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https://www.readbyqxmd.com/read/29213305/a-multiplexed-magnetic-tweezer-with-precision-particle-tracking-and-bi-directional-force-control
#1
Keith C Johnson, Emilie Clemmens, Hani Mahmoud, Robin Kirkpatrick, Juan C Vizcarra, Wendy E Thomas
Background: In the past two decades, methods have been developed to measure the mechanical properties of single biomolecules. One of these methods, Magnetic tweezers, is amenable to aquisition of data on many single molecules simultaneously, but to take full advantage of this "multiplexing" ability, it is necessary to simultaneously incorprorate many capabilities that ahve been only demonstrated separately. Methods: Our custom built magnetic tweezer combines high multiplexing, precision bead tracking, and bi-directional force control into a flexible and stable platform for examining single molecule behavior...
2017: Journal of Biological Engineering
https://www.readbyqxmd.com/read/29211999/a-simple-and-powerful-analysis-of-lateral-subdiffusion-using-single-particle-tracking
#2
Marianne Renner, Lili Wang, Sabine Levi, Laetitia Hennekinne, Antoine Triller
In biological membranes, many factors such as cytoskeleton, lipid composition, crowding, and molecular interactions deviate lateral diffusion from the expected random walks. These factors have different effects on diffusion but act simultaneously, so the observed diffusion is a complex mixture of diffusive behaviors (directed, Brownian, anomalous, or confined). Therefore, commonly used approaches to quantify diffusion based on averaging of the displacements such as the mean square displacement, are not adapted to the analysis of this heterogeneity...
December 5, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/29199833/single-cell-optical-distortion-correction-and-label-free-3d-cell-shape-reconstruction-on-lattices-of-nanostructures
#3
Jürgen Stephan, Felix Keber, Valentin Stierle, Joachim O Rädler, Philipp Paulitschke
Imaging techniques can be compromised by aberrations. Especially when imaging through biological specimens, sample-induced distortions can limit localization accuracy. In particular, this phenomenon affects localization microscopy, traction force measurements, and single-particle tracking, which offer high-resolution insights into biological tissue. Here we present a method for quantifying and correcting the optical distortions induced by single, adherent, living cells. The technique uses periodically patterned gold nanostructures as a reference framework to quantify optically induced displacements with micrometer-scale sampling density and an accuracy of a few nanometers...
December 4, 2017: Nano Letters
https://www.readbyqxmd.com/read/29195554/numerical-insight-into-the-dual-radiation-action-theory
#4
John J Tello, Sébastien Incerti, Ziad Francis, Hoang Tran, M A Bernal
This work studies the first and second order mechanisms for the induction of lethal lesions in DNA after irradiation with protons and α-particles. The purpose is to numerically study the mechanisms behind the Dual Radiation Action Theory (DRAT) for these heavy particles. A genetic material geometrical model with atomic resolution is used. It accounts for the explicit position of 5.47 × 109 base pairs, organized up to the chromatin level. The GEANT4-DNA Monte Carlo code was employed to simulate the interaction of these ions with the genetic material model...
November 2017: Physica Medica: PM
https://www.readbyqxmd.com/read/29192503/dynamics-of-nanoparticles-in-entangled-polymer-solutions
#5
Pooja Nath, Rahul Mangal, Ferdinand Friedrich Erich Kohle, Snehashis Choudhury, Suresh Narayanan, Ulrich B Wiesner, Lynden A Archer
The mean square displacement of nanoparticle probes dispersed in simple isotropic liquids and in polymer solutions is interrogated using Fluorescence Correlation Spectroscopy (FCS) and single particle tracking (SPT) experiments. Probe dynamics in different regimes of particle diameter (d) relative to characteristic polymer length scales, including the correlation length (ξ), the entanglement mesh size (a) and radius of gyration (Rg), are investigated. In simple fluids and for polymer solutions in which d > Rg, long-time particle dynamics obey random walk statistics , with the bulk zero-shear viscosity of the polymer solution determining the frictional resistance to particle motion...
