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Atomic force microscopy

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https://www.readbyqxmd.com/read/27925727/can-point-defects-in-surfaces-in-solution-be-atomically-resolved-by-atomic-force-microscopy
#1
Bernhard Reischl, Paolo Raiteri, Julian D Gale, Andrew L Rohl
While the atomic force microscope (AFM) is able to image mineral surfaces in solution with atomic resolution, so far, it has been a matter of debate whether imaging point defects is also possible under these conditions. The difficulties stem from the limited knowledge of what types of defects may be stable in the presence of an AFM tip, as well as from the complicated imaging mechanism involving interactions between hydration layers over the surface and around the tip apex. Here, we present atomistic molecular dynamics and free energy calculations of the AFM imaging of vacancies and ionic substitutions in the calcite (101[over ¯]4) surface in water, using a new silica AFM tip model...
November 25, 2016: Physical Review Letters
https://www.readbyqxmd.com/read/27922069/formation-mechanism-of-ruddlesden-popper-type-antiphase-boundaries-during-the-kinetically-limited-growth-of-sr-rich-srtio3-thin-films
#2
Chencheng Xu, Hongchu Du, Alexander J H van der Torren, Jan Aarts, Chun-Lin Jia, Regina Dittmann
We elucidated the formation process for Ruddlesden-Popper-type defects during pulsed laser deposition of Sr rich SrTiO3 thin films by a combined analysis of in-situ atomic force microscopy, low energy electron diffraction and high resolution scanning transmission electron microscopy. At the early growth stage of 1.5 unit cells, the excess Sr results in the formation of SrO on the surface, resulting in a local termination change from TiO2 to SrO, thereby forming a Sr rich (2 × 2) surface reconstruction...
December 6, 2016: Scientific Reports
https://www.readbyqxmd.com/read/27921029/nanoscale-structure-and-spectroscopic-probing-of-a%C3%AE-1-40-fibril-bundle-formation
#3
Katarzyna M Psonka-Antonczyk, Per Hammarström, Leif B G Johansson, Mikael Lindgren, Bjørn T Stokke, K Peter R Nilsson, Sofie Nyström
Amyloid plaques composed of fibrillar Amyloid-β (Aβ) are hallmarks of Alzheimer's disease. However, Aβ fibrils are morphologically heterogeneous. Conformation sensitive luminescent conjugated oligothiophenes (LCOs) are versatile tools for monitoring such fibril polymorphism in vivo and in vitro. Biophysical methods applied on in vitro generated Aβ fibrils, stained with LCOs with different binding and fluorescence properties, can be used to characterize the Aβ fibrillation in depth, far beyond that possible for in vivo generated amyloid plaques...
2016: Frontiers in Chemistry
https://www.readbyqxmd.com/read/27920895/organosilane-functionalization-of-nanostructured-indium-tin-oxide-films
#4
R Pruna, F Palacio, M Martínez, O Blázquez, S Hernández, B Garrido, M López
Fabrication and organosilane-functionalization and characterization of nanostructured ITO electrodes are reported. Nanostructured ITO electrodes were obtained by electron beam evaporation, and a subsequent annealing treatment was selectively performed to modify their crystalline state. An increase in geometrical surface area in comparison with thin-film electrodes area was observed by atomic force microscopy, implying higher electroactive surface area for nanostructured ITO electrodes and thus higher detection levels...
December 6, 2016: Interface Focus
https://www.readbyqxmd.com/read/27920533/effect-of-inserted-spacer-in-hepatic-cell-penetrating-multifunctional-peptide-component-on-the-dna-intracellular-delivery-of-quaternary-complexes-based-on-modular-design
#5
Luchen Zhang, Zhenbo Li, Fangli Sun, Yuhong Xu, Zixiu Du
A safe and efficient quaternary gene delivery system (named Q-complexes) was constructed based on self-assembly of molecules through noncovalent bonds. This system was formulated through the cooperation and competing interactions of cationic liposomes, multifunctional peptides, and DNA, followed by coating hyaluronic acid on the surface of the ternary complexes. The multifunctional peptide was composed of two functional domains: penetrating hepatic tumor-targeted cell moiety (KRPTMRFRYTWNPMK) and a wrapping gene sequence (polyarginine 16)...
