scholarly journals THE STRUCTURE OF ACTIN-RICH FILAMENTS OF MUSCLES ACCORDING TO X-RAY DIFFRACTION

1956 ◽  
Vol 2 (1) ◽  
pp. 71-85 ◽  
Author(s):  
Cecily Cannan Selby ◽  
Richard S. Bear
Keyword(s):  
Large Scale ◽  
Adductor Muscle ◽  
X Ray Diffraction ◽  
Cell Width ◽  
X Ray ◽  
Filament Axis ◽  
Repeat Structure ◽  
Diffraction Patterns ◽  
The Individual ◽  
Macromolecular Component

From analysis of moderate- to small-angle x-ray diffraction patterns, in the light of similar experience with paramyosin, has been derived the following description for the structure of actin-rich filaments in "tinted" portions of the adductor muscle of the clam, Venus mercenaria: 1. Some 11 diffraction maxima, widely streaked along layer lines and occurring at moderate diffraction angles (spacings 7 to 60 A) appear to be accounted for as (hk) reflections of a net whose cell elements are, for dry material: a ≑ 82 A, b = 406 A (filament axis identity period), and γ ≑ 82° (angle between a and b axes). These reflections follow a selection rule which indicates that the net cell is non-primitive and contains 15 equivalent locations (nodes) arranged as shown in Fig. 5. An alternative net has b' = 351 A and 13 nodes per cell. 2. Another interpretation rolls the net into a large-scale helix and places the 15 (or 13) nodes along 7 (or 6) turns of a helical locus projecting 406 (or 351) A along the filament axis. Whether considered to be built of planar-net or helix-net cells, the individual filament contains a single cell width transverse to its axis. Transverse filament dimensions are, therefore, in either case similar (50 to 100 A). 3. Consideration of existing electron-optical, physicochemical, and x-ray diffraction data regarding isolated actin suggests that the net cell is built of rods, each containing in cross-section from one to four actin molecules which run parallel to or twisted about rod axes that extend at 12° to the filament axis along the (21) diagonals of the cell. Depending on monomer shape, 2 to 15 monomers furnish length to reach across two cells, and the actin molecules are built into each rod in such a way as to repeat (or nearly repeat) structure 15 (or 13) times along the double cell length. Further details of intra-rod structure cannot be suggested because of lack of wide-angle diffraction information. 4. The actin system is sensitive to treatment of the muscle with ethanol. Concentrations of 5 per cent or greater abolish the net reflections. Other solvents—water, benzene, ether, pyridine, acetone—do not alter the pattern materially. 5. Two other reflections, occurring at the first and second layer lines of an axial periodicity of about 400 A, do not clearly belong to the actin-net system. They represent either a superstructure built upon the filaments by parts of the actin molecules themselves or by incorporated other molecular species, or they arise from an additional macromolecular component (possibly myosin, or its homologues or fractions) of similar axial periodicity.

scholarly journals X-ray diffraction method application to assess the energy losses on explosive-rock contact under various blasting

2020 ◽  
Vol 168 ◽  
pp. 00051
Author(s):  
Ihor Kratkovskyi ◽  
Ernest Yefremov ◽  
Kostyantyn Ishchenko ◽  
Sergo Khomeriki
Keyword(s):  
Rock Fracture ◽  
Diffraction Method ◽  
Optical Systems ◽  
Energy Losses ◽  
X Ray Diffraction ◽  
X Ray ◽  
Wave Nature ◽  
Diffraction Patterns ◽  
The Individual ◽  
Granulometric Characteristics

