Effect of counterions on comb-like polycarboxylate conformation in aqueous solutions

<p>Laser light scattering (LLS) and conductivity experiments were performed to investigate the effect of counterions on the conformation of polycarboxylate comb-like copolymers (PCEs) in aqueous solutions. The addition of monovalent ions (i.e., Na⁺ and K⁺) to dilute polycarboxylate comb-like copolymer solutions induced a slight shrinking of the molecular chains because of the screening of electrostatic intramolecular repulsion. Varying complexation phenomena, such as the formation of intramolecular complexation at certain Ca²⁺ concentrations and a transition between intermolecular and intramolecular complexations at different Ca²⁺ concentrations, were closely associated with Ca²⁺ concentration. Therefore, Ca²⁺ exerted a more complex influence on the conformation of PCEs with side chains containing polyethylene oxide (PEO) with different grafting densities. In addition, various combination types of Ca²⁺ with carboxylic groups were confirmed by theoretical simulation.</p

Supplementary document for Complex Wave and Phase Retrieval from A Single Off-Axis Interferogram - 6140313.pdf

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Synthesis, Structures, and Norbornene Polymerization Behavior of Neutral Nickel(II) and Palladium(II) Complexes Bearing Aryloxide Imidazolidin-2-imine Ligands

A series of novel aryloxide imidazolidin-2-imine bidentate neutral Ni­(II) and Pd­(II) complexes bearing five- and six-membered chelate ring structures were synthesized and characterized. X-ray diffraction analysis results revealed that all of the Ni­(II) complexes (<b>Ni1</b>–<b>Ni3</b>) and Pd­(II) complexes (<b>Pd1</b> and <b>Pd3</b>) adopted an almost square-planar geometry. In the presence of various cocatalysts such as MAO, MMAO, Et₂AlCl, and EtAlCl₂, all of the Ni­(II) and Pd­(II) complexes exhibited remarkably high activities (up to 2.6 × 10⁷ g of PNB (mol of M)⁻¹ h^–1) toward the addition polymerization of norbornene. These catalyst systems produced high-molecular-weight polynorbornene (PNB) with narrow molecular weight distribution, except for the insoluble PNB obtained with <b>Pd1</b>–<b>Pd3</b>/MAO systems. The Pd­(II) complexes showed particularly good thermostability with a high activity of 1.56 × 10⁷ g of PNB (mol of Pd)⁻¹ h^–1 even at 80 °C. These complexes are rare examples of neutral Ni­(II) and Pd­(II) complexes bearing aryloxide-functionalized imidazolidin-2-imine ligands in the field of olefin polymerization

Computational Simulations of Adsorption Behavior of Anionic Surfactants at the Portlandite–Water Interface under Sulfate and Calcium Ions

The adsorption behaviors of two kinds of anionic surfactants (called HSO4 and HPO4, respectively) with different negatively charged hydrophilic head groups (sulfate and phosphate groups) under different concentrations of sulfate and calcium ions at the portlandite–water interface are investigated by molecular dynamics simulations. Although the adsorption strength of HPO4 is much greater than that of HSO4, the desorption energy of HSO4 is slightly greater at an early stage of desorption due to a more perpendicular orientation and denser packing of hydrophobic tail chains. After adding ions, the sulfate ion has a significant weakening effect due to competitive adsorption, and the negative influence of the calcium ion is weaker, and it even slightly promotes the adsorption at low concentration. Due to the stronger electrostatic interaction of phosphate head groups with the portlandite surface, adsorption strength and adsorption stability for HPO4 are always greater than that of HSO4 under the interference of sulfate ions. The competitive adsorption of the sulfate ion significantly weakens the interaction of hydrophilic head groups with portlandite and the dense packing of two surfactants. The calcium ion with low concentration approaches the portlandite surface and acts as an ion bridge to slightly enhance the adsorption of the surfactant. The ion bridging effect is stronger in the HPO4 system than in the HSO4 system

Silver-Mediated C–H Activation: Oxidative Coupling/Cyclization of <i>N</i>-Arylimines and Alkynes for the Synthesis of Quinolines

