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Group 13 cations induce hydrolysis of a rhodamine based dye to cause a sharp color change from colorless to pink and a high increment in fluorescence.

The solvation structures of calcium (Ca2+) and magnesium (Mg2+) ions with the presence of hydroxide (OH−) ion in water are essential for understanding their roles in biological and chemical processes but have not been fully explored.

Modified magnetite chitosan with silver nanoparticles was synthesized and tested for removing cationic and anionic dyes in aqueous solutions. Initial dye concentration, pH, and contact time were examined. Results showed that pH (4.0) was optimal for removing anionic dyes (methyl orange) and pH 8.0 for removing cationic dyes (methylene blue). According to these results, zeta potentials were found to be 8.43 and - 39.17 mV at pH 4.0 and 8.0, respectively. So, it is attracted to positively charged cationic dyes in an alkaline medium and negatively charged anionic dyes in an acidic medium because of their opposite charges. Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), thermal gravimetric analysis (TGA), and zeta potential measurements were used to characterize the synthesized nanosorbents. A pseudo-second-order kinetic model is fitted with the Langmuir adsorption model, with an adsorption capacity of 417 and 476 mg/g for methyl orange and methylene blue, respectively. For both dyes, modified magnetite chitosan with silver nanoparticles showed high regeneration capability and recovery for up to four cycles without adsorption efficiency loss. Furthermore, modified magnetite chitosan with silver nanoparticles, as prepared in the present study, was demonstrated to be an effective adsorbent for organic pollutants in wastewater.

The ion structure of surface active ionic liquids (SAILs), i.e. ion charge group and alkyl chain structure, controls their bulk and interfacial nanostructure and the electrochemical properties near an electrode.The structures in the bulk and at the interface were investigated by small and wide-angle X-ray scattering (SAXS) and atomic force microscopy (AFM), respectively. An investigation was performed using cyclic voltammetry.All SAILs show pronounced sponge-like bulk nanostructure. For the first time, the bulk nanostructures of SAILs are found to change from anion bilayer structures to cation-anion interdigitated structures as the ion structures change from short alkyl chain cations and linear alkyl chain anions to long alkyl chain cations and branched alkyl chain anions. The bulk nanostructure packs more compactly at a higher temperature, likely due to the conformational change and enhanced interdigitations of alkyl chains. The thicknesses of SAIL interfacial layers align with the repeat distances of the bulk nanostructure, similar to conventional ILs with long cation alkyl chains. All SAILs have wide electrochemical windows4 V, which are not affected by the alkyl chain structure and cation charge groups.

Achieving accurate measurements of G-quadruplexes (G4s), especially the characterization of their complicated non-covalent interactions with various components (such as metal ions and ligands) under physiological conditions, is of fundamental significance in unveiling their biological roles and developing antitumor drugs. By employing a nanopore ion emitter (∼30 nm), we demonstrated for the first time that G4 ions, which are free of non-specific adduction and meanwhile maintaining their pre-existing specific bindings with metal ions or ligands, can be directly liberated from common biochemical buffers (consisting of concentrated non-volatile salts of150 mM) for mass spectrometric examination. Notably, the intermediate complexes of G4s with mixed di-cation coordination formed during the Na

Mixtures of hyaluronic acid (HA) with liposomes lead to hybrid colloid-polymer systems with a great interest in drug delivery. However, little is known about their microstructure. Small angle neutron scattering (SANS) is a valuable tool to characterize these systems in the semi-dilute entangled regime (1.5% HA) at high liposome concentration (80 mM lipids). The objective was to elucidate the influence of liposome surface (neutral, cationic, anionic or anionic PEGylated), drug encapsulation and HA concentration in a buffer mimicking biological fluids (37 °C). First, liposomes were characterized by SANS, cryo-electron microscopy, and dynamic light scattering and HA by SANS, size exclusion chromatography, and rheology. Secondly, HA-liposome mixtures were studied by SANS. In HA, liposomes kept their integrity. Anionic and PEGylated liposomes were in close contact within dense clusters with an amorphous organization. The center-to-center distance between liposomes corresponded to twice their diameter. A depletion mechanism could explain these findings. Encapsulation of a corticoid did not modify this organization. Cationic liposomes formed less dense aggregates and were better dispersed due to their complexation with HA. Liposome surface governed the interactions and microstructure of these hybrid systems.

Controlling ion distribution inside a charged nanochannel is central to using such channels in diverse applications. Here, we show the possibility of using a charged polyelectrolyte (PE) brush-grafted nanochannel for triggering diverse nanoscopic ion distribution and nanofluidic electroosmotic transport by controlling the valence and size of the counterions (that screen the charges of the PE brushes) and the strength of an externally applied axial electric field. We atomistically simulate separate cases of fully charged polyacrylic acid (PAA) brush functionalized nanochannels with Na

