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Single molecule microscopy

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https://www.readbyqxmd.com/read/29792710/measuring-the-adhesion-forces-for-the-multivalent-binding-of-vancomycin-conjugated-dendrimer-to-bacterial-cell-wall-peptide
#1
Elizabeth Peterson, Christine Joseph, Hannah Peterson, Rachael Bouwman, Shengzhuang Tang, Jayme Cannon, Kumar Sinniah, Seok Ki Choi
Multivalent ligand-receptor interaction provides the fundamental basis for the hypothetical notion that high binding avidity relates to the strong force of adhesion. Despite its increasing importance in the design of targeted nanoconjugates, an understanding of the physical forces underlying the multivalent interaction remains a subject of urgent investigation. In this study, we designed three vancomycin (Van)-conjugated dendrimers G5(Van)n (n = mean valency = 0, 1, 4) for bacterial targeting with generation 5 (G5) poly(amidoamine) dendrimer as a multivalent scaffold, and evaluated both their binding avidity and physical force of adhesion to a bacterial model surface by employing surface plasmon resonance (SPR) spectroscopy and atomic force microscopy (AFM)...
May 24, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/29786426/influence-of-enzyme-quantity-and-distribution-on-the-self-propulsion-of-non-janus-urease-powered-micromotors
#2
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
https://www.readbyqxmd.com/read/29775295/noncovalent-grafting-of-a-dy-iii-2-single-molecule-magnet-onto-chemically-modified-multiwalled-carbon-nanotubes
#3
Vassilis Tangoulis, Nikolia Lalioti, John Parthenios, Nikos Boukos, Ondřej Malina, Jiří Tuček, Radek Zbořil
While synthetic methods for the grafting of nanoparticles or photoactive molecules onto carbon nanotubes (CNTs) have been developed in the last years, a very limited number of reports have appeared on the grafting of single-molecule magnets (SMMs) onto CNTs. There are many potential causes, mainly focused on the fact that the attachment of molecules on surfaces remains not trivial and their magnetic properties are significantly affected upon attachment. Nevertheless, implementation of this particular type of hybrid material in demanding fields such as spintronic devices makes of utmost importance the investigation of new synthetic protocols for effective grafting...
May 18, 2018: Inorganic Chemistry
https://www.readbyqxmd.com/read/29775278/hybrid-nanomaterials-with-single-site-catalysts-by-spatially-controllable-immobilization-of-nickel-complexes-via-photoclick-chemistry-for-alkene-epoxidation
#4
Dwaipayan Ghosh, Benny Febriansyah, Disha Gupta, Leonard Kia-Sheun Ng, Shibo Xi, Yonghua Du, Tom Baikie, ZhiLi Dong, Han Sen Soo
Catalyst deactivation is a persistent problem not only for the scientific community but also in industry. Isolated single-site heterogeneous catalysts have shown great promise to overcome these problems. Here, a versatile anchoring strategy for molecular complex immobilization on a broad range of semiconducting or insulating metal oxide (e.g. titanium dioxide, mesoporous silica, cerium oxide, and tungsten oxide) nanoparticles to synthesize isolated single-site catalysts has been studied systematically. An oxidatively stable anchoring group, maleimide, is shown to form covalent linkages with surface hydroxyl functionalities of metal oxide nanoparticles by photoclick chemistry...
May 18, 2018: ACS Nano
https://www.readbyqxmd.com/read/29769736/trna-tracking-for-direct-measurements-of-protein-synthesis-kinetics-in-live-cells
#5
Ivan L Volkov, Martin Lindén, Javier Aguirre Rivera, Ka-Weng Ieong, Mikhail Metelev, Johan Elf, Magnus Johansson
Our ability to directly relate results from test-tube biochemical experiments to the kinetics in living cells is very limited. Here we present experimental and analytical tools to directly study the kinetics of fast biochemical reactions in live cells. Dye-labeled molecules are electroporated into bacterial cells and tracked using super-resolved single-molecule microscopy. Trajectories are analyzed by machine-learning algorithms to directly monitor transitions between bound and free states. In particular, we measure the dwell time of tRNAs on ribosomes, and hence achieve direct measurements of translation rates inside living cells at codon resolution...
