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https://www.readbyqxmd.com/read/28821110/unraveling-the-reaction-mechanism-of-silver-ions-reduction-by-chitosan-from-so-far-neglected-spectroscopic-features
#1
Ana Patrícia Carapeto, Ana Maria Ferraria, Ana Maria Botelho do Rego
Metallic silver nanoparticles were synthesized in aqueous solution using chitosan, as both reducing and stabilizing agent, and AgNO3 as silver precursor aiming the production of solid ultra-thin films. A systematic characterization of the resulting system as a function of the initial concentrations was performed. The combination of UV-vis absorption - and its quantitative analysis - with X-ray photoelectron spectra, light scattering measurements and atomic force microscopy allowed obtaining a rational picture of silver reduction mechanism through the identification of the nature of the formed reduced/oxidized species...
October 15, 2017: Carbohydrate Polymers
https://www.readbyqxmd.com/read/28821085/dissolution-mechanism-of-cellulose-in-quaternary-ammonium-hydroxide-revisiting-through-molecular-interactions
#2
Chao Zhong, Fang Cheng, Yingkui Zhu, Zhen Gao, Honghua Jia, Ping Wei
Quaternary ammonium hydroxide (QAH) solution has been used to dissolve cellulose and made great progress in recent years. While, its cellulose dissolution mechanism is still in unclear. Here, series of QAH with varied cationic alkyl chains were chosen for the investigation. The solubility of cellulose in QAH was measured, which allowed us to study the effect of cationic structure on cellulose dissolution. Also, the Kamlet-Taft parameters as well as 1D and 2D NMR analyses of QAH-cellulose/cellobiose system were measured...
October 15, 2017: Carbohydrate Polymers
https://www.readbyqxmd.com/read/28821041/regulation-of-structure-rheological-and-surface-properties-of-chitin-nanocrystal-dispersions
#3
M A Torlopov, I S Martakov, V I Mikhaylov, N V Tsvetkov, P V Krivoshapkin
The hydrosols of chitin nanocrystals (ChN) are promising as modifiers of properties, drug delivery systems, and media. The purpose of this work is to clarify the mechanisms for regulating processes of stability and structure formation occurring in the ChN hydrosols under the influence of varying ionic strength. ChN were isolated from the crab shell; ChN hydrosols are obtained with different concentrations of the dispersed phase. The structure and morphology of the particles was studied by atomic force microscopy and X-ray diffraction...
October 15, 2017: Carbohydrate Polymers
https://www.readbyqxmd.com/read/28820907/positive-regulatory-interactions-between-yap-and-hedgehog-signalling-in-skin-homeostasis-and-bcc-development-in-mouse-skin-in-vivo
#4
Bassem Akladios, Veronica Mendoza Reinoso, Jason E Cain, Taopeng Wang, Duncan L Lambie, D Neil Watkins, Annemiek Beverdam
Skin is a highly plastic tissue that undergoes tissue turnover throughout life, but also in response to injury. YAP and Hedgehog signalling play a central role in the control of epidermal stem/progenitor cells in the skin during embryonic development, in postnatal tissue homeostasis and in skin carcinogenesis. However, the genetic contexts in which they act to control tissue homeostasis remain mostly unresolved. We provide compelling evidence that epidermal YAP and Hedgehog/GLI2 signalling undergo positive regulatory interactions in the control of normal epidermal homeostasis and in basal cell carcinoma (BCC) development, which in the large majority of cases is caused by aberrant Hedgehog signalling activity...
2017: PloS One
https://www.readbyqxmd.com/read/28820741/electromagnetic-and-optical-characteristics-of-nb5-doped-double-crossover-and-salmon-dna-thin-films
#5
Mitta Sekhar Babu, Sreekantha Reddy Dugasani, Soon-Gil Jung, Srivithya Vellampatti, Tuson Park, Sung Ha Park
We report the fabrication and physical characteristics of niobium ion (Nb5+)-doped double-crossover DNA (DX-DNA) and salmon DNA (SDNA) thin films. Different concentrations of Nb5+ ([Nb5+]) are coordinated into the DNA molecules, and the thin films are fabricated via substrate-assisted growth (DX-DNA) and drop-casting (SDNA) on oxygen plasma treated substrates. We conducted atomic force microscopy to estimate the optimum concentration of Nb5+ ([Nb5+]O = 0.08 mM) in Nb5+-doped DX-DNA thin films, up to which the DX-DNA lattices maintain their structures without deformation...
