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Cryo electron microscopy

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https://www.readbyqxmd.com/read/28342772/elucidating-the-structural-organization-of-a-novel-low-density-lipoprotein-nanoparticle-reconstituted-with-docosahexaenoic-acid
#1
Rohit S Mulik, Hui Zheng, Kumar Pichumani, James Ratnakar, Qiu-Xing Jiang, Ian R Corbin
Low-density lipoprotein nanoparticles reconstituted with unesterified docosahexaenoic acid (LDL-DHA) is promising nanomedicine with enhanced physicochemical stability and selective anticancer cytotoxic activity. The unique functionality of LDL-DHA ultimately relates to the structure of this nanoparticle. To date, however, little is known about the structural organization of this nanoparticle. In this study chemical, spectroscopic and electron microscopy analyses were undertaken to elucidate the structural and molecular organization of LDL-DHA nanoparticles...
March 22, 2017: Chemistry and Physics of Lipids
https://www.readbyqxmd.com/read/28342396/high-resolution-cryo-em-the-nuts-and-bolts
#2
REVIEW
Dominika Elmlund, Sarah N Le, Hans Elmlund
Cryogenic electron microscopy (cryo-EM) and single-particle analysis now enables the determination of high-resolution structures of macromolecular assemblies that have resisted X-ray crystallography and other approaches. Successful high-resolution structure determination by cryo-EM always depends on the quality of the protein sample. While structural heterogeneity remains a key challenge for cryo-EM, it also represents a rare opportunity to study the intrinsic conformational flexibility of macromolecular assemblies...
March 22, 2017: Current Opinion in Structural Biology
https://www.readbyqxmd.com/read/28340349/structure-reveals-mechanisms-of-viral-suppressors-that-intercept-a-crispr-rna-guided-surveillance-complex
#3
Saikat Chowdhury, Joshua Carter, MaryClare F Rollins, Sarah M Golden, Ryan N Jackson, Connor Hoffmann, Lyn'Al Nosaka, Joseph Bondy-Denomy, Karen L Maxwell, Alan R Davidson, Elizabeth R Fischer, Gabriel C Lander, Blake Wiedenheft
Genetic conflict between viruses and their hosts drives evolution and genetic innovation. Prokaryotes evolved CRISPR-mediated adaptive immune systems for protection from viral infection, and viruses have evolved diverse anti-CRISPR (Acr) proteins that subvert these immune systems. The adaptive immune system in Pseudomonas aeruginosa (type I-F) relies on a 350 kDa CRISPR RNA (crRNA)-guided surveillance complex (Csy complex) to bind foreign DNA and recruit a trans-acting nuclease for target degradation. Here, we report the cryo-electron microscopy (cryo-EM) structure of the Csy complex bound to two different Acr proteins, AcrF1 and AcrF2, at an average resolution of 3...
March 23, 2017: Cell
https://www.readbyqxmd.com/read/28340337/structural-basis-of-rna-polymerase-i-transcription-initiation
#4
Christoph Engel, Tobias Gubbey, Simon Neyer, Sarah Sainsbury, Christiane Oberthuer, Carlo Baejen, Carrie Bernecky, Patrick Cramer
Transcription initiation at the ribosomal RNA promoter requires RNA polymerase (Pol) I and the initiation factors Rrn3 and core factor (CF). Here, we combine X-ray crystallography and cryo-electron microscopy (cryo-EM) to obtain a molecular model for basal Pol I initiation. The three-subunit CF binds upstream promoter DNA, docks to the Pol I-Rrn3 complex, and loads DNA into the expanded active center cleft of the polymerase. DNA unwinding between the Pol I protrusion and clamp domains enables cleft contraction, resulting in an active Pol I conformation and RNA synthesis...
March 23, 2017: Cell
https://www.readbyqxmd.com/read/28340334/advances-in-phase-plate-cryo-em-imaging-of-dna-and-nucleosomes
#5
Eugene Y D Chua, Sara Sandin
Contrast in electron cryo-microscopy (cryo-EM) is limited by the weak phase and radiation sensitive nature of biologic samples embedded in vitrified ice. We have recently shown that a new contrast enhancement technique utilizing the Volta phase plate can be combined with single particle analysis to determine the structure of a small chromatin complex, the nucleosome core particle, at near-atomic resolution. Here, we discuss advantages and limitations of the technique in terms of data collection, particle detection, and visualization of individual DNA molecules and higher-order chromatin structure...