2016: International Journal of Nanomedicine
https://www.readbyqxmd.com/read/27919816/surface-rearrangement-of-adsorbed-egcg-mucin-complexes-on-hydrophilic-surfaces
#6
J McColl, R Horvath, G E Yakubov, J J Ramsden
The kinetic adsorption-desorption behaviour of porcine gastric mucin in the presence of physiologically relevant concentrations of the polyphenol epigallocatechin gallate (EGCG) was investigated using high-resolution kinetic optical waveguide lightmode spectroscopy (OWLS) and atomic force microscopy (AFM). Comparison with dynamic light scattering results from EGCG-mucin mixtures indicates that discrete particles are formed whose size increases with increasing EGCG:mucin ratio. These particles are deduced to be the adsorbing entities, which fuse on the surface to form complex surface layers...
December 2, 2016: International Journal of Biological Macromolecules
https://www.readbyqxmd.com/read/27919690/comparative-analysis-of-different-xanthan-samples-by-atomic-force-microscopy
#7
Julia Teckentrup, Orooba Al-Hammood, Tim Steffens, Hanna Bednarz, Volker Walhorn, Karsten Niehaus, Dario Anselmetti
The polysaccharide xanthan which is produced by the γ-proteobacterium Xanthomonas campestris is used as a food thickening agent and rheologic modifier in numerous food, cosmetics and technical applications. Its great commercial importance stimulated biotechnological approaches to optimize the xanthan production. By targeted genetic modification the metabolism of Xanthomonas can be modified in such a way that the xanthan production efficiency and/or the shear-thickening potency is optimized. Using atomic force microscopy (AFM) the secondary structure of single xanthan polymers produced by the wild type Xanthomonas campestris B100 and several genetically modified variations were analyzed...
December 2, 2016: Journal of Biotechnology
https://www.readbyqxmd.com/read/27916851/controlled-synthesis-of-atomically-layered-hexagonal-boron-nitride-via-chemical-vapor-deposition
#8
Juanjuan Liu, R Govindan Kutty, Zheng Liu
Hexagonal boron nitrite (h-BN) is an attractive material for many applications including electronics as a complement to graphene, anti-oxidation coatings, light emitters, etc. However, the synthesis of high-quality h-BN is still a great challenge. In this work, via controlled chemical vapor deposition, we demonstrate the synthesis of h-BN films with a controlled thickness down to atomic layers. The quality of as-grown h-BN is confirmed by complementary characterizations including high-resolution transition electron microscopy, atomic force microscopy, Raman spectroscopy and X-ray photo-electron spectroscopy...
November 29, 2016: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/27916801/macromolecular-interactions-control-structural-and-thermal-properties-of-regenerated-tri-component-blended-films
#9
Ashley Lewis, Joshua C Waters, John Stanton, Joseph Hess, David Salas-de la Cruz
With a growing need for sustainable resources research has become highly interested in investigating the structure and physical properties of biomaterials composed of natural macromolecules. In this study, we assessed the structural, morphological, and thermal properties of blended, regenerated films comprised of cellulose, lignin, and hemicellulose (xylan) using the ionic liquid 1-allyl-3-methylimidazolium chloride (AMIMCl). Attenuated total reflectance Fourier transform infrared (ATR-FTIR) analysis, scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray scattering, and thermogravimetric analysis (TGA) were used to qualitatively and quantitatively measure bonding interactions, morphology, and thermal stability of the regenerated films...
November 28, 2016: International Journal of Molecular Sciences
https://www.readbyqxmd.com/read/27916605/modulation-of-drug-resistance-and-biofilm-formation-of-staphylococcus-aureus-isolated-from-the-oral-cavity-of-tunisian-children
#10
Tarek Zmantar, Rihab Ben Slama, Kais Fdhila, Bochra Kouidhi, Amina Bakhrouf, Kamel Chaieb
OBJECTIVES: This study aims to investigate the antimicrobial and the anti-biofilm activities of Lactobacillus plantarum extract (LPE) against a panel of oral Staphylococcus aureus (n=9) and S. aureus ATCC 25923. The in vitro ability of LPE to modulate bacterial resistance to tetracycline, benzalchonium chloride (BC), and chlorhexidine (CHX) were tested also. METHODS: The MICs and MBCs of LPE, tetracycline (TET), CHX and BC were determined in absence and in presence of a sub-MIC doses of LPE (1/2 MIC)...
