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https://www.readbyqxmd.com/read/28102411/defect-driven-shapes-in-nematic-droplets-analogies-with-cell-division
#1
Marco Leoni, Oksana V Manyuhina, Mark J Bowick, M Cristina Marchetti
Building on the striking similarity between the structure of the spindle during mitosis in living cells and nematic textures in confined liquid crystals, we use a continuum model of two-dimensional nematic liquid crystal droplets to examine the physical aspects of cell division. The model investigates the interplay between bulk elasticity of the microtubule assembly, described as a nematic liquid crystal, and surface elasticity of the cell cortex, modeled as a bounding flexible membrane, in controlling cell shape and division...
January 19, 2017: Soft Matter
https://www.readbyqxmd.com/read/28102390/reactions-in-silicon-nitrogen-plasma
#2
Goran Kovačević, Branko Pivac
Reaction mechanisms that lead to creation of silicon-nitrogen bonds are studied in detail. These reactions are of fundamental importance for silicon nitride synthesis by plasma enhanced chemical vapour deposition from the gas mixture of silane (SiH4) and ammonia (NH3). All reactions in SiH4-NH3 plasma can be categorised as some of the basic types of reactions: bond dissociation, neutral nucleophilic substitution, radical neutralisation, neutral-radical addition, silylene addition, silylene rearrangement, radical nucleophilic addition or hydrogen abstraction reaction...
January 19, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28102001/evaluation-of-the-hybrid-resolution-pace-model-for-the-study-of-folding-insertion-and-pore-formation-of-membrane-associated-peptides
#3
Michael D Ward, Shivangi Nangia, Eric R May
The PACE force field presents an attractive model for conducting molecular dynamics simulations of membrane-protein systems. PACE is a hybrid model, in which lipids and solvents are coarse-grained consistent with the MARTINI mapping, while proteins are described by a united atom model. However, given PACE is linked to MARTINI, which is widely used to study membranes, the behavior of proteins interacting with membranes has only been limitedly examined in PACE. In this study, PACE is used to examine the behavior of several peptides in membrane environments, namely WALP peptides, melittin and influenza hemagglutinin fusion peptide (HAfp)...
January 19, 2017: Journal of Computational Chemistry
https://www.readbyqxmd.com/read/28101950/molecular-binding-of-toxic-phenothiazinium-derivatives-azures-to-bovine-serum-albumin-a-comparative-spectroscopic-calorimetric-and-in-silico-study
#4
Somnath Das, Md Maidul Islam, Gopal Chandra Jana, Anirudha Patra, Pradeep K Jha, Maidul Hossain
In this paper, the comparative binding behavior of antimalarial drug azure A, azure B and azure C with bovine serum albumin (BSA) has been studied. The interaction has been confirmed by multispectroscopic (UV, fluorescence, Fourier transform infrared (FT-IR), and circular dichroism) and molecular docking techniques. The experimental results show that azure B has the highest BSA binding affinity followed by azure A and azure C. The experimental evidence of binding showed a static quenching mechanism in the interaction azures with BSA...
January 19, 2017: Journal of Molecular Recognition: JMR
https://www.readbyqxmd.com/read/28101854/impurity-location-dependent-relaxation-dynamics-of-cu-cds-quantum-dots
#5
Dayeon Choi, Ji-Young Pyo, Du-Jeon Jang
Various types of 2% Cu-incorporated CdS (Cu:CdS) quantum dots (QDs) with very similar sizes have been prepared via a water soluble colloidal method. The locations of Cu impurities in CdS host nanocrystals have been controlled by adopting three different synthetic ways of doping, exchange, and adsorption to understand the impurity location-dependent relaxation dynamics of charge carriers. The oxidation state of incorporated Cu impurities has been found to be +1 and the band-gap energy of Cu:CdS QDs decreases as Cu2S forms at the surfaces of CdS QDs...
December 2017: Nanoscale Research Letters
https://www.readbyqxmd.com/read/28100050/charge-carrier-hopping-dynamics-in-homogeneously-broadened-pbs-quantum-dot-solids
#6
Rachel H Gilmore, Elizabeth M Y Lee, Mark C Weidman, Adam P Willard, William A Tisdale
Energetic disorder in quantum dot solids adversely impacts charge carrier transport in quantum dot solar cells and electronic devices. Here, we use ultrafast transient absorption spectroscopy to show that homogeneously broadened PbS quantum dot arrays (σhom(2):σinh(2)>19:1, σinh/kBT<0.4) can be realized if quantum dot batches are sufficiently monodisperse (δ ≲ 3.3%). Homogeneous linewidth is found to be an inverse function of quantum dot size, monotonically increasing from ~25 meV for the largest quantum dots (5...