Aberrant activation of Wnt/β-catenin induces renal dysfunction by initiating pro-apoptotic cascades, fibrosis, oxidative and inflammatory burden. This study tested the therapeutic effects of Wnt/β-catenin inhibitor pyrvinium against cisplatin-induced acute kidney injury (AKI) in rats. Cisplatin was administered at a single dose of 5 mg/kg (i.p.) and renal cisplatin accumulation and uptake in cortical slices were determined after the fifth day by atomic absorption spectroscopy. Levels of pro-inflammatory cytokines were checked by ELISA, and organic cation transporter-2 (OCT-2) transcription and expression in renal tissue were evaluated by RT-PCR and immunohistochemical technique. Cisplatin administration produced renal dysfunction manifested as increase in serum creatinine, blood urea nitrogen, proteinuria, reduced clearance and electrolyte imbalance. Oxidative stress indices, pro-inflammatory cytokines, fibronectin, and caspase-3 activity were elevated in cisplatin-challenged rats. Moreover, increased renal OCT-2 transcription and immunostaining were detected in cisplatin kidneys which resulted in platinum accumulation. Additional docking studies depicted strong interaction between the β-catenin and OCT-2 protein. These manifestations induced mitochondrial dysfunction, histological damage and fibrosis. Notably, Wnt/β-catenin inhibitor pyrvinium (60 µg/kg; p.o.) treatment reduced the renal OCT-2 gene transcription causing a decline in platinum levels. Thus, the present study concludes that Wnt/β-catenin inhibition attenuates cisplatin-induced AKI in rats, partly by down-regulating OCT-2 expression.

The positive charge on liposome surface is known to promote the crossing of the Blood brain barrier (BBB). However, when diastereomeric cationic gemini amphiphiles are among lipid membrane components, also the stereochemistry may affect the permeability of the vesicle across the BBB.Liposomes featuring cationic diasteromeric gemini amphiphiles were formulated, characterized, and their interaction with cell culture models of BBB investigated.Liposomes featuring the gemini amphiphiles were internalized in a monolayer of brain microvascular endothelial cells derived from human induced pluripotent stem cells (hiPSC) through an energy dependent transport, internalization involving both clathrin- and caveolae-mediated endocytosis. On the same formulations, the permeability was also evaluated across a human derived in vitro BBB transport model. The permeability of liposomes featuring the gemini amphiphiles was significantly higher compared to that of neutral liposomes (DPPC/Cholesterol), that were not able to cross BBB. Most importantly, the permeability was influenced by the stereochemistry of the gemini and pegylation of these formulations did not result in a drastic reduction of the crossing ability. The in vitro iPSC-derived BBB models used in this work represent an important advancement in the drug discovery research of novel brain delivery strategies and therapeutics for central nervous system diseases.

Triazole hosts allow cooperative binding of anions via hydrogen bonds, which makes them versatile systems for application in anion binding catalysis to be performed in organic solvents. The anion binding behavior of a tetratriazole host is systematically studied by employing a variety of salts, including chloride, acetate, and benzoate, as well as different cations. Classical nuclear magnetic resonance (

Conditions that cause the loss of epithelial barrier integrity are often accompanied by dysregulation of tight junction protein expression and/or localization. Recently, we have reported that patients with mutations in SLC12A2, the gene encoding the basolateral Na+-K+-2Cl− cotransporter (NKCC1), suffer from severe gastrointestinal deficits, including chronic gastrointestinal inflammation, gastrointestinal hemorrhage, intestinal obstruction, and constipation. Although the intestinal inflammation observed in patients with loss of NKCC1 function may or may not be due to tight junction dysfunction, we investigated whether the loss of NKCC1 function affects paracellular ion transport and epithelial barrier function. Wild-type HT29-MTX-E12 and CRISPR/Cas9-mediated NKCC1 knockout (KO) HT29 clones were tested for tight junction protein expression and localization. Tightness of epithelial cell monolayer was assessed by measurement of transepithelial electrical resistance and permeability of molecular tracers in transwell filters. Tight junction protein localization was assessed by immunofluorescence. Loss of NKCC1 expression strongly increases the expression of claudin-2 and occludin in epithelial cell monolayers. Loss of NKCC1 significantly reduces the transepithelial electrical resistance (TER) indicating an increase in paracellular ions flux, consistent with upregulation of the cation-selective and channel-forming claudin-2. In addition, NKCC1-KO monolayers showed a significant increase in the paracellular flux of small molecules like fluorescein (0.33 kDa), whereas the permeability of higher molecular weight TRITC-Dextran (4 kDa and 70 kDa) remained unchanged. Thus, NKCC1 regulates tight junction protein expression and loss of NKCC1 function affects epithelial barrier integrity.

A catanionic surfactant system is an aqueous solution or dispersion of cationic and anionic surfactants that spontaneously self-assemble into structures such as micelles, vesicles, and coacervates. Their structural diversity varies depending on the ratios of cationic and anionic surfactants (compositions), the chemical structure of the constituent molecules, etc. Herein, two types of catanionic surfactant systems were systematically characterized: (i) cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS), both typical ionic surfactants; and (ii) dodecylmethylimidazolium ammonium bromide ([C

Healthcare-associated infections can occur and spread through direct contact with contaminated fomites in a hospital, such as mobile phones, tablets, computer keyboards, doorknobs, and other surfaces. Herein, this study shows a transparent, robust, and visible light-activated antibacterial surface based on hydrogen bonds between a transparent silica-alumina (Si-Al) sol-gel and a visible light-activated photosensitizer, such as crystal violet (CV). The study of the bonding mechanisms revealed that hydrogen bonding predominantly occurs between the N of CV and Al-OH. Apart from CV, Si-Al can be combined with a variety of dyes, highlighting its potential for wide application. The Si-Al@CV film selectively generates singlet oxygen using ambient visible light, triggering potent photochemical antibacterial performance against Gram-positive and Gram-negative bacteria. Additionally, the Si-Al@CV film is stable even after mechanical stability tests such as tape adhesion, scratch, bending, and water immersion.

