Intercalated State Research Articles

MTORC1 Activity Promotes an Intercalated Cell State Which Is Suppressed by Hes1 to Maintain Principal Cells in a Mature State

mTORC1 Activity Promotes an Intercalated Cell State Which Is Suppressed by Hes1 to Maintain Principal Cells in a Mature State

Properties of Solutions of Cellulose and Chitin with Montmorillonite Nanoparticles in Aqueous Alkali with Urea and Thiourea Additions and of Composite Films Prepared from These Solutions

Rheological properties of cellulose and chitin solutions with additions of montmorillonite nanoparticles in NaOH/urea/thiourea aqueous-alkaline solutions were studied. X-ray diffraction analysis shows that montmorillonite nanoparticles in hydrated cellulose and chitin films are in the intercalated state. Analysis of the Fourier IR spectra of the composite films reveals the shift of the Si–O absorption band in both polymer systems. Introduction of montmorillonite into hydrated cellulose and chitin matrices leads to an increase in the residual weight (at 800°C) and to a slight decrease in the degradation onset temperature and in the temperature of the maximal degradation rate.

Binding affinity and in vitro cytotoxicity of harmaline targeting different motifs of nucleic acids: An ultimate drug designing approach

The work focuses towards interaction of harmaline, with nucleic acids of different motifs by multispectroscopic and calorimetric techniques. Findings of this study suggest that binding constant varied in the order single-stranded (ss) poly(A)>double-stranded calf thymus (CT) DNA>double-stranded poly(G)·poly(C)>clover leaf tRNAPhe . Prominent structural changes of ss poly(A), CT DNA, and poly(G)· poly(C) with concomitant induction of optical activity in the bound achiral alkaloid molecule was observed, while with tRNAPhe , very weak induced circular dichroism perturbation was seen. The interaction was predominantly exothermic, enthalpy driven, and entropy favored with CT DNA and poly(G)·poly(C), while it was entropy driven with poly(A) and tRNAPhe . Intercalated state of harmaline inside poly(A), CT DNA, and poly(G)·poly(C) was shown by viscometry, ferrocyanide quenching, and molecular docking. All these findings unequivocally pointed out preference of harmaline towards ss poly(A) inducing self-structure formation. Furthermore, harmaline administration caused a significant decrease in proliferation of HeLa and HepG2 cells with GI50 of 28μM and 11.2μM, respectively. Nucleic acid fragmentation, cellular ultramorphological changes, decreased mitochondrial membrane potential, upregulation of p53 and caspase 3, generation of reactive oxygen species, and a significant increase in the G2 /M population made HepG2 more prone to apoptosis than are HeLa cells.

Adsorbed or intercalated: Na on graphene/Ir(111)

Interaction of sodium with graphene (Gr) on Ir(111) was studied with the aim to resolve the issue of Na adsorption/intercalation kinetics. The system Na/Gr/Ir(111) was studied by means of angle-resolved photoemission spectroscopy, low-energy electron diffraction, and ab initio density functional theory (DFT) calculation. It has been found that at room temperature (RT) and low concentrations Na is dominantly adsorbed on graphene. At higher concentrations, an intercalation process sets in so that it is possible to observe the coexistence of these two states. Eventually, all Na atoms are found in the intercalated state as determined by exposure to oxygen. While adsorption of Na on graphene already intercalated by Na [Na/Gr/Na/Ir(111) system] at RT was not possible, we could observe Li adsorption through the increase of Dirac point binding energy. Li coadsorption strongly affects the binding energy of the iridium surface state as well. This finding was supported by DFT calculations of adsorption energy of Na and Li on bare and fully Na intercalated graphene.

Effect of Curcumin Addition on the Adsorption and Transport of a Cationic Dye across DPPG-POPG Liposomes Probed by Second Harmonic Spectroscopy.

