In ionophore

Heterocycles as ligands in ionophores for potentiometric and optical sensors 98CRV1593. 

A major advance in ionophore-based ISEs is the finding that their detection limits can be lowered from the micromolar range to the nanomolar or picomolar level. Discuss recent developments and the new understanding that led to such dramatic improvements in the detectability. 

Workers at Lilly have reported the synthesis of 8,9-LTA3 (51), 8,9-LTC3 (52a), and 8,9-LTD3 (52b),leukotrienes that are reported to be produced from dihomo-y-linolenic acid in ionophore-stimulated murine mastocytoma cells. The natural stereochemistry was assumed to be (85,9/f,10,12 ,14Z) by analogy with arachidonic acid metabolism in the same cell system. The chiral synthesis was achieved (93% ee) via Sharpless epoxidation of an appropriate allylic alcohol (53) (Scheme 5.17). 

Our quest in ionophore and receptor design emerged from one of the seemingly intractable problems of contemporary biochemistry the selective recognition of the ammonium cation (NH/) [141], Much of the problem, as discussed in earlier section is due to the nearly equivalent sizes of NH/ and the potassium cation (K ) [67]. One also learns from our discussion of the cation-7i interaction, that receptors providing improved dispersion stabilization are more selective forNH/ [67,71,72]. 

While there has been only a limited interest in ionophore-based ISEs for Be " ", Sr " ", and Ba " "," the development of Mg + and Ca + ISEs suitable for measurements in blood samples has been for several decades one of the most competitive topics in the field of ion-selective potentiometry. Success came much faster for Ca + than for the smaller and more hydrophilic Mg +, for which ionophoie-based ISE were finally introduced in clinical analyzers in 1994. This can be at least partially explained by the fact that, as a result of the stronger hydration of Mg +, the use of a hypothetical ionophore that binds Mg + and Ca + equally strong would result in an ISE with selectivity for Ca + over Mg " ". Therefore, binding of Mg + by the ionophore has not only to be selective over Ca +, but it also has to compensate for the difference in the free energies of ionophore-unassisted phase transfer from the aqueous into the sensing membrane. Analogous problems arise in the development of other strongly hydrophilic cations (e.g., Li+) and anions (e.g., sulfate and phosphate). 

The two units (56) and (57) which are differentially-protected versions of a chiral array found in ionophoric antibiotics such as zincophorin, have been prepared from the D-mannitol-derived ditosylate (58) by means of regioselective openings of epoxides (Scheme 12).45... 

In this work, we have investigated the effect of attaching one, two or four lipophilic, linear alkyl groups directly to the macrocyclic ring of 18-crown-6 in ionophores 3-7 (Figure 2). The objective was to maintain the flexibility of the macrocyclic polyether ring while enhancing the lipophilicity of the crown ether compound. In addition to these lipophilic 18-crown-6 derivatives, the lipophilic 15-crown-5 compound 8 was also studied. 

Lindner, E., R.E. Gyurcsanyi, and E. Pretsch 2012. Potentiometric ion sensors Host-guest supramolecu-lar chemistry in ionophore-based ion-selective membranes. In Applications ofSupramolecular Chemistry for 21st Century Technology, ed. Schneider, H.-J., xi, 441 p. Boca Raton, FL Taylor Francis. 

Rouzer CA, Ford-Hutchinson AW, Morton HE, Gillard JW. MK-886, a potent and specific leukotriene biosynthesis inhibitor blocks and reverses the membrane association of 5-lipoxygenase in ionophore-challenged leukocytes. J Biol Chem 1990 265 1436-1442. 

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