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Single particle electron microscopy

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https://www.readbyqxmd.com/read/28223502/cryo-em-structure-of-the-replisome-reveals-multiple-interactions-coordinating-dna-synthesis
#1
Arkadiusz W Kulczyk, Arne Moeller, Peter Meyer, Piotr Sliz, Charles C Richardson
We present a structure of the ∼650-kDa functional replisome of bacteriophage T7 assembled on DNA resembling a replication fork. A structure of the complex consisting of six domains of DNA helicase, five domains of RNA primase, two DNA polymerases, and two thioredoxin (processivity factor) molecules was determined by single-particle cryo-electron microscopy. The two molecules of DNA polymerase adopt a different spatial arrangement at the replication fork, reflecting their roles in leading- and lagging-strand synthesis...
February 21, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28218402/characterization-of-the-%C3%AE-and-p-phase-precipitates-in-the-cmsx-4-single-crystal-superalloy
#2
B Dubiel, P Indyka, T Moskalewicz, A Kruk, M Zubko, I Kalemba-Rec, K Berent
A combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and scanning-transmission electron microscopy (STEM) using high-angle annular-dark-field (HAADF) imaging, focussed ion beam- scanning electron microscopy (FIB-SEM) tomography, selected area electron diffraction with beam precession (PED), as well as spatially resolved energy-dispersive X-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS), was used to investigate topologically close-packed (TCP) phases, occurring in the CMSX-4 superalloy subjected to high temperature annealing and creep deformation...
February 20, 2017: Journal of Microscopy
https://www.readbyqxmd.com/read/28217720/a-graph-partitioning-approach-to-simultaneous-angular-reconstitution
#3
Gabi Pragier, Ido Greenberg, Xiuyuan Cheng, Yoel Shkolnisky
One of the primary challenges in single particle reconstruction with cryo-electron microscopy is to find a three-dimensional model of a molecule using its noisy two-dimensional projection-images. As the imaging orientations of the projection-images are unknown, we suggest a common-lines-based method to simultaneously estimate the imaging orientations of all images that is independent of the distribution of the orientations. Since the relative orientation of each pair of images may only be estimated up to a two-way handedness ambiguity, we suggest an efficient procedure to consistently assign the same handedness to all relative orientations...
September 2016: IEEE Transactions on Computational Imaging
https://www.readbyqxmd.com/read/28207240/interfaces-in-heterogeneous-catalysts-advancing-mechanistic-understanding-through-atomic-scale-measurements
#4
Wenpei Gao, Zachary D Hood, Miaofang Chi
Developing novel catalysts with high efficiency and selectivity is critical for enabling future clean energy conversion technologies. Interfaces in catalyst systems have long been considered the most critical factor in controlling catalytic reaction mechanisms. Interfaces include not only the catalyst surface but also interfaces within catalyst particles and those formed by constructing heterogeneous catalysts. The atomic and electronic structures of catalytic surfaces govern the kinetics of binding and release of reactant molecules from surface atoms...
February 16, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28206760/nano-engineered-eggshell-silver-tailored-co-polyester-polymer-blend-film-with-antimicrobial-properties
#5
Boniface J Tiimob, Gregory Mwinyelle, Woubit Abdela, Temesgen Samuel, Shaik Jeelani, Vijaya K Rangari
In this study, the reinforcement effect of different proportions of eggshell/silver nanomaterial (ES-Ag) on structural and antimicrobial properties of 70/30 poly (butylene-co-adipate terephthalate)/polylactic acid (PBAT/PLA) immiscible blends were investigated. The ES-Ag was synthesized using a single step ball milling process, and characterized with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). These results confirmed the existence of silver nanoparticles (Ag NPs) in the interstitial spaces of the eggshell particles...
February 16, 2017: Journal of Agricultural and Food Chemistry
https://www.readbyqxmd.com/read/28202543/nucleosome-like-ssdna-histone-octamer-complexes-and-the-implication-for-dna-double-strand-break-repair
#6
Nicholas L Adkins, Sarah G Swygert, Parminder Kaur, Hengyao Niu, Sergei A Grigoryev, Patrick Sung, Hong Wang, Craig L Peterson
Repair of DNA double strand breaks (DSBs) is key for maintenance of genome integrity. When DSBs are repaired by homologous recombination, DNA ends can undergo extensive processing, producing long stretches of single-stranded DNA (ssDNA). In vivo, DSB processing occurs in the context of chromatin, and studies indicate that histones may remain associated with processed DSBs. Here we demonstrate that histones are not evicted from ssDNA after in vitro chromatin resection. In addition, we reconstitute histone-ssDNA complexes (termed ssNucs) with ssDNA and recombinant histones and analyze these particles by a combination of native gel electrophoresis, sedimentation velocity, electron microscopy, and a recently developed electrostatic force microscopy technique, DREEM (Dual-Resonance-frequency-Enhanced Electrostatic force Microscopy)...