Aqueous solubility and interfacial adsorption of surfactants are important for numerous applications. Using molecular dynamics, we have studied the effect of the type of the polar headgroup (cationic quaternary ammonium and charge-neutral amine) and length of the alkyl tail on the hydration free energy of surfactants in infinite dilution. In addition, we have studied the effect of replacing the terminal methyl group of the alkyl tail with a more polar hydroxyl group on the hydration free energy. Quaternary ammonium surfactants have strongly favorable hydration free energies, whereas charge-neutral amine surfactants have unfavorable hydration free energies. The contribution of the quaternary ammonium group in reducing the hydration free energy is estimated to be as large as ∼63

Conventional wisdom suggests that cations play a minimal role in the assembly of cationic amphiphiles. Here, we show that at liquid/liquid (L/L) interfaces, specific cation effects can modulate the assemblies of hydrophobic tails in an oil phase despite being attached to cationic headgroups in the aqueous phase. We used oligo-dimethylsiloxane (ODMS) methyl imidazolium amphiphiles to identify these specific interactions at hexadecane/aqueous interfaces. Small cations, such as Li

Herein, a synthetic method was developed to prepare a series of tris(dialkylamino)sulfonium and sulfoxonium cations from sulfur monochloride. Alkaline stability studies of these two cation families in 2 M KOH/CD

Characterization and quality control of biotherapeutic proteins commonly require the application of several orthogonal separation techniques in order to establish product identity and purity. Many of the techniques used rely on a buffered aqueous mobile phase system to maintain the native conformation of the protein and its variants. Optimal pH, buffer substance(s), and chromatography methods vary with each protein of interest and result in tedious method development for each new drug product. Linear controlled pH gradient systems from pH 5.6 to pH 10.2 has been shown to provide a global method for the separation of charge variants of monoclonal antibodies. This can be realized using two balanced zwitterionic buffer blends. The pH linearity of the resulting system, with a cation ion exchange column in place, can generate any pH value in this accessible pH range. This study expands the scope of this buffer system and demonstrates its application in conjunction with a quaternary HPLC pump for several analytical techniques: the pH optimization of salt gradient-based anion and cation exchange during method development, as well as performing pH gradient elution. In addition, the same universal buffers are used for hydrophobic interaction and size exclusion chromatography. This eluent system omits the need to prepare different buffers for each method and flushing of the HPLC system between method changes. The implementation of this concept is further demonstrated to allow an automated method scouting approach and selection of different methods that requires minimal manual intervention.

Improving the stability of the gold nanoparticles (AuNPs) is an important challenge in nanoscience, given that the activity and ubiquitous application of the AuNPs in different fields depend largely on their stability in the solution phase. Ionic liquids (ILs) can be used as new alternatives in comparison to water and organic solvents due to their considerable properties to elevate the stability and resistance of the AuNPs against aggregation for a long period of storage. In this study, we employ molecular dynamics simulation and quantum chemistry calculations to investigate the effects of amino acid ILs ([BMIM][Gly], [BMIM][Leu], [BMIM][Pro], [BMIM][Val], and [BMIM][Ala]) on the stability and aggregation process of the AuNPs from the molecular viewpoint. Our results suggest that ILs can prevent AuNP aggregation. These ILs penetrate the solvation shell of the nanoparticles and by increasing the electrostatic repulsions on the surface of the AuNPs improve their stability against aggregation. Moreover, the [BMIM]

Protein nanoparticles have been demonstrated as effective carriers for protein antigens and therapeutics due to properties endowed by their protein composition. They exhibit high protein to carrier yields, biocompatibility, and heterogeneous surface properties. While protein nanoparticles have been delivered via multiple routes, including intranasal, their interactions with mucosal barriers have not been well studied or modified. Biological barriers associated with intranasal delivery consist of viscoelastic mucus that hinders material transport through surface interactions and the underlying epithelium. Herein, we altered protein nanoparticle surface properties and characterized interactions with nasal mucus and the subsequent effects on diffusion, cellular uptake, and immune cell maturation. Ovalbumin protein nanoparticles were used, serving as a model vaccine nanoparticle. Unmodified ovalbumin protein nanoparticles were compared to cationic ovalbumin particles functionalized with amine groups, neutral particles functionalized with polyethylene glycol, and zwitterionic particles coated layer-by-layer (LBL) with chitosan and oligonucleotides. Transport analysis indicated rapid diffusion of polyethylene glycol and LBL-modified ovalbumin nanoparticles in porcine nasal mucus, while cationic particles were mucoadhesive. Cellular uptake in the presence of mucus by epithelial and dendritic cells was highest for particles containing positive charges, both LBL and amine-functionalized. These particles also exhibited the most diverse adsorbed protein corona from nasal fluids. The corona impacted both dendritic cell uptake and maturation, with polyethylene glycol and LBL modifications improving CD86 expression. Altogether, surface modifications on protein-based nanocarriers are shown to facilitate distinctive physical and cellular behavior associated with mucosal delivery.

