Search results for "ionic"
showing 10 items of 2016 documents
Solution properties of polyelectrolytes. II. Comparison of the effects of both polyion and eluent salt concentrations on the calibrations in aqueous …
1987
The elution behaviour of charged water-soluble polymers (sodium polystyrene sulphonate) in both salt-free and NaCl-containing aqueous mobile phases has been investigated by size-exclusion chromatography. A comparative analysis has been established between the results as a function of polyion and salt concentrations, which demonstrates that the chromatographic behaviour is similar in both cases. The variation of the slopes of the different concentration-dependent calibration curves is discussed in terms of polyelectrolyte conformational changes. Finally, a semi-empirical model has been developed to predict the dependence of the elution volume in either polyion or salt concentration, and its …
Über den mechanismus der anionischen polymerisation von acrylnitril mit triphenylphosphin. 7. Mitt. über makrozwitterionen
1972
Die anionische Polymerisation von Acrylnitril mit Triathylphosphin als Initiator in Dimethylformamid wurde bei verschiedenen Temperaturen und unterschiedlichem Verhaltnis der Monomer/Initiator-Konzentrationen untersucht. Erganzt durch spektroskopische Endgruppenbestimmung der Polymeranionen konnte mittels 1H-NMR-Spektroskopie und Gelchromatographie (GPC) sowie emissionsspektralanalytischer Phosphorbestimmung an den rohen und den durch Umfallungen bzw. GPC fraktionierten Polymerproben gezeigt werden, das hier neben einer ubertragung teilweise eine Polymerisation Uber Makrozwitterionen auftritt. Fur die Bildung von Makrozwitterionen, , sind jedoch Mindestwerte des Monomer/Initiator-Verhaltnis…
Expression, regulation and function of carrier proteins for cationic amino acids.
2001
Different carrier proteins exhibiting distinct transport properties participate in cationic amino acid transport. There are sodium-independent systems, such as b+, y+, y+L and b0,+, and a sodium-dependent system B0,+, most of which have now been identified at the molecular level. In most non-epithelial cells, members of the cationic amino acid transporter (CAT) family mediating system y+ activity seem to be the major entry pathway for cationic amino acids. CAT proteins underlie complex regulation at the transcriptional, post-transcriptional and activity levels. Recent evidence indicates that individual CAT isoforms are necessary for providing the substrate for nitric oxide synthesis, for ex…
Cationic Amino Acid Transporters (CATs)
2002
When the transport properties of mCAT-1 were described in 1991, the y+ carrier and major transporter for cationic amino acids seemed to be discovered. Today, we know that there are at least three different CAT isoforms that mediate y+ activity and the family might be growing. In addition, transport systems for cationic amino acids other than y + have been described and proteins that induce the respective transport activities have been identified. Consequently, the transport of cationic amino acids appears to be a complex process involving many proteins— carriers and possibly also regulatory proteins—whose expression is cell-specific and dependent on a variety of external stimuli. The multit…
Interpenetrated 3D porous scaffolds of silk fibroin with an amino and octadecyl functionalized hyaluronic acid
2015
An ethylenediamine (EDA) and octadecylamine (-C18) hyaluronic acid (HA) derivative, named HA-EDA-C18, has been used for the production of interpenetrated composite biomaterials with silk fibroin. The peculiar ionic strength sensibility of this HA derivative allows the production of porous matrices without the need for chemical crosslinking. Scaffolds have been produced through a salt leaching procedure by exploiting the properties of silk fibroin and HA-EDA-C18 to physically crosslink when forced through a syringe loaded with NaCl. The porosity of the sponges, comprised between 70-80%, was dependent on the amount of each polymer and NaCl size distribution. Moreover, through FT-IR analysis, …
