Functional and structural correlations of individual αIIbβ3 molecules

Blood ◽  
2004 ◽  
Vol 104 (13) ◽  
pp. 3979-3985 ◽  
Author(s):  
Rustem I. Litvinov ◽  
Chandrasekaran Nagaswami ◽  
Gaston Vilaire ◽  
Henry Shuman ◽  
Joel S. Bennett ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Divalent Cation ◽  
Structural Changes ◽  
Laser Tweezers ◽  
Structural Rearrangements ◽  
Integrin Αiibβ3 ◽  
Open Conformation ◽  
Transmission Electron ◽  
Open Structures

Abstract The divalent cation Mn2+ and the reducing agent dithiothreitol directly shift integrins from their inactive to their active states. We used transmission electron microscopy and laser tweezers-based force spectroscopy to determine whether structural rearrangements induced by these agents in the integrin αIIbβ3 correlate with its ability to bind fibrinogen. Mn2+ increased the probability of specific fibrinogen-αIIbβ3 interactions nearly 20-fold in platelets, and both Mn2+ and dithiothreitol increased the probability more than 2-fold using purified proteins. Of 3 αIIbβ3 conformations, closed with stalks touching, open with stalks separated, and globular without visible stalks, Mn2+ and dithiothreitol induced a significant increase in the proportion of open structures, as well as structural changes in the αIIbβ3 headpiece. Mn2+ also increased the number of complexes between fibrinogen and purified αIIbβ3 molecules, all of which were in the open conformation. Finally, Mn2+ induced the formation of αIIbβ3 clusters that resulted from interactions exclusively involving the distal ends of the stalks. These results indicate that there is a direct correlation between αIIbβ3 activation and the overall conformation of the molecule. Further, they are consistent with the presence of a linked equilibrium between single inactive and single active αIIbβ3 molecules and active αIIbβ3 clusters. (Blood. 2004;104:3979-3985)

Embedding Procedure for Water Swollen Samples

1970 ◽  
Vol 28 ◽  
pp. 504-505
Author(s):  
Ann M. Thomas ◽  
Virginia Shemeley
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Ion Exchange ◽  
Structural Changes ◽  
Cross Linking ◽  
Ion Exchange Resins ◽  
Transmission Electron ◽  
First Pass ◽  
Exchange Resins

Those samples which swell rapidly when exposed to water are, at best, difficult to section for transmission electron microscopy. Some materials literally burst out of the embedding block with the first pass by the knife, and even the most rapid cutting cycle produces sections of limited value. Many ion exchange resins swell in water; some undergo irreversible structural changes when dried. We developed our embedding procedure to handle this type of sample, but it should be applicable to many materials that present similar sectioning difficulties.The purpose of our embedding procedure is to build up a cross-linking network throughout the sample, while it is in a water swollen state. Our procedure was suggested to us by the work of Rosenberg, where he mentioned the formation of a tridimensional structure by the polymerization of the GMA biproduct, triglycol dimethacrylate.

Ultrastructures of Epibiotic Suctorian, Tokophrya huangmeiensis 

Zootaxa ◽  
2018 ◽  
Vol 4521 (1) ◽  
pp. 145
Author(s):  
URFA BIN TAHIR ◽  
DENG QIONG ◽  
WANG ZHE ◽  
LI SEN ◽  
LIU YANG ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Light Microscopy ◽  
Structural Changes ◽  
Small Subunit ◽  
Free Living ◽  
Transmission Electron ◽  
Small Subunit Ribosomal Dna ◽  
Ribosomal Dna Sequence ◽  
Freshwater Ciliates

Tokophrya species are either free-living or facultative ectosymbiotic suctorians associated with copepods, isopods, mysids, decapods and amphipods. Tokophrya huangmeiensis in particular is found to be epizoic with the redclaw crayfish Cherax quadricarinatus Von Martens, 1868, which has been observed as part of an ongoing investigation of freshwater ciliates biodiversity in Huanggang, Hubei, China (Tahir et al. 2017). This first study on T. huangmeiensis based on morphological features using light microscopy and small subunit ribosomal DNA sequence (Tahir et al. 2017), suggested that more detailed descriptions on the physiological and structural changes of this species should be done. Thus, in this study, we looked at the ultrastructures of T. huangmeiensis using electron microscopy, including both scanning (SEM) and transmission electron microscopy (TEM). 