The effect of addition of curcumin on the adsorption and transport characteristics of a cationic dye, LDS+, across negatively charged bilayers composed of POPG and DPPG lipids were investigated by the interface selective second harmonic (SH) spectroscopic technique. Curcumin induced changes in the SH electric field signal of the LDS+ ions (E2ω (LDS+)) were observed to depend critically on the bilayer acyl chain saturation/unsaturation ratio (S/U). Following earlier works, the increase in the E2ω (LDS+) signal is attributed to the release of the Na+ counterions present in the head group region of the bilayer by curcumin and the decay of the E2ω (LDS+) signal is attributed to the bilayer intercalated state of curcumin. While the changes observed in the E2ω (LDS+) signal in the presence of POPG liposomes were consistent with our earlier study ( Varshney, G. K. et al. Langmuir , 2016 , 32 , 10415 - 10421 ), they were significantly different for DPPG liposomes, following curcumin addition. While the increase in the E2ω (LDS+) signal in the presence of POPG liposomes, is marginal (∼10-20%) and instantaneous (<1 s) followed by a rapid decay (completed within ∼100 s), in the presence of DPPG liposomes it was observed to increase slowly and at saturation shows a substantial increase (100-200%), following curcumin addition. When liposomes consisting of a mixture of POPG and DPPG lipids are used, curcumin induced kinetic characteristics of the E2ω (LDS+) signal showed a mixture of the individual kinetic characteristics observed for the unsaturated (POPG) and saturated (DPPG) liposomes. The observed kinetic trends of the E2ω (LDS+) signal following curcumin addition are explained on the basis of the relative strength of the Na+-POPG and Na+-DPPG interaction. Higher ordering of the lipid acyl chain region in DPPG liposome makes the Na+-DPPG interaction much stronger than the Na+-POPG interaction. Further, it is proposed that, in POPG-DPPG liposomes, individual domains of POPG and DPPG lipids exist at low temperature as suggested by the observed temperature dependent kinetic characteristics of the E2ω (LDS+) signal following curcumin addition. These domains are dependent on the S/U ratio and phase state of the bilayer. The gel phase was observed to be more conducive for individual domain formation. Results presented in this work not only support the notion that biological activity of curcumin is associated with its bilayer altering properties, but more interestingly it provides a qualitative insight about how bilayer phase separation can be achieved by modulating the hydrophobic interactions between the lipid acyl chains.

Lithium ion adsorption and diffusion on black phosphorene nanotube: A first-principles study

Li ion storage performance of the single-walled black phosphorene nanotube (PNT), which is considered as potential anode materials for high-performance Li-ion batteries (LIBs), is studied from first-principles calculations. The Li ion adsorption, diffusion and structural evolution of the one-dimensional armchair type PNT (aPNT) upon Li intercalation on the inside (in-PNT) and outside (out-PNT) surfaces were explored, comparing with that of the two-dimensional phosphorene (Psheet). A maximum Li storage capacity (at the intercalated state of Li22P44) is evaluated to be 432 mAh/g. It is also shown that the in-PNT system has higher adsorption energy and lower Li diffusion energy barrier compared with that of the Psheet and the out-PNT systems. The reason on why the better Li storage performance of the in-PNT is also studied from charge distribution and transfer analysis. These results suggest that PNT can be served as potential anode material for LIBs.

Intercalated samarium as an agent enabling the intercalation of oxygen under a monolayer graphene film on iridium

Using thermal desorption time-of-flight mass spectrometry and thermionic methods, it is shown that oxygen does not intercalate under a graphene monolayer grown correctly on iridium, at least at temperatures of T = 300–400 K and exposures below 12000 L. However, if the graphene film on iridium is preliminary intercalated with samarium atoms (up to coverage of θSm = 0.2–0.45), the penetration of oxygen atoms under the graphene film is observed. The oxygen atoms in the intercalated state are chemically bonded to samarium atoms and remain under graphene up to high temperatures (~2150 K).

2D Electrides as Promising Anode Materials for Na-Ion Batteries from First-Principles Study.

Searching for suitable anodes with good performance is a key challenge for rechargeable Na-ion batteries (NIBs). Using the first-principles method, we predict that 2D nitrogen electride materials can be served as anode materials for NIBs. Particularly, we show that Ca2N meets almost all the requirements of a good NIB anode. Each formula unit of a monolayer Ca2N sheet can absorb up to four Na atoms, corresponding to a theoretical specific capacity of 1138 mAh·g(-1). The metallic character for both pristine Ca2N and its Na intercalated state NaxCa2N ensures good electronic conduction. Na diffusion along the 2D monolayer plane can be very fast even at room temperature, with a Na migration energy barrier as small as 0.084 eV. These properties are key to the excellent rate performance of an anode material. The average open-circuit voltage is calculated to be 0.18 V vs Na/Na(+) for the chemical stoichiometry of Na2Ca2N and 0.09 V for Na4Ca2N. The relatively low average open-circuit voltage is beneficial to the overall voltage of the cell. In addition, the 2D monolayers have very small lattice change upon Na intercalation, which ensures a good cycling stability. All these results demonstrate that the Ca2N monolayer could be an excellent anode material for NIBs.