February 15, 2017: Journal of Biological Chemistry
https://www.readbyqxmd.com/read/28198180/engineering-recombinant-virus-like-nanoparticles-from-plants-for-cellular-delivery
#7
Lou Brillault, Philippe V Jutras, Noor Dashti, Eva C Thuenemann, Garry Morgan, George P Lomonossoff, Michael J Landsberg, Frank Sainsbury
Understanding capsid assembly following recombinant expression of viral structural proteins is critical to the design and modification of virus-like nanoparticles for biomedical and nanotechnology applications. Here, we use plant-based transient expression of the Bluetongue virus (BTV) structural proteins, VP3 and VP7, to obtain high yields of empty and green fluorescent protein (GFP)-encapsidating core-like particles (CLPs) from leaves. Single-particle cryo-electron microscopy of both types of particles revealed considerable differences in CLP structure compared to the crystal structure of infection-derived CLPs; in contrast, the two recombinant CLPs have an identical external structure...
February 15, 2017: ACS Nano
https://www.readbyqxmd.com/read/28196962/spatial-and-temporal-analysis-of-alphavirus-replication-and-assembly-in-mammalian-and-mosquito-cells
#8
Joyce Jose, Aaron B Taylor, Richard J Kuhn
Sindbis virus (SINV [genus Alphavirus, family Togaviridae]) is an enveloped, mosquito-borne virus. Alphaviruses cause cytolytic infections in mammalian cells while establishing noncytopathic, persistent infections in mosquito cells. Mosquito vector adaptation of alphaviruses is a major factor in the transmission of epidemic strains of alphaviruses. Though extensive studies have been performed on infected mammalian cells, the morphological and structural elements of alphavirus replication and assembly remain poorly understood in mosquito cells...
February 14, 2017: MBio
https://www.readbyqxmd.com/read/28196397/evolved-distal-tail-carbohydrate-binding-modules-of-lactobacillus-phage-j-1-a-novel-type-of-anti-receptor-widespread-among-lactic-acid-bacteria-phages
#9
Maria-Eugenia Dieterle, Silvia Spinelli, Irina Sadovskaya, Mariana Piuri, Christian Cambillau
Bacteriophage replication requires specific host-recognition. Some siphophages harbour a large complex, the baseplate, at the tip of their non-contractile tail. This baseplate holds receptor binding proteins (RBPs) that can recognize the host cell-wall polysaccharide (CWPS) and specifically attach the phage to its host. While most phages possess a dedicated RBP, the phage J-1 that infects Lactobacillus casei seemed to lack one. We have shown that the phage J-1 distal tail protein (Dit) plays a role in host recognition and that its sequence comprises two inserted modules compared to "classical" Dits...
February 14, 2017: Molecular Microbiology
https://www.readbyqxmd.com/read/28195734/bovine-serum-albumin-adsorption-on-tio2-colloids-the-effect-of-particle-agglomeration-and-surface-composition
#10
Augusto Márquez, Thomas Berger, Andrea Feinle, Nicola Huesing, Martin Himly, Albert Duschl, Oliver Diwald
Protein adsorption at nanostructured oxides strongly depends on synthesis conditions and sample history of the material investigated. We measured the adsorption of bovine serum albumin (BSA) to commercial Aeroxide TiO2 P25 nanoparticles in aqueous dispersions. Significant changes in adsorption capacity were induced by mild sample washing procedures and attributed to the structural modification of adsorbed water and surface hydroxyls. Motivated by the lack of information about the sample history of commercial TiO2 nanoparticle samples we used vapor phase grown TiO2 nanoparticles, a well-established model system for adsorption and photo-catalysis studies, and performed on this material for the first time a systematic and quantitative BSA adsorption study...
