scholarly journals CURT1A and CURT1C mediate distinct stages of plastid conversion in Arabidopsis

2021 ◽  
Author(s):  
Zizhen Liang ◽  
Wai Tsun Yeung ◽  
Keith Ka Ki Mai ◽  
Juncai Ma ◽  
Zhongyuan Liu ◽  
...  
Keyword(s):  
Electron Tomography ◽  
Tomographic Reconstruction ◽  
Chloroplast Biogenesis ◽  
Chemical Fixation ◽  
Cubic Crystal ◽  
Zinc Blende ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Type Lattice ◽  
Curved Membrane

AbstractThe crystalline structure of prolamellar bodies (PLBs) and light-induced etioplasts-to-chloroplasts transformation have been investigated with electron microscopy methods. However, these studies suffer from chemical fixation artifacts and limited volumes of tomographic reconstruction. We have examined Arabidopsis thaliana cotyledon samples preserved by high-pressure freezing with scanning transmission electron tomography to visualize larger volumes in etioplasts and their conversion into chloroplasts. PLB tubules were arranged in a zinc blende-type lattice like carbon atoms in diamonds. Within 2 hours after illumination, the lattice collapsed from the PLB exterior and the disorganized tubules merged to form fenestrated sheets that eventually matured into lamellar thylakoids. These planar thylakoids emerging from PLBs overlapped or folded into grana stacks in PLBs’ vicinity. Since the nascent lamellae had curved membrane at their tips, we examined the localization of CURT1 proteins. CURT1A transcript was most abundant in de-etiolating cotyledon samples, and CURT1A concentrated at the peripheral PLB. In curt1a mutant etioplasts, thylakoid sheets were swollen and failed to develop stacks. In curt1c mutant, however, PLBs had cracks in their lattices, indicating that CURT1C contributes to cubic crystal growth under darkness. Our data provide evidence that CURT1A and CURT1C play distinct roles in the etioplast and chloroplast biogenesis.

Cryo-scanning transmission electron tomography of vitrified cells

2014 ◽  
Vol 11 (4) ◽  
pp. 423-428 ◽  
Author(s):  
Sharon Grayer Wolf ◽  
Lothar Houben ◽  
Michael Elbaum
Keyword(s):  
Electron Tomography ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission

scholarly journals Exploring the Capability of HAADF-STEM Techniques to Characterize Graphene Distribution in Nanocomposites by Simulations

2018 ◽  
Vol 2018 ◽  
pp. 1-12
Author(s):  
N. Baladés ◽  
D. L. Sales ◽  
M. Herrera ◽  
A. M. Raya ◽  
J. C. Hernández-Garrido ◽  
...  
Keyword(s):  
Electron Tomography ◽  
Carbon Matrix ◽  
Reconstruction Algorithm ◽  
Dark Field ◽  
Graphene Layers ◽  
Transmission Electron ◽  
Dispersion Degree ◽  
Scanning Transmission ◽  
The Matrix ◽  
Annular Dark Field

This paper explores the capability of scanning transmission electron microscopy (STEM) techniques in determining the dispersion degree of graphene layers within the carbon matrix by using simulated high-angle annular dark-field (HAADF) images. Results ensure that unmarked graphene layers are only detectable if their orientation is parallel to the microscope beam. Additionally, gold-marked graphene layers allow evaluating the dispersion degree in structural composites. Moreover, electron tomography has been demonstrated to provide truthfully 3D distribution of the graphene sheets inside the matrix when an appropriate reconstruction algorithm and 2D projections including channelling effect are used.

Three-Dimensional Imaging of Shear Band Produced by ECAP Process in Al-Ag Alloy

2006 ◽  
Vol 503-504 ◽  
pp. 603-608
Author(s):  
Koji Inoke ◽  
Kenji Kaneko ◽  
Z. Horita
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Tomography ◽  
Shear Bands ◽  
Three Dimensional ◽  
Angular Pressing ◽  
Ecap Process ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
The Matrix

A significant change in microstructure occurs during the application of severe plastic deformation (SPD) such as by equal-channel angular pressing (ECAP). In this study, intense plastic strain was imposed on an Al-10.8wt%Ag alloy by the ECAP process. The amount of strain was controlled by the numbers of passes. After 1 pass of ECAP, shear bands became visible within the matrix. With increasing numbers of ECAP passes, the fraction of shear bands was increased. In this study, the change in microstructures was examined by three-dimensional electron tomography (3D-ET) in transmission electron microscopy (TEM) or scanning transmission electron microscopy (STEM). With this 3D-ET method, it was possible to conduct a precise analysis of the sizes, widths and distributions of the shear bands produced by the ECAP process. It is demonstrated that the 3D-ET method is promising to understand mechanisms of microstructural refinement using the ECAP process.

scholarly journals Stem-EDX and FIB-SEM Tomography of ALLVAC 718Plus Superalloy

2016 ◽  
Vol 61 (2) ◽  
pp. 535-542 ◽  
Author(s):  
A. Kruk ◽  
G. Cempura ◽  
S. Lech ◽  
A. Czyrska -Filemonowicz
Keyword(s):  
Electron Microscope ◽  
Focused Ion Beam ◽  
Electron Tomography ◽  
Ion Beam ◽  
High Strength ◽  
Strengthening Mechanism ◽  
Scanning Transmission Electron Microscope ◽  
Particle Analysis ◽  
Transmission Electron ◽  
Scanning Transmission