December 1, 2016: Brazilian Journal of Infectious Diseases
https://www.readbyqxmd.com/read/27915030/the-effect-of-anionic-dicephalic-surfactants-on-fabrication-of-varied-core-nanocarriers-for-sustained-release-of-porphyrin-photosensitizers
#11
Urszula Bazylińska, Renata Frąckowiak, Zbigniew Brzózka, Kazimiera A Wilk
Double-headed anionic surfactants could provide a profound group of efficient stabilizers of new template-mediated nanocarriers for effective encapsulation and sustained release of highly hydrophobic photosensitizers, and therefore their improved therapeutic activity in photodynamic therapy (PDT) protocols. We have thus encapsulated porphyrin-origin dyes, i.e., verteporfin (VP) and meso-tetraphenylporphyrin (TPP) in different types of sodium alkyliminobisacetates, Cn(COONa)2-stabilized nanosystems including biocompatible poly(l-glutamic acid)/poly(l-lysine) - PGA/PLL, multilayer nanocapsules (NCs)...
November 19, 2016: Journal of Photochemistry and Photobiology. B, Biology
https://www.readbyqxmd.com/read/27914268/anti-adhesive-antimicrobial-peptide-coating-prevents-catheter-associated-infection-in-a-mouse-urinary-infection-model
#12
Kai Yu, Joey C Y Lo, Mei Yan, Xiaoqiang Yang, Donald E Brooks, Robert E W Hancock, Dirk Lange, Jayachandran N Kizhakkedathu
Catheter-associated urinary tract infections (CAUTIs) represent one of the most common hospital acquired infections with significant economic consequences and increased patient morbidity. CAUTIs often start with pathogen adhesion and colonization on the catheter surface followed by biofilm formation. Current strategies to prevent CAUTIs are insufficiently effective and antimicrobial coatings based on antimicrobial peptides (AMPs) hold promise in curbing CAUTIs. Here we report an effective surface tethering strategy to prepare AMP coatings on polyurethane (PU), a common biomedical plastic used for catheter manufacture, by using an anti-adhesive hydrophilic polymer coating...
November 24, 2016: Biomaterials
https://www.readbyqxmd.com/read/27913854/the-role-of-macromolecules-in-the-formation-of-kidney-stones
#13
REVIEW
Jeffrey D Rimer, Ann M Kolbach-Mandel, Michael D Ward, Jeffrey A Wesson
The formation of crystal aggregates, one of the critical processes in kidney stone pathogenesis, involves interactions between crystals (predominantly calcium oxalate monohydrate, COM) and urinary constituents (e.g., proteins), which serve as an adhesive "glue" between crystals in stones. To develop a better understanding of the protein-crystal interactions that lead to crystal aggregation, we have measured the effect of model proteins on bulk COM crystal properties as well as their adsorption on crystal surfaces using three synthetic polyanions: poly(aspartic acid) (polyD), poly(glutamic acid) (polyE), and poly(acrylic acid) (polyAA)...
December 2, 2016: Urolithiasis
https://www.readbyqxmd.com/read/27912185/sorption-of-vanadium-v-onto-natural-soil-colloids-under-various-solution-ph-and-ionic-strength-conditions
#14
Xiuhua Luo, Lin Yu, Changzhao Wang, Xianqiang Yin, Ahmed Mosa, Jialong Lv, Huimin Sun
Batch sorption kinetics and isothermal characteristics of V(V) were investigated on three natural soil colloids (manual loessial soil colloid (MSC), aeolian sandy soil colloid (ASC), and cultivated loessial soil colloid (CSC)) under various solution pH and ionic strength (IS) conditions. Colloids were characterized by atomic force microscopy (AFM), X-ray diffraction (XRD), and fourier transform infrared spectroscopy (FTIR). AFM micrographs showed CSC with an aggregated shape with larger particle diameter as compared with ASC and MSC...
November 29, 2016: Chemosphere
https://www.readbyqxmd.com/read/27911778/enhanced-stochastic-fluctuations-to-measure-steep-adhesive-energy-landscapes
#15
Ahmad Haider, Daniel Potter, Todd A Sulchek
Free-energy landscapes govern the behavior of all interactions in the presence of thermal fluctuations in the fields of physical chemistry, materials sciences, and the biological sciences. From the energy landscape, critical information about an interaction, such as the reaction kinetic rates, bond lifetimes, and the presence of intermediate states, can be determined. Despite the importance of energy landscapes to understanding reaction mechanisms, most experiments do not directly measure energy landscapes, particularly for interactions with steep force gradients that lead to premature jump to contact of the probe and insufficient sampling of transition regions...