December 1, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/29185702/tailoring-fluorescence-brightness-and-switching-of-nanoparticles-through-dye-organization-in-the-polymer-matrix
#6
Andreas Reisch, Kateryna Trofymchuk, Anne Runser, Guillaume Fleith, Michel Rawiso, Andrey S Klymchenko
Fluorescent nanoparticles (NPs) help to increase spatial and temporal resolution in bioimaging. Advanced microscopy techniques require very bright NPs that exhibit either stable emission for single-particle tracking or complete on/off switching (blinking) for super-resolution imaging. Here, ultrabright dye-loaded polymer NPs with controlled switching properties are developed. To this aim, the salt of a dye (rhodamine B octadecyl ester) with a hydrophobic counterion (fluorinated tetraphenylborate) is encapsulated at very high concentrations up to 30 wt % in NPs made of poly(lactic-co-glycolic acid) (PLGA), poly(methyl methacrylate) (PMMA), and polycaprolactone (PCL) through nanoprecipitation...
November 29, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/29185579/subnanometer-structure-and-function-from-ion-beams-through-complex-fluidics-to-fluorescent-particles
#7
Kuo-Tang Liao, Joshua Schumacher, Henri J Lezec, Samuel M Stavis
The vertical dimensions of complex nanostructures determine the functions of diverse nanotechnologies. In this paper, we investigate the unknown limits of such structure-function relationships at subnanometer scales. We begin with a quantitative evaluation of measurement uncertainty from atomic force microscopy, which propagates through our investigation from ion beam fabrication to fluorescent particle characterization. We use a focused beam of gallium ions to subtractively pattern silicon surfaces, and silicon nitride and silicon dioxide films...
November 29, 2017: Lab on a Chip
https://www.readbyqxmd.com/read/29185459/analysis-and-correction-of-errors-in-nanoscale-particle-tracking-using-the-single-pixel-interior-filling-function-spiff-algorithm
#8
Yuval Yifat, Nishant Sule, Yihan Lin, Norbert F Scherer
Particle tracking, which is an essential tool in many fields of scientific research, uses algorithms that retrieve the centroid of tracked particles with sub-pixel accuracy. However, images in which the particles occupy a small number of pixels on the detector, are in close proximity to other particles or suffer from background noise, show a systematic error in which the particle sub-pixel positions are biased towards the center of the pixel. This "pixel locking" effect greatly reduces particle tracking accuracy...
November 29, 2017: Scientific Reports
https://www.readbyqxmd.com/read/29180451/molecular-mimicking-of-c-terminal-phosphorylation-tunes-the-surface-dynamics-of-cav1-2-calcium-channels-in-hippocampal-neurons
#9
Alessandra Folci, Angela Steinberger, Boram Lee, Ruslan Stanika, Susanne Scheruebel, Marta Campiglio, Claudia Ramprecht, Brigitte Pelzmann, Johannes W Hell, Gerald J Obermair, Martin Heine, Valentina Di Biase
L-type voltage gated CaV1.2 calcium channels (CaV1.2) are key regulators of neuronal excitability, synaptic plasticity, and excitation-transcription coupling. Surface exposed CaV1.2 distributes in clusters along the dendrites of hippocampal neurons. A permanent exchange between stably clustered and laterally diffusive extra-clustered channels maintains steady-state levels of CaV1.2 at dendritic signaling domains. A dynamic equilibrium between anchored and diffusive receptors is a common feature among ion channels and is crucial to modulate signaling transduction...
November 27, 2017: Journal of Biological Chemistry
https://www.readbyqxmd.com/read/29178595/a-simplified-monte-carlo-algorithm-considering-large-angle-scattering-for-fast-and-accurate-calculation-of-proton-dose
#10
Taisuke Takayanagi, Shusuke Hirayama, Shinichiro Fujitaka, Rintaro Fujimoto
PURPOSE: The purpose of this study is to improve dose calculation accuracy of the simplified Monte Carlo (SMC) algorithm in the low-dose region. Because conventional SMC algorithms calculate particle scattering in consideration of multiple Coulomb scattering (MCS) only, they approximate lateral dose profiles by a single Gaussian function. However, it is well known that the low-dose region spreads away from the beam axis, and it has been pointed out that modeling of the low-dose region is important to calculated dose accurately...
