scholarly journals Liquid electron microscopy: then, now and future

2019 ◽  
Vol 49 (1) ◽  
Author(s):  
Anahita Vispi Bharda ◽  
Hyun Suk Jung
Keyword(s):  
Electron Microscopy ◽  
Functional Characterization ◽  
Analytical Tool ◽  
Electron Microscopic ◽  
Liquid Environment ◽  
Microscopic Imaging ◽  
The Past ◽  
Technical Developments ◽  
Comprehensive Framework

Abstract Contemporary microscopic imaging at near-atomic resolution of diverse embodiments in liquid environment has gained keen interest. In particular, Electron Microscopy (EM) can provide comprehensive framework on the structural and functional characterization of samples in liquid phase. In the past few decades, liquid based electron microscopic modalities have developed tremendously to provide insights into various backgrounds like biological, chemical, nanoparticle and material researches. It serves to be a promising analytical tool in deciphering unique insights from solvated systems. Here, the basics of liquid electron microscopy with few examples of its applications are summarized in brief. The technical developments made so far and its preference over other approaches is shortly presented. Finally, the experimental limitations and an outlook on the future technical advancement for liquid EM have been discussed.

Electron Microscopic Detection and Characterization of Nonhuman Primate Enteric Viruses

1982 ◽  
Vol 40 ◽  
pp. 306-307
Author(s):  
G. C. Smith ◽  
R. L. Heberling ◽  
S. S. Kalter
Keyword(s):  
Electron Microscopy ◽  
Animal Model ◽  
Nonhuman Primate ◽  
Clinical Condition ◽  
Intestinal Tract ◽  
Enteric Viruses ◽  
Electron Microscopic ◽  
Microscopic Detection

A number of viral agents are recognized as and suspected of causing the clinical condition “gastroenteritis.” In our attempts to establish an animal model for studies of this entity, we have been examining the nonhuman primate to ascertain what viruses may be found in the intestinal tract of “normal” animals as well as animals with diarrhea. Several virus types including coronavirus, adenovirus, herpesvirus, and picornavirus (Table I) were detected in our colony; however, rotavirus, astrovirus, and calicivirus have not yet been observed. Fecal specimens were prepared for electron microscopy by procedures reported previously.

scholarly journals Conjuring up a ghost: structural and functional characterization of FhuF, a ferric siderophore reductase from E. coli

2021 ◽  
Author(s):  
I. B. Trindade ◽  
G. Hernandez ◽  
E. Lebègue ◽  
F. Barrière ◽  
T. Cordeiro ◽  
...  
Keyword(s):  
Functional Characterization ◽  
Paramagnetic Nmr ◽  
E Coli ◽  
The Past ◽  
Internal Cavities ◽  
Structural Differences ◽  
Bond Strengths ◽  
Redox Bohr Effect ◽  
Micromolar Range

AbstractIron is a fundamental element for virtually all forms of life. Despite its abundance, its bioavailability is limited, and thus, microbes developed siderophores, small molecules, which are synthesized inside the cell and then released outside for iron scavenging. Once inside the cell, iron removal does not occur spontaneously, instead this process is mediated by siderophore-interacting proteins (SIP) and/or by ferric-siderophore reductases (FSR). In the past two decades, representatives of the SIP subfamily have been structurally and biochemically characterized; however, the same was not achieved for the FSR subfamily. Here, we initiate the structural and functional characterization of FhuF, the first and only FSR ever isolated. FhuF is a globular monomeric protein mainly composed by α-helices sheltering internal cavities in a fold resembling the “palm” domain found in siderophore biosynthetic enzymes. Paramagnetic NMR spectroscopy revealed that the core of the cluster has electronic properties in line with those of previously characterized 2Fe–2S ferredoxins and differences appear to be confined to the coordination of Fe(III) in the reduced protein. In particular, the two cysteines coordinating this iron appear to have substantially different bond strengths. In similarity with the proteins from the SIP subfamily, FhuF binds both the iron-loaded and the apo forms of ferrichrome in the micromolar range and cyclic voltammetry reveals the presence of redox-Bohr effect, which broadens the range of ferric-siderophore substrates that can be thermodynamically accessible for reduction. This study suggests that despite the structural differences between FSR and SIP proteins, mechanistic similarities exist between the two classes of proteins. Graphic abstract

Characterization of Electrophoretic Lipoprotein Fractions: Immunochemical and Electron Microscopic Studies