August 18, 2017: Nanotechnology
https://www.readbyqxmd.com/read/28820594/on-the-restrained-proton-indicator-in-combined-quantum-mechanics-molecular-mechanics-dynamics-simulations-of-proton-transfer-through-a-carbon-nanotube
#6
Adam W Duster, Hai Lin
Recently, a collective variable "proton indicator" was purposed for tracking an excess proton solvated in bulk water in molecular dynamics simulations. In this work, we demonstrate the feasibility of utilizing the position of this proton indicator as a reaction coordinate to model an excess proton migrating through a hydrophobic carbon nanotube in combined quantum-mechanics/molecular-mechanics simulations. Our results indicate that applying a harmonic restraint to the proton indicator in the bulk solvent near the nanotube pore entrance leads to the recruitment of water molecules into the pore...
August 18, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28820526/silica-nanoparticle-monolayers-on-a-macroion-modified-surface-formation-mechanism-and-stability
#7
M Morga, Z Adamczyk, D Kosior
Even though silica nanoparticles and their monolayers find a broad field of applications, only a few studies providing a quantitative description of silica nanoparticle deposition at solid/liquid interfaces have been reported in the literature. Given the deficit of reliable experimental data, the goal of this work is to acquire thorough physicochemical characteristics of amorphous silica nanoparticle deposition. Silica nanoparticle monolayers of controlled coverage were formed on macroion (PAH)-modified mica...
August 18, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28820467/aquaporin-4-functionality-and-virchow-robin-space-water-dynamics-physiological-model-for-neurovascular-coupling-and-glymphatic-flow
#8
REVIEW
Tsutomu Nakada, Ingrid L Kwee, Hironaka Igarashi, Yuji Suzuki
The unique properties of brain capillary endothelium, critical in maintaining the blood-brain barrier (BBB) and restricting water permeability across the BBB, have important consequences on fluid hydrodynamics inside the BBB hereto inadequately recognized. Recent studies indicate that the mechanisms underlying brain water dynamics are distinct from systemic tissue water dynamics. Hydrostatic pressure created by the systolic force of the heart, essential for interstitial circulation and lymphatic flow in systemic circulation, is effectively impeded from propagating into the interstitial fluid inside the BBB by the tightly sealed endothelium of brain capillaries...
August 18, 2017: International Journal of Molecular Sciences
https://www.readbyqxmd.com/read/28820314/flow-pattern-dependent-endothelial-cell-responses-through-transcriptional-regulation
#9
Hiroyuki Nakajima, Naoki Mochizuki
Blood flow provides endothelial cells (ECs) lining the inside of blood vessels with mechanical stimuli as well as humoral stimuli. Fluid shear stress, the frictional force between flowing blood and ECs, is recognized as an essential mechanical cue for vascular growth, remodeling, and homeostasis. ECs differentially respond to distinct flow patterns. High laminar shear flow leads to inhibition of cell cycle progression and stabilizes vessels, whereas low shear flow or disturbed flow leads to increased turnover of ECs and inflammatory responses of ECs prone to atherogenic...
August 18, 2017: Cell Cycle
https://www.readbyqxmd.com/read/28820203/excess-charge-driven-dissociative-hydrogen-adsorption-on-ti2o4
#10
Xiaowei Song, Matias R Fagiani, Sreekanta Debnath, Min Gao, Satoshi Maeda, Tetsuya Taketsugu, Sandy Gewinner, Wieland Schöllkopf, Knut R Asmis, Andrey Lyalin
The mechanism of dissociative D2 adsorption on Ti2O4(-), which serves as a model for an oxygen vacancy on a titania surface, is studied using infrared photodissociation spectroscopy in combination with density functional theory calculations and a recently developed single-component artificial force induced reaction method. Ti2O4(-) readily reacts with D2 under multiple collision conditions in a gas-filled ion trap held at 16 K forming a global minimum-energy structure (DO-Ti-(O)2-Ti(D)-O)(-). The highly exergonic reaction proceeds quasi barrier-free via several intermediate species, involving heterolytic D2-bond cleavage followed by D-atom migration...