Abstract Allvac 718Plus (718Plus) is a high strength, corrosion resistant nickel- based superalloy used for application in power generation, aeronautics and aerospace industry. The 718Plus microstructure consists of a γ matrix with γ’-Ni3(Al,Ti) and some δ- Ni3Nb phases as well as lamellar particles (η-Ni3Ti, η*-Ni6AlNb or Ni6(Al,Ti)Nb) precipitated at the grain boundaries. The primary strengthening mechanism for this alloy is a precipitation hardening, therefore size and distribution of precipitates are critical for the performance of the alloy. The aim of this study was to characterize precipitates in the 718Plus superalloy using Scanning Transmission Electron Microscope combined with Energy Dispersive X-ray Spectroscopy (STEM-EDX) and Focused Ion Beam Scanning Electron Microscope (FIB-SEM). The STEM-EDX and FIB-SEM tomography techniques were used for 3D imaging and metrology of the precipitates. Transmission electron microscopy and EDX spectroscopy were used to reveal details of the 718Plus microstructure and allow determine chemical composition of the phases. The study showed that electron tomography techniques permit to obtain complementary information about microstructural features (precipitates size, shape and their 3D distribution) in the reconstructed volume with comparison to conventional particle analysis methods, e.g. quantitative TEM and SEM metallography

Three-dimensional real-space crystallography of MCM-48 mesoporous silica revealed by scanning transmission electron tomography

2006 ◽  
Vol 418 (4-6) ◽  
pp. 540-543 ◽  
Author(s):  
Timothy J.V. Yates ◽  
John Meurig Thomas ◽  
Jose-Jesus Fernandez ◽  
Osamu Terasaki ◽  
Ryong Ryoo ◽  
...  
Keyword(s):  
Mesoporous Silica ◽  
Electron Tomography ◽  
Three Dimensional ◽  
Real Space ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission

scholarly journals Catabolism of lysosome-related organelles in color-changing spiders supports intracellular turnover of pigments

2021 ◽  
Vol 118 (35) ◽  
pp. e2103020118
Author(s):  
Florent Figon ◽  
Ilse Hurbain ◽  
Xavier Heiligenstein ◽  
Sylvain Trépout ◽  
Arnaud Lanoue ◽  
...  
Keyword(s):  
Electron Tomography ◽  
Strong Support ◽  
Human Vision ◽  
Ultrastructural Changes ◽  
Adverse Conditions ◽  
Body Coloration ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Lysosome Related Organelles ◽  
Crab Spiders

Pigment organelles of vertebrates belong to the lysosome-related organelle (LRO) family, of which melanin-producing melanosomes are the prototypes. While their anabolism has been extensively unraveled through the study of melanosomes in skin melanocytes, their catabolism remains poorly known. Here, we tap into the unique ability of crab spiders to reversibly change body coloration to examine the catabolism of their pigment organelles. By combining ultrastructural and metal analyses on high-pressure frozen integuments, we first assess whether pigment organelles of crab spiders belong to the LRO family and second, how their catabolism is intracellularly processed. Using scanning transmission electron microscopy, electron tomography, and nanoscale Synchrotron-based scanning X-ray fluorescence, we show that pigment organelles possess ultrastructural and chemical hallmarks of LROs, including intraluminal vesicles and metal deposits, similar to melanosomes. Monitoring ultrastructural changes during bleaching suggests that the catabolism of pigment organelles involves the degradation and removal of their intraluminal content, possibly through lysosomal mechanisms. In contrast to skin melanosomes, anabolism and catabolism of pigments proceed within the same cell without requiring either cell death or secretion/phagocytosis. Our work hence provides support for the hypothesis that the endolysosomal system is fully functionalized for within-cell turnover of pigments, leading to functional maintenance under adverse conditions and phenotypic plasticity. First formulated for eye melanosomes in the context of human vision, the hypothesis of intracellular turnover of pigments gets unprecedented strong support from pigment organelles of spiders.

scholarly journals FastTomo: A SerialEM Script for Collecting Electron Tomography Data

2021 ◽  
Author(s):  
Albert Xu ◽  
Chen Xu
Keyword(s):  
Target Tracking ◽  
Electron Tomography ◽  
Tomographic Reconstruction ◽  
Field Of View ◽  
Proportional Control ◽  
Transmission Electron ◽  
Tilt Series ◽  
Electron Microscopes ◽  
Tomography Data ◽  
Separate Calibration

AbstractFastTomo is a SerialEM script for collecting tilted specimen images in transmission electron microscopes to be further used in tomographic reconstruction. It achieves a speedup over conventional tracking methods by minimizing the usage of off-target tracking shots, and instead applies proportional control to the specimen images. Movement in the Z coordinate is estimated prior to each tilt series in a separate calibration routine. Overall, this method is fast and reliable when the field of view is at least 1 um, and can tolerate minor errors in setting eucentric height. The implemented tilt series schemes include the unidirectional, bidirectional, and dose-symmetric schemes.

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