of negatively stained filaments appear highly periodic with a well-preserved myosin cross-bridge array. Optical diffraction patterns of the electron micrographs show a wealth of detail and are consistent with a myosin helical repeat of 43.8 nm, similar to that observed by x-ray diffraction. Analysis of the optical diffraction patterns, in conjunction with the appearance in electron micrographs of the filaments, supports a model for the filament in which the myosin cross-bridges are arranged on a four-stranded helix, with 12 cross-bridges per turn or each helix, thus giving an axial repeat every third level of cross-bridges (43.8 nm).

A Study Of Microcrystals Of Fibrinogen

1981 ◽  
Author(s):  
L Tranqui ◽  
E Hewatt ◽  
R Wade
Keyword(s):  
Electron Microscope ◽  
Exchange Chromatography ◽  
Unit Cell ◽  
Optical Diffraction ◽  
Ordered Structures ◽  
System A ◽  
Diffraction Patterns ◽  
Low Ionic Strength ◽  
Selection Of

We are interested in the application of image analysis to the structural determination of fibrinogen. This analysis is performed on the electron microscope images obtained from microcrystals of slightly degraded fibrinogen. The proteolysis of fibrinogen is carried out using bacterial proteases fixed onto sepharose. In our study 3 mg of sepharose-proteases are mixed with 16 mg of fibrinogen. Digestion-times of 30 min. to 4 h. are employed. The analysis of reduced fibrinogen lysates, by polyacrylamide gels in SDS,shows a progressive disappearance of the Aα chain, while lighter chains appeared with a MW of 30000. After 4 h. of digestion, the MW of the degraded fibrinogen is about 267.000, it clots after exposure to thrombin. As shown on unreduced samples on 5 % acrylamide gels in SDS, the digest is heterogeneous ; homogeneous samples are obtained by a separation on ion exchange-chromatography. From the crude fibrinogen lysates,several forms of microcrystals are obtained after a dialysis at low ionic strength (μ=0,005 ; pH = 6,2). Different forms of microcrystals are obtained from some fractions after chromatography. All these microcrystals are observed in the electron microscope after negative staining. The optical diffraction patterns obtained from these micrographs permit the selection of the most ordered regions ; thus we have established that the largest regions of ordered structures are obtained when the Aα chain of fibrinogen is degraded into a lighter chain of MW 30.000. One of the forms obtained from the crude fibrinogen digests has been studied in more details, it has a unit cell of 450 Å x 90 Å its optical diffraction shows a resolution of 30 ft. The microcrystals obtained from the fractions of chromatography have a unit cell of 440 Å/150 Å, their optical diffraction patterns show details to 35 Å. They have pgg projection symetry down the c-axis. The structures are examined after the elimination of the noise on a computer system. A first conclusion is that it is not evident that these images are simply related to the supposed elongated form of the fibrinogen molecule.

A D -periodic narrow filament in collagen

1974 ◽  
Vol 186 (1082) ◽  
pp. 67-74 ◽  
Keyword(s):  
Diffraction Analysis ◽  
Electron Micrographs ◽  
Optical Diffraction

Collagen may be reprecipitated as obliquely striated fibrils. The oblique striations are due to D -periodic subfibrils staggered axially by approxi­mately 9.0 nm with respect to their neighbours (Bruns, Trelstad & Gross 1973). The diameter of the subfibrils is variable. Optical diffraction analysis of the electron micrographs reveals instances of subfibrils with the D -repeat having diameter 3.7─4.0 nm. We argue that this structure is probably the five-stranded microfibril suggested by Smith (1968).

scholarly journals OPTICAL DIFFRACTION STUDIES OF CRYSTALLINE STRUCTURES IN ELECTRON MICROGRAPHS

1969 ◽  
Vol 43 (3) ◽  
pp. 448-455 ◽  
Author(s):  
Irmin Sternlieb ◽  
Jacob E. Berger
Keyword(s):  
Electron Micrographs ◽  
Normal Subjects ◽  
Unit Cell ◽  
Optical Diffraction ◽  
Large Size ◽  
Phospholipid Micelles ◽  
Cell Dimensions ◽  
Unit Cells ◽  
Unit Cell Dimensions ◽  
Identical Unit

Unit cell dimensions of mitochondrial crystals were determined by optical diffraction analysis of electron micrographs of human liver biopsy specimens. Identical unit cells were found in pathologic material obtained from six patients with Wilson's disease, from one patient with sickle-cell hepatitis, and from two normal subjects. These measurements led to the conclusion that the crystals observed in patients and in normal subjects were probably chemically identical. Furthermore, the relatively large size of the unit cell limits the choices for its constituents to phospholipid micelles or to relatively large protein molecules.

The External Shape of Human γ GI Immunoglobulin from Crystal Sections

1971 ◽  
Vol 29 ◽  
pp. 428-429
Author(s):  
L. W. Labaw
Keyword(s):  
Molecular Weight ◽  
Sodium Phosphate ◽  
Osmium Tetroxide ◽  
Unit Cell ◽  
Monoclinic Space Group ◽  
X Ray ◽  
Large Molecular Weight ◽  
Cell Dimensions ◽  
Unit Cell Dimensions ◽  
Crystallographic Axes

Crystals of a human γGl immunoglobulin have the external morphology of diamond shaped prisms. X-ray studies have shown them to be monoclinic, space group C2, with 2 molecules per unit cell. The unit cell dimensions are a = 194.1, b = 91.7, c = 51.6Å, 8 = 102°. The relatively large molecular weight of 151,000 and these unit cell dimensions made this a promising crystal to study in the EM.Crystals similar to those used in the x-ray studies were fixed at 5°C for three weeks in a solution of mother liquor containing 5 x 10-5M sodium phosphate, pH 7.0, and 0.03% glutaraldehyde. They were postfixed with 1% osmium tetroxide for 15 min. and embedded in Maraglas the usual way. Sections were cut perpendicular to the three crystallographic axes. Such a section cut with its plane perpendicular to the z direction is shown in Fig. 1.This projection of the crystal in the z direction shows periodicities in at least four different directions but these are only seen clearly by sighting obliquely along the micrograph.

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