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Jiansen Jiang, Yaqiang Wang, Lukas Sušac, Henry Chan, Ritwika Basu, Z Hong Zhou, Juli Feigon
Telomerase is an RNA-protein complex (RNP) that extends telomeric DNA at the 3' ends of chromosomes using its telomerase reverse transcriptase (TERT) and integral template-containing telomerase RNA (TER). Its activity is a critical determinant of human health, affecting aging, cancer, and stem cell renewal. Lack of atomic models of telomerase, particularly one with DNA bound, has limited our mechanistic understanding of telomeric DNA repeat synthesis. We report the 4.8 Å resolution cryoelectron microscopy structure of active Tetrahymena telomerase bound to telomeric DNA...
May 17, 2018: Cell
Ryan Manger, Douglas Rahn, Jeremy Hoisak, Irena Dragojević
PURPOSE: To develop an improved Xoft electronic skin brachytherapy process and identify areas of further improvement. METHODS AND MATERIALS: A multidisciplinary team conducted a failure modes and effects analysis (FMEA) by developing a process map and a corresponding list of failure modes. The failure modes were scored for their occurrence, severity, and detectability, and a risk priority number (RPN) was calculated for each failure mode as the product of occurrence, severity, and detectability...
May 14, 2018: Brachytherapy
Ruiqing Wu, Jingjuan Lai, Yi Pan, Zhaohui Zheng, Xiaobin Ding
To enable shape-memory polymer networks to achieve recoverable high deformability with a simultaneous high shape-fixity ratio and shape-recovery ratio, novel semi-crystalline slide-ring shape-memory polycaprolactone-based polyurethane (SR-SMPCLU) with movable net-points constructed by a topologically interlocked slide-ring structure was designed and fabricated. The SR-SMPCLU not only exhibited good shape fixity, almost complete shape recovery, and a fast shape-recovery speed, it also showed an outstanding recoverable high-strain capacity with 95...
May 17, 2018: Soft Matter
Peng Jia, Feng-Cheng Lu, Kifayat Ullah, Man Zhang, Yan-Sheng Dong, Chao Xiong, Zhi-Hui Zhao, Jin-Feng Wang, Ju-Wen Chen, Yong-Qing Wang
OBJECTIVE: Angle stable interlocking intramedullary nail (ASIN), a novel technique, has rarely been used for treatment of tibial plateau fractures (TPF). This retrospective study was designed to introduce this novel technique, ASIN, as well as to describe the initial experience and verify the effectiveness when ASIN was used for the management for TPF. METHODS: A cohort of 19 cases with closed TPF aged from 18-70 years with at least 23 months follow-up from November 2008 to September 2013 was analyzed retrospectively...
May 16, 2018: Orthopaedic Surgery
Yong Huang, Guiqin Song, Xiaotong Chang, Zhenhui Wang, Xuejiao Zhang, Shuguang Han, Zhuobin Su, Hejie Yang, Dongdong Yang, Xiaojun Zhang
Background: Poor mechanical properties, undesirable fast dissolution rate, and lack of antibacterial activity limit the application of hydroxyapatite (HA) as an implant coating material. To overcome these limitations, a hybrid coating of Ag+ -substituted fluorhydroxyapatite and titania nanotube (TNT) was prepared. Methods: The incorporation of silver into the HA-TiO2 hybrid coating improves its antimicrobial properties. The addition of F as a second binary element increases the structural stability of the coating...
2018: International Journal of Nanomedicine
Simon Alford, Heidi Hamm, Shelagh Rodriguez, Zack Zurawski
Presynaptic terminals possess interlocking molecular mechanisms that control exocytosis. An example of such complexity is the modulation of release by presynaptic G Protein Coupled Receptors (GPCRs). GPCR ubiquity at synapses-GPCRs are present at every studied presynaptic terminal-underlies their critical importance in synaptic function. GPCRs mediate presynaptic modulation by mechanisms including via classical Gα effectors, but membrane-delimited actions of Gβγ can also alter probability of release by altering presynaptic ionic conductances...
May 11, 2018: Neurochemical Research
Alex Inthasot, Shun-Te Tung, Sheng-Hsien Chiu
In 1987, Pedersen, Cram, and Lehn were awarded the Nobel Prize in Chemistry to honor their achievements in, among other things, the selective recognition of alkali metal ions by synthetic hosts. Almost three decades later, the 2016 Nobel Prize went to Stoddart, Sauvage, and Feringa for the development of artificial molecular machines, in which interlocked molecules play a significant role. Surprisingly, although many rotaxane- and catenane-based molecular machines have been constructed using various templating approaches, alkali metal ions, which are good templates for crown ether synthesis, have only rarely been applied as templates for the assembly of these interlocked molecules...
