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Peter S Shen, Xiaoyong Yang, Paul G DeCaen, Xiaowen Liu, David Bulkley, David E Clapham, Erhu Cao
The Polycystic Kidney Disease 2 (Pkd2) gene is mutated in autosomal dominant polycystic kidney disease (ADPKD), one of the most common human monogenic disorders. Here, we present the cryo-EM structure of PKD2 in lipid bilayers at 3.0 Å resolution, which establishes PKD2 as a homotetrameric ion channel and provides insight into potential mechanisms for its activation. The PKD2 voltage-sensor domain retains two of four gating charges commonly found in those of voltage-gated ion channels. The PKD2 ion permeation pathway is constricted at the selectivity filter and near the cytoplasmic end of S6, suggesting that two gates regulate ion conduction...
October 20, 2016: Cell
Tofayel Ahmed, Zhan Yin, Shashi Bhushan
Protein synthesis in the chloroplast is mediated by the chloroplast ribosome (chloro-ribosome). Overall architecture of the chloro-ribosome is considerably similar to the Escherichia coli (E. coli) ribosome but certain differences are evident. The chloro-ribosome proteins are generally larger because of the presence of chloroplast-specific extensions in their N- and C-termini. The chloro-ribosome harbours six plastid-specific ribosomal proteins (PSRPs); four in the small subunit and two in the large subunit...
October 20, 2016: Scientific Reports
Daniel R Ripoll, Ilja Khavrutskii, Anders Wallqvist, Sidhartha Chaudhury
Cryo-electron-microscopy (cryo-EM) structures of flaviviruses reveal significant variation in epitope occupancy across different monoclonal antibodies that have largely been attributed to epitope-level differences in conformation or accessibility that affect antibody binding. The consequences of these variations for macroscopic properties such as antibody binding and neutralization are the results of the law of mass action-a stochastic process of innumerable binding and unbinding events between antibodies and the multiple binding sites on the flavivirus in equilibrium-that cannot be directly imputed from structure alone...
October 18, 2016: Biophysical Journal
Emil F Khisamutdinov, Daniel L Jasinski, Hui Li, Kaiming Zhang, Wah Chiu, Peixuan Guo
Constructing containers with defined shape and size to load and protect therapeutics and subsequently control their release in the human body has long been a dream. The fabrication of 3D RNA prisms, characterized by atomic force microscopy, cryo-electron microscopy, dynamic light scattering, and polyacrylamide gel electrophoresis, is reported for the loading and protection of small molecules, proteins, small RNA molecules, and their controlled release.
October 19, 2016: Advanced Materials
Anna Mularski, Jonathan Wilksch, Eric Hanssen, Jian Li, Takehiro Tomita, Sacha James Pidot, Tim Stinear, Frances Separovic, Dick Strugnell
Atomic force microscopy measurements of capsule thickness revealed that that the wild-type Klebsiella pneumoniae AJ218 capsular polysaccharides were rearranged by exposure to colistin. The increase in capsule thickness measured near minimum inhibitory/bactericidal concentration (MIC/MBC) is consistent with the idea that colistin displaces the divalent cations that cross-bridge adjacent lipopolysaccharide (LPS) molecules through the capsule network. Cryo-electron microscopy demonstrated that the measured capsule thickness at near MIC/MBC of 1...
October 17, 2016: European Biophysics Journal: EBJ
Zheng Liu, Cristina Gutierrez-Vargas, Jia Wei, Robert A Grassucci, Noel Espina, Susan Madison-Antenucci, Liang Tong, Joachim Frank
With the advance of new instruments and algorithms, and the accumulation of experience over decades, single-particle cryo-EM has become a pivotal part of structural biology. Recently, we determined the structure of a eukaryotic ribosome at 2.5 Å for the large subunit. The ribosome was derived from Trypanosoma cruzi, the protozoan pathogen of Chagas disease. The high-resolution density map allowed us to discern a large number of unprecedented details including rRNA modifications, water molecules, and ions such as Mg(2+) and Zn(2+) ...
October 17, 2016: Protein Science: a Publication of the Protein Society
Christopher J Benjamin, Kyle J Wright, Scott C Bolton, Seok-Hee Hyun, Kyle Krynski, Mahima Grover, Guimei Yu, Fei Guo, Tamara L Kinzer-Ursem, Wen Jiang, David H Thompson
We report the fabrication of transmission electron microscopy (TEM) grids bearing graphene oxide (GO) sheets that have been modified with N(α), N(α)-dicarboxymethyllysine (NTA) and deactivating agents to block non-selective binding between GO-NTA sheets and non-target proteins. The resulting GO-NTA-coated grids with these improved antifouling properties were then used to isolate His6-T7 bacteriophage and His6-GroEL directly from cell lysates. To demonstrate the utility and simplified workflow enabled by these grids, we performed cryo-electron microscopy (cryo-EM) of His6-GroEL obtained from clarified E...