February 7, 2017: Nucleus
https://www.readbyqxmd.com/read/28339813/microstructural-observation-of-fuel-cell-catalyst-inks-by-cryo-sem-and-cryo-tem
#6
Junichi Shimanuki, Shinichi Takahashi, Hajime Tohma, Atsushi Ohma, Ayumi Ishihara, Yoshiko Ito, Yuri Nishino, Atsuo Miyazawa
In order to improve the electricity generation performance of fuel cell electric vehicles, it is necessary to optimize the microstructure of the catalyst layer of a polymer electrolyte fuel cell. The catalyst layer is formed by a wet coating process using catalyst inks. Therefore, it is very important to observe the microstructure of the catalyst ink. In this study, the morphology of carbon-supported platinum (Pt/C) particles in catalyst inks with a different solvent composition was investigated by cryogenic scanning electron microscopy (cryo-SEM)...
February 9, 2017: Microscopy
https://www.readbyqxmd.com/read/28339603/optimization-of-stem-imaging-conditions-for-cryo-tomography
#7
Kazuhiro Aoyama, Kotaro Nagano, Kaoru Mitsuoka
For three-dimensional analysis of cryo-specimens using tomography at low and medium magnifications, the use of STEM images has some important advantages over TEM. A clear understanding of the electron dose in STEM is essential for optimized cryo-microscopy so a dose estimation technique for STEM imaging has been developed. The STEM convergence angle was shown to have a large impact on the image quality, in particular on the signal-to-noise ratio in the acquired images. Importantly, there is a clear trade-off between good STEM spatial resolution in the images with a large convergence angle and the signal-to-noise ratio, which is improved by reducing the convergence angle as much as possible...
February 9, 2017: Microscopy
https://www.readbyqxmd.com/read/28336870/evidence-of-protein-adsorption-in-pegylated-liposomes-influence-of-liposomal-decoration
#8
Marc Sangrà, Joan Estelrich, Raimon Sabaté, Alba Espargaró, Maria Antònia Busquets
In order to contribute to a better knowledge of the events involved in the formation of the protein corona when nanoparticles (NPs) come in contact with proteins, we report a study about the changes on the physicochemical properties of pristine, PEGylated and Cyclic Arginine-Glycine-Aspartate peptide (RGD)-functionalized large unilamelar liposomes (LUVs) or magnetoliposomes (MLs) upon incubation with Bovine Serum Albumin (BSA). The main phospholipid component of both LUVs and MLs was l-α-phosphatydylcholine (PC) or 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) with 20% of cholesterol...
February 10, 2017: Nanomaterials
https://www.readbyqxmd.com/read/28335215/rapamycin-loaded-solid-lipid-nanoparticles-as-a-new-tool-to-deliver-mtor-inhibitors-formulation-and-in-vitro-characterization
#9
Alice Polchi, Alessandro Magini, Jarosław Mazuryk, Brunella Tancini, Jacek Gapiński, Adam Patkowski, Stefano Giovagnoli, Carla Emiliani
Recently, the use of mammalian target of rapamycin (mTOR) inhibitors, in particular rapamycin (Rp), has been suggested to improve the treatment of neurodegenerative diseases. However, as Rp is a strong immunosuppressant, specific delivery to the brain has been postulated to avoid systemic exposure. In this work, we fabricated new Rp loaded solid lipid nanoparticles (Rp-SLN) stabilized with polysorbate 80 (PS80), comparing two different methods and lipids. The formulations were characterized by differential scanning calorimetry (DSC), nuclear magnetic resonance (NMR), wide angle X-ray scattering (WAXS), cryo-transmission electron microscopy (cryo-TEM), dynamic light scattering (DLS) and particle tracking...
May 9, 2016: Nanomaterials
https://www.readbyqxmd.com/read/28331315/improved-chemotherapeutic-efficacy-of-injectable-chrysin-encapsulated-by-copolymer-nanoparticles
#10
Kyoung Mee Kim, Hyun Kyung Lim, Sang Hee Shim, Joohee Jung
Chrysin is a flavone that is found in several plants and in honeycomb and possesses various biological activities. However, its low solubility means it has poor bioavailability, which must be resolved to enable its pharmaceutical applications. In the present study, chrysin was incorporated into methoxy poly(ethylene glycol)-β-polycaprolactone nanoparticles (chrysin-NPs) using the oil-in-water technique in order to overcome problems associated with chrysin. The properties of chrysin-NPs were analyzed, and their anticancer effects were investigated in vitro and in vivo...
