The 3-Dimensional Molecular Structure of the Actin Filament Revisited

1985 ◽  
Vol 43 ◽  
pp. 480-481
Author(s):  
U. Aebi ◽  
R. Millonig ◽  
H. Salvo
Keyword(s):  
Actin Filament ◽  
Supramolecular Assembly ◽  
Specimen Preparation ◽  
X Ray Diffraction ◽  
Single Filament ◽  
X Ray ◽  
3 Dimensional ◽  
Filament Diameter ◽  
Preparation Conditions ◽  
Apparent Diameter

To date, most 3-D reconstructions of undecorated actin filaments have been obtained from actin filament paracrystal data (for refs, see 1,2). However, due to the fact that (a) the paracrystals may be several filament layers thick, and (b) adjacent filaments may sustantially interdigitate, these reconstructions may be subject to significant artifacts. None of these reconstructions has permitted unambiguous tracing or orientation of the actin subunits within the filament. Furthermore, measured values for the maximal filament diameter both determined by EM and by X-ray diffraction analysis, vary between 6 and 10 nm. Obviously, the apparent diameter of the actin filament revealed in the EM will critically depend on specimen preparation, since it is a rather flexible supramolecular assembly which can easily be bent or distorted. To resolve some of these ambiguities, we have explored specimen preparation conditions which may preserve single filaments sufficiently straight and helically ordered to be suitable for single filament 3-D reconstructions, possibly revealing molecular detail.

Determination of the 'true' width of the actin filament

1983 ◽  
Vol 41 ◽  
pp. 534-535
Author(s):  
Walter E. Fowler ◽  
Ueli Aebi
Keyword(s):  
Electron Microscopy ◽  
Actin Filament ◽  
Specimen Preparation ◽  
Molecular Models ◽  
X Ray Diffraction ◽  
Preparation Methods ◽  
Average Width ◽  
X Ray ◽  
Lower Limits

Although the structure of the actin filament has been studied extensively both, by X-ray diffraction analysis and by electron microscopy and structure reconstruction, molecular models of actin have been obtained only recently. However none of the crystalline forms used in these latter studies are made directly from filaments. Since the resolution of current filament models is insufficient to allow unambiguous tracing of the actin subunits within them [e.g.2], the orientation of molecular models within such filament models is speculative. A primary constraint on the overall orientation of the elongated and polar actin subunit model within the actin filament is the 'true' width of the filament: reported values as obtained by electron microscopy range from 6 to 8nm for negatively stained specimens and to 9.5nm or more for rotary shadowed filaments [reviewed in 3]. Furthermore, X-ray solution scattering of actin filaments has revealed an average width of 7nm. Using a variety of different specimen preparation methods, we have endeavoured to set realistic upper and lower limits for this crucial parameter.

Gold nanoclusters reductively deposited on porous silicon: morphology and electronic structures

1998 ◽  
Vol 76 (11) ◽  
pp. 1707-1716 ◽  
Author(s):  
I Coulthard ◽  
S Degen ◽  
Y -J Zhu ◽  
T K Sham
Keyword(s):  
Gold Nanoparticles ◽  
Porous Silicon ◽  
Photoelectron Spectroscopy ◽  
Gold Nanoclusters ◽  
Gold Complex ◽  
X Ray Diffraction ◽  
Complex Ions ◽  
X Ray ◽  
Preparation Conditions ◽  
P Type

Utilizing porous silicon as a reducing agent and a substrate, gold complex ions [AuCl4]- were reduced from aqueous solution to produce nanoparticles of gold upon the surface of porous silicon. Scanning electron microscopy (SEM) was utilized to study the morphology of the porous silicon layers and the deposits of gold nanoparticles. It is found that preparation conditions have a profound effect on the morphology of the deposits, especially on porous silicon prepared from a p-type wafer. The gold nanoparticles, varying from micrometric aggregates of clusters of the order of 10 nm, to a distribution of nearly spherical clusters of the order of 10 nm, to strings of ~10 nm were observed and compared to bulk gold metal using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XAS). These techniques confirm and complement the SEM findings. The potential for this reductive deposition technique is noted.Key words: gold nanostructures, reductive deposition, porous silicon, morphology, X-ray spectroscopy.

