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single particle tracking

Utku Gülan, Christelle Calen, Firat Duru, Markus Holzner
An aortic aneurysm is defined as a balloon-shaped bulging of all three histologic components of the aortic vessel walls (intima, media and adventitia). This dilation results from vessel weakening owing to remodeling, i.e. due to cystic degeneration of the Tunica media (Marfan), progression of atherosclerosis or presence of a bicuspid aortic valve. The growth rate of the aortic diameter varies from patient to patient and may progress until the aneurysm ultimately ruptures. The role of hemodynamics, i.e. blood flow patterns, and shear stresses that are supposed to intensify during aneurysm growth are not yet fully understood, but thought to play a key role in the enlargement process...
June 8, 2018: Journal of Biomechanics
Takuma Akimoto, Eli Barkai, Keiji Saito
Tracking tracer particles in heterogeneous environments plays an important role in unraveling material properties. These heterogeneous structures are often static and depend on the sample realizations. Sample-to-sample fluctuations of such disorder realizations sometimes become considerably large. When we investigate the sample-to-sample fluctuations, fundamental averaging procedures are a thermal average for a single disorder realization and the disorder average for different disorder realizations. Here we report on non-self-averaging phenomena in quenched trap models with finite system sizes, where we consider the periodic and the reflecting boundary conditions...
May 2018: Physical Review. E
Itay Gdor, Xiaolei Wang, Matthew Daddysman, Yuval Yifat, Rosemarie Wilton, Mark Hereld, Marie-Françoise Noirot-Gros, Norbert F Scherer
Accurate and rapid particle tracking is essential for addressing many research problems in single molecule and cellular biophysics and colloidal soft condensed matter physics. We developed a novel three-dimensional interferometric fluorescent particle tracking approach that does not require any sample scanning. By periodically shifting the interferometer phase, the information stored in the interference pattern of the emitted light allows localizing particles positions with nanometer resolution. This tracking protocol was demonstrated by measuring a known trajectory of a fluorescent bead with sub-5 nm axial localization error at 5 Hz...
June 15, 2018: Optics Letters
Yantao Yang, Na Qu, Jie Tan, Muaz N Rushdi, Christopher J Krueger, Antony K Chen
During HIV-1 assembly, the retroviral structural protein Gag forms an immature capsid, containing thousands of Gag molecules, at the plasma membrane (PM). Interactions between Gag nucleocapsid (NC) and viral RNA (vRNA) are thought to drive assembly, but the exact roles of these interactions have remained poorly understood. Since previous studies have shown that Gag dimer- or trimer-forming mutants (GagZiL ) lacking an NC domain can form immature capsids independent of RNA binding, it is often hypothesized that vRNA drives Gag assembly by inducing Gag to form low-ordered multimers, but is dispensable for subsequent assembly...
June 11, 2018: Proceedings of the National Academy of Sciences of the United States of America
Daniel T Youmans, Jens C Schmidt, Thomas R Cech
Polycomb-repressive complex 2 (PRC2) is a histone methyltransferase that promotes epigenetic gene silencing, but the dynamics of its interactions with chromatin are largely unknown. Here we quantitatively measured the binding of PRC2 to chromatin in human cancer cells. Genome editing of a HaloTag into the endogenous EZH2 and SUZ12 loci and single-particle tracking revealed that ∼80% of PRC2 rapidly diffuses through the nucleus, while ∼20% is chromatin-bound. Short-term treatment with a small molecule inhibitor of the EED-H3K27me3 interaction had no immediate effect on the chromatin residence time of PRC2...
June 11, 2018: Genes & Development
Sergey Zaichik, Christian Steinbring, Claudia Menzel, Ludwig Knabl, Dorothea Orth-Höller, Helmut Ellemunter, Katharina Niedermayr, Andreas Bernkop-Schnürch
The aim of this study was to develop a self-emulsifying drug delivery system (SEDDS) containing the fluoroquinolone antibiotic ciprofloxacin (CIP) exhibiting highly mucus permeating properties and antimicrobial activity in in vitro models. Various SEDDS formulations were developed and evaluated regarding droplet size, polydispersity index, zeta potential and formulation stability. Furthermore, SEDDS permeating properties were investigated in porcine intestinal mucus, as well as in cystic fibrosis (CF) sputum freshly collected from CF patients using Transwell® setup and single particle tracking (SPT), respectively...