February 14, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28194956/direct-imaging-of-single-plasmonic-metal-nanoparticles-in-capillary-with-laser-light-sheet-scattering-imaging
#11
Xuan Cao, Jingjing Feng, Qi Pan, Bin Xiong, Yan He, Edward S Yeung
Understanding the heterogeneous distribution of the physical and chemical properties of plasmonic metal nanoparticles is fundamentally important to their basic and applied research. Traditionally, they are obtained either indirectly via bulk spectroscopic measurements plus electron microscopic characterizations, or through single molecule/particle imaging of nanoparticles immobilized on planar substrates. In this study, by using light-sheet scattering microscopy with a supercontinuum white laser, highly sensitive imaging of individual MNPs flowing inside a capillary, driven by either pressure or electric field, was achieved for the first time...
February 13, 2017: Analytical Chemistry
https://www.readbyqxmd.com/read/28191458/structural-study-of-heterogeneous-biological-samples-by-cryoelectron-microscopy-and-image-processing
#12
REVIEW
H E White, A Ignatiou, D K Clare, E V Orlova
In living organisms, biological macromolecules are intrinsically flexible and naturally exist in multiple conformations. Modern electron microscopy, especially at liquid nitrogen temperatures (cryo-EM), is able to visualise biocomplexes in nearly native conditions and in multiple conformational states. The advances made during the last decade in electronic technology and software development have led to the revelation of structural variations in complexes and also improved the resolution of EM structures. Nowadays, structural studies based on single particle analysis (SPA) suggests several approaches for the separation of different conformational states and therefore disclosure of the mechanisms for functioning of complexes...
2017: BioMed Research International
https://www.readbyqxmd.com/read/28181467/quantifying-alumina-nanoparticle-dispersion-in-hybrid-carbon-fiber-composites-using-photoluminescent-spectroscopy
#13
Imad Hanhan, Alex Selimov, Declan Carolan, Ambrose C Taylor, Seetha Raghavan
Composites modified with nanoparticles are of interest to many researchers due to the large surface-area-to-volume ratio of nano-scale fillers. One challenge with nanoscale materials that has received significant attention is the dispersion of nanoparticles in a matrix material. A random distribution of particles often ensures good material properties, especially as it relates to the thermal and mechanical performance of composites. Typical methods to quantify particle dispersion in a matrix material include optical, scanning electron, and transmission electron microscopy...
February 2017: Applied Spectroscopy
https://www.readbyqxmd.com/read/28181368/diamond-burr-debridement-vs-grid-keratotomy-in-canine-scced-with-scanning-electron-microscopy-diamond-burr-tip-analysis
#14
Chloe B Spertus, Josef M Brown, Elizabeth A Giuliano
OBJECTIVES: (i) Compare the outcome of canine SCCED treated with grid keratotomy (GK) or diamond burr debridement (DBD); (ii) Serially evaluate morphologic and elemental composition changes to diamond burr tips. ANIMALS STUDIED: A total of 91 eyes of 88 canine SCCED patients treated at the University of Missouri (2005-2015); 75 fresh cadaver porcine globes. PROCEDURES: (i) Medical records were reviewed retrospectively. Data were analyzed for age, sex, breed, procedure performed, eye(s) on which the procedure was performed, time to healing after a single surgical procedure, performance of a second surgical procedure, contact lens placement, and postprocedural complications...
February 9, 2017: Veterinary Ophthalmology
https://www.readbyqxmd.com/read/28180226/facile-fabrication-of-sudan-red-particle-microcapsules-by-a-polymerizable-gemini-surfactant-and-molecular-assembly-mechanisms
#15
Yaqian Wu, Haike Yan, Xuefeng Shi, Jinben Wang
An efficient method was developed to encapsulate water insoluble organic particles of Sudan red III (SR) in aqueous suspensions by using a polymerizable cationic gemini surfactant, 1,3-bis(N,N-dimethyl-N-cetylammonium)-2-(propylacrylate dibromide) (AGC16). The AGC16 coated SR microcapsules (AGC16@SR) were prepared by absorption of AGC16 on the surface of SR, followed by in situ homopolymerization (PAGC16). Several measurements, including transmission and scanning electron microscopy, isothermal titration calorimetry, zeta potential, electron paramagnetic resonance and small angle X-ray scattering, were performed to determine the adsorption amount of AGC16, and the layer structures and the molecular assembly mechanism in the AGC16@SR and PAGC16@SR systems, respectively...