The Effects of Preparation Conditions And Chemical Composition On CMAS Glass Ceramics With One Step Process

2021 ◽  
Author(s):  
Yuliang Guo ◽  
Huixin Jin ◽  
Yuandan Xiao ◽  
Huahao Song ◽  
Shangjiefu Wang
Keyword(s):  
Solid Waste ◽  
Theoretical Basis ◽  
Chromium Content ◽  
Glass Ceramics ◽  
X Ray Diffraction ◽  
Crystallization Activation Energy ◽  
X Ray ◽  
Preparation Conditions ◽  
Treatment Conditions ◽  
One Step

Abstract Based on the composition of Cr-doped solid waste, other oxides were added to adjust the composition to prepare glass-ceramics with on step composition, and the effect of heat treatment system (including temperature and holding time), chromium content, MnO and Fe2O3 doped on the crystallization and physical properties of glass-ceramics was studied. The samples were characterized by X-ray diffraction, differential thermal analysis and scanning electron microscopy. The results show that the best treatment conditions are 1090 ℃ for 4h, and the amount of dissolved chromium reaches 5%. The main crystallization phase is diopside and anorthite. The hardness and chemical stability of the material were measured. The doping of MnO and Fe2O3 increases the crystallization activation energy of glass ceramics, and makes the crystal phase more uniform as the SEM results. This experiment provides a theoretical basis for the preparation of CMAS glass ceramics from chromium containing solid waste.

Supramolecular assemblies of phenolic metalloporphyrins: Structures and electrochemical studies

2019 ◽  
Vol 23 (01n02) ◽  
pp. 103-116 ◽  
Author(s):  
Gia Co Quan ◽  
Morgane Denis ◽  
Brian Abeykoon ◽  
Jean-Bernard Tommasino ◽  
Erwann Jeanneau ◽  
...  
Keyword(s):  
Supramolecular Assembly ◽  
Electrochemical Studies ◽  
Redox Behavior ◽  
Metallic Ions ◽  
X Ray Diffraction ◽  
Supramolecular Compounds ◽  
One Dimensional ◽  
X Ray ◽  
Axial Coordination ◽  
Supramolecular Architectures

The reactivity of two phenolic porphyrins bearing respectively catechol and gallol-derived meso substituents (5,10,15,20-tetrakis(3,4-dihydroxyphenyl)porphyrin and 5,10,15,20-tetrakis(3,4,5-trihydroxyphenyl)porphyrin) with trivalent metallic ions (Fe, Mn, In) was studied. Six supramolecular compounds were obtained and structurally characterized by single crystal X-ray diffraction. In each compound, the supramolecular assembly was based on the axial coordination of a phenolate function to the metallic ion lying in the porphyrinic core. A great diversity of supramolecular architectures was accessible through such simple arrangements, and objects ranging from dimers to one-dimensional polymers were isolated. Some of these assemblies were further investigated in solution by mass spectrometry and by UV-vis absorption spectroscopy. For the iron-based materials, the redox behavior was studied in solution through cyclic voltammetry experiments in inert conditions and under air.

The Structure of a Zn(II) Metaphosphate Glass. I. The Cation Coordination by a Combination of X-Ray and Neutron Diffraction, EXAFS and X-Ray Anomalous Scattering

1996 ◽  
Vol 51 (12) ◽  
pp. 1209-1215 ◽  
Author(s):  
M. Bionducci ◽  
G. Licheri ◽  
A. Musinu ◽  
G. Navarra ◽  
G. Piccaluga ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Anomalous Scattering ◽  
Extended Model ◽  
X Ray Diffraction ◽  
X Ray ◽  
Preparation Conditions ◽  
Zinc Coordination ◽  
Cation Coordination ◽  
X Ray Absorption ◽  
Zn Ions

Abstract In order to clarify the reason of some discrepancies existing in literature, the zinc coordination in a Zn metaphosphate glass has been investigated by the complementary use of X-Ray Diffraction, Neutron Diffraction, Extended X-ray Absorption Fine Structure Spectroscopy and X-Ray Anoma-lous Scattering. All the techniques indicate a tetrahedral coordination of O atoms around Zn :+ ions, the Zn-O distance being 1.94 ± 0.01 Å. The simultaneous modelling of all the experimental data by Reverse Monte Carlo technique demonstrated that this coordination is consistent with an extended model in which metal ions are interposed between phosphate chains. The importance of describing the preparation conditions of the glasses is stressed when structural results have to be compared.

scholarly journals Thermal Decomposition Study on Li2O2 for Li2NiO2 Synthesis as a Sacrificing Positive Additive of Lithium-Ion Batteries

Molecules ◽  
2019 ◽  
Vol 24 (24) ◽  
pp. 4624 ◽  
Author(s):  
Jaekwang Kim ◽  
Hyunchul Kang ◽  
Keebum Hwang ◽  
Songhun Yoon
Keyword(s):  
Thermal Decomposition ◽  
Lithium Ion ◽  
X Ray Diffraction ◽  
Irreversible Capacity ◽  
Powder Preparation ◽  
X Ray ◽  
Preparation Conditions ◽  
Lithium Peroxide ◽  
Lithium Nickel Oxide ◽  
Decomposition Experiments