June 5, 2018: International Journal of Pharmaceutics
Zoltán Szakács, Tamás Mészáros, Marien I de Jonge, Róbert E Gyurcsányi
Detection and counting of single virus particles in liquid samples are largely limited to narrow size distribution of viruses and purified formulations. To address these limitations, here we propose a calibration-free method that enables concurrently the selective recognition, counting and sizing of virus particles as demonstrated through the detection of human respiratory syncytial virus (RSV), an enveloped virus with a broad size distribution, in throat swab samples. RSV viruses were selectively labeled through their attachment glycoproteins (G) with fluorescent aptamers, which further enabled their identification, sizing and counting at the single particle level by fluorescent nanoparticle tracking analysis...
May 30, 2018: Nanoscale
Souvik Modi, Nathalie F Higgs, David Sheehan, Lewis D Griffin, Josef T Kittler
Neurons communicate with each other through synapses, which show enrichment for specialized receptors. Although many studies have explored spatial enrichment and diffusion of these receptors in dissociated neurons using single particle tracking, much less is known about their dynamic properties at synapses in complex tissue like brain slices. Here we report the use of smaller and highly specific quantum dots conjugated with a recombinant single domain antibody fragment (VHH fragment) against green fluorescent protein to provide information on diffusion of adhesion molecules at the growth cone and neurotransmitter receptors at synapses...
May 23, 2018: Nanoscale
Danielle M Bailey, Mackenzie A Catron, Oleg Kovtun, Robert L Macdonald, Qi Zhang, Sandra J Rosenthal
Serotonin transporter (SERT) terminates serotonin signaling in the brain by enabling rapid clearance of the neurotransmitter. SERT dysfunction has been associated with a variety of psychiatric disorders, including depression, anxiety, and autism. Visualizing SERT behavior at the single molecule level in endogenous systems remains a challenge. In this study, we utilize quantum dot (QD) single particle tracking (SPT) to capture SERT dynamics in primary rat midbrain neurons. Membrane microenvironment, specifically membrane cholesterol, plays a key role in SERT regulation and has been found to affect SERT conformational state...
May 24, 2018: ACS Chemical Neuroscience
Tania Patiño, Natalia Feiner-Gracia, Xavier Arque, Albert Miguel-López, Anita Jannasch, Tom Stumpp, Erik Schäffer, Lorenzo Albertazzi, Samuel Sanchez
The use of enzyme catalysis to power micro and nanomachines offers unique features such as biocompatibility, versatili-ty and fuel bioavailability. Yet, the key parameters underlying the motion behavior of enzyme-powered motors are not completely understood. Here, we investigate the role of enzyme distribution and quantity on the generation of active mo-tion. Two different micromotor architectures based on either polystyrene (PS) or polystyrene coated with a rough silicon dioxide shell (PS@SiO2) were explored...
May 22, 2018: Journal of the American Chemical Society
Shanshan Wang, Hidetaka Sawada, Xiaoyu Han, Si Zhou, Sha Li, Zheng Xiao Guo, Angus I Kirkland, Jamie H Warner
We show that Pt nanoclusters preferentially nucleate along the grain boundaries (GBs) in polycrystalline MoS2 monolayer films, with dislocations acting as the seed site. Atomic resolution studies by aberration-corrected annular dark-field scanning transmission electron microscopy reveal periodic spacing of Pt nanoclusters with dependence on GB tilt angles and random spacings for the antiphase boundaries ( i.e., 60°). Individual Pt atoms are imaged within the dislocation core sections of the GB region, with various positions observed, including both the substitutional sites of Mo and the hollow center of the octahedral ring...
May 15, 2018: ACS Nano
Achillefs N Kapanidis, Stephan Uphoff, Mathew Stracy
Protein diffusion is crucial for understanding the formation of protein complexes in vivo, and has been the subject of many fluorescence microscopy studies in cells; however, such microscopy efforts are often limited by low sensitivity and resolution. During the past decade, these limitations have been addressed by new super-resolution imaging methods, most of which rely on single-particle tracking and single-molecule detection; these methods are revolutionizing our understanding of molecular diffusion inside bacterial cells by directly visualizing the motion of proteins and the effects of the local and global environment on diffusion...
May 10, 2018: Journal of Molecular Biology
Nagma Parveen, Doortje Borrenberghs, Susana Rocha, Jelle Hendrix
Viruses are simple agents exhibiting complex reproductive mechanisms. Decades of research have provided crucial basic insights, antiviral medication and moderately successful gene therapy trials. The most infectious viral particle is, however, not always the most abundant one in a population, questioning the utility of classic ensemble-averaging virology. Indeed, viral replication is often not particularly efficient, prone to errors or containing parallel routes. Here, we review different single-molecule sensitive fluorescence methods that we employ routinely to investigate viruses...