May 16, 2018: Nature Chemical Biology
https://www.readbyqxmd.com/read/29769611/highly-reproducible-alkali-metal-doping-system-for-organic-crystals-through-enhanced-diffusion-of-alkali-metal-by-secondary-thermal-activation
#6
Jinho Lee, Chibeom Park, Intek Song, Jin Young Koo, Taekyung Yoon, Jun Sung Kim, Hee Cheul Choi
In this paper, we report an efficient alkali metal doping system for organic single crystals. Our system employs an enhanced diffusion method for the introduction of alkali metal into organic single crystals by controlling the sample temperature to induce secondary thermal activation. Using this system, we achieved intercalation of potassium into picene single crystals with closed packed crystal structures. Using optical microscopy and Raman spectroscopy, we confirmed that the resulting samples were uniformly doped and became K2 picene single crystal, while only parts of the crystal are doped and transformed into K2 picene without secondary thermal activation...
May 16, 2018: Scientific Reports
https://www.readbyqxmd.com/read/29767633/nanopatterning-on-calixarene-thin-films-via-low-energy-field-emission-scanning-probe-lithography
#7
Xiaoyue He, Peng Li, Pengchong Liu, Xiaoxian Zhang, Xiangqian Zhou, Wei Liu, Xiaohui Qiu
Field-emitted, low-energy electrons from the conducting tip of an atomic force microscope were adopted for nanolithography on calixarene ultrathin films coated on silicon wafers. A structural evolution from protrusion to depression down to a 30 nm spatial resolution was reproducibly obtained by tuning the sample voltage and exposure current in the lithography process. Close analyses of the profiles showed that the nanostructures formed by a single exposure with a high current are almost identical to those created by cumulative exposure with a lower current but an equal number of injected electrons...
May 16, 2018: Nanotechnology
https://www.readbyqxmd.com/read/29767428/photonic-crystal-enhanced-fluorescence-immunoassay-on-diatom-biosilica
#8
Kenneth Squire, Xianming Kong, Paul LeDuff, Gregory L Rorrer, Alan X Wang
Fluorescence biosensing is one of the most established biosensing methods, particularly fluorescence spectroscopy and microscopy. These are two highly sensitive techniques but require high grade electronics and optics to achieve the desired sensitivity. Efforts have been made to implement these methods using consumer grade electronics and simple optical setups for applications such as point-of-care diagnostics, but the sensitivity inherently suffers. Sensing substrates, capable of enhancing fluorescence are thus needed to achieve high sensitivity for such applications...
May 16, 2018: Journal of Biophotonics
https://www.readbyqxmd.com/read/29760498/hierarchical-mechanism-of-amino-acid-sensing-by-the-t-box-riboswitch
#9
Krishna C Suddala, Javier Cabello-Villegas, Malgorzata Michnicka, Collin Marshall, Edward P Nikonowicz, Nils G Walter
In Gram-positive bacteria, T-box riboswitches control gene expression to maintain the cellular pools of aminoacylated tRNAs essential for protein biosynthesis. Co-transcriptional binding of an uncharged tRNA to the riboswitch stabilizes an antiterminator, allowing transcription read-through, whereas an aminoacylated tRNA does not. Recent structural studies have resolved two contact points between tRNA and Stem-I in the 5' half of the T-box riboswitch, but little is known about the mechanism empowering transcriptional control by a small, distal aminoacyl modification...
May 14, 2018: Nature Communications
https://www.readbyqxmd.com/read/29760468/the-effect-of-hydration-number-on-the-interfacial-transport-of-sodium-ions
#10
Jinbo Peng, Duanyun Cao, Zhili He, Jing Guo, Prokop Hapala, Runze Ma, Bowei Cheng, Ji Chen, Wen Jun Xie, Xin-Zheng Li, Pavel Jelínek, Li-Mei Xu, Yi Qin Gao, En-Ge Wang, Ying Jiang
Ion hydration and transport at interfaces are relevant to a wide range of applied fields and natural processes1-5 . Interfacial effects are particularly profound in confined geometries such as nanometre-sized channels6-8 , where the mechanisms of ion transport in bulk solutions may not apply9,10 . To correlate atomic structure with the transport properties of hydrated ions, both the interfacial inhomogeneity and the complex competing interactions among ions, water and surfaces require detailed molecular-level characterization...