August 18, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28820200/statistical-thermodynamics-unveils-the-dissolution-mechanism-of-cellobiose
#11
Thomas W J Nicol, Noriyuki Isobe, James H Clark, Seishi Shimizu
In the study of the cellulose dissolution mechanism opinion is still divided. Here, the solution interaction components of the most prominent hypotheses for the driving force of cellulose dissolution were evaluated quantitatively. Combining a rigorous statistical thermodynamic theory and cellobiose solubility data in the presence of chloride salts, whose cations progress in the Hofmeister series (KCl, NaCl, LiCl and ZnCl2), we have shown that cellobiose solubilization is driven by the preferential accumulation of salts around the solutes which is stronger than cellobiose hydration...
August 18, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28819695/theoretical-modeling-of-mechanical-homeostasis-of-a-mammalian-cell-under-gravity-directed-vector
#12
Lüwen Zhou, Chen Zhang, Fan Zhang, Shouqin Lü, Shujin Sun, Dongyuan Lü, Mian Long
Translocation of dense nucleus along gravity vector initiates mechanical remodeling of a eukaryotic cell. In our previous experiments, we quantified the impact of gravity vector on cell remodeling by placing an MC3T3-E1 cell onto upward (U)-, downward (D)-, or edge-on (E)- orientated substrate. Our experimental data demonstrate that orientation dependence of nucleus longitudinal translocation is positively correlated with cytoskeletal (CSK) remodeling of their expressions and structures and also is associated with rearrangement of focal adhesion complex (FAC)...
August 17, 2017: Biomechanics and Modeling in Mechanobiology
https://www.readbyqxmd.com/read/28819212/quantifying-the-free-energy-landscape-between-polymers-and-minerals
#13
K K Sand, R W Friddle, J J DeYoreo
Higher organisms as well as medical and technological materials exploit mineral-polymer interactions, however, mechanistic understanding of these interactions is poorly constrained. Dynamic force spectroscopy can probe the free energy landscape of interacting bonds, but interpretations are challenged by the complex mechanical behavior of polymers. Here we restate the difficulties inherent to applying DFS to polymer-linked adhesion and present an approach to gain quantitative insight into polymer-mineral binding...
August 17, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28819208/extrinsic-mechanical-forces-mediate-retrograde-axon-extension-in-a-developing-neuronal-circuit
#14
M A Breau, I Bonnet, J Stoufflet, J Xie, S De Castro, S Schneider-Maunoury
To form functional neural circuits, neurons migrate to their final destination and extend axons towards their targets. Whether and how these two processes are coordinated in vivo remains elusive. We use the zebrafish olfactory placode as a system to address the underlying mechanisms. Quantitative live imaging uncovers a choreography of directed cell movements that shapes the placode neuronal cluster: convergence of cells towards the centre of the placodal domain and lateral cell movements away from the brain...
August 17, 2017: Nature Communications
https://www.readbyqxmd.com/read/28819173/disentangling-the-coupling-between-sea-ice-and-tundra-productivity-in-svalbard
#15
Marc Macias-Fauria, Stein Rune Karlsen, Bruce C Forbes
The rapid decline in Arctic sea ice poses urgent questions concerning its ecological effects, such as on tundra terrestrial productivity. However, reported sea ice/terrestrial productivity linkages have seldom been constrained, and the mechanism governing them remains elusive, with a diversity of spatial scales and metrics proposed, at times in contradiction to each other. In this study, we use spatially explicit remotely sensed sea ice concentration and high-resolution terrestrial productivity estimates (Normalised Difference Vegetation Index, NDVI) across the Svalbard Archipelago to describe local/sub-regional and large-scale components of sea ice/terrestrial productivity coupling...
