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Single particle electron microscopy

Peng Dong, Runhua Yao, Zheng Yan, Zhifeng Yan, Wenxian Wang, Xiuli He, Jun Zhou
Laser welding has been considered to be one of the most promising joining processes for Nitinol medical device manufacturing. Presently, there is still a limited understanding about how laser welding affects the microstructure and the resultant corrosion behaviors. This work aimed to reveal the microstructural factors that influence the corrosion resistance of laser-welded crossed Nitinol joints. The microstructures within various zones of the joints were characterized by using transmission electron microscopy (TEM), and the corrosion behaviors of the joints in 0...
May 18, 2018: Materials
Min Woo Sung, Rahamthulla Shaik, Allan D TerBush, Katherine W Osteryoung, Stanislav Vitha, Andreas Holzenburg
Chloroplasts host photosynthesis and fulfill other metabolic functions that are essential to plant life. They have to divide by binary fission to maintain their numbers throughout cycles of cell division. Chloroplast division is achieved by a complex ring-shaped division machinery located on both the inner (stromal) and the outer (cytosolic) side of the chloroplast envelope. The inner division ring (termed the Z ring) is formed by the assembly of tubulin-like FtsZ1 and FtsZ2 proteins. ARC6 is a key chloroplast division protein that interacts with the Z ring...
May 16, 2018: Journal of Biological Chemistry
Shanshan Wang, Hidetaka Sawada, Xiaoyu Han, Si Zhou, Sha Li, Zheng Xiao Guo, Angus I Kirkland, Jamie H Warner
We show that Pt nanoclusters preferentially nucleate along the grain boundaries (GBs) in polycrystalline MoS2 monolayer films, with dislocations acting as the seed site. Atomic resolution studies by aberration-corrected annular dark-field scanning transmission electron microscopy reveal periodic spacing of Pt nanoclusters with dependence on GB tilt angles and random spacings for the antiphase boundaries ( i.e., 60°). Individual Pt atoms are imaged within the dislocation core sections of the GB region, with various positions observed, including both the substitutional sites of Mo and the hollow center of the octahedral ring...
May 15, 2018: ACS Nano
Alberto Bartesaghi, Cecilia Aguerrebere, Veronica Falconieri, Soojay Banerjee, Lesley A Earl, Xing Zhu, Nikolaus Grigorieff, Jacqueline L S Milne, Guillermo Sapiro, Xiongwu Wu, Sriram Subramaniam
The advent of direct electron detectors has enabled the routine use of single-particle cryo-electron microscopy (EM) approaches to determine structures of a variety of protein complexes at near-atomic resolution. Here, we report the development of methods to account for local variations in defocus and beam-induced drift, and the implementation of a data-driven dose compensation scheme that significantly improves the extraction of high-resolution information recorded during exposure of the specimen to the electron beam...
April 30, 2018: Structure
Philipp A M Schmidpeter, Xiaolong Gao, Vikrant Uphadyay, Jan Rheinberger, Crina M Nimigean
Cyclic nucleotide-modulated ion channels play several essential physiological roles. They are involved in signal transduction in photoreceptors and olfactory sensory neurons as well as pacemaking activity in the heart and brain. Investigations of the molecular mechanism of their actions, including structural and electrophysiological characterization, are restricted by the availability of stable, purified protein obtained from accessible systems. Here, we establish that SthK, a cyclic nucleotide-gated (CNG) channel from Spirochaeta thermophila , is an excellent model for investigating the gating of eukaryotic CNG channels at the molecular level...
May 11, 2018: Journal of General Physiology
Mahdi Hesari, Xianwen Mao, Peng Chen
Understanding the fundamental properties of charge carriers on the surface of semiconductor photo(electro)catalysts is key to the rational design of efficient photo(electro)catalytic devices for sunlight-driven energy conversion. Here high spatial resolution information is always desirable because of the ubiquitous heterogeneity in semiconductor particles. In this Perspective we review the latest advances in nanoscale imaging and quantitative analysis of charge carrier activities on individual semiconductor particles down to sub-particle resolution, covering the approaches of single-molecule super-resolution fluorescence imaging, scanning electron microscopy, and photoluminescence microscopy...
May 11, 2018: Journal of the American Chemical Society
Nicholas Nunn, Marta d'Amora, Neeraj Prabhakar, Alexander M Panich, Natalya Froumin, Marco D Torelli, Igor Vlasov, Philipp Reineck, Brant Gibson, Jessica M Rosenholm, Silvia Giordani, Olga Shenderova
Detonation nanodiamonds (DNDs) have emerged as promising candidates for a variety of biomedical applications, thanks to different physicochemical and biological properties, such as small size and reactive surfaces. In this study, we propose carbon dot decorated single digit (4-5 nm diameter) primary particles of detonation nanodiamond as promising fluorescent probes. Due to their intrinsic fluorescence originating from tiny (1-2 atomic layer thickness) carbonaceous structures on their surfaces, they exhibit brightness suitable for in vitro imaging...
