title: Norbadione a: kinetics and thermodynamics of cesium uptake in aqueous and alcoholic media.
abstract: 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.
authors.affiliation: Interfaces, Traitements, Organisation et Dynamique des Systèmes, Université Paris 7-CNRS UMR 7086, Bât. Lavoisier, 15 rue Jean Antoine de Baïf, 75205 Paris Cedex 13, France.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Korovitch
authors.forename: Jean-Baptiste
authors.initials: JB
authors.lastname: Mulon
authors.forename: Vincent
authors.initials: V
authors.lastname: Souchon
authors.forename: Isabelle
authors.initials: I
authors.lastname: Leray
authors.forename: Bernard
authors.initials: B
authors.lastname: Valeur
authors.forename: Aurélie
authors.initials: A
authors.lastname: Mallinger
authors.forename: Brice
authors.initials: B
authors.lastname: Nadal
authors.forename: Thierry
authors.initials: T
authors.lastname: Le Gall
authors.forename: Claude
authors.initials: C
authors.lastname: Lion
authors.forename: Nguyêt-Thanh
authors.initials: NT
authors.lastname: Ha-Duong
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: El Hage Chahine
mesh_terms: D015107:4-Butyrolactone / Q000031:analogs & derivatives* / Q000737:chemistry; D000363:Agaricales / Q000737:chemistry; D002586:Cesium / Q000737:chemistry* / Q000378:metabolism; D002588:Cesium Radioisotopes / Q000737:chemistry / Q000378:metabolism; D056831:Coordination Complexes / Q000737:chemistry; D000431:Ethanol / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010648:Phenylacetates / Q000737:chemistry*; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
chemical_list: D002588:Cesium Radioisotopes; D056831:Coordination Complexes; D010648:Phenylacetates; D014867:Water; D002586:Cesium; D000431:Ethanol; C464564:norbadione A; D015107:4-Butyrolactone