Norbadione A: Kinetics and Thermodynamics of Cesium Uptake in Aqueous and Alcoholic Media
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- 作者：Alexandre Korovitch ; Jean-Baptiste Mulon ; Vincent Souchon ; Isabelle Leray ; Bernard Valeur ; Aurlie Mallinger ; Brice Nadal ; Thierry Le Gall ; Claude Lion ; Nguyt-Thanh Ha-Duong ; Jean-Michel El Hage Chahine
- 刊名：Journal of Physical Chemistry B
- 出版年：2010
- 出版时间：October 7, 2010
- 年：2010
- 卷：114
- 期：39
- 页码：12655-12665
- 全文大小：412K
- 年卷期：v.114,no.39(October 7, 2010)
- ISSN：1520-5207
文摘
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 K1EtOH = (1.1 ± 0.25) × 105 and K2EtOH = (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: K1M1 = (1.5 ± 0.3) × 105 and K2M1 = (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, k1 = (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, K1Exchange = (9 ± 4) × 10−3. In M1, the quenching of A2 fluorescence by NbA is used to determine the kinetics of complex formation with Cs+: k2 = (1.8 ± 0.4) × 109 M−1 s−1; k−2 = (1.80 ± 0.15) × 104 s−1; and K1M1 = (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.