January 19, 2017: Nano Letters
https://www.readbyqxmd.com/read/28099881/mesencephalic-astrocyte-derived-neurotrophic-factor-alleviated-6-ohda-induced-cell-damage-via-ros-ampk-mtor-mediated-autophagic-inhibition
#7
Jingxing Zhang, Qiong Cai, Ming Jiang, Yigang Liu, Hua Gu, Jia Guo, Hui Sun, Jianmin Fang, Lingjing Jin
Autophagy and apoptosis are commonly involved in the dopaminergic neuron damage in the pathogenesis of Parkinson's disease. Recently, the autophagy pathway is thought to be critical to the process of PD. Therefore, the regulation of autophagy may be a potential strategy for PD treatment. Mesencephalic astrocyte-derived neurotrophic factor (MANF) has been reported to have neuroprotective effects through anti-apoptosis, anti-oxidative, and anti-inflammatory mechanisms in PD. In this study, we investigated the role of autophagy system in MANF-mediated neuroprotection against 6-hydroxydopamine (6-OHDA)-induced neurotoxicity...
January 15, 2017: Experimental Gerontology
https://www.readbyqxmd.com/read/28099841/targeted-inhibition-of-egfr-and-glutaminase-induces-metabolic-crisis-in-egfr-mutant-lung-cancer
#8
Milica Momcilovic, Sean T Bailey, Jason T Lee, Michael C Fishbein, Clara Magyar, Daniel Braas, Thomas Graeber, Nicholas J Jackson, Johannes Czernin, Ethan Emberley, Matthew Gross, Julie Janes, Andy Mackinnon, Alison Pan, Mirna Rodriguez, Melissa Works, Winter Zhang, Francesco Parlati, Susan Demo, Edward Garon, Kostyantyn Krysan, Tonya C Walser, Steven M Dubinett, Saman Sadeghi, Heather R Christofk, David B Shackelford
Cancer cells exhibit increased use of nutrients, including glucose and glutamine, to support the bioenergetic and biosynthetic demands of proliferation. We tested the small-molecule inhibitor of glutaminase CB-839 in combination with erlotinib on epidermal growth factor receptor (EGFR) mutant non-small cell lung cancer (NSCLC) as a therapeutic strategy to simultaneously impair cancer glucose and glutamine utilization and thereby suppress tumor growth. Here, we show that CB-839 cooperates with erlotinib to drive energetic stress and activate the AMP-activated protein kinase (AMPK) pathway in EGFR (del19) lung tumors...
January 17, 2017: Cell Reports
https://www.readbyqxmd.com/read/28099171/an-approach-to-estimate-spatial-distribution-of-analyte-within-cells-using-spectrally-resolved-fluorescence-microscopy
#9
Dharmendar Kumar Sharma, Mir Irfanullah, Santanu Kumar Basu, Sheri Madhu, Suman De, Sameer Jadhav, Mangalampalli Ravikanth, Arindam Chowdhury
While fluorescence microscopy has become an essential tool amongst chemists and biologists for the detection of various analyte within cellular environments, non-uniform spatial distribution of sensors within cells often restricts extraction of reliable information on relative abundance of analytes in different subcellular regions. As an alternative to existing sensing methodologies such as ratiometric or FRET imaging, where relative proportion of analyte with respect to the sensor can be obtained within cells, we propose a methodology using spectrally-resolved fluorescence microscopy, via which both the relative abundance of sensor as well as their relative proportion with respect to the analyte can be simultaneously extracted for local subcellular regions...
January 18, 2017: Methods and Applications in Fluorescence
https://www.readbyqxmd.com/read/28099029/energy-transfer-between-coherently-delocalized-states-in-thin-films-of-the-explosive-pentaerythritol-tetranitrate-petn-revealed-by-two-dimensional-infrared-spectroscopy
#10
Joshua S Ostrander, Robert Knepper, Alexander S Tappan, Jeffrey J Kay, Martin T Zanni, Darcie A Farrow
Pentaerythritol tetranitrate (PETN) is a common secondary explosive and has been used extensively to study shock initiation and energy propagation in energetic materials. We report 2D IR measurements of PETN thin films that resolve vibrational energy transfer and relaxation mechanisms. Ultrafast anisotropy measurements reveal a sub-500 fs reorientation of transition dipoles in thin films of vapor-deposited PETN that is absent in solution measurements, consistent with intermolecular energy transfer. The anisotropy is frequency dependent, suggesting spectrally heterogeneous vibrational relaxation...