In the present study, semi-interpenetrating polymer networks (semi-IPNs) were synthesized based on xanthan gum (XG)-cl-2-(N-morpholinoethyl methacrylate) (MEMA)/titanium dioxide (TiO

Magnetic nanoparticle-incorporated liposomes (magnetic liposomes) are considered a promising site-specific drug delivery carrier. Although there are many reports on the development of magnetic liposomes, most of them focus on the characteristics of magnetic nanoparticles, rather than liposomes. Therefore, we first evaluated the effect of the physicochemical properties of magnetic liposomes on their interaction with cells. The highest cellular uptake and retention under a magnetic field was observed using small magnetic cationic liposomes. However, magnetic cationic liposomes exhibited strong cytotoxicity. Based on these results, we constructed complexes of less toxic magnetic anionic liposomes (Mag-AL) and atelocollagen (ATCOL), a biocompatible cationic biomaterial. The cellular associated amount of Mag-AL under a magnetic field was significantly increased when Mag-AL was complexed with ATCOL, and it was comparable to that of magnetic cationic liposomes. Additionally, Mag-AL/ATCOL complexes produced no cytotoxic effect. Moreover, liver accumulation of Mag-AL/ATCOL complexes was significantly increased at a magnetic field-exposed region after intravenous injection in rats. These results indicate that Mag-AL/ATCOL complexes may be a safe and efficient magnetic responsive drug carrier. Next, we applied Mag-AL/ATCOL complexes to prepare magnetized cells for effective cell therapy. Mesenchymal stem cells (MSCs), which have the capacity to suppress tissue inflammation, were efficiently magnetized by incubation with Mag-AL/ATCOL complexes under a magnetic field. Intramuscularly injected magnetized MSCs were significantly retained in mouse skeletal muscle in the presence of a magnetic field and modulated tissue inflammatory responses. These results suggest that magnetized MSCs are useful for muscle regeneration.

A separable spherical bio-adsorbent (CMC-Cr) was prepared for capturing heavy metal ions by simple coordination and cross-linking between targeted ions of Cr

Specific ion effects are manifest universally across many systems and solvents. Whilst broad understanding of these effects is emerging particularly for bulk effects, the perturbation introduced by the interfaces are generally not understood. We hypothesise that through a careful investigation of the distribution of ions at the glycerol-vapor interface we can better understand specific ion effects in this system and at interfaces.Neutral impact collision ion scattering spectroscopy (NICISS) is used to obtain and compare individual ion concentration depth profiles (CDP) for a range of monovalent inorganic anions and cations at 12 glycerol electrolyte solutions surfaces.The distribution of ions at the vapor - glycerol interface is non-monotonic. Broadly, anions are concentrated at the outermost region of the interface and cations are depleted from the interface. The distribution of Cl

The fabrication of reusable, sustainable adsorbents from low-cost, renewable resources via energy efficient methods is challenging. This paper presents wet-stable, carboxymethylated cellulose nanofibril (CNF) and amyloid nanofibril (ANF) based aerogel-like adsorbents prepared through efficient and green processes for the removal of metal ions and dyes from water. The aerogels exhibit tunable densities (18-28 kg m

A novel mechanism of organobase-mediated Brook rearrangement and C-C coupling in the copper-catalyzed reductive coupling of benzaldehyde and benzophenone is proposed. The results demonstrate that this reaction proceeds mainly through five sequential elementary steps: transmetalation, carbonyl addition, σ-bond metathesis, Brook rearrangement, and C-C coupling. The organobases played a significant role not only in forming the active catalyst but also in mediating the Brook rearrangement and chemoselectivity in homo- and cross-coupling. Brook rearrangement mediated by organobases is more favored than that without organobases. In the C-C coupling step, the cation bridge combines two O atoms with the same electronegativity to form a pre-reaction complex. Moreover, a significant charge difference is a major factor in the selectivity of carbonyl addition and C-C coupling.

