- ETUDE THERMODYNAMIQUE DE LA COMPLEXATION DES IONS SODIUM, POTASSIUM ET RUBIDIUM PAR LES IONOPHORES BACTERIENS: MONENSINE, GRISORIXINE ET NIGERICINE
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Enthalpies in anhydrous methanol for both dissociation of carboxylic group and complexation of alkali metal cations by these natural ionophores (as 1-1 neutral association between the cation and the carboxylate form of the ionophore) are obtained from calorimetric measurements.Using equilibrium constants measured independently, it is possible to reach the corresponding entropies.The results now obtained on the thermodynamic of these two reactions are discussed in terms of "opened" or "closed" structure of the ionophores and of interactions with the solvent medium: - both acid and "empty" anion form can be considered as open in methanol; - nigericin and grisorixin have, as far as G, H, S, are concerned a very similar behaviour.The standard quantities are only shifted from grisorixin to nigericin, owing to the solvation of the supplementary OH group of the second ionophore; - monensin have a very distinct behaviour from the two other ionophores.Such thermodynamic studies are expected to give some informations on the mechanism of action of these bacterial ionophores.
- Pointud, Yvon,Juillard, Jean,Jeminet, Georges,David, Lucien
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