Norbadione A: Kinetics and Thermodynamics of Cesium Uptake in Aqueous and Alcoholic Media
| Autor: | Alexandre Korovitch, Thierry Le Gall, Vincent Souchon, Jean-Baptiste Mulon, Brice Nadal, Claude Lion, Jean-Michel El Hage Chahine, Isabelle Leray, Bernard Valeur, Aurélie Mallinger, Nguyêt-Thanh Ha-Duong |
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| Rok vydání: | 2010 |
| Předmět: |
Stereochemistry
Carboxylic acid Kinetics Ionophore Cesium Medicinal chemistry chemistry.chemical_compound Reaction rate constant Deprotonation 4-Butyrolactone Coordination Complexes Materials Chemistry Physical and Theoretical Chemistry Phenylacetates chemistry.chemical_classification Aqueous solution Ethanol Water Hydrogen-Ion Concentration Surfaces Coatings and Films Norbadione A chemistry Cesium Radioisotopes Thermodynamics Agaricales |
| Zdroj: | The Journal of Physical Chemistry B. 114:12655-12665 |
| ISSN: | 1520-5207 1520-6106 |
| DOI: | 10.1021/jp1060232 |
| Popis: | Norbadione A (NbA) is a mushroom pigment, which is assumed to be involved in (137)Cs accumulation all over Europe during the Chernobyl nuclear accident. NbA bears seven acid-base functional groups, among which are two enolic and two carboxylic acid moieties. This work deals with complex formation of Cs(+) and NbA in ethanol, ethanol/water (9:1) (M1), and water with, when required, the support of two Cs(+) ionophore probes, calix[4]arene-bis(crown-6-ether)dioxycoumarine (A1) and its tetrasuslfonated form (A2). In ethanol, two Cs(+) complexes are formed, with the affinity constants K(1EtOH) = (1.1 ± 0.25) × 10(5) and K(2EtOH) = (2.1 ± 0.4) × 10(3). In M1, a single Cs(+) complex occurs when only the enols are deprotonated, whereas a bicomplex is formed when both enols and carboxylic acids are deprotonated: K(1M1) = (1.5 ± 0.3) × 10(5) and K(2M1) = (4 ± 2) × 10(3). These data are confirmed by stopped-flow and T-jump kinetics. In ethanol, a fast Cs(+) exchange occurs between NbA and A1: direct rate constant, k(1) = (3.1 ± 0.1) × 10(7) M(-1) s(-1); reverse rate constant k(-1) = (2.8 ± 1) × 10(5) M(-1) s(-1); and Cs(+) exchange constant, K(1Exchange) = (9 ± 4) × 10(-3). In M1, the quenching of A2 fluorescence by NbA is used to determine the kinetics of complex formation with Cs(+): k(2) = (1.8 ± 0.4) × 10(9) M(-1) s(-1); k(-2) = (1.80 ± 0.15) × 10(4) s(-1); and K(1M1) = (1.5 ± 0.5) × 10(5). The affinity of NbA for Cs(+) is probably the result of the particular structure in which the two pulvinic acid arms adopt a conformation that forms two complexation sites composed of the two enolates and/or the two carboxylates. This renders the efficiency in Cs(+) uptake comparable to that of some calixarenes or crown ethers. |
| Databáze: | OpenAIRE |
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