January 18, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28099016/influence-of-energetic-disorder-on-exciton-lifetime-and-photoluminescence-efficiency-in-conjugated-polymers
#11
Irina Rörich, Oleksandr V Mikhnenko, Dominik W Gehrig, Paul W M Blom, Nicoleta Irina Craciun
Using time-resolved photoluminescence (TRPL) spectroscopy the exciton lifetime in a range of conjugated polymers is investigated. For poly(p-phenylene vinylene) (PPV)-based derivatives and a polyspirobifluorene copolymer (PSBF) we find that the exciton lifetime is correlated with the energetic disorder. Better ordered polymers exhibit a single exponential PL decay with exciton lifetimes of a few hundred picoseconds, whereas polymers with a larger degree of disorder show multi-exponential PL decays with exciton lifetimes in the nanosecond regime...
January 18, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28099009/thickness-controlled-quasi-two-dimensional-colloidal-pbse-nanoplatelets
#12
Weon-Kyu Koh, Naveen Kumar Dandu, Andrew F Fidler, Victor I Klimov, Jeffrey M Pietryga, Svetlana V Kilina
We demonstrate controlled synthesis of discrete two-dimensional (2D) PbSe nanoplatelets (NPLs), with measureable photoluminescence, via oriented attachment directed by quantum dot (QD) surface chemistry. Halide passivation is critical to the growth of these (100) face-dominated NPLs, as corroborated by density functional theory studies. PbCl2 moieties attached to the (111) and (110) of small nanocrystals form interparticle bridges, aligning the QDs and leading to attachment. We find that a 2D bridging network is energetically favored over a 3D network, driving the formation of NPLs...
January 18, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28098843/perm-hypothesis-the-fundamental-machinery-able-to-elucidate-the-role-of-xenobiotics-and-hormesis-in-cell-survival-and-homeostasis
#13
REVIEW
Salvatore Chirumbolo, Geir Bjørklund
In this article the Proteasome, Endoplasmic Reticulum and Mitochondria (PERM) hypothesis is discussed. The complex machinery made by three homeostatic mechanisms involving the proteasome (P), endoplasmic reticulum (ER) and mitochondria (M) is addressed in order to elucidate the beneficial role of many xenobiotics, either trace metals or phytochemicals, which are spread in the human environment and in dietary habits, exerting their actions on the mechanisms underlying cell survival (apoptosis, cell cycle regulation, DNA repair and turnover, autophagy) and stress response...
January 15, 2017: International Journal of Molecular Sciences
https://www.readbyqxmd.com/read/28098451/the-effect-of-injection-layer-sub-bandgap-states-on-electron-injection-in-organic-light-emitting-diodes
#14
Carsten Hinzmann, Osnat Magen, Yvonne J Hofstetter, Paul Edward Hopkinson, Nir Tessler, Yana Vaynzof
It is generally considered that the injection of charges into an active layer of an organic light-emitting diode (OLED) is solely determined by the energetic injection barrier formed at the device interfaces. Here, we demonstrate that the density of surface states of the electron-injecting ZnO layer has a profound effect on both the charge injection and the overall performance of the OLED device. Introducing a dopant into ZnO reduces both the energy depth and density of surface states without altering the position of the energy levels - thus the magnitude of the injection barrier formed at the organic/ZnO interface remains unchanged...
January 18, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28097727/energetics-kinetics-and-pathway-of-snare-folding-and-assembly-revealed-by-optical-tweezers
#15
REVIEW
Yongli Zhang
Soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) are universal molecular engines that drive membrane fusion. Particularly, synaptic SNAREs mediate fast calcium-triggered fusion of neurotransmitter-containing vesicles with plasma membranes for synaptic transmission, the basis of all thought and action. During membrane fusion, complementary SNAREs located on two apposed membranes (often called t- and v-SNAREs) join together to assemble into a parallel four-helix bundle, releasing the energy to overcome the energy barrier for fusion...