May 9, 2018: Methods and Applications in Fluorescence
Marianna Lorenzo, Conrad Escher, Tatiana Latychevskaia, Hans-Werner Fink
The interaction of metals with carbon materials, specifically with graphene, is of importance for various technological applications. In particular, intercalation of alkali metals is believed to provide a means for tuning the electronic properties of graphene for device applications. While the macroscopic effects of such intercalation events can readily be studied, following the related processes at an atomic scale in detail and under well-defined experimental conditions constitutes a challenge. Here, we investigate in situ the adsorption and nucleation of the alkali metals K, Cs, and Li on free-standing graphene by means of low-energy electron point source microscopy...
May 7, 2018: Nano Letters
Ákos Gellért, Tímea Pósa, Attila Fábián, László Szabó, Károly Bóka, Barbara Forró, Katalin Salánki, László Drahos, Eszter Tóth, Angéla Juhász, Ervin Balázs
A previous study showed that a single amino acid difference in the cucumber mosaic virus (CMV) capsid protein (CP) elicits unusual symptoms. The wild-type strain (CMV-R) induces green mosaic symptoms and malformation while the mutant strain (CMV-R3E79R) causes chlorotic lesions on inoculated leaves and strong stunting with necrosis on systemic leaves. Virion preparations of CMV-R and CMV-R3E79R were partially purified from Nicotiana clevelandii A. Gray and analysed by two-dimensional gel electrophoresis. Their separated protein patterns showed remarkable differences at the 50-75 kDa range, both in numbers and intensity of spots, with more protein spots for the mutant CMV...
May 3, 2018: Virus Research
Aharon Azagury, Vera C Fonseca, Daniel Y Cho, James Perez-Rogers, Christopher M Baker, Elaine Steranka, Victoria Goldenshtein, Dominick Calvao, Eric M Darling, Edith Mathiowitz
A quick fabrication method for making double-walled (DW) polymeric nanospheres is presented. The process uses sequential precipitation of two polymers. By choosing an appropriate solvent and non-solvent polymer pair, and engineering two sequential phase inversions which induces first precipitation of the core polymer followed by precipitation of the shell polymer, DW nanospheres can be created instantaneously. A series of DW formulations were prepared with various core and shell polymers, then characterized using laser diffraction particle sizing, scanning electron microscopy, atomic force microscopy, Fourier transform infrared spectroscopy, and differential scanning calorimetry (DSC)...
May 2, 2018: Journal of Controlled Release: Official Journal of the Controlled Release Society
Maria Camila Garcia Toro, Joshua P Schlegel, Carlos H C Giraldo
We report the synthesis of radioactive gold nanoparticles in a single step process with appropriate activity and size to be used in cancer treatment and diagnosis. Methods: A 2 mM solution of gold chloride (HAuCl4), 1 mM of polyvinylpyrrolidone (PVP, M.W: 360,000), and 60 mM of 2-propanol was prepared in deionized water. Seven different samples of the solution were irradiated in a total neutron flux of 7.45 x 1012 n/cm2 s in a research reactor for 0.5, 1, 3, 5, 10, 30, and 60 minutes. The resulting nanoparticles were characterized for morphology and chemical composition using a Transmission Electron Microscopy (TEM) and ImageJ...
May 3, 2018: Journal of Nuclear Medicine Technology
Richard M Walsh, Soung-Hun Roh, Anant Gharpure, Claudio L Morales-Perez, Jinfeng Teng, Ryan E Hibbs
Fast chemical communication in the nervous system is mediated by neurotransmitter-gated ion channels. The prototypical member of this class of cell surface receptors is the cation-selective nicotinic acetylcholine receptor. As with most ligand-gated ion channels, nicotinic receptors assemble as oligomers of subunits, usually as hetero-oligomers and often with variable stoichiometries 1 . This intrinsic heterogeneity in protein composition provides fine tunability in channel properties, which is essential to brain function, but frustrates structural and biophysical characterization...
May 2, 2018: Nature
Rasha Ghunaim, Maik Scholz, Christine Damm, Bernd Rellinghaus, Rüdiger Klingeler, Bernd Büchner, Michael Mertig, Silke Hampel
In the present work, we demonstrate different synthesis procedures for filling carbon nanotubes (CNTs) with equimolar binary nanoparticles of the type Fe-Co. The CNTs act as templates for the encapsulation of magnetic nanoparticles and provide a protective shield against oxidation as well as prevent nanoparticle agglomeration. By variation of the reaction parameters, we were able to tailor the sample purity, degree of filling, the composition and size of the filling particles, and therefore, the magnetic properties...