May 14, 2018: Nature
https://www.readbyqxmd.com/read/29757613/confocal-raman-microscopy-for-in-situ-measurement-of-phospholipid-water-partitioning-into-model-phospholipid-bilayers-within-individual-chromatographic-particles
#11
Jay P Kitt, David A Bryce, Shelley D Minteer, Joel M Harris
The phospholipid-water partition coefficient is a commonly measured parameter that correlates with drug efficacy, small-molecule toxicity, and accumulation of molecules in biological systems in the environment. Despite the utility of this parameter, methods for measuring phospholipid-water partition coefficients are limited. This is due to the difficulty of making quantitative measurements in vesicle membranes or supported phospholipid bilayers, both of which are small-volume phases that challenge the sensitivity of many analytical techniques...
May 14, 2018: Analytical Chemistry
https://www.readbyqxmd.com/read/29757611/simple-synthetic-molecular-hydrogels-from-self-assembling-alkylgalactonamides-as-scaffold-for-3d-neuronal-cell-growth
#12
Anaïs Chalard, Laurence Vaysse, Pierre Joseph, Laurent Malaquin, Sandrine Souleille, Barbara Lonetti, Jean-Christophe Sol, Isabelle Loubinoux, Juliette Fitremann
In this work, we demonstrated that the hydrogel obtained from a very simple and single synthetic molecule, N-heptyl-galactonamide was a suitable scaffold for the growth of neuronal cells in 3D. We evidenced by confocal microscopy the presence of the cells into the gel up to a depth of around 200 μm, demonstrating that the latter was permissive to cell growth and enabled a true 3D colonization and organization. It also supported successfully the differentiation of adult human neuronal stem cells (hNSCs) into both glial and neuronal cells and the development of a really dense neurofilament network...
May 14, 2018: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/29754588/evaluating-seroprevalence-to-circumsporozoite-protein-to-estimate-exposure-to-three-species-of-plasmodium-in-the-brazilian-amazon
#13
Virginia Araujo Pereira, Juan Camilo Sánchez-Arcila, Mariana Pinheiro Alves Vasconcelos, Amanda Ribeiro Ferreira, Lorene de Souza Videira, Antonio Teva, Daiana Perce-da-Silva, Maria Teresa Queiroz Marques, Luzia Helena de Carvalho, Dalma Maria Banic, Luiz Cristóvão Sobrino Pôrto, Joseli Oliveira-Ferreira
BACKGROUND: Brazil has seen a great decline in malaria and the country is moving towards elimination. However, for eventual elimination, the control program needs efficient tools in order to monitor malaria exposure and transmission. In this study, we aimed to evaluate whether seroprevalence to the circumsporozoite protein (CSP) is a good tool for monitoring the exposure to and/or evaluating the burden and distribution of Plasmodium species in the Brazilian Amazon. METHODS: Cross-sectional surveys were conducted in a rural area of Porto Velho, Rondônia state...
May 14, 2018: Infectious Diseases of Poverty
https://www.readbyqxmd.com/read/29753778/understanding-protein-mobility-in-bacteria-by-tracking-single-molecules
#14
REVIEW
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
https://www.readbyqxmd.com/read/29750519/charge-carrier-activity-on-single-particle-photo-electro-catalysts-toward-function-in-solar-energy-conversion
#15
Mahdi Hesari, Xianwen Mao, Peng Chen
Understanding the fundamental properties of charge carriers on the surface of semiconductor photo(electro)catalysts is key to the rational design of efficient photo(electro)catalytic devices for sunlight-driven energy conversion. Here high spatial resolution information is always desirable because of the ubiquitous heterogeneity in semiconductor particles. In this Perspective we review the latest advances in nanoscale imaging and quantitative analysis of charge carrier activities on individual semiconductor particles down to sub-particle resolution, covering the approaches of single-molecule super-resolution fluorescence imaging, scanning electron microscopy, and photoluminescence microscopy...