2017: International Journal of Nanomedicine
https://www.readbyqxmd.com/read/28331084/structural-insights-into-emerging-pediatric-pathogens-human-bocaparvoviruses
#11
Mario Mietzsch, Shweta Kailasan, Jamie Garrison, Maria Ilyas, Paul Chipman, Kalle Kantola, Mandy E Janssen, John Spear, Duncan Sousa, Robert McKenna, Kevin Brown, Maria Söderlund-Venermo, Timothy Baker, Mavis Agbandje-McKenna
Bocaparvoviruses are emerging pathogens of the Parvoviridae family. Human bocaviruses 1 (HBoV1) causes severe respiratory infections and HBoV2-4 gastrointestinal infections in young children. Recent reports of life threatening cases, lack of direct treatment or vaccination, and a limited understanding of their disease mechanisms demand the need to study these pathogens on a molecular and structural level for the development of therapeutics. Towards this end, the capsid structures of HBoV1, HBoV3, and HBoV4 were determined to 2...
March 22, 2017: Journal of Virology
https://www.readbyqxmd.com/read/28330771/deciphering-the-molecular-architecture-of-membrane-contact-sites-by-cryo-electron-tomography
#12
REVIEW
Javier Collado, Rubén Fernández-Busnadiego
At membrane contact sites (MCS) two cellular membranes form tight appositions that play critical roles in fundamental phenomena such as lipid metabolism or Ca(2+) homeostasis. The interest for these structures has surged in recent years, bringing about the characterization of a plethora of MCS-resident molecules. How those molecules are structurally organized at MCS remains enigmatic, limiting our understanding of MCS function. Whereas such molecular detail is obscured by conventional electron microscopy sample preparation, cryo-electron tomography (cryo-ET) is uniquely positioned to address this challenge by allowing high resolution imaging of cellular landscapes in close-to-native conditions...
March 19, 2017: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/28324604/imaging-the-dynamics-of-cell-wall-polymer-deposition-in-the-unicellular-model-plant-penium-margaritaceum
#13
David Domozych, Anna Lietz, Molly Patten, Emily Singer, Berke Tinaz, Sandra C Raimundo
The unicellular green alga, Penium margaritaceum, represents a novel and valuable model organism for elucidating cell wall dynamics in plants. This organism's cell wall contains several polymers that are highly similar to those found in the primary cell walls of land plants. Penium is easily grown in laboratory culture and is effectively manipulated in various experimental protocols including microplate assays and correlative microscopy. Most importantly, Penium can be live labeled with cell wall-specific antibodies or other probes and returned to culture where specific cell wall developmental events can be monitored...
2017: Methods in Molecular Biology
https://www.readbyqxmd.com/read/28320961/structure-of-a-headful-dna-packaging-bacterial-virus-at-2-9-%C3%A3-resolution-by-electron-cryo-microscopy
#14
Haiyan Zhao, Kunpeng Li, Anna Y Lynn, Keith E Aron, Guimei Yu, Wen Jiang, Liang Tang
The enormous prevalence of tailed DNA bacteriophages on this planet is enabled by highly efficient self-assembly of hundreds of protein subunits into highly stable capsids. These capsids can stand with an internal pressure as high as ∼50 atmospheres as a result of the phage DNA-packaging process. Here we report the complete atomic model of the headful DNA-packaging bacteriophage Sf6 at 2.9 Å resolution determined by electron cryo-microscopy. The structure reveals the DNA-inflated, tensed state of a robust protein shell assembled via noncovalent interactions...
March 20, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28318486/structural-basis-of-transcription-arrest-by-coliphage-hk022-nun-in-an-escherichia-coli-rna-polymerase-elongation-complex
#15
Jin Young Kang, Paul Dominic B Olinares, James Chen, Elizabeth A Campbell, Arkady Mustaev, Brian T Chait, Max E Gottesman, Seth A Darst
Coliphage HK022 Nun blocks superinfection by coliphage λ by stalling RNA polymerase (RNAP) translocation specifically on λΔNA.To provide a structural framework to understand how Nun blocks RNAP translocation, we determined structures of Escherichia coli RNAP ternary elongation complexes (TECs) with and without Nun by single-particle cryo-electron microscopy. Nun fits tightly into the TEC by taking advantage of gaps between the RNAP and the nucleic acids. The C-terminal segment of Nun interacts with the RNAP β and β' subunits inside the RNAP active site cleft as well as with nearly every element of the nucleic-acid scaffold, essentially crosslinking the RNAP and the nucleic acids to prevent translocation, a mechanism supported by the effects of Nun amino acid substitutions...