Intercalation of graphene on iridium with sodium atoms

It has been shown that sodium atoms deposited on the surface of graphene atop iridium at T ≤ 850 K diffuse under the graphene layer into an intercalated state and accumulate there in significant concentrations ∼(2–3) × 1014 atoms cm−2. The release of the atoms from under the graphene “carpet” takes place upon destruction of the layer at T ≥ 1800 K. The physical nature of the differences in the processes of release of atoms of different alkali metals from under graphene has been discussed.

Uveal melanoma cells utilize a novel route for transendothelial migration.

Uveal melanoma arises in the eye, and it spreads to distant organs in almost half of patients, leading to a fatal outcome. To metastasize, uveal melanoma cells must transmigrate into and out of the microvasculature, crossing the monolayer of endothelial cells that separates the vessel lumen from surrounding tissues. We investigated how human uveal melanoma cells cross the endothelial cell monolayer, using a cultured cell system with primary human endothelial cell monolayers on hydrogel substrates. We found that uveal melanoma cells transmigrate by a novel and unexpected mechanism. Uveal melanoma cells intercalate into the endothelial cell monolayer and flatten out, assuming a shape and geometry similar to those of endothelial cells in the monolayer. After an extended period of time in the intercalated state, the uveal melanoma cells round up and migrate underneath the monolayer. VCAM is present on endothelial cells, and anti-VCAM antibodies slowed the process of intercalation. Depletion of BAP1, a known suppressor of metastasis in patients, increased the amount of transmigration of uveal melanoma cells in transwell assays; but BAP1 depletion did not affect the rate of intercalation, based on movies of living cells. Our results reveal a novel route of transendothelial migration for uveal melanoma cells, and they provide insight into the mechanism by which loss of BAP1 promotes metastasis.

Understanding the Role of H-Bonding in Aqueous Self-Assembly of Two Naphthalene Diimide (NDI)-Conjugated Amphiphiles

Supramolecular architectures with the synchronized combination of various directional noncovalent forces are ubiquitous in biological systems. However, reports of such abiotic synthetic systems involving H-bonding in aqueous medium are rare due to the challenge faced in the formation of such structures by overcoming the competition from the water molecules. In this paper we have studied self-assembly of two structurally related naphthalene-diimide (NDI) conjugated bola-amphiphiles (NDI-1 and NDI-2) in water with an aim to realize the specific role of H-bonding among the hydrazide units present in one of the two building blocks (NDI-2) on the self-assembly. Both chromophores showed vesicular assembly in aqueous solution driven primarily by π-stacking among the NDI chromophores, which could be probed by UV-vis absorption spectra. Contrary to common belief, the lack of an H-bonding group in NDI-1 was found to be a boon in disguise in terms of the stability of the aggregates. Whereas NDI-2 aggregates showed LCST around 65-70 °C owing to the breaking of the H-bonds with increased temperature, the NDI-1 aggregates were found to be structurally intact until 90 °C, which may be attributed to the increased hydrophobicity introduced by the absence of the polar hydrazide group. Further concentration- and solvent-dependent UV-vis studies showed that NDI-1 formed assembled structure at greatly dilute solution and also in a solvent such as THF, confirming greater propensity for its self-assembly. As both bola-amphiphiles contain an electron-deficient NDI chromophore, interaction of their vesicles was studied with an externally added electron-rich pyrene derivative. Surprisingly, NDI-1 did not show any charge-transfer interaction with the donor, whereas NDI-2 could effectively intercalate, leading to a functional membrane with tunable surface functionalities. This was attributed to the additional stability of the intercalated state by H-bonding among the hydrazide units.

In situ polymerization of cationic polyacrylamide/montmorillonite composites and its flocculation characteristics

In order to improve the waste sludge dewaterability of polyacrylamide (PAM), composite conditioner of cationic PAM/montmorillonite (CPAM/MMT) was synthesized by in situ polymerization. The structure and property of the composite were studied in terms of intermolecular hydrogen bonding, melting behavior, intercalation behavior, and dewaterability of the waste sludge. The results revealed that the molecular weight and cationic degree of CPAM/MMT composites decreased with the increase of MMT content. The hydrogen bonding between –OH groups of MMT and –NH groups of CPAM was confirmed by Fourier transform infrared spectroscopic analysis, which led to a relatively high elastic modulus values and low tan δ values at 5 wt% MMT content, indicating the possible formation of a physically cross-linked network in aqueous solution for the composite. The melting temperature of the composites presented decreasing trend first and then became higher as the content of MMT increased. The MMT platelets dispersed well with an intercalated state in CPAM matrix as indicated by x-ray diffraction analysis and transmission electron microscopic observation. The addition of MMT reduced the specific resistance to filtration of the waste sludge, with a minimum value being achieved at 5 wt% MMT content, while the ultraviolet transmittance of the supernatant of the waste sludge was also improved, and the turbidity was reduced. This synergistic effect of the two components in the composite through charge neutrality and bridging action of CPAM as well as the adsorption capacity of MMT resulted in an enhanced dewaterability of waste sludge.