May 11, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/29749224/photoactivatable-rhodamine-spiroamides-and-diazoketones-decorated-with-universal-hydrophilizer-or-hydroxyl-groups
#16
Benoit Roubinet, Matthias Bischoff, Shamil Nizamov, Sergey Yan, Claudia Geisler, Stefan Stoldt, Gyuzel Y Mitronova, Vladimir N Belov, Mariano L Bossi, Stefan W Hell
Photoactivatable rhodamine spiroamides and spirocyclic diazoketones emerged recently as synthetic markers applicable in multicolor superresolution microscopy. However, their applicability in single molecule localization microscopy (SMLM) is often limited by aggregation, unspecific adhesion and low reactivity caused by insufficient solubility and precipitation from aqueous solutions. We report here two synthetic modifications increasing the polarity of compact polycyclic and hydrophobic labels decorated with a reactive group: attachment of 3-sulfo-L-alanyl - beta-alanine dipeptide (a "universal hydrophilizer") or allylic hydroxylation in photosensitive rhodamine diazoketones (and spiroamides)...
May 11, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29748537/single-molecule-fate-of-hiv-1-envelope-reveals-late-stage-viral-lattice-incorporation
#17
Carmen A Buttler, Nairi Pezeshkian, Melissa V Fernandez, Jesse Aaron, Sofya Norman, Eric O Freed, Schuyler B van Engelenburg
Human immunodeficiency virus type 1 (HIV-1) assembly occurs on the inner leaflet of the host cell plasma membrane, incorporating the essential viral envelope glycoprotein (Env) within a budding lattice of HIV-1 Gag structural proteins. The mechanism by which Env incorporates into viral particles remains poorly understood. To determine the mechanism of recruitment of Env to assembly sites, we interrogate the subviral angular distribution of Env on cell-associated virus using multicolor, three-dimensional (3D) superresolution microscopy...
May 10, 2018: Nature Communications
https://www.readbyqxmd.com/read/29748498/single-viruses-on-the-fluorescence-microscope-imaging-molecular-mobility-interactions-and-structure-sheds-new-light-on-viral-replication
#18
REVIEW
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
https://www.readbyqxmd.com/read/29745943/tuning-the-ease-of-formation-of-on-surface-metal-adatom-coordination-polymers-featuring-diketones
#19
Anthoula C Papageorgiou, Jiang Li, Seung Cheol Oh, Bodong Zhang, Özge Sağlam, Yuanyuan Guo, Joachim Reichert, A Belén Marco, Diego Cortizo-Lacalle, Aurelio Mateo-Alonso, Johannes V Barth
We use pyrene-4,5,9,10-tetraketone molecules with substituents of varying bulkiness in the 2,7 positions to probe the generality and versatility of the previously reported on-surface coordination of two diketones with a single metal atom, leading to one-dimensional coordination polymers. Three different low index surfaces of group 11 metals (Cu, Ag and Au) are used to provide both the support and the metal atoms for metal-organic coordination. By real space visualisation with single molecule resolution employing scanning tunnelling microscopy we investigate the molecular self-assembly and show how this can be substantiated with the formation of metal-organic linear and cyclic oligomers, depending on the employed substrate...
May 10, 2018: Nanoscale
https://www.readbyqxmd.com/read/29742417/nuclear-transport-and-accumulation-of-smad-proteins-studied-by-single-molecule-microscopy
#20
Yichen Li, Wangxi Luo, Weidong Yang
Nuclear translocation of stimulated Smad heterocomplexes is a critical step in the signal transduction of transforming growth factor β (TGF-β) from transmembrane receptors into the nucleus. Specifically, normal nuclear accumulation of Smad2/Smad4 heterocomplexes induced by TGF-β1 is involved in carcinogenesis. However, the relationship between nuclear accumulation and the nucleocytoplasmic transport kinetics of Smad proteins in the presence of TGF-β1 remains obscure. By combining a high-speed single-molecule tracking microscopy and Förster resonance energy transfer technique, we tracked the entire TGF-β1-induced process of Smad2/Smad4 heterocomplex formation, as well as their transport through nuclear pore complexes in live cells, with a high single-molecule localization precision of 2 ms and <20 nm...
May 8, 2018: Biophysical Journal
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