Norbadione A: Kinetics and Thermodynamics of Cesium Uptake in Aqueous and Alcoholic Media

• Published in: The journal of physical chemistry. B Vol. 114; no. 39; pp. 12655 - 12665
• Main Authors: Korovitch, Alexandre, Mulon, Jean-Baptiste, Souchon, Vincent, Leray, Isabelle, Valeur, Bernard, Mallinger, Aurélie, Nadal, Brice, Le Gall, Thierry, Lion, Claude, Ha-Duong, Nguyêt-Thanh, El Hage Chahine, Jean-Michel
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 07.10.2010
• Subjects: 4-Butyrolactone - analogs & derivatives; 4-Butyrolactone - chemistry; Agaricales - chemistry; B: Biophysical Chemistry; Cesium - chemistry; Cesium - metabolism; Cesium Radioisotopes - chemistry; Cesium Radioisotopes - metabolism; Coordination Complexes - chemistry; Ethanol - chemistry; Hydrogen-Ion Concentration; Kinetics; Phenylacetates - chemistry; Thermodynamics; Water - chemistry
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/jp1060232

Norbadione A (NbA) is a mushroom pigment, which is assumed to be involved in 137Cs 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) × 105 and K 2EtOH = (2.1 ± 0.4) × 103. 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) × 105 and K 2M1 = (4 ± 2) × 103. 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) × 107 M−1 s−1; reverse rate constant k −1 = (2.8 ± 1) × 105 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) × 109 M−1 s−1; k −2 = (1.80 ± 0.15) × 104 s−1; and K 1M1 = (1.5 ± 0.5) × 105. 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.