May 10, 2018: Accounts of Chemical Research
Tyler Burge
Among psychologists, it is widely thought that infants well under age 3, monkeys, apes, birds, and dogs have been shown to have rudimentary capacities for representing and attributing mental states or relations. I believe this view to be mistaken. It rests on overinterpreting experiments. It also often rests on assuming that one must choose between taking these individuals to be mentalists and taking them to be behaviorists. This assumption underestimates a powerful nonmentalistic, nonbehavioristic explanatory scheme that centers on attributing action with targets and on causation of action by interlocking, internal conative, and sensory states...
April 2018: Psychological Review
D M Chevrier, V D Thanthirige, Z Luo, S Driscoll, P Cho, M A MacDonald, Q Yao, R Guda, J Xie, E R Johnson, A Chatt, N Zheng, P Zhang
Highly luminescent gold clusters simultaneously synthesized and stabilized by protein molecules represent a remarkable category of nanoscale materials with promising applications in bionanotechnology as sensors. Nevertheless, the atomic structure and luminescence mechanism of these gold clusters are still unknown after several years of developments. Herein, we report findings on the structure, luminescence and biomolecular self-assembly of gold clusters stabilized by the large globular protein, bovine serum albumin...
March 14, 2018: Chemical Science
Beien Wang, Rob Kreuger, Freek J Beekman, Marlies C Goorden
Anger cameras based on monolithic NaI scintillators read out by an array of PMTs are predominant in planar gamma imaging and SPECT. However, position estimation of gamma interactions is usually severely degraded near the edges of the scintillator which can be extremely undesirable for applications like breast imaging. Here we propose a relatively cost-effective solution based on the use of scintillators with absorptive edges with an unconventional light-guide-PMT layout employing a maximum likelihood positioning algorithm...
April 2018: Physica Medica: PM
Xirui Gong, Jiawang Zhou, Karel J Hartlieb, Claire Miller, Peng Li, Omar K Farha, Joseph T Hupp, Ryan M Young, Michael R Wasielewski, J Fraser Stoddart
An octacationic diazaperopyrenium (DAPP2+ )-based homo[2]catenane (DAPPHC8+ ), wherein no less than eight positive charges are associated within a mechanically interlocked molecule, has been produced in 30% yield under ambient conditions as a result of favorable homophilic interactions, reflecting a delicate balance between strong π-π interactions and the destabilizing penalty arising from Coulombic repulsions between DAPP2+ units. This DAPPHC8+ catenane is composed of two identical mechanically interlocked tetracationic cyclophanes, namely DAPPBox4+ , each of which contains one DAPP2+ unit and one extended viologen (ExBIPY2+ ) unit, linked together by two p-xylylene bridges...
May 3, 2018: Journal of the American Chemical Society
Anne Ulfkjær, Frederik W Nielsen, Hana Al-Kerdi, Tamara Ruβ, Zaki K Nielsen, Jens Ulstrup, Lanlan Sun, Kasper Moth-Poulsen, Jingdong Zhang, Michael Pittelkow
The construction of molecular machines has captured the imagination of scientists for decades. Despite significant progress in the synthesis and studies of the properties of small-molecule components (smaller than 2-5 kilo Dalton), challenges regarding the incorporation of molecular components into real devices are still eminent. Nano-sized molecular machines operate the complex biological machinery of life, and the idea of mimicking the amazing functions using artificial nano-structures is intriguing. Both in small-molecule molecular machine components and in many naturally occurring molecular machines, mechanically interlocked molecules and structures are key functional components...
May 3, 2018: Nanoscale
Kevin Jeanne Dit Fouque, Javier Moreno, Julian D Hegemann, Séverine Zirah, Sylvie Rebuffat, Francisco Fernandez-Lima
Metal ions can play a significant role in a variety of important functions in protein systems including cofactor for catalysis, protein folding, assembly, structural stability and conformational change. In the present work, we examined the influence of alkali (Na, K and Cs), alkaline earth (Mg and Ca) and transition (Co, Ni and Zn) metal ions on the conformational space and analytical separation of mechanically interlocked lasso peptides. Syanodin I, sphingonodin I, caulonodin III and microcin J25, selected as models of lasso peptides, and their respective branched-cyclic topoisomers were submitted to native nESI trapped ion mobility spectrometry-mass spectrometry (TIMS-MS)...