January 18, 2017: Protein Science: a Publication of the Protein Society
https://www.readbyqxmd.com/read/28096234/glutamate-oxaloacetate-transaminase-enables-anaplerotic-refilling-of-tca-cycle-intermediates-in-stroke-affected-brain
#16
Cameron Rink, Surya Gnyawali, Richard Stewart, Seth Teplitsky, Hallie Harris, Sashwati Roy, Chandan K Sen, Savita Khanna
Ischemic stroke results in excessive release of glutamate, which contributes to neuronal cell death. Here, we test the hypothesis that otherwise neurotoxic glutamate can be productively metabolized by glutamate oxaloacetate transaminase (GOT) to maintain cellular energetics and protect the brain from ischemic stroke injury. The GOT-dependent metabolism of glutamate was studied in primary neural cells and in stroke-affected C57-BL6 mice using magnetic resonance spectroscopy and GC-MS. Extracellular Glu sustained cell viability under hypoglycemic conditions and increased GOT-mediated metabolism in vitro Correction of stroke-induced hypoxia using supplemental oxygen in vivo lowered Glu levels as measured by (1)H magnetic resonance spectroscopy...
January 17, 2017: FASEB Journal: Official Publication of the Federation of American Societies for Experimental Biology
https://www.readbyqxmd.com/read/28094993/the-biophysics-of-artificially-expanded-genetic-information-systems-thermodynamics-of-dna-duplexes-containing-matches-and-mismatches-involving-2-amino-3-nitropyridin-6-one-z-and-imidazo-1-2-a-1-3-5-triazin-4-8h-one-p
#17
Xiaoyu Wang, Shuichi Hoshika, Raymond J Peterson, Myong-Jung Kim, Steven A Benner, Jason D Kahn
Synthetic nucleobases presenting non-Watson Crick arrangements of hydrogen bond donor and acceptor groups can form additional nucleotide pairs that stabilize duplex DNA independent of the standard A:T and G:C pairs. The pair between 2-amino-3-nitropyridin-6-one 2'-deoxyriboside (presenting a {donor-donor-acceptor} hydrogen bonding pattern on the Watson-Crick face of the small component, trivially designated Z) and imidazo[1,2-a]-1,3,5-triazin-4(8H)one 2'-deoxyriboside (presenting an {acceptor-acceptor-donor} hydrogen bonding pattern on the large component, trivially designated P) is one of these extra pairs for which a substantial amount of molecular biology has been developed...
January 17, 2017: ACS Synthetic Biology
https://www.readbyqxmd.com/read/28094988/multi-reference-perturbation-theory-with-cholesky-decomposition-for-the-density-matrix-renormalization-group
#18
Leon Freitag, Stefan Knecht, Celestino Angeli, Markus Reiher
We present a second-order N-electron valence state perturbation theory (NEVPT2) based on a density matrix renormalization group (DMRG) reference wave function that exploits a Cholesky decomposition of the two-electron repulsion integrals (CD-DMRG-NEVPT2). With a parameter-free multireference perturbation theory approach at hand, the latter allows us to efficiently describe static and dynamic correlation in large molecular systems. We demonstrate the applicability of CD-DMRG-NEVPT2 for spin-state energetics of spin-crossover complexes involving calculations with more than 1000 atomic basis functions...
January 17, 2017: Journal of Chemical Theory and Computation
https://www.readbyqxmd.com/read/28094946/competing-e2-and-sn2-mechanisms-for-the-f-ch3ch2i-reaction
#19
Li Yang, Jiaxu Zhang, Jing Xie, Xinyou Ma, Linyao Zhang, Chenyang Zhao, William Louis Hase
Anti-, syn-E2 and inv-, ret-SN2 reaction channels for the gas-phase reaction of F- + CH3CH2I were characterized with a variety of electronic structure calculations. A geometrical analysis confirmed the synchronous E2-type transition states for the elimination of current reaction, instead of nonconcerted processes through E1cb-like and E1-like mechanisms. Importantly, the controversy concerning reactant complex for anti-E2 and inv-SN2 paths have been clarified in the present work. A positive barrier of + 19...
January 17, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28094917/tuning-the-ignition-performance-of-a-micro-chip-initiator-by-integrating-various-al-moo3-rmfs-on-a-semiconductor-bridge
#20
Jianbing Xu, Yu Tai, Chengbo Ru, Ji Dai, Yinghua Ye, Ruiqi Shen, Peng Zhu
Reactive multilayer films (RMFs) can be integrated into semiconducting electronic structures with the use of microelectromechanical systems (MEMS) technology, and represent potential applications in the advancement of microscale energy-demanding systems. In this study, aluminum/ molybdenum trioxide (Al/MoO3) -based RMFs with different modulation periods were integrated on a semiconductor bridge (SCB) using a combination of image reversal lift-off process and magnetron sputtering technology. This produced an energetic semiconductor bridge (ESCB)-chip initiator with controlled ignition performance...
January 17, 2017: ACS Applied Materials & Interfaces
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