Optical diffraction studies of myofibrillar structure

1971 ◽  
Vol 261 (837) ◽  
pp. 201-208 ◽  
Keyword(s):  
Electron Micrographs ◽  
Focal Length ◽  
Optical Diffraction ◽  
Myofibrillar Proteins ◽  
Electron Micrograph ◽  
X Ray Diffraction ◽  
Optical Filtering ◽  
X Ray ◽  
The Subject ◽  
Diffraction Patterns

We have used the techniques of optical diffraction and optical filtering to study electron micrographs of myofibrils and of paracrystals of myofibrillar proteins. The optical diffraction patterns provide information about periodic structure in the micrographs, and sometimes may reveal periodicities not apparent to the eye. We compare the optical diffraction patterns with the X-ray diffraction patterns obtained from living muscle, and this comparison can assist our interpretation of both the X-ray diffraction patterns and the electron micrographs. The optical diffractometer we have used is essentially similar to those described by Taylor & Lipson (1964), and by Klug & DeRosier (1966). The apparatus incorporates several refinements to facilitate operation. The recombining lens has a focal length, f , of about 1 m, and is placed so that the recombined image is formed at 2 f and has the same size as the subject. The diffraction subjects are not usually the electron micrographs themselves but copies on film. The film is of more uniform optical thickness than the glass electron micrograph, and is less fragile. Moreover, a set of films of varying contrast can be made from one micrograph.

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).

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.

The Structure of the Macromolecular Units on the Cell Walls of Bacillus Polymyxa

1967 ◽  
Vol 2 (4) ◽  
pp. 587-591
Author(s):  
J. T. FINCH ◽  
A. KLUG ◽  
M.V. NERMUT
Keyword(s):  
Cell Wall ◽  
Electron Micrographs ◽  
Electron Scattering ◽  
Cell Walls ◽  
Single Layer ◽  
Optical Diffraction ◽  
Square Lattice ◽  
Bacillus Polymyxa ◽  
Optical Filtering ◽  
Diffraction Patterns

Electron micrographs of negatively stained preparations of cell walls of Bacillus polymyxa have been investigated by optical diffraction and optical filtering techniques. Images of single layers of the cell wall, from which the ‘noise’ has been filtered optically, show hollow, square-shaped morphological units arranged on a square lattice of side 100 Å. Single-layer images showing the same pattern have been filtered from moiré patterns arising from two overlapping single layers. The morphological units are composed of four smaller subunits. The optical diffraction patterns from regions of two overlapping layers show extra reflexions which are attributed to multiple electron scattering.

Three-dimensional optical transforms

1961 ◽  
Vol 264 (1318) ◽  
pp. 339-354 ◽  
Keyword(s):  
Fourier Transforms ◽  
Three Dimensional ◽  
Polarized Light ◽  
Continuous Phase ◽  
Optical Diffraction ◽  
X Ray Diffraction ◽  
Circularly Polarized Light ◽  
X Ray ◽  
Half Wave ◽  
Diffraction Patterns

In recent years optical diffraction patterns have been used to assist in the solution of certain X-ray diffraction problems. The most useful technique—which is based partly on the properties of Fourier transforms and partly on optical experiments—is usually known as the optical-transform technique. It has, however, so far been confined to problems involving the projection of crystal structures on to a plane. The present work is aimed at extending the application to full three-dimensional structures. It is shown that this is most simply achieved by controlling the relative phases of beams of light; a method of phase control using circularly polarized light and half-wave plates of mica is described. The theory of the method, experimental details, and the demonstration of its validity are given. In order to gain experience in the use of three-dimensional optical transforms for solving X-ray diffraction problems a known structure has been examined, and the results of this work are included. Although this work has been primarily concerned with applications to X-ray diffraction, it is thought that the method of continuous phase changing, which is simple and linear, may find uses in other fields.

A direct investigation of lattice relaxation at a crystal surface by optical transforms of surface profile images

1989 ◽  
Vol 22 (6) ◽  
pp. 592-600 ◽  
Author(s):  
J. Harada ◽  
M. Takata ◽  
H. Miyatake ◽  
H. Koyama
Keyword(s):  
Crystal Surface ◽  
Surface Profile ◽  
Lattice Relaxation ◽  
Optical Diffraction ◽  
Wafer Surface ◽  
X Ray Diffraction ◽  
X Ray ◽  
Resolution Electron ◽  
Surface Modulation ◽  
Diffraction Patterns

Rod-shaped scattering, referred to as crystal truncation rod (CTR) scattering in X-ray diffraction, can also be observed in optical diffraction patterns obtained from the surface profile image of high-resolution electron micrographs. The characteristics of the CTR scattering are shown to be in agreement with those observed by X-ray scattering. With this technique, information about the lattice relaxation of the image of surfaces or interface boundaries observed in the electron microscope (EM) can be easily obtained and the lattice spacing of a GaAs crystal is shown to be shrunk at the interface boundary between the (001) surface and the amorphous oxide layer. This is precisely opposite to the effect observed for an Si (001) wafer surface. Several effects of surface modulation on CTR scattering are demonstrated using an optical diffractometer and masks of the f.c.c. lattice.

scholarly journals Frog skeletal muscle thick filaments are three-stranded.