Insights into the Formation and Structures of Molecular Gels by Diimidazolium Salt Gelators in Ionic Liquids or “Normal” Solvents
2016
Insights are provided into the properties of molecular gels formed by diimidazolium salts both in “normal” solvents and ionic liquids. These materials can be interesting for applications in green and sustainable chemistry in which ionic liquids play a significant role, like catalysis and energy. In particular, two positional isomers of a diimidazolium cation have been examined with a wide range of anions for their ability to form gel phases. In particular, di-, tri-, and tetravalent anions bearing aliphatic or aromatic spacers were paired with the divalent cations. The properties of the organo- and ionogels formed have been analyzed by means of several different techniques, including calori…
Photoresponsive ionic liquid crystals assembled: Via halogen bond: En route towards light-controllable ion transporters
2017
We demonstrate that halogen bonding (XB) can offer a novel approach for the construction of photoresponsive ionic liquid crystals. In particular, we assembled two new supramolecular complexes based on 1-ethyl-3-methylimidazolium iodides and azobenzene derivatives containing an iodotetrafluoro-benzene ring as XB donor, where the iodide anion acted as an XB acceptor. DSC and X-ray diffraction analyses revealed that the preferred stoichiometry between the XB donors and acceptors is 2 : 1, and that the iodide anions act as bidentate XB-acceptors, binding two azobenzene derivatives. Due to the high directionality of the XB, calamitic superanions are obtained, while the segregation occurring betw…
Unexpected Structural Diversity in Alkali Metal Azide-Crown Ether Complexes: Syntheses, X-ray Structures, and Quantum-Chemical Calculations
2005
A series of alkali metal azide-crown ether complexes, [Li([12]crown-4)(N-3)], [Na([15]crown-5)(N-3)], [Na([15]crown-5)(H2O)(2)]N-3, [K([18]crown-6)(N-3)(H2O)], [Rb([18]crown-6)(N-3)(H2O)], [Cs([18]crown-6)(N-3)](2), and [Cs([18]crown-6)(N-3)(H2O)(MeOH)], has been synthesised. In most cases, single crystals were obtained, which allowed X-ray crystal structures to be derived. The structures obtained have been compared with molecular structures computed by density functional theory (DFT) calculations. This has allowed the effects of the crystal lattice on the structures to be investigated. Also, a study of the M-N-terminal metalazide bond length and charge densities on the metal (M) and termin…
2D Bimetallic Oxalate‐Based Ferromagnets with Inserted [Fe(4‐Br‐sal 2 ‐trien)] + and [Fe(3‐R‐sal 2 ‐trien)] + (R = Br, Cl and CH 3 O) Fe III Spin‐Cro…
2012
The syntheses, structures and magnetic properties of the compounds of formula [FeIII(4-Br-sal2-trien)][MnIICrIII(ox)3]0.67Cl0.33·CH3OH_solvate (1), [FeIII(3-Br-sal2-trien)][MnIICrIII(ox)3]·(CH3CN)2 (2), [FeIII(3-Cl-sal2-trien)][MnIICrIII(ox)3]·(CH3OH)2·(CH3CN)2 (3) and [FeIII(3-CH3O-sal2-trien)][MnIICrIII(ox)3]·(CH3OH)·(H2O)1.5·(CH2Cl2)0.5 (4) are reported. The four structures present a 2D honeycomb anionic layer formed by MnII and CrIII ions linked through oxalate ligands and a cationic layer of the FeIII complexes intercalated between the 2D oxalate network. The main differences compared with previous 2D oxalate-based structures are the presence of double layers of cations in compounds 1,…
Synthesis, characterization and thermal properties of small R2R′2N+X−-type quaternary ammonium halides
2005
Twenty-one R {sub 2} R {sup '} {sub 2}N{sup +} X {sup -} -type (R=methyl or ethyl, R {sup '}=alkyl, X=Br or I) quaternary ammonium (QA) halides have been prepared by using a novel one-pot synthetic route in which a formamide (dimethyl-, diethylformamide, etc.) is treated with alkyl halide in the presence of sodium or potassium carbonate. The formation of QA halides was verified with {sup 1}H-NMR, {sup 13}C-NMR, MS and elemental analysis. The crystal structures of four QA halides (two bromide and two iodide) were determined using X-ray single crystal diffraction, and the powder diffraction method was used to study the structural similarities between the single crystal and microcrystalline bu…