The dissipative energy losses of the explosion on the explosive-rock contact are usually evaluated with comparative analysis of the particle size distribution of finely dispersed fractions (0-100 microns). The more tiny particles contained in the destruction products, the higher there is a level of energy loss during the explosion. Fine dust granulometric characteristics are determined by processing the mass measurements data of the individual smallest particles sizes when decoding microphotographs obtained by a microscope. However due to the chromatic aberrations due the wave nature of light and the optical systems imperfection, it is not possible to reliably estimate the mass and granulometric characteristics particles of micron size. X-ray diffraction method for studying ultrafine rock fracture products makes it possible to estimate the dissipative energy losses on explosive-rock contact based on the reflected X-ray beam total intensity in diffractograms. In order to establish the effectiveness of methods for reducing the level of dissipative energy losses of an explosion, X-ray diffraction patterns of finely dispersed fracture products of rock samples under various conditions of dynamic loading are analyzed (using different charge designs, attenuating the rocks by the action of a surfactant, and the force action of a different gradient stress field).

Simulations of X-ray diffraction of shock-compressed single-crystal tantalum with synchrotron undulator sources

2018 ◽  
Vol 25 (3) ◽  
pp. 748-756 ◽  
Author(s):  
M. X. Tang ◽  
Y. Y. Zhang ◽  
J. C. E ◽  
S. N. Luo
Keyword(s):  
Single Crystal ◽  
Large Scale ◽  
Incident Beam ◽  
Wave Structure ◽  
X Ray Diffraction ◽  
Single Crystal Diffraction ◽  
X Ray ◽  
Diffraction Patterns ◽  
Case Transmission ◽  
Dynamics Simulations

Polychromatic synchrotron undulator X-ray sources are useful for ultrafast single-crystal diffraction under shock compression. Here, simulations of X-ray diffraction of shock-compressed single-crystal tantalum with realistic undulator sources are reported, based on large-scale molecular dynamics simulations. Purely elastic deformation, elastic–plastic two-wave structure, and severe plastic deformation under different impact velocities are explored, as well as an edge release case. Transmission-mode diffraction simulations consider crystallographic orientation, loading direction, incident beam direction, X-ray spectrum bandwidth and realistic detector size. Diffraction patterns and reciprocal space nodes are obtained from atomic configurations for different loading (elastic and plastic) and detection conditions, and interpretation of the diffraction patterns is discussed.

An Application of Multigrain Approaches to the Structural Solution of Grains from Polycrystalline Samples

2019 ◽  
Vol 288 ◽  
pp. 119-123 ◽  
Author(s):  
Jav Davaasambuu ◽  
Jon Wright ◽  
Henning O. Soerensen ◽  
Soeren Schmidt ◽  
Henning F. Poulsen ◽  
...  
Keyword(s):  
Structural Refinement ◽  
X Ray Diffraction ◽  
X Ray ◽  
Experimental Parameters ◽  
Resolution Level ◽  
Diffraction Patterns ◽  
The Individual ◽  
Individual Grains ◽  
Comparison Of The Results ◽  
Good Agreement

The overlap of diffraction spots from different grains was investigated to understand the influence of experimental factors on the x-ray diffraction data quality and to optimize the experimental parameters for data collection on polycrystalline samples. Diffraction patterns for photoactive polycrystals were indexed and sorted with respect to grains using multigrain approaches. The indexing of diffraction spots and the identification of grains for tetrathiafulvalene-p-chloranil samples were performed using the ImageD11, GrainSpotter, GRAINDEX and Cell_now programs. In many cases, comparison of the results from these programs shows good agreement. For the individual grains from polycrystalline samples, the crystal structure was solved and refined using the SHELXTL program. After the structural refinement of the grains, the best and the average R1 values were 1.93% and 2.06%, respectively, which are on a comparable resolution level with that obtained from the x-ray single crystal measurements.

scholarly journals THE STRUCTURE OF PARAMYOSIN FIBRILS ACCORDING TO X-RAY DIFFRACTION

1956 ◽  
Vol 2 (1) ◽  
pp. 55-69 ◽  
Author(s):  
Richard S. Bear ◽  
Cecily Cannan Selby
Keyword(s):  
Small Angle ◽  
Selection Rule ◽  
Adductor Muscle ◽  
Alternative Interpretation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Fibrous Protein ◽  
X Ray Scattering ◽  
Large Particles ◽  
Diffraction Patterns