1983 ◽  
Vol 96 (6) ◽  
pp. 1797-1802 ◽  
Author(s):  
R W Kensler ◽  
M Stewart
Keyword(s):  
Skeletal Muscle ◽  
Optical Diffraction ◽  
Layer Line ◽  
X Ray Diffraction ◽  
Computer Image Analysis ◽  
X Ray ◽  
Thick Filaments ◽  
Diffraction Patterns ◽  
Meridional Reflection ◽  
Vertebrate Skeletal Muscle

A procedure has been developed for isolating and negatively staining vertebrate skeletal muscle thick filaments that preserves the arrangement of the myosin crossbridges. Electron micrographs of these filaments showed a clear periodicity associated with crossbridges with an axial repeat of 42.9 nm. Optical diffraction patterns of these images showed clear layer lines and were qualitatively similar to published x-ray diffraction patterns, except that the 1/14.3-nm meridional reflection was somewhat weaker. Computer image analysis of negatively stained images of these filaments has enabled the number of strands to be established unequivocally. Both reconstructed images from layer line data and analysis of the phases of the inner maxima of the first layer line are consistent only with a three-stranded structure and cannot be reconciled with either two- or four-stranded models.

Low-angle X-ray diffraction patterns of collagen

1956 ◽  
Vol 235 (1201) ◽  
pp. 189-201 ◽  
Keyword(s):  
Electron Microscopy ◽  
Density Distribution ◽  
Electron Density ◽  
Electron Micrographs ◽  
Electron Density Distribution ◽  
X Ray Diffraction ◽  
Collagen Fibres ◽  
X Ray ◽  
Diffraction Patterns ◽  
Different Sources

Measurements have been made of the intensities of up to 25 orders of the low-angle X-ray diffraction patterns of wet and dry collagen fibres from three different sources. From these data Patterson functions have been plotted, and using these curves, and the known results of electron microscopy as guides in making initial assumptions about the electron density distribution in collagen fibres, satisfactory interpretations of the diffraction patterns of wet and dry fibres have been reached. These results show that the conspicuous periodic raised bands seen in electron micrographs of metal-shadowed fibres change in length on wetting the fibres, while the regions between them are but little affected, and it is concluded that these bands are highly disordered regions in dry fibres, becoming more orderly on hydration, while the interbands are always well ordered. Some evidence has also been obtained for the existence of an axial periodicity of about 32·8 Å.

Evaluation of Freezing Methods by Low Temperature X-Ray Diffraction

1977 ◽  
Vol 35 ◽  
pp. 330-333
Author(s):  
T. Gulik-Krzywicki ◽  
M.J. Costello
Keyword(s):  
Biological Materials ◽  
Molecular Organization ◽  
X Ray Diffraction ◽  
Glass Capillary ◽  
X Ray ◽  
Rate Dependent ◽  
Before And After ◽  
Freeze Etching ◽  
Diffraction Patterns ◽  
Set Up

Freeze-etching electron microscopy is currently one of the best methods for studying molecular organization of biological materials. Its application, however, is still limited by our imprecise knowledge about the perturbations of the original organization which may occur during quenching and fracturing of the samples and during the replication of fractured surfaces. Although it is well known that the preservation of the molecular organization of biological materials is critically dependent on the rate of freezing of the samples, little information is presently available concerning the nature and the extent of freezing-rate dependent perturbations of the original organizations. In order to obtain this information, we have developed a method based on the comparison of x-ray diffraction patterns of samples before and after freezing, prior to fracturing and replication.Our experimental set-up is shown in Fig. 1. The sample to be quenched is placed on its holder which is then mounted on a small metal holder (O) fixed on a glass capillary (p), whose position is controlled by a micromanipulator.

Examination of Rabbit Fc Crystals

1968 ◽  
Vol 26 ◽  
pp. 140-141
Author(s):  
J. P. Robinson ◽  
P. G. Lenhert
Keyword(s):  
Molecular Weight ◽  
Flat Plate ◽  
Phosphate Buffer ◽  
Asymmetric Unit ◽  
X Ray Diffraction ◽  
X Ray ◽  
Neutral Ph ◽  
Small Crystals ◽  
Carbon Coated ◽  
Diffraction Patterns

Crystallographic studies of rabbit Fc using X-ray diffraction patterns were recently reported. The unit cell constants were reported to be a = 69. 2 A°, b = 73. 1 A°, c = 60. 6 A°, B = 104° 30', space group P21, monoclinic, volume of asymmetric unit V = 148, 000 A°3. The molecular weight of the fragment was determined to be 55, 000 ± 2000 which is in agreement with earlier determinations by other methods.Fc crystals were formed in water or dilute phosphate buffer at neutral pH. The resulting crystal was a flat plate as previously described. Preparations of small crystals were negatively stained by mixing the suspension with equal volumes of 2% silicotungstate at neutral pH. A drop of the mixture was placed on a carbon coated grid and allowed to stand for a few minutes. The excess liquid was removed and the grid was immediately put in the microscope.

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