2018: Beilstein Journal of Nanotechnology
Wilnelly Martinez-Ortiz, Timothy J Cardozo
Voltage-gated ion channels (VGICs) are associated with hundreds of human diseases. To date, 3D structural models of human VGICs have not been reported. We developed a 3D structural integrity metric to rank the accuracy of all VGIC structures deposited in the PDB. The metric revealed inaccuracies in structural models built from recent single-particle, non-crystalline cryo-electron microscopy maps and enabled the building of highly accurate homology models of human Cav channel α1 subunits at atomic resolution...
May 1, 2018: Cell Reports
Joana S Sousa, Filipa Calisto, Julian D Langer, Deryck J Mills, Patrícia N Refojo, Miguel Teixeira, Werner Kühlbrandt, Janet Vonck, Manuela M Pereira
Electron transfer in respiratory chains generates the electrochemical potential that serves as energy source for the cell. Prokaryotes can use a wide range of electron donors and acceptors and may have alternative complexes performing the same catalytic reactions as the mitochondrial complexes. This is the case for the alternative complex III (ACIII), a quinol:cytochrome c/HiPIP oxidoreductase. In order to understand the catalytic mechanism of this respiratory enzyme, we determined the structure of ACIII from Rhodothermus marinus at 3...
April 30, 2018: Nature Communications
Nhat Tai Nguyen, Jaysen Nelayah, Damien Alloyeau, Guillaume Wang, Laurent Piccolo, Pavel Afanasiev, Christian Ricolleau
Many physical properties of nanoparticles (NPs) are driven by their equilibrium shape (ES). Thus, knowing the kinetic and thermodynamic parameters that affect the particle morphology is key for the rational design of NPs with targeted properties. Here, we report on the thermodynamic ES of supported monometallic palladium and bimetallic palladium-gold (Pd-Au) single-crystalline truncated nano-octahedra (TOs) studied using aberration-corrected transmission electron microscopy (TEM). Monometallic palladium and bimetallic Pd62Au38 and Pd43Au57 TOs were grown by pulsed laser deposition on rutile titania (r-TiO2) nanorods exposing mainly (110) facets...
April 30, 2018: Physical Chemistry Chemical Physics: PCCP
Nopnithi Thonghin, Vasileios Kargas, Jack Clews, Robert C Ford
Membrane proteins represent a large proportion of the proteome, but have characteristics that are problematic for many methods in modern molecular biology (that have often been developed with soluble proteins in mind). For structural studies, low levels of expression and the presence of detergent have been thorns in the flesh of the membrane protein experimentalist. Here we discuss the use of cryo-electron microscopy in breakthrough studies of the structures of membrane proteins. This method can cope with relatively small quantities of sample and with the presence of detergent...
April 24, 2018: Methods: a Companion to Methods in Enzymology
Emmanuelle R Quemin, Simon Corroyer-Dulmont, Jacomine Krijnse-Locker
Nucleocytoplasmic large DNA viruses (NCLDVs) are a steadily growing group of viruses that infect a wide range of hosts and are characterized by large particle dimensions and genome sizes. Understanding how they enter into the host cell and deliver their genome in the cytoplasm is therefore particularly intriguing. Here, we review the current knowledge on the entry of two of the best-characterized NCLDVs: the poxvirus Vaccinia virus (VACV) and the giant virus Mimivirus. While previous studies on VACV had proposed both direct fusion at the plasma membrane and endocytosis as entry routes, more recent biochemical and morphological data argue for macropinocytosis as well...
April 24, 2018: Journal of Molecular Biology
Qinglin Tang, Wenjun Guo, Li Zheng, Jing-Xiang Wu, Meng Liu, Xindi Zhou, Xiaolin Zhang, Lei Chen
TRPC6 and TRPC3 are receptor-activated nonselective cation channels that belong to the family of canonical transient receptor potential (TRPC) channels. They are activated by diacylglycerol, a lipid second messenger. TRPC6 and TRPC3 are involved in many physiological processes and implicated in human genetic diseases. Here we present the structure of human TRPC6 homotetramer in complex with a newly identified high-affinity inhibitor BTDM solved by single-particle cryo-electron microscopy to 3.8 Å resolution...
April 26, 2018: Cell Research
Mohammad Chaheen, Noelia M Sanchez-Ballester, Bernard Bataille, Ahmad Yassine, Emmanuel Belamie, Tahmer Sharkawi
Due to the increasing interest in multifunctional excipients for tableting, coprocessing of individual excipients is regularly used to produce excipients of improved multifunctionality superior to that of individual excipients or their physical mix. The use of chitin as an excipient in tablet formulation is limited due to certain drawbacks such as poor flowability and low true density. The objective of this work is to improve these properties through coprocessing of chitin with calcium carbonate (CaCO3 ) by precipitating CaCO3 on chitin particles using different methods...
April 23, 2018: Journal of Pharmaceutical Sciences
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