August 17, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28819170/self-shedding-and-sweeping-of-condensate-on-composite-nano-surface-under-external-force-field-enhancement-mechanism-for-dropwise-and-filmwise-condensation-modes
#16
Jie Sun, Hua Sheng Wang
In this work, we propose the concept to use the hydrophilic or neutral surface for condensation heat transfer and to use the superhydrophobic surface for enhancement by self-shedding and sweeping of condensate. Molecular dynamics simulation results show that no matter the vapor condenses on the solid surface in dropwise or filmwise mode, the grown-up condensate self-sheds and falls off the superhydrophobic surface, sweeping the growing condensate on the condensing surface downstream. We characterize the dynamics of condensate that the continuous self-shedding and sweeping effectively remove the droplets from the solid surface in dropwise mode or thin the condensate film on the solid surface in filmwise mode, which significantly enhances the condensation heat transfer...
August 17, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28818948/vinculin-forms-a-directionally-asymmetric-catch-bond-with-f-actin
#17
Derek L Huang, Nicolas A Bax, Craig D Buckley, William I Weis, Alexander R Dunn
Vinculin is an actin-binding protein thought to reinforce cell-cell and cell-matrix adhesions. However, how mechanical load affects the vinculin-F-actin bond is unclear. Using a single-molecule optical trap assay, we found that vinculin forms a force-dependent catch bond with F-actin through its tail domain, but with lifetimes that depend strongly on the direction of the applied force. Force toward the pointed (-) end of the actin filament resulted in a bond that was maximally stable at 8 piconewtons, with a mean lifetime (12 seconds) 10 times as long as the mean lifetime when force was applied toward the barbed (+) end...
August 18, 2017: Science
https://www.readbyqxmd.com/read/28818840/hcn4-ion-channel-function-is-required-for-early-events-that-regulate-anatomical-left-right-patterning-in-a-nodal-and-lefty-asymmetric-gene-expression-independent-manner
#18
Vaibhav P Pai, Valerie Willocq, Emily J Pitcairn, Joan M Lemire, Jean-François Paré, Nian-Qing Shi, Kelly A McLaughlin, Michael Levin
Laterality is a basic characteristic of all life forms, from single cell organisms to complex plants and animals. For many metazoans, consistent left-right asymmetric patterning is essential for the correct anatomy of internal organs, such as the heart, gut, and brain; disruption of left-right asymmetry patterning leads to an important class of birth defects in human patients. Laterality functions across multiple scales, where early embryonic, subcellular and chiral cytoskeletal events are coupled with asymmetric amplification mechanisms and gene regulatory networks leading to asymmetric physical forces that ultimately result in distinct left and right anatomical organ patterning...
August 17, 2017: Biology Open
https://www.readbyqxmd.com/read/28818747/antidepressant-like-activity-of-methyl-jasmonate-involves-modulation-of-monoaminergic-pathways-in-mice
#19
Solomon Umukoro, Adaeze Adebesin, Gladys Agu, Osarume Omorogbe, Stephen Babajide Asehinde
PURPOSE: The efficacy of current antidepressant drugs has been compromised by adverse effects, low remission and delay onset of action necessitating the search for alternative agents. Methyl jasmonate (MJ), a bioactive compound isolated from Jasminum grandiflorum has been shown to demonstrate antidepressant activity but its mechanism of action remains unknown. Thus, the role of monoaminergic systems in the antidepression-like activity of MJ was investigated in this study. MATERIALS AND METHODS: Mice were given i...
August 14, 2017: Advances in Medical Sciences
https://www.readbyqxmd.com/read/28818723/chitosan-a-macromolecule-as-green-corrosion-inhibitor-for-mild-steel-in-sulfamic-acid-useful-for-sugar-industry
#20
Neeraj Kumar Gupta, P G Joshi, Vandana Srivastava, M A Quraishi
The present investigation aims at investigation of low cost nontoxic carbohydrate biopolymer chitosan as corrosion inhibitor alone and in combination with KI for mild steel in 1M sulfamic acid medium using gravimetric, electrochemical and surface analysis techniques. It is found that chitosan alone exhibits inhibition efficiency of 73.8% at 200ppm concentration. However, in combination with KI (5ppm), it gave more than 90% inhibition efficiency. The significant increase in the inhibition performance of chitosan has been explained by the synergistic mechanism...
August 14, 2017: International Journal of Biological Macromolecules
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