October 17, 2016: Scientific Reports
Huan-Yuan Chen, Dapi Meng-Lin Chiang, Zi-Jing Lin, Chia-Chun Hsieh, Gung-Chian Yin, I-Chun Weng, Peter Guttermann, Stephan Werner, Katja Henzler, Gerd Schneider, Lee-Jene Lai, Fu-Tong Liu
Mast cells play an important role in allergic responses. During activation, these cells undergo degranulation, a process by which various kinds of mediators stored in the granules are released. Granule homeostasis in mast cells has mainly been studied by electron microscopy (EM), where the fine structures of subcellular organelles are partially destroyed during sample preparation. Migration and fusion of granules have not been studied in detail in three dimensions (3D) in unmodified samples. Here, we utilized soft X-ray tomography (SXT) coupled with fluorescence microscopy to study the detailed structures of organelles during mast cell activation...
October 17, 2016: Scientific Reports
Joshua Xu, Jessica G Y Luc, Kevin Phan
Atrial fibrillation (AF) is the most prevalent cardiac arrhythmia in modern clinical practice, with an estimated prevalence of 1.5-2%. The prevalence of AF is expected to double in the next decades, progressing with age and increasingly becoming a global medical challenge. The first-line treatment for AF is often medical treatment with either rate control or anti-arrhythmic agents for rhythm control, in addition to anti-coagulants such as warfarin for stroke prevention in patient at risk. Catheter ablation has emerged as an alternative for AF treatment, which involves myocardial tissue lesions to disrupt the underlying triggers and substrates for AF...
September 2016: Journal of Thoracic Disease
Sean Ekins, John Liebler, Bruno J Neves, Warren G Lewis, Megan Coffee, Rachelle Bienstock, Christopher Southan, Carolina H Andrade
The Zika virus (ZIKV) is a flavivirus of the family Flaviviridae, which is similar to dengue virus, yellow fever and West Nile virus. Recent outbreaks in South America, Latin America, the Caribbean and in particular Brazil have led to concern for the spread of the disease and potential to cause Guillain-Barré syndrome and microcephaly. Although ZIKV has been known of for over 60 years there is very little in the way of knowledge of the virus with few publications and no crystal structures. No antivirals have been tested against it either in vitro or in vivo...
2016: F1000Research
Tian-Min Fu, Yang Li, Alvin Lu, Zongli Li, Parimala R Vajjhala, Anthony C Cruz, Devendra B Srivastava, Frank DiMaio, Pawel A Penczek, Richard M Siegel, Katryn J Stacey, Edward H Egelman, Hao Wu
Caspase-8 activation can be triggered by death receptor-mediated formation of the death-inducing signaling complex (DISC) and by the inflammasome adaptor ASC. Caspase-8 assembles with FADD at the DISC and with ASC at the inflammasome through its tandem death effector domain (tDED), which is regulated by the tDED-containing cellular inhibitor cFLIP and the viral inhibitor MC159. Here we present the caspase-8 tDED filament structure determined by cryoelectron microscopy. Extensive assembly interfaces not predicted by the previously proposed linear DED chain model were uncovered, and were further confirmed by structure-based mutagenesis in filament formation in vitro and Fas-induced apoptosis and ASC-mediated caspase-8 recruitment in cells...
October 20, 2016: Molecular Cell
Ching-Yu Chou, Minglee Chu, Chi-Fon Chang, Tsunai Yu, Tai-Huang Huang, Dimitris Sakellariou
Field-dependent NMR studies of bio-molecular systems using a sample shuttling hardware operating on a high-field NMR apparatus have provided valuable structural and dynamic information. We have recently published a design of a compact sample transportation device, called "field-cycler", which was installed in a commercial spectrometer and which provided highly precise positioning and stability during high speed shuttling. In this communication, we demonstrate the first use of a sample shuttling device on a commercial high field standard bore NMR spectrometer, equipped with a commercial triple resonance cryogenically cooled NMR probe...
October 15, 2016: Journal of Biomolecular NMR
Vladan Lučić, Rubén Fernández-Busnadiego, Ulrike Laugks, Wolfgang Baumeister
Molecular complexes, arguably the basic units carrying cellular function, can be visualized directly in their native environment by cryo-electron tomography. Here we describe a procedure for the detection of small, pleomorphic membrane-bound molecular complexes in cryo-tomograms by a hierarchical connectivity segmentation. Validation on phantom and real data showed above 90% true positive rates. This segmentation procedure is implemented in the Pyto software package, together with methods for quantitative characterization and classification of complexes detected by our segmentation procedure and for statistical analysis between experimental conditions...
October 11, 2016: Journal of Structural Biology
Yong-Jiang Zhang, Fulton E Rockwell, Adam C Graham, Teressa Alexander, N Michele Holbrook
We report a novel form of xylem dysfunction in angiosperms: reversible collapse of the xylem conduits of the smallest vein orders that demarcate and intrusively irrigate the areoles of Quercus rubra leaves. Cryo-scanning electron microscopy revealed gradual increases in collapse from ~ -2 MPa down to ~ -3 MPa, saturating thereafter (to -4 MPa). Over this range cavitation remained negligible in these veins. Imaging of rehydration experiments showed spatially variable recovery from collapse within 20 seconds, and complete recovery after two minutes...
