Search results for "Anions"
showing 10 items of 126 documents
Conductance and Ion Selectivity of a Mesoscopic Protein Nanopore Probed with Cysteine Scanning Mutagenesis
2005
Nanometer-scale proteinaceous pores are the basis of ion and macromolecular transport in cells and organelles. Recent studies suggest that ion channels and synthetic nanopores may prove useful in biotechnological applications. To better understand the structure-function relationship of nanopores, we are studying the ion-conducting properties of channels formed by wild-type and genetically engineered versions of Staphylococcus aureus alpha-hemolysin (alphaHL) reconstituted into planar lipid bilayer membranes. Specifically, we measured the ion selectivities and current-voltage relationships of channels formed with 24 different alphaHL point cysteine mutants before and after derivatizing the c…
Sterically geared tris-thioureas; transmembrane chloride transporters with unusual activity and accessibility
2015
Tris-N-arylthioureas derived in one step from 1,3,5-tris(aminomethyl)-2,4,6-triethylbenzene are remarkably effective anion carriers. With optimised aryl substituents their activities come close to the best currently known, suggesting that they might find use as readily available standards in anion transport research.
A bis(triazole)benzamide receptor for the complexation of halide anions and neutral carboxylic acid guests. Guest-controlled topicity and self-assemb…
2012
Bis(triazole)benzamide 1 has been readily synthesized by means of Cu-catalyzed 1,3-dipolar cycloaddition and its ability to bind halide anions and neutral gallic acid derivative 12GA has been theoretically and experimentally investigated. The cavity defined by the N-H amide group and the vicinal aromatic hydrogens is suitable to form H-bonding arrays with halide guests. The stability of complexes 1·Cl- and 1·Br- is very similar, as DFT calculations predict and 1H NMR titration experiments confirm. The zigzag "anti" conformation of the molecule generates two regions with complementary positive and negative potentials that favor the statistical complexation of two molecules of the neutral car…
Bis(5-tert-butyl-2-hydroxy-3-methylbenzyl)(6-hydroxyhexyl)ammonium chloride monohydrate, an anion receptor complex
2007
In the title compound, C(30)H(48)NO(3)(+) x Cl(-) x H(2)O, the cation acts with a water molecule as a chloride ion receptor. The chloride ion forms three strong intramolecular hydrogen bonds. The water molecule forms both an intramolecular bridge between one phenol H atom and the chloride ion, and an intermolecular link to the aliphatic alcohol O atom. Weak intermolecular C-H...Cl and C-H ...O hydrogen bonds provide additional packing interactions.
Anion-Exchange Properties of Trifluoroacetate and Triflate Salts of N-Alkylammonium Resorcinarenes
2016
The synthesis of N-benzyl- and N-cyclohexylammonium resorcinarene trifluoroacetate (TFA) and triflate (OTf) salt receptors was investigated. Solid-state analysis by single-crystal X-ray diffraction revealed that the N-alkylammonium resorcinarene salts (NARSs) with different upper substituents had different cavity sizes and different affinities for anions. Anion-exchange experiments by mixing equimolar amounts of N-benzylammonium resorcinarene trifluoroacetate and N-cyclohexylammonium resorcinarene triflate, as well as N-benzylammonium resorcinarene triflate and N-cyclohexylammonium resorcinarene trifluoroacetate showed that the NARS with flexible benzyl groups preferred the larger OTf anion…
Facilitated Anion Transport Induces Hyperpolarization of the Cell Membrane That Triggers Differentiation and Cell Death in Cancer Stem Cells
2015
Facilitated anion transport potentially represents a powerful tool to modulate various cellular functions. However, research into the biological effects of small molecule anionophores is still at an early stage. Here we have used two potent anionophore molecules inspired in the structure of marine metabolites tambjamines to gain insight into the effect induced by these compounds at the cellular level. We show how active anionophores, capable of facilitating the transmembrane transport of chloride and bicarbonate in model phospholipid liposomes, induce acidification of the cytosol and hyperpolarization of plasma cell membranes. We demonstrate how this combined effect can be used against canc…
Synthesis, Structure and Anion Sensing Properties of a Dicationic Bis(imidazolium)-Based Cyclophane
2018
The preparation and sensing properties of a tetracyclic cyclophane receptor containing two imidazolium rings as anion binding sites and two fluorene rings as fluorescent signaling units, are reported. The receptor behaves as a selective fluorescent chemosensor molecule for inorganic phosphates. H-NMR spectroscopical data clearly indicate the simultaneous occurrence of charge-assisted aromatic and aliphatic C−H noncovalent interactions. PCM/DFT calculations have been carried out to predict the structures of the complexes formed with one and two molecules of PF , HPO and HPO .
Thermo-responsive hydrogels from cellulose-based polyelectrolytes and catanionic vesicles for biomedical application.
2016
In this study, negatively charged catanionic vesicles/hydrophobically modified hydroxyethylcellulose polymers thermo-responsive hydrogels have been fabricated. Vesicular aggregates were found to act as multifunctional junctions for networking of modified-cellulose water solutions. The contributions of the electrostatic and hydrophobic interactions were evaluated by changing either vesicles composition or the polymer hydrophobic substitution. Thermal-induced size and lamellarity of hydrogel-enclosed vesicles were detected, with further polygonal shape changes induced by cellulose-based polymer addition. The thermal transition was also found to tune hydrogel mechanical behaviour. The network …
N-Propyl-N′-2-pyridylurea-modified silica as mixed-mode stationary phase with moderate weak anion exchange capacity and pH-dependent surface charge r…
2018
Herein, we present a novel silica-based stationary phase modified with N-propyl-N'-2-pyridylurea selector. Due to the weakly basic properties of the pyridine selector and the presence of residual silanols after selector immobilization, a zwitterionic surface with a pI observed at approximately pH 5.5 was measured by electrophoretic light scattering in pH-dependent ζ-potential determinations. The capability of the new N-propyl-N'-2-pyridylurea-modified silica to serve as mixed-mode stationary phase was investigated. For this purpose, it was characterized under RP and HILIC conditions using test mixtures. Subsequent classification of this stationary phase in comparison to in-house and commerc…
The Radical Trap in Atom Transfer Radical Polymerization Need Not Be Thermodynamically Stable. A Study of the MoX3(PMe3)3 Catalysts
2005
The molybdenum(III) coordination complexes MoX(3)(PMe(3))(3) (X = Cl, Br, and I) are capable of controlling styrene polymerization under typical atom transfer radical polymerization (ATRP) conditions, in conjunction with 2-bromoethylbenzene (BEB) as an initiator. The process is accelerated by the presence of Al(OPr(i))(3) as a cocatalyst. Electrochemical and synthetic studies aimed at identifying the nature of the spin trap have been carried out. The cyclic voltammogram of MoX(3)(PMe(3))(3) (X = Cl, Br, I) shows partial reversibility (increasing in the order ClBrI) for the one-electron oxidation wave. Addition of X(-) changes the voltammogram, indicating the formation of MoX(4)(PMe(3))(3) f…