Herein, thermal decomposition experiments of lithium peroxide (Li2O2) were performed to prepare a precursor (Li2O) for sacrificing cathode material, Li2NiO2. The Li2O2 was prepared by a hydrometallurgical reaction between LiOH·H2O and H2O2. The overall reaction during annealing was found to involve the following three steps: (1) dehydration of LiOH·H2O, (2) decomposition of Li2O2, and (3) pyrolysis of the remaining anhydrous LiOH. This stepwise reaction was elucidated by thermal gravimetric and quantitative X-ray diffraction analyses. Furthermore, over-lithiated lithium nickel oxide (Li2NiO2) using our lithium precursor was synthesized, which exhibited a larger yield of 90.9% and higher irreversible capacity of 261 to 265 mAh g−1 than the sample prepared by commercially purchased Li2O (45.6% and 177 to 185 mAh g−1, respectively) due to optimal powder preparation conditions.

Magnetic Composite Microspheres of Cassava Starch: Preparation and Characterization

2014 ◽  
Vol 926-930 ◽  
pp. 145-149
Author(s):  
Ping Lan ◽  
Yu Xian Feng ◽  
Ri Mei He ◽  
Lei Lei Qiao ◽  
Li Hong Lan ◽  
...  
Keyword(s):  
Cassava Starch ◽  
Magnetic Composite ◽  
X Ray Diffraction ◽  
X Ray ◽  
Preparation Conditions ◽  
Composite Microspheres ◽  
Condition Effect ◽  
Initial Ph ◽  
One Step ◽  
Solution Volume

The magnetic composite microspheres of cassava starch have been prepared by magnetization of one-step oxidation, using cassava starch as natural macromolecule material. The condition effect on magnetic content was evaluated by single factor experiments, such as the mass concentration of starch, reaction temperature, reaction time, stirring speed, initial pH and ferrous solution volume. Preparation conditions were optimized by these evaluation experiments. The prepared magnetic composite microspheres were characterized by infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM), and other means.

Diffraction apparatus and procedure in tomography X-ray diffraction imaging for biological cells at cryogenic temperature using synchrotron X-ray radiation

2018 ◽  
Vol 25 (6) ◽  
pp. 1803-1818 ◽  
Author(s):  
Amane Kobayashi ◽  
Yuki Takayama ◽  
Koji Okajima ◽  
Mao Oide ◽  
Takahiro Yamamoto ◽  
...  
Keyword(s):  
Dimensional Structure ◽  
Cyanidioschyzon Merolae ◽  
Specimen Preparation ◽  
Biological Cells ◽  
Cryogenic Temperatures ◽  
Resolution Limit ◽  
X Ray Diffraction ◽  
Experimental Conditions ◽  
X Ray ◽  
Diffraction Imaging

X-ray diffraction imaging is a technique for visualizing the structure of biological cells. In X-ray diffraction imaging experiments using synchrotron radiation, cryogenic conditions are necessary in order to reduce radiation damage in the biological cells. Frozen-hydrated biological specimens kept at cryogenic temperatures are also free from drying and bubbling, which occurs in wet specimens under vacuum conditions. In a previous study, the diffraction apparatus KOTOBUKI-1 [Nakasako et al. (2013), Rev. Sci. Instrum. 84, 093705] was constructed for X-ray diffraction imaging at cryogenic temperatures by utilizing a cryogenic pot, which is a cooling device developed in low-temperature physics. In this study a new cryogenic pot, suitable for tomography experiments, has been developed. The pot can rotate a biological cell over an angular range of ±170° against the direction of the incident X-ray beam. Herein, the details and the performance of the pot and miscellaneous devices are reported, along with established experimental procedures including specimen preparation. The apparatus has been used in tomography experiments for visualizing the three-dimensional structure of a Cyanidioschyzon merolae cell with an approximate size of 5 µm at a resolution of 136 nm. Based on the experimental results, the necessary improvements for future experiments and the resolution limit achievable under experimental conditions within a maximum tolerable dose are discussed.

Recrystallization of AA1050 Studied by 3DXRD

2006 ◽  
Vol 519-521 ◽  
pp. 1569-1578
Author(s):  
Dorte Juul Jensen
Keyword(s):  
Single Crystals ◽  
High Energy ◽  
Nucleation And Growth ◽  
X Rays ◽  
X Ray Diffraction ◽  
Orientation Relationships ◽  
X Ray ◽  
3 Dimensional ◽  
Kinetics Of

By 3 dimensional X-ray diffraction (3DXRD) using high energy X-rays from synchrotron sources it is possible to study in-situ the nucleation and growth during recrystallization. In this paper it is described and discussed how 3DXRD can supplement EBSP measurements of nucleation and growth. Three types of studies are considered: i) orientation relationships between nuclei and parent deformed matrix, ii) recrystallization kinetics of individual bulk grains and iii) filming of growing grains in deformed single crystals.

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