From analysis of x-ray diffraction patterns obtained with improved small-angle techniques has been derived the following description for the structure of the fibrils of the fibrous protein, paramyosin, obtained in this case from "white" portions of the adductor muscle of the clam, Venus mercenaria: 1. About 25 significantly different diffraction maxima have been resolved and found accounted for as (hk) reflections of a net whose cell elements are, for the dry material: a = 250 A, b = 720 A (fibril axis identity period), and γ = 90.5° (angle included between a and b axes). For rehydrated material a is larger (ca. 325 A), b is essentially unchanged, and γ is slightly larger. There remains an unresolved discrepancy between the electron-optically derived, cell's a dimension (193 A) and that here reported for dry samples. 2. The h = ±1 row lines are crossed on the diagrams (because γ is not 90°) and thus can be distinguished in spite of natural "rotation" of fibrils (within the massive fibrous specimens) about their commonly oriented axes. The observed reflections are then found to obey a selection rule which indicates that the net cell is non-primitive and contains 5 equivalent locations (nodes) arranged as shown in Fig. 5. The nodal distribution is the same as has been previously photographed electron-optically. 3. Analysis of reflection lengths indicates that the native fibrils are not noticeably ribbon-like, having dimensions normal to the ordered net layers approximating their width across the fibril in the plane of the net layers. Corresponding transverse, interlayer spacings (possibly ca. 100 A) have not been observed, however, and may be hidden in troublesome central scatter. 4. Since paramyosin's wide-angle diffraction is very probably of α-type, supercoiled α-helices must be involved according to current interpretations of α-diagrams. Physicochemical evidence suggests that cables of this type, ca. 1400 A in length, may extend over two cells. Of two possible nodal connections, a favored one is shown in Fig. 5 to join 5 nodes in this way. Considerations of space filling, of transverse distribution of small-angle x-ray scattering, and of nodal significance, suggest that the cable units may be further aggregated into supercables, essentially forming rather solid rods of ca. 100 A diameter. 5. An alternative interpretation of the paramyosin small-angle diffraction, in particular of the observed selection rule, would conclude that large particles are arranged in a helical way, with minimum helix diameter about 150 A (dry). The simplest (genetic) particle connection would have 5 particles in 2 coil turns along 720 A of fibril or helix axis. This view is distinctly different from the arrangement of "rods" in net-like layers as given above, even though the rods are said to be made of supercoils or cables. Reasons are given for preferring the net-of-rods explanation over the particulate-helix model. The helix- vs. true-net ambiguity arises whenever the two types of structure are conceivable, and decision between them is difficult on the basis of the diffraction data alone.

Intergrowth of several solid phases from the Y–Ni–B–C system in a large YNi2B2C crystal

2008 ◽  
Vol 41 (4) ◽  
pp. 738-746 ◽  
Author(s):  
Torsten Weissbach ◽  
Tilmann Leisegang ◽  
Andreas Kreyssig ◽  
Matthias Frontzek ◽  
Jens-Uwe Hoffmann ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
X Ray Diffraction ◽  
Orientation Relation ◽  
X Ray ◽  
Polished Cross Section ◽  
Diffraction Patterns ◽  
The Individual ◽  
Microscopy Images ◽  
Scanning Electron

A YNi2B2C single crystal containing traces of foreign phases was inspected by means of neutron and X-ray diffraction as well as scanning electron microscopy and X-ray spectroscopy methods. The diffraction patterns obtained from the experiments look similar to those expected for a superstructure. Nevertheless, they can be interpreted as crystallographically oriented precipitations of YB2C2and Ni2B within the YNi2B2C crystal, formed during the cooling process. The orientation relation between the lattices was obtained from experimental neutron and X-ray data. Structure refinements of the collected X-ray data were performed by separation of the intensity data of the individual phases. Scanning electron microscopy images of the inclusions found on a polished cross section of the crystal are presented; their chemical composition was determined using wavelength-dispersive X-ray analysis.