Effect of nano-sized layered silicate on AC electrical treeing behavior of epoxy/layered silicate nanocomposite in needle-plate electrodes

A layered silicate at 1–10 wt% was incorporated into an epoxy matrix in order to prepare an insulation material for heavy electric equipments using a three roll mill for nanoparticle dispersion, and then alternating current (AC) electrical treeing and breakdown tests were carried out. Wide-angle X-ray diffraction (WAXD) analysis and transmission electron microscopy (TEM) observation showed that the multilayered silicate at 1 wt% was fully exfoliated into nano-sized monolayers in the epoxy matrix, however the silicate layers at over 3 wt% were in an intercalated state. When 1 wt% nano-sized silicate layers were incorporated, the tree initiation time in the needle-plate electrodes geometry was 18.0 times longer and the breakdown time was 16.7 times longer than those of the neat epoxy resin under the applied electrical field of 520.9 kV mm−1 at 30 °C. But these values were in great decline at over 3 wt% of the layered silicate content. These results meant that the exfoliated nano silicates blocked the tree initiation and propagation processes effectively, however the effect largely decreased with the increasing silicate content in the intercalated state.

Intercalation and de-intercalation pathway of proflavine through the minor and major grooves of DNA: roles of water and entropy

DNA intercalation is a clinically relevant biophysical process due to its potential to inhibit the growth and survival of tumor cells and microbes through the arrest of the transcription and replication processes. Extensive kinetic and thermodynamic studies have followed since the discovery of the intercalative binding mode. However, the molecular mechanism and the origin of the thermodynamic and kinetic profile of the process are still not clear. Here we have constructed the free energy landscape of intercalation, de-intercalation and dissociation from both the major and minor grooves of DNA using extensive all-atom metadynamics simulations, capturing both the free energy barriers and stability in close agreement with fluorescence kinetic experiments. In the intercalated state, an alternate orientation of proflavine is found with an almost equal stability compared to the crystal orientation, however, separated by a 5.0 kcal mol(-1) barrier that decreases as the drug approaches the groove edges. This study provides a comprehensive picture in comparison with experiments, which indicates that the intercalation and de-intercalation of proflavine happen through the major groove side, although the effective intercalation barrier increases because the path of intercalation goes through the stable (abortive) minor groove bound state, making the process a millisecond long one in excellent agreement with the experiments. The molecular origin of the higher barrier for the intercalation from the minor groove side is attributed to the desolvation energy of DNA and the loss of entropy, while the barrier from the major groove, in the absence of desolvation energy, is primarily entropic.

Cesium ion emission from a graphene surface on iridium in a high-intensity electric field

Features of cesium ion emission from a graphene film on iridium in a 107–108 V cm−1 electric field of are studied. Field electron and desorption images demonstrate that the film consists of regions (islands) 20–100 nm in size. Intercalated cesium lies under the film. There is continuous desorption of cesium ions from the defects in the graphene film and the regions of where islands abut one another. Cesium ions arrive at the desorption sites from the intercalated state.

Nanocomposites of novolac type phenolic resins and organoclays: The effects of the resin molecular weight and the amine salt structure on the morphology and the mechanical properties of the composites

Nanocomposites of novolac-type phenolic resins having various molecular weights with a series of organoclays containing organic amine salts were prepared by melt processing. The effects of the molecular weight of novolac resin and the amine structure of organoclay on composite morphology and physical properties were examined. Composites containing organoclay exhibited the intercalated state with shifts in gallery spacing regardless of the molecular weight of novolac resin. The extent of silicate platelet intercalation increased as molecular weight of novolac resin increased and the number of long alkyl tails decreased from two to one. Novolac resin/organoclay composites cured with hexamethylenetetramine (HMTA) always exhibited better flexural and Izod impact strengths than the novolac resin cured with HMTA when the molecular weight of novolac resin was fixed. Among the nanocomposites prepared here using organoclays, those with higher platelet intercalation generally showed better flexural and Izod impact strengths. However, resin-coated sands prepared from organoclay containing one long alkyl tail exhibited only better flexural strength than that prepared from novolac resin.