The synthesis, structural, thermal, and magnetic properties of a series of simple binary organic salts based on the radical anion of 7,7,8,8-tetracyanoquinodimethane (TCNQ) and 4-(N-alkylpyridinium-3-yl)-1,2,3,5-dithiadiazolyl (DTDA), 1R (R = Et, Pr, Bu), radical cations and their heavier selenium analogues (DSDA), 2R, are described. Single-crystal X-ray structural analyses reveal that short alkyl substituents on the pyridinium moiety of DTDA/DSDA cations lead to crystallization of isostructural acetonitrile (MeCN) solvates 1Et·MeCN, 1Pr·MeCN, 2Et·MeCN, and 2Pr·MeCN with trans-cofacial DTDA radical cation and eclipsed-cofacial TCNQ radical anion dimers. A slight increase in the substituent chain length to butyl affords the solvate 1Bu·0.5MeCN or the nonsolvate 1Bu. The nonsolvate 1Bu can be exclusively isolated using propionitrile (EtCN), whereas the isostructural selenium analogue 2Bu crystallizes from MeCN. The crystal packing in 1Bu·0.5MeCN and 1Bu/2Bu is distinctively different: rare one-dimensional (1D) columnar π-stacks of evenly spaced TCNQ radical anions with periodic distortions along the vertical stacking direction and cis-cofacial DTDA dimers in 1Bu·0.5MeCNvs discrete, non-eclipsed-cofacial TCNQ dimers and trans-antarafacial DTDA/DSDA dimers in 1Bu/2Bu. The nonsolvated structure 1Pr with trans-cofacial DTDA and non-eclipsed-cofacial TCNQ dimers can be isolated from EtCN. Single-crystal and powder X-ray diffraction methods confirmed a thermally driven, irreversible, single-crystal-to-single-crystal structural transformation between 1Pr·MeCN and 1Pr. Thermogravimetric analyses of all nonsolvated salts show varied, yet robust, thermal behavior, while the thermal behavior of the solvates is consistent with more facile lattice solvent loss from structures with longer N-alkyl chains. Variable-temperature magnetic susceptibility measurements indicate that all structures are diamagnetic at low temperatures. However, thermally populated magnetic states could be observed for 1Et·MeCN, 1Et·EtCN, 1Pr·MeCN, 1Bu·0.5MeCN, 1Bu, and 2Bu at higher temperatures. This can be correlated with desolvation and structural changes that lead to the generation of weakly antiferromagnetically coupled non-eclipsed-cofacial TCNQ dimers, in agreement with results from density functional theory (DFT) calculations. peerReviewed

Controllable preparation is the current frontier in the field of inorganic nanomaterial-based artificial enzymes (nanozymes). For ferrites, the factors affecting cation occupancy are very complex, making the modulation of cation occupancy extremely challenging. Herein, we report a new strategy to modulate the cation occupancy of manganese ferrite (MFO) based on the structural properties of nanoclay (i.e., montmorillonite K10). It demonstrates that montmorillonite K10 mainly changes the valence state and occupancy of manganese ions in manganese ferrite and not iron ions. K10 increases the proportion of Mn (II) in manganese ferrite and causes more manganese ions to migrate to the tetrahedral sites. As expected, the prepared new inorganic compound possesses excellent enzyme-like catalytic activities and antibacterial functional properties, which are attributed to Mn (II) accelerating Fe (III) reduction and hydroxyl radical formation. Furthermore, steady-state kinetic assays are used to study the reaction mechanism in detail.

The influence of dynamical ion-ion correlations and ion pairing on salt transport in ion exchange membranes remain poorly understood. In this study, we use the framework of Onsager transport coefficients within atomistic molecular dynamics simulations to study the impact of ion-ion correlated motion on salt transport in hydrated polystyrene sulfonate membranes and compare with the results from aqueous salt solutions. At sufficiently high salt concentrations, cation-anion dynamical correlations exert a significant influence on both salt diffusivities and conductivities. Anion-anion distinct correlations, arising from the imbalance between the concentration of free (mobile) cations and anions, and the retarding effect of the fixed charge groups on cations, proves to be an additional important feature for polymer membranes. Our results demonstrate that dynamical correlations should become an important consideration in experimental measurements of salt diffusivities and conductivities for non-dilute salt solutions in polymer membranes.

Antisense oligonucleotides (ASOs) are an important emerging therapeutic; however, they struggle to enter cells without a delivery vehicle, such as a cationic polymer. To understand the role of polymer architecture for ASO delivery, five linear polymers and five diblock polymers (capable of self-assembly into micelles) were synthesized with varying cationic groups. After complexation of each polymer/micelle with ASO, it was found that less bulky cationic moieties transfected the ASO more effectively. Interestingly, however the ASO internalization trend was the opposite of the transfection trend for cationic moiety, indicating internalization is not the major factor in determining transfection efficiency for this series. Micelleplexes (micelle-ASO complexes) generally enable higher transfection efficacy as compared to polyplexes (linear polymer-ASO complexes). Additionally, the order of addition of cells and complexes was explored. Linear polyplexes showed better transfection efficiency in adhered cells, whereas micelleplexes delivered the ASO more efficiently when the cells and micelleplexes were added simultaneously. This phenomenon may be due to increased cell-complex interactions as micelleplexes have increased colloidal stability compared to polyplexes. These findings emphasize the importance of polymer composition and architecture in governing the cellular interactions necessary for transfection, thus allowing advancement in the design principles for nonviral nucleic acid delivery formulations.

We report observation and photoelectron spectroscopic characterization of sodium cationization on four doubly deprotonated mononucleotide dianions Na

Herein, we report a highly efficient and unprecedented approach for heteroarylation of congested α-bromoamides via electrophilic aromatic substitution of imidazo-heteroarenes and indolizines under mild reaction conditions (room temperature, metal, and oxidant free). The participation of an in situ generated aza-oxyallyl cation as an alkylating agent is the hallmark of this transformation. The method was readily adapted to synthesize novel imidazo-heteroarene-fused dibenzoazepinone architectures of potential medicinal value.