The structural changes of polycrystalline film C60/C70: Ni caused by Ni diffusion

1996 ◽  
Vol 11 (12) ◽  
pp. 3146-3151 ◽  
Author(s):  
E. Czerwosz ◽  
P. Byszewski ◽  
R. Diduszko ◽  
H. Wronka ◽  
P. Dluźewski ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Raman Spectroscopy ◽  
Structural Changes ◽  
Thermal Conditions ◽  
Vacuum Deposition ◽  
X Ray Diffraction ◽  
Polycrystalline Structure ◽  
X Ray ◽  
Transmission Electron

C60/C70: Ni films with 1.5 wt. % Ni concentration obtained by vacuum deposition under different thermal conditions have been investigated. The structural changes of the layers were investigated by transmission electron microscopy, electron and x-ray diffraction, and Raman spectroscopy. The polycrystalline structure was detected for the layers grown at approximately 450 K on the substrate. At elevated temperature and maintained temperature gradient on the substrate during the process, the changes of the layer's structure and the formation of Ni microcrystals were observed. The Ni microcrystals (5–10 nm in the diameter) and the elongated shapes dimensioned 10 × 150 nm were perceived.

Techniques for Characterising Artificial Layer Structures using Transmission Electron Microscopy

1987 ◽  
Vol 103 ◽  
Author(s):  
W. M. Stobbs
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Structural Changes ◽  
Dark Field ◽  
Multilayer Structures ◽  
Dark Field Imaging ◽  
Transmission Electron ◽  
Layer Structures ◽  
Quantitative Characterisation ◽  
Field Imaging

ABSTRACTT.E.M. methods are described for the quantitative characterisation of the compositional and structural changes at interfaces and in homo- and hetero-phase multilayer structures. Many of the newer approaches described including the Fresnel and Centre Stop Dark Field Imaging Methods were developed specifically for such characterisations. The range of applications of each of the techniques is assessed as is the importance of delineating the limiting effects of inelastic and inelastic/elastic multiple scattering.

scholarly journals Enabling Lab-in-Gap Transmission Electron Microscopy at Atomic Resolution

2016 ◽  
Vol 24 (1) ◽  
pp. 24-29 ◽  
Author(s):  
Xiao Feng Zhang
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Structural Changes ◽  
Pole Piece ◽  
Large Area ◽  
Electrical Fields ◽  
Transmission Electron ◽  
Environmental Tem ◽  
New Generation

Abstract: Hitachi Lab-in-Gap transmission electron microscopy (TEM) technologies are introduced. The term Lab-in-Gap refers to a special function that allows in situ and in operando TEM studies of materials in gas or liquid environments while stimulations, such as thermal or electrical fields, are applied to the specimen sitting in the pole piece gap in a TEM system. Physical or chemical process can be activated and imaged in real time using TEM or other imaging modes. The new generation environmental TEM platform with large pole piece gap and advanced aberration correctors opens wide possibilities for integrating multiple stimuli sources as well as large-area, sub-Å resolution live imaging for dynamic structural changes.