1972 ◽  
Vol 18 (6) ◽  
pp. 534-538
Author(s):  
Mario Werner ◽  
Albert L Jones
Keyword(s):  
Electron Microscopy ◽  
Particle Size ◽  
Electrophoretic Pattern ◽  
Electron Microscopic ◽  
Lipoprotein Subfractions ◽  
New Techniques ◽  
Microscopic Studies ◽  
Insight Into

Abstract To improve the characterization of electrophoretic lipoprotein subfractions, we developed two new techniques for analyzing lipoproteins after electrophoresis on thin agarose layers. Overlay with antisera exactly localizes specific apoproteins without any distortion caused by antigen diffusion; electron microscopy of eluted fractions determines the varying particle-size distribution. Applied together, these methods can detect individual differences between hyperlipemic samples that are not immediately apparent in the electrophoretic pattern, and should provide valuable new insight into the classification of hyperlipoproteinemias.

Electron Microscope Characterization of Pulse Annealed Semiconductors

1980 ◽  
Vol 2 ◽  
Author(s):  
A. G. CULLIS
Keyword(s):  
Electron Microscopy ◽  
Defect Structure ◽  
Device Fabrication ◽  
Fabrication Technology ◽  
The Past ◽  
Semiconductor Structures ◽  
Pulse Processing ◽  
Processing Techniques

ABSTRACTThe pulse processing techniques that have assumed prominence over the past few years offer various important advantages for device fabrication technology. However, the usefulness of each individual method depends substantially upon the specific annealing mechanism involved. This article demonstrates the role of electron microscopy in elucidating such mechanisms and in analysing annealed semiconductor structures of importance to both research workers and semiconductor technologists. The range of laser and electron beam pulse annealing methods is covered and defect structure transitions observed are related to the solid and liquid phase processes occurring. Characteristic impurity trapping and segregation phenomena are described.

Hematopoietic Stem and Progenitor Cell Biology in the Zebrafish.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 4160-4160
Author(s):  
David Traver ◽  
Julien Bertrand ◽  
Albert Kim ◽  
Jennifer Cisson ◽  
Emily Violette
Keyword(s):  
Cell Biology ◽  
Progenitor Cell ◽  
Zebrafish Embryo ◽  
Functional Characterization ◽  
Hematopoietic Stem ◽  
Blood Island ◽  
The Past ◽  
Transgenic Lines ◽  
Zebrafish Embryogenesis

Abstract Over the past decade, the development of forward genetic approaches in the zebrafish system has provided unprecedented power in understanding the molecular basis of vertebrate blood development. Establishment of cellular and hematological approaches to better understand the biology of resulting blood mutants, however, has lagged behind these efforts. We have recently developed the means to identify zebrafish hematopoietic stem cells (HSCs), transgenic lines to mark hematopoietic precursors and their progeny, and the assays to test these populations functionally. Like other vertebrates, zebrafish demonstrate differential waves of hematopoiesis during embryogenesis. These waves can be visualized directly by fluorescent transgenesis in living embryos. The earliest blood-forming cells in the zebrafish embryo express the scl and lmo2 genes. By directing expression of GFP to early blood precursors using the lmo2 promoter, we have isolated early hematopoietic cells by flow cytometry and tested them functionally by transplantation. Transplantation of lmo2::GFP+ cells isolated from embryos at 14 hours post-fertilization (hpf) resulted in only transient reconstitution of erythrocytes, suggesting that the earliest identifiable blood-forming cells are committed to the erythroid lineage. Later in embryogenesis, lmo2:GFP+ GATA-1:dsRED+ cells are found in the posterior blood island (PBI) from approximately 30–60 hpf. Molecular and functional characterization of these cells suggests that they possess limited myeloid and erythroid, but not lymphoid differentiation potentials. This suggests that committed progenitors with definitive hematopoietic potential arise in the embryo before HSCs can be identified. Additional studies have suggested that the first multipotent HSCs are born later in the zebrafish aorta/gonad/mesonephros (AGM) region. We have visualized putative HSCs in the AGM by their expression of the lmo2 and cd41 transgenes. Using confocal timelapse imaging in living embryos, lmo2::GFP+ cells have been observed to emigrate from the AGM region into circulation. Transplantation studies are underway to test putative HSC populations for repopulation activity. Taken together, our findings suggest that at least three independent waves of blood cell precursors are formed during zebrafish embryogenesis.