A silver-mediated tandem protocol for the synthesis of quinolines involving the oxidative coupling/cyclization of <i>N</i>-arylimines and alkynes has been developed. We demonstrated that scenario-dependent metalation could occur either at the <i>ortho</i> C–H bond of an <i>N</i>-arylimine through protonation-driven enhancement of acidity or at the terminal C–H bond of an alkyne by virtue of the carbophilic π-acidity of silver. The diverse set of mechanistic manifolds implemented with a single type of experimental protocol points toward the importance of stringent reactivity analysis of each individual potentially reactive molecular site. Importantly, the direct arene C–H bond activation provides a unique and distinct mechanistic handle for the expansion of reactivity paradigms for silver. As expected, the protocol allows for the incorporation of both internal and terminal alkynes into the products, and in addition, both electron-withdrawing and -donating groups are tolerated on <i>N</i>-arylimines, thus enabling the vast expansion of substituent architectures on quinoline framework. Further, an intriguing phenomenon of structural isomerization and chemical bond cleavage has been observed for aliphatic internal alkynes

Ultrafast Kinetic DNA Hybridization Assay Based on the Visualization of Threshold Turbidity

We report herein the development of an ultrafast kinetic DNA hybridization assay system based on the visualization of threshold turbidity associated with the assembly of polystyrene nanospheres. Initial testing of our diagnostic protocol on a sequence associated with the anthrax lethal factor indicates that a visually identifiable, turbidity-definitive, and kinetic threshold state could be reached at a time as short as 1 min. The assay scheme allows for both target concentration quantification and differentiation of single base mismatches through registry of the threshold turbidity onset time. The positively charged environment on nanospheres not only contributes to expedited signal generation but also imparts cooperative DNA binding properties. The kinetic visual protocol complements conventionally used thermodynamic strategies and provides an entry point for the circumvention of assay issues associated with ill-defined thermodynamic end points

Doping Metal Elements of WO₃ for Enhancement of NO₂‑Sensing Performance at Room Temperature

WO₃ nanoparticles doped with Sb, Cd, and Ce were synthesized by a chemical method to enhance the sensing performance of WO₃ for NO₂ at room temperature. The doping with Sb element can significantly enhance the NO₂-sensing properties of WO₃. Upon exposure to 10 ppm of NO₂, particularly the 2 wt % Sb-doped WO₃ sample exhibits a 6.8-times higher response and an improved selectivity at room temperature compared with those of undoped WO₃. The enhanced NO₂-sensing mechanism of WO₃ by doping is discussed in detail, which is mainly ascribed to the increase of oxygen vacancies in the doped WO₃ samples as confirmed by Raman, photoluminescence, and X-ray photoelectron spectroscopy spectra. In addition, the narrower band gap may also be responsible for the enhancement of response as observed from the corresponding ultraviolet–visible spectra

Diversified Nanoparticle Assembly Pathways: Materials Architecture Control Beyond the Amphiphilicity Paradigm

The functional versatility of a chemical system is ultimately dictated by the availability of distinctly accessible architectures. The generation of a diverse array of assembled constructs from a single type of nanoscale building block is a promising yet largely elusive goal. We report herein the utility of a monolayer-modified nanoparticle for the creation of a broad range of architectures. The versatile modes of assembly complement the conventionally used, amphiphilicity-driven strategy. We demonstrate that one can vary the nanoparticle assembly pathways within the confines of solvent media through the modulation of interactions and partitioning of nanoparticles. Merging of the molecular-scale design and higher-ordered arrangement enables diversified assembly through the manipulation of experimental parameters such as solvent, pH, affinity molecule, and temperature. Microfluidics provides an effective channel to control the monodispersity and size on all the architectures attainable in the bulk solution phase. These observations could be further explored for an understanding of diversified matter organization and order generation beyond the amphiphilicity paradigm

Additional file 1 of RAGE displays sex-specific differences in obesity-induced adipose tissue insulin resistance

Additional file 1: Figure S1. Female RAGE deficiency improved glucose and insulin tolerance in normal diet mice. (A) Glucose tolerance tests (GTT) and Area under the curve (AUC) in each group. n = 6 per group. *p < 0.05 vs. female RAGE−/−-HFD-F mice; #p < 0.05 vs. female RAGE−/−-ND-F mice. (B) Insulin tolerance tests (ITT) and AUC in each group. n = 6 per group. *p < 0.05 vs. female RAGE−/−-HFD-F mice; #p < 0.05 vs. female RAGE−/−-ND-F mice. ND; normal diet. All group data are shown as mean ± SEM

Additional file 2 of RAGE displays sex-specific differences in obesity-induced adipose tissue insulin resistance

Additional file 2: Table S1. Sequences of primers used in the study