The direct conversion of methane to methanol would have wide reaching environmental and industrial impact. Copper containing zeolites can perform this reaction at low temperatures and pressures at a previously defined O(2) activated [Cu(2)O](2+) site. However, after autoreduction of the copper containing zeolite mordenite and removal of the [Cu(2)O](2+) active site, the zeolite is still methane reactive. In this study, we use diffuse reflectance UV-Vis, magnetic circular dichroism, resonance Raman, electron paramagnetic resonance, and X-ray absorption spectroscopies to unambiguously define a mononuclear [CuOH](+) as the CH(4) reactive active site of the autoreduced zeolite. The rigorous identification of a mononuclear active site allows a reactivity comparison to the previously defined [Cu(2)O](2+) active site. We perform kinetic experiments to compare the reactivity of the [CuOH](+) and [Cu(2)O](2+) sites and find that the binuclear site is significantly more reactive. From analysis of density functional theory calculations, we elucidate that this increased reactivity is a direct result of stabilization of the [Cu(2)OH](2+) H-atom abstraction product by electron delocalization over the two Cu cations via the bridging ligand. This significant increase in reactivity from electron delocalization over a binuclear active site provides new insight for the design of highly reactive oxidative catalysts.

The transformation of colloidal semiconductor magic-size clusters (MSCs) from zinc to cadmium chalcogenide (ZnE to CdE) at low temperatures has received scant attention. Here, we report the first room-temperature evolution of CdE MSCs from ZnE samples and our interpretation of the transformation pathway. We show that when prenucleation stage samples of ZnE are mixed with cadmium oleate (Cd(OA)₂), CdE MSCs evolve; without this mixing, ZnE MSCs develop. When ZnE MSCs and Cd(OA)₂ are mixed, CdE MSCs also form. We propose that Cd(OA)2 reacts with the precursor compounds (PCs) of the ZnE MSCs but not directly with the ZnE MSCs. The cation exchange reaction transforms the ZnE PCs into CdE PCs, from which CdE MSCs develop. Our findings suggest that in reactions that lead to the production of binary ME quantum dots, the E precursor dominates the formation of binary ME PCs (M = Zn or Cd) to have similar stoichiometry. The present study provides a much more profound view of the formation and transformation mechanisms of the ME PCs.

As a toxic substance on human health produced in food thermal treatment, simple analytical approaches are highly desired for the detection of acrylamide (ACR) in foods. With the aid of exonuclease III (Exo III), a simple fluorescence sensor was proposed based on carboxyfluorescein-labeled double-stranded DNA (FAM-dsDNA) and a cationic conjugated polymer (PFP). Fluorescence resonance energy transfer (FRET) efficiency between FAM and PFP was changed with and without ACR. When ACR was present, ACR and single-stranded DNA (P1, ssDNA) formed an adduct, allowing free FAM-labeled complementarity strand DNA (P2, FAM-csDNA) to appear in the solution and avoiding the digestion of P2 by Exo III. After the addition of PFP, the interaction of PFP and FAM induced strong FRET. Under optimized conditions, ACR was detected with a limit of detection (LOD) of 0.16 μM. According to this biosensor, a LOD of 1.3 μM in water extract samples was observed with a good recovery rate (95-110 %).

In a randomized complete block design, 40 lactating Holstein cows (average 98 d in milk and 41 kg/d of milk yield) were randomly assigned to 1 of 4 diets: (1) containing soybean meal as the major protein supplement (CON diet); (2) CON diet with high-protein dried corn distillers grains at 20% on a dry matter (DM) basis by replacing mainly soybean meal (DG diet); (3) DG diet except that high-protein dried corn distillers grains with yeast bodies (extracted after corn ethanol production) was used (DGY diet); or (4) DG diet supplemented with sodium bicarbonate and potassium carbonate to elevate the dietary cation and anion difference (DCAD; DG-DCAD diet). The DCAD of CON, DG, DGY, and DG-DCAD were 185, 62, 67, and 187 mEq/kg of DM, respectively. The experiment began with a 10-d covariate period and then cows were fed the experimental diets for 5 wk (2-wk diet adaptation and 3-wk data collection periods). Dry matter intake and milk yield were measured daily, and spot urine and fecal samples were collected in the last week of the experiment to measure nutrient digestibility; N, S, and P utilization and excretion; and in vitro NH

Mechanosensitive cation channels and Ca2+ influx through these channels play an important role in the regulation of endothelial cell functions. Transient receptor potential canonical channel 6 (TRPC6) is a diacylglycerol-sensitive nonselective cation channel that forms receptor-operated Ca2+ channels in a variety of cell types. Piezo1 is a mechanosensitive cation channel activated by membrane stretch and shear stress in lung endothelial cells. In this study, we report that TRPC6 and Piezo1 channels both contribute to membrane stretch-mediated cation currents and Ca2+ influx or increase in cytosolic-free Ca2+ concentration ([Ca2+]cyt) in human pulmonary arterial endothelial cells (PAECs). The membrane stretch-mediated cation currents and increase in [Ca2+]cyt in human PAECs were significantly decreased by GsMTX4, a blocker of Piezo1 channels, and by BI-749327, a selective blocker of TRPC6 channels. Extracellular application of 1-oleoyl-2-acetyl- sn-glycerol (OAG), a membrane permeable analog of diacylglycerol, rapidly induced whole cell cation currents and increased [Ca2+]cyt in human PAECs and human embryonic kidney (HEK)-cells transiently transfected with the human TRPC6 gene. Furthermore, membrane stretch with hypo-osmotic or hypotonic solution enhances the cation currents in TRPC6-transfected HEK cells. In HEK cells transfected with the Piezo1 gene, however, OAG had little effect on the cation currents, but membrane stretch significantly enhanced the cation currents. These data indicate that, while both TRPC6 and Piezo1 are involved in generating mechanosensitive cation currents and increases in [Ca2+]cyt in human PAECs undergoing mechanical stimulation, only TRPC6 (but not Piezo1) is sensitive to the second messenger diacylglycerol. Selective blockers of these channels may help develop novel therapies for mechanotransduction-associated pulmonary vascular remodeling in patients with pulmonary arterial hypertension.