Transmission electron microscopy analyses of complex ceramics

1978 ◽  
Vol 36 (1) ◽  
pp. 258-259 ◽  
Author(s):  
T. Shaw
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Structural Information ◽  
Ceramic Materials ◽  
Complex Structures ◽  
X Ray ◽  
Transmission Electron ◽  
Open Structures ◽  
Commercially Important ◽  
Microscopy Techniques

Many potentially useful ceramic materials have complex structures which are difficult to determine using x-ray analysis alone. By the use of contemporary transmission electron microscopy-techniques such as lattice fringe imaging and contrast experiments much information can be obtained about such structures greatly simplifying structure determination. It has already been demonstrated that images of “open” structures bearing a one to one correspondence with the projected structure can be obtained. However, in many commercially important ceramics atoms or atom concentrations are two closely spaced to be resolved directly by current microscopes. In this presentation examples are shown of the type of structural information that is obtainable from such “close packed” structures using transmission electron microscopy, two examples being given below.In Fig. 1(a) a two dimensional fringe image of a region of a 15 R polytype from the Be-Si-N system is shown on the left. It can be seen from this image that the structure is made up of three identical blocks of five close packed planes each related by a translation of 1/3[100] giving a repeat stacking in the close packed [001] direction of fifteen close packed layers.

Transmission electron microscopy study of Ge implanted into SiC

2002 ◽  
Vol 17 (2) ◽  
pp. 479-486 ◽  
Author(s):  
T. Gorelik ◽  
U. Kaiser ◽  
Ch. Schubert ◽  
W. Wesch ◽  
U. Glatzel
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Room Temperature ◽  
Structural Changes ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Transmission Electron Microscopy Study ◽  
Transmission Electron ◽  
High Resolution Tem ◽  
Means Of Transmission

Hexagonal 6H– and 4H–SiC wafers were implanted with (1−1.5) × 1016 cm−2 germanium ions at room temperature and at 700 °C with subsequent annealing between 1000 and 1600 °C. Structural changes in the SiC matrix were studied in detail by means of transmission electron microscopy (TEM). After implantation at room temperature the hexagonal SiC matrix becomes amorphous and, after annealing, recrystallizes into cubic SiC. The latter process was accompanied by the creation of voids and cracks. In case of high-temperature (700 °C) implantation, where amorphization was avoided, no polytype change in as-implanted and annealed SiC wafers was observed. In annealed samples nanocrystalline precipitates with high Ge content were observed in high-resolution TEM images.

scholarly journals Sol-Gel Derived Eu3+-Doped Gd2Ti2O7Pyrochlore Nanopowders

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Sanja Ćulubrk ◽  
Željka Antić ◽  
Vesna Lojpur ◽  
Milena Marinović-Cincović ◽  
Miroslav D. Dramićanin
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Structural Changes ◽  
Sol Gel ◽  
Pyrochlore Phase ◽  
Structural Defects ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Sol Gel Synthesis

Herein we presented hydrolytic sol-gel synthesis and photoluminescent properties of Eu3+-doped Gd2Ti2O7pyrochlore nanopowders. According to Gd2Ti2O7precursor gel thermal analysis a temperature of 840°C is identified for the formation of the crystalline pyrochlore phase. Obtained samples were systematically characterized by powder X-ray diffraction, scanning and transmission electron microscopy, and photoluminescence spectroscopy. The powders consist of well-crystalline cubic nanocrystallites of approximately 20 nm in size as evidenced from X-ray diffraction. The scanning and transmission electron microscopy shows that investigated Eu3+-doped Gd2Ti2O7nanopowders consist of compact, dense aggregates composed entirely of nanoparticles with variable both shape and dimension. The influence of Eu3+ions concentration on the optical properties, namely, photoluminescence emission and decay time, is measured and discussed. Emission intensity as a function of Eu3+ions concentration shows that Gd2Ti2O7host can accept Eu3+ions in concentrations up to 10 at.%. On the other hand, lifetime values are similar up to 3 at.% (~2.7 ms) and experience decrease at higher concentrations (2.4 ms for 10 at.% Eu3+). Moreover, photoluminescent spectra and lifetime values clearly revealed presence of structural defects in sol-gel derived materials proposing photoluminescent spectroscopy as a sensitive tool for monitoring structural changes in both steady state and lifetime domains.

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