February 9, 2017: Soft Matter
https://www.readbyqxmd.com/read/28170452/implications-of-wear-at-the-titanium-zirconia-implant-abutment-interface-on-the-health-of-peri-implant-tissues
#16
Andrew Tawse-Smith, Sunyoung Ma, Warwick J Duncan, Andrew Gray, Malcolm R Reid, Alison M Rich
PURPOSE: To investigate the presence of metallic particles in the peri-implant mucosa around titanium dental implants after 5 years of loading using single-implant crowns with respect to clinical signs of peri-implant inflammation. MATERIALS AND METHODS: Sixteen participants from an ongoing, prospective, single-arm clinical trial who had received titanium dental implants restored with single maxillary crowns veneered to zirconia abutments were available for the study...
February 7, 2017: International Journal of Oral & Maxillofacial Implants
https://www.readbyqxmd.com/read/28167262/humidity-affects-the-morphology-of-particles-emitted-from-beclomethasone-dipropionate-pressurized-metered-dose-inhalers
#17
James W Ivey, Pallavi Bhambri, Tanya K Church, David A Lewis, Mark T McDermott, Shereen Elbayomy, Warren H Finlay, Reinhard Vehring
The effects of propellant type, cosolvent content, and air humidity on the morphology and solid phase of the particles produced from solution pressurized metered dose inhalers containing the corticosteroid beclomethasone dipropionate were investigated. The active ingredient was dissolved in the HFA propellants 134a and 227ea with varying levels of the cosolvent ethanol and filled into pressurized metered dose inhalers. Inhalers were actuated into an evaporation chamber under controlled temperature and humidity conditions and sampled using a single nozzle, single stage inertial impactor...
February 3, 2017: International Journal of Pharmaceutics
https://www.readbyqxmd.com/read/28161413/relaxed-and-active-thin-filament-structures-a-new-structural-basis-for-the-regulatory-mechanism
#18
Danielle M Paul, John M Squire, Edward P Morris
The structures of muscle thin filaments reconstituted using skeletal actin and cardiac troponin and tropomyosin have been determined with and without bound Ca(2+) using electron microscopy and reference-free single particle analysis. The resulting density maps have been fitted with atomic models of actin, tropomyosin and troponin showing that: (i) the polarity of the troponin complex is consistent with our 2009 findings, with large shape changes in troponin between the two states; (ii) without Ca(2+) the tropomyosin pseudo-repeats all lie at almost equivalent positions in the 'blocked' position on actin (over subdomains 1 and 2); (iii) in the active state the tropomyosin pseudo-repeats are all displaced towards subdomains 3 and 4 of actin, but the extent of displacement varies within the regulatory unit depending upon the axial location of the pseudo-repeats with respect to troponin...
February 1, 2017: Journal of Structural Biology
https://www.readbyqxmd.com/read/28154074/imaging-rotational-dynamics-of-nanoparticles-in-liquid-by-4d-electron-microscopy
#19
Xuewen Fu, Bin Chen, Jau Tang, Mohammed Th Hassan, Ahmed H Zewail
In real time and space, four-dimensional electron microscopy (4D EM) has enabled observation of transient structures and morphologies of inorganic and organic materials. We have extended 4D EM to include liquid cells without the time resolution being limited by the response of the detector. Our approach permits the imaging of the motion and morphological dynamics of a single, same particle on nanometer and ultrashort time scales. As a first application, we studied the rotational dynamics of gold nanoparticles in aqueous solution...
February 3, 2017: Science
https://www.readbyqxmd.com/read/28138524/uncovering-the-forces-between-nucleosomes-using-dna-origami
#20
Jonas J Funke, Philip Ketterer, Corinna Lieleg, Sarah Schunter, Philipp Korber, Hendrik Dietz
Revealing the energy landscape for nucleosome association may contribute to the understanding of higher-order chromatin structures and their impact on genome regulation. We accomplish this in a direct measurement by integrating two nucleosomes into a DNA origami-based force spectrometer, which enabled subnanometer-resolution measurements of nucleosome-nucleosome distance frequencies via single-particle electron microscopy imaging. From the data, we derived the Boltzmann-weighted distance-dependent energy landscape for nucleosome pair interactions...
November 2016: Science Advances
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