Ionic liquids (ILs), defined as liquid salts composed of anions and cations, have the advantage of allowing constituent ions to be stably absorbed through biological membranes, such as skin. However, limited information is currently available on the effects of the physicochemical properties of constituent ions on the membrane permeation of ILs. Therefore, we herein investigated the effects of the polarity of constituent cations on the membrane permeation of each constituent ion from IL. Various ILs were prepared by selecting lidocaine (LID) as a cation and a series of p-alkylbenzoic acids with different n-octanol/water partition coefficients (K

Despite its critical nature, the role of matrix in calcium oxalate stone formation is poorly understood. The wide diversity of proteins comprising matrix has contributed to the ambiguity. This study compares the protein distributions measured by mass spectrometry in human calcium oxalate stone matrix to that observed in cat stone matrix, because cats share many clinical characteristics of their stone disease with humans. The observed protein distributions were analyzed in the context of a recent model based on the aggregation of strongly anionic and strongly cationic proteins which includes selective adsorption of other proteins based on total charge. Matrix protein distributions shared many common features between species, including enrichment of both strongly anionic and strongly cationic proteins, increased total charge in matrix proteins compared to urine proteins, and a high degree of similarity of prominent strongly anionic proteins in the matrix of both species. However, there was weaker overlap of the specific dominant proteins in other regions of the net charge distribution. Collectively, these observations support the conceptual model where the strongly anionic proteins associate most strongly with the calcium oxalate crystal surfaces, while the other proteins associate with the strongly anionic proteins through non-specific, charge interactions with each other to create stones. Also, cats appear to be the best animal model of human stone disease identified to date based on these similarities.

Rhamnogalacturonan-II (RG-II) is a complex pectic domain in plant primary cell walls. In vivo, most RG-II domains are covalently dimerised via borate diester bridges, essential for correct cell-wall assembly, but the dimerisation of pure RG-II monomers by boric acid in vitro is extremely slow. Cationic ‘chaperones’ can promote dimerisation, probably by overcoming the mutual repulsion between neighbouring anionic RG-II molecules. Highly effective artificial chaperones include Pb2+ and polyhistidine, but the proposed natural chaperones remained elusive. We have now tested cationic peptide fragments of several Arabidopsis thaliana arabinogalactan-proteins (AGPs) as candidates. Fragments of AGP17, 18, 19 and 31 were effective, typically at ∼25 µg/ml (9–19 µM), promoting the boron bridging of 16–20 µM monomeric RG-II at pH 4.8 in vitro. Native AGP31 glycoprotein was also effective, and hexahistidine was moderately so. All chaperones tested interacted reversibly with RG-II and were not consumed during the reaction; thus they acted catalytically, and may constitute the first reported boron-acting enzyme activity, an RG-II borate diesterase. Many of the peptide chaperones became less effective catalysts at higher concentration, which we interpret as due to the formation of RG-II–peptide complexes with a net positive charge, as mutually repulsive as negatively charged pure RG-II molecules. The four unique AGPs studied here may serve an enzymic role in the living plant cell, acting on RG-II within Golgi cisternae and/or in the apoplast after secretion. In this way, RG-II and specific AGPs may contribute to cell-wall assembly and hence plant cell expansion and development.

Studies of protein adsorption on reversed-phase and ion exchange stationary phases demonstrated an increase in retention with increasing pressure, which is interpreted as a standard partial molar volume decrease during the transition of the protein from a mobile to a stationary phase. Investigation of the pressure effect on the retention of lysozyme and IgG on a cation exchange column surprisingly revealed a negative retention trend with the increase of pressure. Further investigation of this phenomenon was performed with β-lactoglobulin, which enabled adsorption to be studied on both cation and anion exchange columns using the same mobile phase with a pH of 5.2. The same surface charge and standard partial molar volume in the mobile phase allowed us to examine only the effect of adsorption. Interestingly, a negative retention trend with a pressure increase occurred on an anion exchange column while a positive trend was present on a cation exchange column. This indicates that the interaction type governs the change in the standard partial molar volume during adsorption, which is independent of the applied pressure. Increasing the protein charge by decreasing the pH of the mobile phase to 4 reversed the retention trend (into a negative) with a pressure increase on the cation exchange column. A further decrease of the pH value resulted in an even more pronounced negative trend. This counterintuitive behavior indicates an increase in the standard partial molar volume during adsorption with the protein charge, possibly due to intermolecular repulsion of adsorbed protein molecules. While a detailed mechanism remains to be elucidated, presented results demonstrate the complexity of ion exchange interactions that can be investigated simply by changing the column pressure.