scholarly journals Cover art

2016 ◽  
Vol 85 (1) ◽  
Author(s):  
Rakesh Gudimella
Keyword(s):  
Large Scale ◽  
Molecular Model ◽  
Essential Medicines ◽  
Chemical Formula ◽  
X Ray Diffraction ◽  
X Ray ◽  
X Ray Crystallography ◽  
Chemical Structures ◽  
Diffraction Patterns ◽  
Cover Art

Cover art by Rakesh Gudimella. In 1964, Dorothy Hodgkin won the Nobel Prize for the discovery of the structure of penicillin using the emerging technique of x-ray crystallography. The original x-ray diffraction patterns and the subsequent molecular model she created is shown in the foreground. Although the chemical formula of penicillin was known, its structure was not, making it difficult to produce on a large scale. Her discovery set us on the path to understanding antibiotic mechanisms and opened the door for the synthesis of cephalosporins and other important medications. The background shows the chemical structures of several lifesaving and influential drugs on the WHO List of Essential Medicines.

Electron microscope and X-ray diffraction studies of filamentous illitic clay from sandstones of the Magnus Field

Clay Minerals ◽  
1982 ◽  
Vol 17 (1) ◽  
pp. 23-40 ◽  
Author(s):  
W. J. McHardy ◽  
M. J. Wilson ◽  
M. Tait
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Pore Space ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Critical Point Drying ◽  
Diffraction Patterns ◽  
The One ◽  
The Individual

AbstractScanning electron microscopy revealed that the organization of the interstitial micaceous mineral in the title sandstones depended on the manner of drying of the specimen. After air- and freeze-drying, the lath-like mineral tended to occur as mats densely packed against the pore walls, whereas after critical-point drying an open tangled web of very long, thin ribbons virtually filling the pore space was observed (this arrangement is the one most likely to occur in situ). The ends of these filamentous ribbons often appear to be bedded in authigenic quartz overgrowths on sand grains, thus anchoring them firmly in the pores. From transmission electron microscope observations, the individual laths were frequently only 2–3 nm thick and, from electron diffraction patterns, elongated along the a-axis: the stacking modification is 1M. X-ray diffraction patterns are those that would be expected from a fully-ordered interstratified mica-smectite containing ∼20% smectite layers. It is difficult to reconcile this with the thickness as observed under the transmission electron microscope, but a possible explanation is that the ‘smectite’ interlayers in reality represent spaces between individual crystals which formed when they sedimented into an oriented aggregate.

Deducing density and strength of nanocrystalline Ta and diamond under extreme conditions from X-ray diffraction

2019 ◽  
Vol 26 (2) ◽  
pp. 413-421 ◽  
Author(s):  
Y. Y. Zhang ◽  
M. X. Tang ◽  
Y. Cai ◽  
J. C. E ◽  
S. N. Luo
Keyword(s):  
Shock Wave ◽  
Molecular Dynamics ◽  
Large Scale ◽  
Density Measurement ◽  
Dynamics Simulation ◽  
Extreme Conditions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diffraction Patterns ◽  
Dynamics Simulations

In situ X-ray diffraction with advanced X-ray sources offers unique opportunities for investigating materials properties under extreme conditions such as shock-wave loading. Here, Singh's theory for deducing high-pressure density and strength from two-dimensional (2D) diffraction patterns is rigorously examined with large-scale molecular dynamics simulations of isothermal compression and shock-wave compression. Two representative solids are explored: nanocrystalline Ta and diamond. Analysis of simulated 2D X-ray diffraction patterns is compared against direct molecular dynamics simulation results. Singh's method is highly accurate for density measurement (within 1%) and reasonable for strength measurement (within 10%), and can be used for such measurements on nanocrystalline and polycrystalline solids under extreme conditions (e.g. in the megabar regime).

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.

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