Study Structure and Properties of Nanocomposite Material Based on Unsaturated Polyester with Clay Modified by Poly(ethylene oxide)

In recent years, polymer clay nanocomposites have been attracting considerable interests in polymers science because of their advantages. There are many scientists who researched about this kind of material and demonstrated that when polymer matrix was added to little weight of clay, properties were enhanced considerably. Because clay is a hydrophilic substance so it is difficult to use as filler in polymer matrix having hydrophobic nature, so clay needs to be modified to become compatible with polymer. In this study, poly(ethylene oxide) was used as a new modifier for clay to replace some traditional ionic surfactants such as primary, secondary, tertiary, and quaternary alkyl ammonium or alkylphosphonium cations having the following disadvantages: disintegrate at high temperature, catalyze polymer degradation, and make nanoproducts colorific, and so forth. In order to evaluate modifying effect of poly(ethylene oxide), modified clay products were characterize d by X‐ray spectrum. Then organoclay was used to prepare nanocomposite based on unsaturated polyester. Morphology and properties of nanocomposites were measure d by X‐ray diffraction, transmission electron microscopy, tensile strength, and thermal stability. The results showed that clay galleries changed to intercalated state in the nanocomposites. Properties of nanocomposites were improved a lot when the loading of the organoclay was used at 1 phr.

POLYPROPYLENE/CLAY NANOCOMPOSITES: SYNTHESIS AND CHARACTERIZATION

abstract Polypropylene nanocomposites were synthesized by using the method of mixing in the molten state. Nanocomposites were obtained in twin-screw co-rotating extruders and the nanocomposites were prepared with percentage of nanoclay (C 2 ) from 5 wt-%, with and without compatibilizer agent (PP- g -MA).The thermal (DSC, TGA), morphology (XRD, TEM), and dynamical mechanical (DMA) properties of the nanocomposites were characterized.All nanocomposites prepared are in intercalated state as corroborated by XRD and TEM. The Tm and Xc were not affected by the presence of clay, PP-g-MA, or processing support. The incorporation of clay and compatibilizer agent increases the thermal stability and heat deflection temperature (HDT). Keywords : Nanocomposites, polypropylene, clays. compatiblizer agent 1. introdUction Polypropylene is a polymer widely used in many applications, and their thermal (1-2), rheological (3), mechanical (4-5), and gas permeation properties (6-7) need to be improved. A large number of studies have focused to improve a range of capabilities for these materials used in the automotive industries, and which show a great potential for use in the aeronautical field (7). The study of polymer nanocomposites has focused on enhancing the conventional properties of this polymeric material (8),

Morphology and Mechanical Properties of Nanocomposites Fabricated from Organoclays and a Novolac Phenolic Resin via Melt Mixing

Nanocomposites of novolac phenolic resin with a series of organoclays based on sodium montmorillonite exchanged with various amine compatibilizers were fabricated via melt processing. The effects of the amine structure on the resulting morphology and physical properties were investigated by employing wide-angle X-ray scattering, transmission electron microscopy, viscosity measurement, flexural strength measurement, and Izod impact strength testing. All of the composites containing organoclay showed evidence of the intercalated state with a shift in the gallery spacing. The extent of silicate platelet intercalation was increased by (1) decreasing the number of long alkyl tails from two to one, (2) using methyl rather than polar hydroxyethyl groups or bulky groups such as 2-ethylhexyl or benzyl groups, and (3) using an equivalent amount of compatibilizer with the montmorillonite. Novolac phenolic resin/organoclay nanocomposites cured with hexamethylenetetramine exhibited better flexural and Izod impact stre...

Penetration (intercalation) of copper atoms under a graphene layer on iridium (111)

The mechanisms of intercalation of a graphene layer (a two-dimensional graphite film) on a metal (iridium, the (111) face) with copper atoms are studied. It is shown that, in the rather narrow temperature range 1100–1200 K, a thin copper film deposited onto the graphene surface at room temperature totally breaks down, and the atoms transfer to the intercalated state, i.e., become arranged between the graphene layer and the substrate. The nature of the asymmetry of intercalation and backward escape of atoms with high ionization potentials is discussed. Due to the asymmetry, the graphene layer plays the role of a trap for such particles.