May 3, 2018: Analyst
Junrong Jiao, Feilong Zhang, Tian Jiao, Zhen Gu, Shutao Wang
Velcro, the most typical hook-loop interlocker, often suffers from undesirable deformation, breaking, and noise because of the structure of the hook. Inspired by the arrester system of dragonfly, a new mechanical interlocker with a nylon pestle instead of the traditional hook is developed. The pestle-loop mechanical interlocker shows a tunable peeling force from 0.4 ± 0.14 to 6.5 ± 0.72 N and the shear adhesion force of pestle-loop mechanical interlocker is about twice as much as that of velcro. The pestle tape can be separated and fastened with the loop tape up to 30 000 cycles while keeping the original adhesive force and the pestle structure...
April 2018: Advanced Science (Weinheim, Baden-Wurttemberg, Germany)
Stephen D P Fielden, David A Leigh, Charlie T McTernan, Borja Pérez-Saavedra, Iñigo J Vitorica-Yrezabal
We report the synthesis of crown ether-ammonium, amide and amine [2]rotaxanes via transition state stabilization of axle-forming reactions. In contrast to the two-step "clipping" and "capping" strategies generally used for rotaxane synthesis, here the components assemble into the interlocked molecule in a single, reagent-less, step under kinetic control. The crown ether accelerates the reaction of the axle-forming components through the cavity to give the threaded product in a form of metal-free active template synthesis...
May 3, 2018: Journal of the American Chemical Society
Chiao-Peng Hsu, Shivaprakash N Ramakrishna, Michele Zanini, Nicholas D Spencer, Lucio Isa
Surface roughness affects many properties of colloids, from depletion and capillary interactions to their dispersibility and use as emulsion stabilizers. It also impacts particle-particle frictional contacts, which have recently emerged as being responsible for the discontinuous shear thickening (DST) of dense suspensions. Tribological properties of these contacts have been rarely experimentally accessed, especially for nonspherical particles. Here, we systematically tackle the effect of nanoscale surface roughness by producing a library of all-silica, raspberry-like colloids and linking their rheology to their tribology...
May 1, 2018: Proceedings of the National Academy of Sciences of the United States of America
Rundong Zhao, Fei Qi, Yan-Ling Zhao, Klaus E Hermann, Rui-Qin Zhang, Michel A Van Hove
Periodic chains of molecular gears in which molecules couple with each other and rotate on surfaces have been previously explored by us theoretically using ab initio simulation tools. Based on the knowledge and experience gained about the interactions between neighboring molecular gears, we here explore the transmission of rotational motion and energy over larger distances, namely through a longer chain of gear-like passive "slave" molecules. Such microscopic gears exhibit quite different behaviors compared to rigid cogwheels in the macroscopic world, due to their structural flexibility affecting intermolecular interaction...
May 1, 2018: Journal of Physical Chemistry Letters
Kelong Zhu, Giorgio Baggi, Stephen J Loeb
Mechanically interlocked molecules such as rotaxanes and catenanes comprise two or more components whose motion relative to each other can be controlled. A [2]rotaxane molecular shuttle, for example, consists of an axle bearing two recognition sites and a single macrocyclic wheel that can undergo a to-and-fro motion along the axle-shuttling between the recognition sites. The ability of mechanically interlocked molecules to undergo this type of large-amplitude change is the core mechanism behind almost every interlocked molecular switch or machine, including sophisticated mechanical systems such as a molecular elevator and a peptide synthesizer...
April 30, 2018: Nature Chemistry
Vinay V Mahajan, Johan T Padding, Tim M J Nijssen, Kay A Buist, J A M Kuipers
Fluidization is widely used in industries and has been extensively studied, both experimentally and theoretically, in the past. However, most of these studies focus on spherical particles while in practice granules are rarely spherical. Particle shape can have a significant effect on fluidization characteristics. It is therefore important to study the effect of particle shape on fluidization behavior in detail. In this study, experiments in pseudo-2D fluidized beds are used to characterize the fluidization of spherocylindrical (rod-like) Geldart D particles of aspect ratio 4...
May 2018: AIChE Journal
Kaitlyn A Mac Leod, Alexandra Seas, Marcy L Wainwright, Riccardo Mozzachiodi
Following exposure to aversive stimuli, organisms budget their behaviors by augmenting defensive responses and reducing/suppressing non-defensive behaviors. This budgeting process must be flexible to accommodate modifications in the animal's internal and/or external state that require the normal balance between defensive and non-defensive behaviors to be adjusted. When exposed to aversive stimuli, the mollusk Aplysia budgets its behaviors by concurrently enhancing defensive withdrawal reflexes (an elementary form of learning known as sensitization) and suppressing feeding...
April 25, 2018: Behavioural Brain Research
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