Search results for "Ion binding"

Synthesis of Quinoline-Based Anion Receptors and Preliminary Anion Binding Studies with Selected Derivatives

2014

Six quinoline-based anion receptors were designed, prepared, and characterized, among which the crystal structure of an indole derivative was obtained. Selected receptors were tested for the recognition of halide anions in solution and showed some selectivity of chloride over bromide and iodide.

Temperature effects on counterion binding to spherical polyelectrolytes: the charge-discharge transition of lignosulfonate

1995

Abstract The effect of temperature on the effective charge numbers and diffusion coefficients of polyelectrolytes has not nobee dealth with in many studies. The present study concerns the temperature behavior of lignosulfonate. Lignosulfonate is a polydisperse polyelectrolyte whose molecules are compact spheres in aqueous solutions. One of its most remarkable properties is that is loses its charge in 0.1 M NaCl aqueous solution at about 40°C. In order to explain this charge-discharge transition, a theory for ion binding to spherical polyelectrolytes based on the relative population of two hydration states of the charged groups is presented. The water molecules adjacent to the charged groups…

Thermodynamics of sulfate anion binding by macrocyclic polyammonium receptors

2001

The interaction of SO42− with polyammonium cations derived from fourteen polyamines (5 polyazacycloalkanes, 2 polyazacyclophanes, 3 phenanthrolinacyclophanes, 2 dibenzenacyclophanes and 2 acyclic polyamines) in aqueous solution has been studied by means of potentiometric and microcalorimetric techniques. Only 1 : 1 receptor–anion complexes have been found in solution. Complexed species of considerable stability are formed, although the two acyclic polyamines (dimethylpentaethylenehexaamine and dimethylhexaethyleneheptaamine) and the smallest phenanthrolinacyclophane do not interact with the anion. The complexation reactions are endothermic, or almost athermic, and promoted by invariably fav…

Multi-channel receptors based on thiopyrylium functionalised with macrocyclic receptors for the recognition of transition metal cations and anions.

2010

We report herein the synthesis and characterization of a family of ligands containing different cation binding sites covalently connected to a thiopyrylium signalling reporter. The receptors L1–L6 are able to signal the presence of certain metal cations via three different channels; i.e. electrochemically, fluorogenically and chromogenically. An acetonitrile solution of L1–L6 shows a bright blue colour due to a charge-transfer band in the 575–585 nm region. The colour variation in acetonitrile of L1–L6 in the presence of the metal cations Ag+, Cd2+, Cu2+, Fe3+, Hg2+, Ni2+, Pb2+ and Zn2+ has been studied. A selective hypsochromic shift of the blue band was found for the systems L4-Pb2+ and L…

Dynamic Refolding of Ion-Pair Catalysts in Response to Different Anions.

2019

Four distinct folding patterns were identified in two foldamer-type urea-thiourea catalysts bearing a basic dimethylamino unit by a combination of X-ray crystallography, solution NMR studies, and computational studies (DFT). These patterns are characterized by different intramolecular hydrogen bonding schemes that arise largely from different thiourea conformers. The free base forms of the catalysts are characterized by folds where the intramolecular hydrogen bonds between the urea and the thiourea units remain intact. In contrast, the catalytically relevant salt forms of the catalyst, where the catalyst forms an ion pair with the substrate or substrate analogues, appear in two entirely dif…

Ion pair recognition by ditopic crown ether based bis-urea and uranyl salophen receptors

2016

The utility of SATB2 immunohistochemical expression in distinguishing between osteosarcomas and their malignant bone tumor mimickers, such as Ewing s…

2016

SATB2 is commonly expressed in osteosarcomas. Although apparently being a valuable diagnostic marker for differentiating between small cell osteosarcoma (SCO) and other small round cell tumors of bone, for instance Ewing sarcoma family of tumors (ESFT), it has not been tested in a large series of ESFT and chondrosarcomas so far. We studied the immunohistochemical expression of SATB2 in 42 osteosarcomas, 31 chondrosarcomas, and 371 genetically confirmed ESFT. SATB2 positivity was detected in 90.4% of osteosarcomas, 87.5% of SCO, 91.3% of osteoblastic osteosarcomas, and in all chondroblastic and parosteal osteosarcomas. The osteoblastic and SCO subtypes expressed SATB2 more intensely than oth…