Morphological and functional characterization of the endosarcomeric elastic filament

1990 ◽  
Vol 259 (1) ◽  
pp. C144-C149 ◽  
Author(s):  
G. Salviati ◽  
R. Betto ◽  
S. Ceoldo ◽  
S. Pierobon-Bormioli
Keyword(s):  
Electron Microscopy ◽  
Functional Characterization ◽  
Psoas Muscle ◽  
Selective Removal ◽  
Skinned Fibers ◽  
Thin Filaments ◽  
Resting Tension ◽  
Thick Filaments ◽  
Elastic Filament

The elastic filament was studied in chemically skinned fibers from rabbit psoas muscle by electron microscopy and resting tension measurements. Extraction of skinned fibers with 40 mM sodium pyrophosphate caused a selective removal of about two-thirds of the thick filaments and formed a gap between the remaining portion of the A band and the I band. Very thin filaments were seen in the gap and were decorated by anti-titin antibody. The resting tension of these fibers was comparable to that of unextracted control fibers. When the M band was completely extracted by a solution containing 0.6 M NaCl, the resting tension completely disappeared at sarcomere lengths from 2.8 to approximately 3.4 microns. These results suggest that the elastic force of short sarcomeres is endowed in the titin filaments and that these filaments are anchored to some structures of the Z and M lines. Other filaments were found in the gap between the two I bands of NaCl-extracted sarcomeres. These filaments differed from titin filaments by a larger diameter and the anchoring points. They may represent the sarcomeric structures responsible for the resting tension of extracted fibers stretched at sarcomere lengths longer than 3.4 microns.

scholarly journals How to find genomic regions relevant for gene regulation

2021 ◽  
Vol 33 (2) ◽  
pp. 157-165
Author(s):  
Xuanzong Guo ◽  
Uwe Ohler ◽  
Ferah Yildirim
Keyword(s):  
Functional Characterization ◽  
Regulatory Elements ◽  
Chromatin Accessibility ◽  
High Throughput Analysis ◽  
Protein Coding ◽  
Coding Regions ◽  
The Past ◽  
Genomic Regions ◽  
Regulatory Functions

Abstract Genetic variants associated with human diseases are often located outside the protein coding regions of the genome. Identification and functional characterization of the regulatory elements in the non-coding genome is therefore of crucial importance for understanding the consequences of genetic variation and the mechanisms of disease. The past decade has seen rapid progress in high-throughput analysis and mapping of chromatin accessibility, looping, structure, and occupancy by transcription factors, as well as epigenetic modifications, all of which contribute to the proper execution of regulatory functions in the non-coding genome. Here, we review the current technologies for the definition and functional validation of non-coding regulatory regions in the genome.

AEM Characterization of Particles in Electrodeposited Chromium Plates

1990 ◽  
Vol 48 (2) ◽  
pp. 46-47
Author(s):  
Li Chang ◽  
Rung-Ywan Tsai ◽  
Shinn-Tyan Wu
Keyword(s):  
Electron Microscopy ◽  
Surface Hardening ◽  
Steel Surface ◽  
Direct Evidence ◽  
Steel Substrate ◽  
Carbon Steels ◽  
The Past ◽  
Standard Solution ◽  
A Current

Electrodeposited Cr plating has been used for steel surface hardening since 1930. It is well known that there are particles precipitated during annealing the plate. However, no direct evidence has been shown to identify the species of the particles. Despite several microstructural characterizations having been carried out about thirty years ago it is surprised that no research has been done yet for the past decade to take the advantage of the powerful strength of modern electron microscopy. The present work reports the identification of the particles on the basis of AEM study.Cr plates were deposited on plain carbon steels by conventional method using a standard solution containing CrO3 250 g/l and H2SO4 2.5 g/l at a current density 40 A/dm2 and 45°C. The plates of 0.1mm thickness were then stripped off from steel substrate by dilute HNO3 before annealing was carried out in vacuum at 600,700, and 800°C for 1 to 6 hours.

Density Gradient Centrifugation and Electron Microscopic Characterization of Subcellular Fractions from Human Blood Platelets

1971 ◽  
Vol 25 (02) ◽  
pp. 252-267 ◽  
Author(s):  
A Siegel ◽  
P. H Burri ◽  
E. R Weibel ◽  
M Bettex-Galland ◽  
E. F Lüscher
Keyword(s):  
Electron Microscopy ◽  
Human Blood ◽  
Density Gradient Centrifugation ◽  
Blood Platelets ◽  
Gradient Centrifugation ◽  
Electron Microscopic ◽  
Osmotic Effect ◽  
Cellular Components ◽  
Human Blood Platelets

SummaryHomogenized human blood platelets have been fractionated by centrifugation in Ficoll and sucrose density gradients. The different fractions were examined by electron microscopy.Although Ficoll allows for the separation of very distinct zones, its ability to form complexes with cellular components made sucrose the preferable gradient. Sucrose, in spite of its unfavorable osmotic effect, allows for an acceptable fractionation of platelet components.

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