November 27, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/29168772/a-survey-of-recent-advances-in-particle-filters-and-remaining-challenges-for-multitarget-tracking
#11
REVIEW
Xuedong Wang, Tiancheng Li, Shudong Sun, Juan M Corchado
We review some advances of the particle filtering (PF) algorithm that have been achieved in the last decade in the context of target tracking, with regard to either a single target or multiple targets in the presence of false or missing data. The first part of our review is on remarkable achievements that have been made for the single-target PF from several aspects including importance proposal, computing efficiency, particle degeneracy/impoverishment and constrained/multi-modal systems. The second part of our review is on analyzing the intractable challenges raised within the general multitarget (multi-sensor) tracking due to random target birth and termination, false alarm, misdetection, measurement-to-track (M2T) uncertainty and track uncertainty...
November 23, 2017: Sensors
https://www.readbyqxmd.com/read/29152858/in-vitro-evaluation-of-anti-aggregation-and-degradation-behavior-of-pegylated-polymeric-nanogels-under-in-vivo-like-conditions
#12
Yinan Chen, George R Dakwar, Kevin Braeckmans, Twan Lammers, Wim E Hennink, Josbert M Metselaar
The in vivo stability and biodegradability of nanocarriers crucially determine therapeutic efficacy as well as safety when used for drug delivery. This study aims to evaluate optimized in vitro techniques predictive for in vivo nanocarrier behavior. Polymeric biodegradable nanogels based on hydroxyethyl methacrylamide-oligoglycolates-derivatized poly(hydroxyethyl methacrylamide-co-N-(2-azidoethyl)methacrylamide) and with various degrees of PEGylation and crosslinking densities are prepared. Three techniques are chosen and refined for specific in vitro evaluation of the nanocarrier performance: (1) fluorescence single particle tracking (fSPT) to study the stability of nanogels in human plasma, (2) tangential flow filtration (TFF) to study the degradation and filtration of nanogel degradation products, and (3) fluorescence fluctuation spectroscopy (FFS) to evaluate and compare the degradation behavior of nanogels in buffer and plasma...
November 20, 2017: Macromolecular Bioscience
https://www.readbyqxmd.com/read/29152448/vision-assisted-micromanipulation-using-closed-loop-actuation-of-multiple-microrobots
#13
M Arifur Rahman, Noboru Takahashi, Kawai F Siliga, Nigel K Ng, Zhidong Wang, Aaron T Ohta
Accurate control and precise positioning of opto-thermocapillary flow-addressed bubble microrobots are necessary for micromanipulation. In addition, micromanipulation using the simultaneous actuation of multiple microrobots requires a robust control system to enable independent motion. This paper demonstrates a hybrid closed-loop vision-assisted control system capable of actuating multiple microrobots simultaneously and positioning them at precise locations relative to micro-objects under manipulation. A vision-assisted grasp-planning application was developed and used to calculate the necessary trajectories of the microrobots to form cages around micro-objects...
2017: Robotics and Biomimetics
https://www.readbyqxmd.com/read/29150949/chromium-hazard-and-risk-assessment-new-insights-from-a-detailed-speciation-study-in-a-standard-test-medium
#14
Imad Aharchaou, Jean-Sebastien Py, Sebastien Cambier, Jean-Luc Loizeau, Geert Cornelis, Philippe Rousselle, Eric Battaglia, Davide A L Vignati
Despite the consensus about the importance of chemical speciation in controlling the bioavailability and ecotoxicity of trace elements, detailed speciation studies during laboratory ecotoxicity testing remain scarce, contributing to uncertainty when extrapolating laboratory findings to real field situations in risk assessment. We characterized the speciation and ecotoxicological effects of Cr(III) and Cr(VI) in the ISO medium for algal ecotoxicity testing. Total and dissolved (<0.22 μm) Cr concentrations showed little variability in media spiked with Cr(VI) , while dissolved Cr concentration decreased by as much as 80% over 72 hours in medium amended with Cr(III) ...
November 18, 2017: Environmental Toxicology and Chemistry
https://www.readbyqxmd.com/read/29144410/evaluation-of-different-single-walled-carbon-nanotube-surface-coatings-for-single-particle-tracking-applications-in-biological-environments
#15
Zhenghong Gao, Noémie Danné, Antoine Guillaume Godin, Brahim Lounis, Laurent Cognet
Fluorescence imaging of biological systems down to the single-molecule level has generated many advances in cellular biology. For applications within intact tissue, single-walled carbon nanotubes (SWCNTs) are emerging as distinctive single-molecule nanoprobes, due to their near-infrared photoluminescence properties. For this, SWCNT surfaces must be coated using adequate molecular moieties. Yet, the choice of the suspension agent is critical since it influences both the chemical and emission properties of the SWCNTs within their environment...