March 20, 2017: ELife
https://www.readbyqxmd.com/read/28302852/structures-of-the-cyanobacterial-circadian-oscillator-frozen-in-a-fully-assembled-state
#16
Joost Snijder, Jan M Schuller, Anika Wiegard, Philip Lössl, Nicolas Schmelling, Ilka M Axmann, Jürgen M Plitzko, Friedrich Förster, Albert J R Heck
Cyanobacteria have a robust circadian oscillator, known as the Kai system. Reconstituted from the purified protein components KaiC, KaiB, and KaiA, it can tick autonomously in the presence of adenosine 5'-triphosphate (ATP). The KaiC hexamers enter a natural 24-hour reaction cycle of autophosphorylation and assembly with KaiB and KaiA in numerous diverse forms. We describe the preparation of stoichiometrically well-defined assemblies of KaiCB and KaiCBA, as monitored by native mass spectrometry, allowing for a structural characterization by single-particle cryo-electron microscopy and mass spectrometry...
March 17, 2017: Science
https://www.readbyqxmd.com/read/28301767/progress-in-human-and-tetrahymena-telomerase-structure
#17
Henry Chan, Yaqiang Wang, Juli Feigon
Telomerase is an RNA-protein complex that extends the 3' ends of linear chromosomes, using a unique telomerase reverse transcriptase (TERT) and template in the telomerase RNA (TR), thereby helping to maintain genome integrity. TR assembles with TERT and species-specific proteins, and telomerase function in vivo requires interaction with telomere-associated proteins. Over the past two decades, structures of domains of TR and TERT as well as other telomerase- and telomere-interacting proteins have provided insights into telomerase function...
March 15, 2017: Annual Review of Biophysics
https://www.readbyqxmd.com/read/28300075/a-human-antibody-against-zika-virus-crosslinks-the-e-protein-to-prevent-infection
#18
S Saif Hasan, Andrew Miller, Gopal Sapparapu, Estefania Fernandez, Thomas Klose, Feng Long, Andrei Fokine, Jason C Porta, Wen Jiang, Michael S Diamond, James E Crowe, Richard J Kuhn, Michael G Rossmann
The recent Zika virus (ZIKV) epidemic has been linked to unusual and severe clinical manifestations including microcephaly in fetuses of infected pregnant women and Guillian-Barré syndrome in adults. Neutralizing antibodies present a possible therapeutic approach to prevent and control ZIKV infection. Here we present a 6.2 Å resolution three-dimensional cryo-electron microscopy (cryoEM) structure of an infectious ZIKV (strain H/PF/2013, French Polynesia) in complex with the Fab fragment of a highly therapeutic and neutralizing human monoclonal antibody, ZIKV-117...
March 16, 2017: Nature Communications
https://www.readbyqxmd.com/read/28298612/cell-scientist-to-watch-gaia-pigino
#19
(no author information available yet)
Gaia Pigino received her master's degree in natural science followed by a PhD in evolutionary biology - focusing on zoology and ecotoxicology - in the laboratory of Fabio Bernini at the University of Siena, Italy. She then joined the electron microscopy laboratory of Pietro Lupetti for her first postdoctoral position before moving to Zürich. There, supported by an EMBO Long-Term Fellowship, she worked with Takashi Ishikawa at the Swiss Federal Institute of Technology and the Paul Scherrer Institute in Villigen...
March 15, 2017: Journal of Cell Science
https://www.readbyqxmd.com/read/28288098/mefloquine-targets-the-plasmodium-falciparum-80s-ribosome-to-inhibit-protein-synthesis
#20
Wilson Wong, Xiao-Chen Bai, Brad E Sleebs, Tony Triglia, Alan Brown, Jennifer K Thompson, Katherine E Jackson, Eric Hanssen, Danushka S Marapana, Israel S Fernandez, Stuart A Ralph, Alan F Cowman, Sjors H W Scheres, Jake Baum
Malaria control is heavily dependent on chemotherapeutic agents for disease prevention and drug treatment. Defining the mechanism of action for licensed drugs, for which no target is characterized, is critical to the development of their second-generation derivatives to improve drug potency towards inhibition of their molecular targets. Mefloquine is a widely used antimalarial without a known mode of action. Here, we demonstrate that mefloquine is a protein synthesis inhibitor. We solved a 3.2 Å cryo-electron microscopy structure of the Plasmodium falciparum 80S ribosome with the (+)-mefloquine enantiomer bound to the ribosome GTPase-associated centre...
March 13, 2017: Nature Microbiology
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