May 10, 2018: Viruses
Travis J Armiger, Marsha C Lampi, Cynthia A Reinhart-King, Kris N Dahl
Force generation within cells, mediated by motor proteins along cytoskeletal networks, maintains the function of multicellular structures during homeostasis and when generating collective forces. Here, we describe the use of chromatin dynamics to detect cellular force propagation (a technique termed Sensors from IntraNuclear Kinetics (SINK)) and investigate the force response of cells to disruption of the monolayer and changes in substrate stiffness. We find that chromatin dynamics change in a substrate stiffness dependent manner within epithelial monolayers...
May 10, 2018: Journal of Cell Science
Vedat Karakas, Aisha Gokce, Ali Taha Habiboglu, Sevdenur Arpaci, Kaan Ozbozduman, Ibrahim Cinar, Cenk Yanik, Riccardo Tomasello, Silvia Tacchi, Giulio Siracusano, Mario Carpentieri, Giovanni Finocchio, Thomas Hauet, Ozhan Ozatay
Recently discovered exotic magnetic configurations, namely magnetic solitons appearing in the presence of bulk or interfacial Dzyaloshinskii-Moriya Interaction (i-DMI), have excited scientists to explore their potential applications in emerging spintronic technologies such as race-track magnetic memory, spin logic, radio frequency nano-oscillators and sensors. Such studies are motivated by their foreseeable advantages over conventional micro-magnetic structures due to their small size, topological stability and easy spin-torque driven manipulation with much lower threshold current densities giving way to improved storage capacity, and faster operation with efficient use of energy...
May 8, 2018: Scientific Reports
Mohammad U Zahid, Liang Ma, Sung Jun Lim, Andrew M Smith
Inefficient delivery of macromolecules and nanoparticles to intracellular targets is a major bottleneck in drug delivery, genetic engineering, and molecular imaging. Here we apply live-cell single-quantum-dot imaging and tracking to analyze and classify nanoparticle states after intracellular delivery. By merging trajectory diffusion parameters with brightness measurements, multidimensional analysis reveals distinct and heterogeneous populations that are indistinguishable using single parameters alone. We derive new quantitative metrics of particle loading, cluster distribution, and vesicular release in single cells, and evaluate intracellular nanoparticles with diverse surfaces following osmotic delivery...
May 8, 2018: Nature Communications
Jieming Li, Alexander Johnson-Buck, Yuhe Renee Yang, William M Shih, Hao Yan, Nils G Walter
Dynamic DNA nanotechnology has yielded nontrivial autonomous behaviours such as stimulus-guided locomotion, computation and programmable molecular assembly. Despite these successes, DNA-based nanomachines suffer from slow kinetics, requiring several minutes or longer to carry out a handful of operations. Here, we pursue the speed limit of an important class of reactions in DNA nanotechnology-toehold exchange-through the single-molecule optimization of a novel class of DNA walker that undergoes cartwheeling movements over a field of complementary oligonucleotides...
May 7, 2018: Nature Nanotechnology
Matthew D Wehrman, Melissa J Milstrey, Seth Lindberg, Kelly M Schultz
The microstructure of soft matter directly impacts macroscopic rheological properties and can be changed by factors including colloidal rearrangement during previous phase changes and applied shear. To determine the extent of these changes, we have developed a microfluidic device that enables repeated phase transitions induced by exchange of the surrounding fluid and microrheological characterization while limiting shear on the sample. This technique is µ2 rheology, the combination of microfluidics and microrheology...
April 19, 2018: Journal of Visualized Experiments: JoVE
Jagadish Sankaran, Andreas Karampatzakis, Scott A Rice, Thorsten Wohland
Light microscopy has enabled the observation of the structure and organisation of biofilms. Typically, the contrast in an image obtained from light microscopy is given by the time-averaged intensity that is effective in visualising the overall structure. Technological advancements in light microscopy have led to the creation of techniques that not only provide a static intensity image of the biofilm, but also enable one to quantify various dynamic physicochemical properties of biomolecules in microbial biofilms...
May 1, 2018: FEMS Microbiology Letters
Mengning Liang, Ross Harder, Ian Robinson
Focused synchrotron beams can influence a studied sample via heating, or radiation pressure effects due to intensity gradients. The high angular sensitivity of rotational X-ray tracking of crystalline particles via their Bragg reflections can detect extremely small forces such as those caused by field gradients. By tracking the rotational motion of single-crystal nanoparticles embedded in a viscous or viscoelastic medium, the effects of heating in a uniform gradient beam and radiation pressure in a Gaussian profile beam were observed...
May 1, 2018: Journal of Synchrotron Radiation
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