November 23, 2016: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/27911372/quantitative-hardness-measurement-by-instrumented-afm-indentation
#16
Arnaud Caron
In this work, a combination of amplitude-modulated non-contact atomic force microscopy and atomic force spectroscopy is applied for instrumented hardness measurements on an Au(111) surface with atomistic resolution of single plasticity events. A careful experimental procedure is described that includes the force sensor selection, its calibration, the calibration of the cantilever deflection detection system, and the minimization of instrumental drift for accurate and reproducible force-distance measurements...
November 22, 2016: Journal of Visualized Experiments: JoVE
https://www.readbyqxmd.com/read/27910935/disentangling-the-roles-of-cholesterol-and-cd59-in-intermedilysin-pore-formation
#17
Courtney M Boyd, Edward S Parsons, Richard A G Smith, John M Seddon, Oscar Ces, Doryen Bubeck
The plasma membrane provides an essential barrier, shielding a cell from the pressures of its external environment. Pore-forming proteins, deployed by both hosts and pathogens alike, breach this barrier to lyse target cells. Intermedilysin is a cholesterol-dependent cytolysin that requires the human immune receptor CD59, in addition to cholesterol, to form giant β-barrel pores in host membranes. Here we integrate biochemical assays with electron microscopy and atomic force microscopy to distinguish the roles of these two receptors in mediating structural transitions of pore formation...
December 2, 2016: Scientific Reports
https://www.readbyqxmd.com/read/27908499/a-strategy-to-modulate-the-electrophoretic-behavior-in-plastic-microchips-using-sodium-polystyrene-sulfonate
#18
Jinxiu Guo, Yu Chen, Lizhi Zhao, Ping Sun, Hongli Li, Lei Zhou, Xiayan Wang, Qiaosheng Pu
Plastic microchips have been broadly used as disposable microfluidic devices, but the poorly defined surface properties limit their application. Herein, we proved that an anionic polymer could be used as the background electrolyte (BGE) to provide a strong and stable cathodic electroosmotic flow (EOF) and modulate the electrophoretic behavior for efficient separation in relative thicker microchannels (∼75μm id). A cathodic EOF of ∼3.3×10(-4)cm(2)V(-1)s(-1) was maintained using sodium polystyrene sulfonate (PSSNa) with a molecular weight of 5×10(5) as the BGE, which ensured fluorescein isothiocyanate labeled biogenic amines (BAs) appeared ahead of other components in the electropherograms obtained with microchips of cyclic olefin copolymer...
November 23, 2016: Journal of Chromatography. A
https://www.readbyqxmd.com/read/27907987/microrheology-of-growing-escherichia-coli-biofilms-investigated-by-using-magnetic-force-modulation-atomic-force-microscopy
#19
Tiansheng Gan, Xiangjun Gong, Holger Schönherr, Guangzhao Zhang
Microrheology of growing biofilms provides insightful information about its structural evolution and properties. In this study, the authors have investigated the microrheology of Escherichia coli (strain HCB1) biofilms at different indentation depth (δ) by using magnetic force modulation atomic force microscopy as a function of disturbing frequency (f). As δ increases, the dynamic stiffness (ks) for the biofilms in the early stage significantly increases. However, it levels off when the biofilms are matured...
December 1, 2016: Biointerphases
https://www.readbyqxmd.com/read/27907861/in-situ-time-lapse-study-of-extracellular-polymeric-substance-discharge-in-streptococcus-mutans-biofilm
#20
Bernard Haochih Liu, Li-Chieh Yu
Streptococcus mutans is one of the main pathogens that cause tooth decay. By metabolizing carbohydrates, S. mutans emits extracellular polymeric substance (EPS) that adheres to the tooth surface and forms layers of biofilm. Periodontal disease occurs due to the low pH environment created by S. mutans biofilm, and such an acidic environment gradually erodes tooth enamel. Since the existence of EPS is essential in the formation of biofilm, the in-situ investigation of its generation and distribution in real time is the key to the control and suppression of S...
November 24, 2016: Colloids and Surfaces. B, Biointerfaces
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