The last decade has witnessed a rapid development of nano- and microparticle-based optical ion sensors, including ion-selective optodes (ISOs). While the application of nano-ISOs has shown promising performance for sensing inorganic ions, polyion sensing using nanoscale ISOs has encountered significant interference in complex samples such as blood plasma. Recently, we have reported on a new polyion sensing principle that operates through a novel mechanism to overcome this challenge. The new sensing mechanism showed improved characteristics not observed with conventional ion-exchange type sensors, but the precise mechanism of operation remained thus far unclear. This paper aims to clarify how protamine, the arginine-rich target polycation, behaves during optical signal transduction to give dramatically improved selectivity. Based on thermodynamic data, sensor performance and ζ-potential analysis, two discrete phases of protamine extraction are identified. Initially, protamine extracts into the bulk nanosensor phase, a process that is concurrent with the optical signal change. This is then followed by protamine accumulation onto the nanosensor surface, which starts only upon saturation of the optical signal change. The data indicate that the improved selectivity is due to the inability of small ions to form a sufficiently strong interaction with an active sensing ingredient, DNNS

A strong anion exchanger applied for ion chromatography is described by grafting methacrylamido propyl trimethyl ammonium chloride onto hydrolyzed poly(glycidyl methacrylate-divinylbenzene) substrate. The anion exchanger has been in detail characterized and the final capacity of the anion exchanger can be readily manipulated by different monomer amounts. It exhibited obvious temperature-sensitive properties and large tolerance to the samples with high ionic strength. The obtained anion exchanger demonstrated effective separation ability towards the common seven inorganic anions within 12 min and high separation efficiency, for example, 58 000/m of theoretical plate count for chloride.

Room temperature molecular dynamics (MD) simulations of the globular protein α-lactalbumin in aqueous solutions containing BMIM (1-butyl-3-methylimidazolium) based ionic liquids (ILs) with a series of Hofmeister anions have been carried out. In particular, effects of anions of different shapes/sizes and hydrophobic/hydrophilic characters, namely, thiocyanate (SCN

Ion-surface interactions can alter the properties of nanopores and dictate nanofluidic transport in engineered and biological systems central to the water-energy nexus. The ion adsorption process, known as "charge regulation", is ion-specific and is dependent on the extent of confinement when the electric double layers (EDLs) between two charged surfaces overlap. A fundamental understanding of the mechanisms behind charge regulation remains lacking. Herein, we study the thermodynamics of charge regulation reactions in 20 nm SiO

Organic cation transporters (OCTs) 1, 2, and 3 facilitate cellular uptake of structurally diverse endogenous and exogenous substances. However, their substrate and inhibitor specificity are not fully understood. We performed a broad

Counterions are important constituents for the structure and function of nucleic acids. Using

Nucleophilic substitution covalent modification ion/ion reactions were carried out in a linear quadrupole ion trap between the doubly protonated peptides KGAILKGAILR, RARARAA, and RKRARAA and isomers of either singly deprotonated 3- or 4-sulfobenzoic acid (

The development of high quality, non-toxic (i.e., heavy-metal-free), and functional quantum dots (QDs) via ‘green’ and scalable synthesis routes is critical for realizing truly sustainable QD-based solutions to diverse technological challenges. Herein, we demonstrate the low-temperature all-aqueous-phase synthesis of silver indium sulfide/zinc (AIS/Zn) QDs with a process initiated by the biomineralization of highly crystalline indium sulfide nanocrystals, and followed by the sequential staging of Ag(+) cation exchange and Zn(2+) addition directly within the biomineralization media without any intermediate product purification. Therein, we exploit solution phase cation concentration, the duration of incubation in the presence of In(2)S(3) precursor nanocrystals, and the subsequent addition of Zn(2+) as facile handles under biomineralization conditions for controlling QD composition, tuning optical properties, and improving the photoluminescence quantum yield of the AIS/Zn product. We demonstrate how engineering biomineralization for the synthesis of intrinsically hydrophilic and thus readily functionalizable AIS/Zn QDs with a quantum yield of 18% offers a ‘green’ and non-toxic materials platform for targeted bioimaging in sensitive cellular systems. Ultimately, the decoupling of synthetic steps helps unravel the complexities of ion exchange-based synthesis within the biomineralization platform, enabling its adaptation for the sustainable synthesis of ‘green’, compositionally diverse QDs.

Visible light-regulated metal-free polymerizations have attracted considerable attention for macromolecular syntheses in recent years. However, few organic photocatalysts show high efficiency and strict photocontrol in cationic polymerizations. Herein, we introduce monophosphonium-doped polycyclic arenes as an organic photocatalyst, which features the high tunability, broad redox window, long excited state lifetime, and excellent temporal control in the cationic reversible addition-fragmentation chain transfer polymerization of vinyl ethers. A correlation of the catalytic performance and the photophysical and electrochemical properties of photocatalysts is also discussed.