INTERACTIONS IN METHANOL OF DIVALENT META L-CATIONS WITH BACTERIAL IONOPHORES, LASALOCID AND MONENSIN - THERMODYNAMICAL ASPECTS

Interactions in methanol of divalent metal cations with bacterial iono phores, lasalocid and monensin : thermodynamical aspects. New data con cerning interactions in methanol of Cd2+, Hg2+ and pb(2+) With bacteri al ionophores monensin and lasalocid and reference compounds, acetic a nd salicylic acids are reported. Gibbs functions and enthalpies and th us entropies for the formation of both 1-1 and the 2-1 complexes are o btained from potentiometric and calorimetric measurements. Analogous d ata were already acquired for most of the other divalent metal cations . The whole of these results is then discussed here. Both ionophores a ce more efficient ligands than the reference acids, such an efficiency being mainly determined by entropy increases. But, differencies in th e complexing ability of the two ionophores as a function of the nature and the size of the cation occur. Then reported differencies in ionop horic properties for divalent cations of monensin and lasalocid are te ntatively explained considering also what is known, mainly from NMR ex periments, on the structure of these complexes in solution.