November 16, 2017: Nanomaterials
https://www.readbyqxmd.com/read/29143174/single-cell-imaging-using-radioluminescence-microscopy-reveals-unexpected-binding-target-for-18f-hfb
#16
Louise Kiru, Tae Jin Kim, Bin Shen, Frederick T Chin, Guillem Pratx
PURPOSE: Cell-based therapies are showing great promise for a variety of diseases, but remain hindered by the limited information available regarding the biological fate, migration routes and differentiation patterns of infused cells in trials. Previous studies have demonstrated the feasibility of using positron emission tomography (PET) to track single cells utilising an approach known as positron emission particle tracking (PEPT). The radiolabel hexadecyl-4-[(18)F]fluorobenzoate ([(18)F]HFB) was identified as a promising candidate for PEPT, due to its efficient and long-lasting labelling capabilities...
November 15, 2017: Molecular Imaging and Biology: MIB: the Official Publication of the Academy of Molecular Imaging
https://www.readbyqxmd.com/read/29127741/plpa-a-pilz-like-protein-regulates-directed-motility-of-the-bacterium-myxococcus-xanthus
#17
Connor B Pogue, Tianyi Zhou, Beiyan Nan
The rod-shaped bacterium Myxococcus xanthus moves on surfaces along its long cell axis and reverses its moving direction regularly. Current models propose that the asymmetric localization of a Ras-like GTPase, MglA, to leading cell poles determines the moving direction of cells. However, cells are still motile in the mutants where MglA localizes symmetrically, suggesting the existence of additional regulators that control moving direction. In this study, we identified PlpA, a PilZ-like protein that regulates the direction of motility...
November 11, 2017: Molecular Microbiology
https://www.readbyqxmd.com/read/29118122/unique-directional-motility-of-influenza-c-virus-controlled-by-its-filamentous-morphology-and-short-range-motions
#18
Tatsuya Sakai, Hiroaki Takagi, Yasushi Muraki, Mineki Saito
Influenza virus motility is based on cooperation between two viral spike proteins, hemagglutinin (HA) and neuraminidase (NA), and is a major determinant of virus infectivity. To translocate a virus particle on the cell surface, HA molecules exchange viral receptors and NA molecules accelerate the receptor exchange of HA. This type of virus motility was recently identified in influenza A virus (IAV). To determine if other influenza virus types have a similar receptor-exchange mechanism-driven motility, we investigated influenza C virus (ICV) motility on a receptor-fixed glass surface...
November 8, 2017: Journal of Virology
https://www.readbyqxmd.com/read/29116055/improvement-of-single-detector-proton-radiography-by-incorporating-intensity-of-time-resolved-dose-rate-functions
#19
Rongxiao Zhang, Kyung-Wook Jee, Ethan W Cascio, Gregory C Sharp, Jacob B Flanz, Hsiao-Ming Lu
Proton radiography, which images patients with the same type of particles as what they are to be treated with, is a promising approach to image guidance and water equivalent path length (WEPL) verification in proton radiation therapy. We have shown recently that proton radiographs could be obtained by measuring time-resolved dose rate functions (DRF) using an x-ray amorphous silicon flat panel. The WEPL values were derived solely from the root-mean-square (RMS) of DRFs while the intensity information in the DRFs was filtered out...
November 8, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/29114055/immature-hiv-1-lattice-assembly-dynamics-are-regulated-by-scaffolding-from-nucleic-acid-and-the-plasma-membrane
#20
Alexander J Pak, John M A Grime, Prabuddha Sengupta, Antony K Chen, Aleksander E P Durumeric, Anand Srivastava, Mark Yeager, John A G Briggs, Jennifer Lippincott-Schwartz, Gregory A Voth
The packaging and budding of Gag polyprotein and viral RNA is a critical step in the HIV-1 life cycle. High-resolution structures of the Gag polyprotein have revealed that the capsid (CA) and spacer peptide 1 (SP1) domains contain important interfaces for Gag self-assembly. However, the molecular details of the multimerization process, especially in the presence of RNA and the cell membrane, have remained unclear. In this work, we investigate the mechanisms that work in concert between the polyproteins, RNA, and membrane to promote immature lattice growth...
November 7, 2017: Proceedings of the National Academy of Sciences of the United States of America
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