October 12, 2016: Plant Physiology
Kazuyoshi Murata, Sayuri Hagiwara, Yoshitaka Kimori, Yasuko Kaneko
Some cyanobacteria exhibit compaction of DNA in synchrony with their circadian rhythms accompanying cell division. Since the structure is transient, it has not yet been described in detail. Here, we successfully visualize the ultrastructure of compacted DNA in the cyanobacterium Synechococcus elongatus PCC 7942 under rigorous synchronized cultivation by means of high-voltage cryo-electron tomography. In 3D reconstructions of rapidly frozen cells, the compacted DNA appears as an undulating rod resembling a eukaryotic condensed chromosome...
October 12, 2016: Scientific Reports
Igor Orlov, Alexander G Myasnikov, Leonid Andronov, S Kundhavai Natchiar, Heena Khatter, Brice Beinsteiner, Jean-François Ménétret, Isabelle Hazemann, Kareem Mohideen, Karima Tazibt, Rachel Tabaroni, Hanna Kratzat, Nadia Djabeur, Tatiana Bruxelles, Finaritra Raivoniaina, Lorenza di Pompeo, Morgan Torchy, Isabelle Billas, Alexandre Urzhumtsev, Bruno P Klaholz
After gradually moving away from preparation methods prone to artefacts such as plastic embedding and negative staining for cell sections and single particles, the field of cryo electron microscopy is now heading off at unprecedented speed towards high-resolution analysis of biological objects of various sizes. This "revolution in resolution" is happening largely thanks to new developments of new-generation cameras used for recording the images in the cryo electron microscope which have much increased sensitivity being based on CMOS devices...
October 12, 2016: Biology of the Cell
Joanna Rorbach, Fei Gao, Christopher A Powell, Aaron D'Souza, Robert N Lightowlers, Michal Minczuk, Zofia M Chrzanowska-Lightowlers
The recent developments in cryo-EM have revolutionized our access to previously refractory structures. In particular, such studies of mammalian mitoribosomes have confirmed the absence of any 5S rRNA species and revealed the unexpected presence of a mitochondrially encoded tRNA (mt-tRNA) that usurps this position. Although the cryo-EM structures resolved the conundrum of whether mammalian mitoribosomes contain a 5S rRNA, they introduced a new dilemma: Why do human and porcine mitoribosomes integrate contrasting mt-tRNAs? Human mitoribosomes have been shown to integrate mt-tRNA(Val) compared with the porcine use of mt-tRNA(Phe) We have explored this observation further...
October 11, 2016: Proceedings of the National Academy of Sciences of the United States of America
Andrea D Merg, Jennifer C Boatz, Abhishek Mandal, Gongpu Zhao, Soumitra Mokashi-Punekar, Chong Liu, Xianting Wang, Peijun Zhang, Patrick C A van der Wel, Nathaniel L Rosi
Chiral nanoparticle assemblies are an interesting class of materials whose chiroptical properties make them attractive for a variety of applications. Here, C18-(PEPAu(M-ox))2 (PEPAu(M-ox) = AYSSGAPPM(ox)PPF) is shown to direct the assembly of single-helical gold nanoparticle superstructures that exhibit exceptionally strong chiroptical activity at the plasmon frequency with absolute g-factor values up to 0.04. Transmission electron microscopy (TEM) and cryogenic electron tomography (cryo-ET) results indicate that the single helices have a periodic pitch of approximately 100 nm and consist of oblong gold nanoparticles...
October 11, 2016: Journal of the American Chemical Society
Yaser Kashcooli, Keunhan Park, Arijit Bose, Michael Lewis Greenfield, Geoffrey D Bothun
Layer-by-layer deposition of polyelectrolytes (PEs) onto self-assembled liposomes represents an alternative to PE deposition on solid particles for the formation of hollow nanoscale capsules. This work examines how competition between PE-liposome and inter-PE interactions drives the structure and colloidal stability of layersomes. Unlike solid particles, liposomes respond to adsorbed material through lipid reorganization and changes in size and shape. This responsive nature could yield new types of layered PE structures...
October 10, 2016: Biomacromolecules
Yi Liu, Nathalie Claes, Bastian Trepka, Sara Bals, Peter R Lang
In this article we report on the synthesis and characterization of a system of colloidal spheres suspended in an aqueous solvent which can be refractive index-matched, thus allowing for investigations of the particle near-wall dynamics by evanescent wave dynamic light scattering at concentrations up to the isotropic to ordered transition and beyond. The particles are synthesized by copolymerization of a fluorinated acrylic ester monomer with a polyethylene-glycol (PEG) oligomer by surfactant free emulsion polymerization...
September 5, 2016: Soft Matter
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