Ionophore activity

Dahlgren, C. (1987). Difference in extracellular radical release after chemotactic factor and calcium ionophore activation of the oxygen radical-generating system in human neutrophils. Biochim. Biophys. Acta 930, 33-8. 

A group of antibiotics isolated from soil fungi, the enniatins,77 also show ionophoric activity. Enniatin B (16), a cyclohexadepsipeptide, has a greater selectivity for Na+ over K+. With the latter ion stoichiometries other than 1 1 are found in solution. These are attributed to stacking interactions between the adjacent disc-like molecules as observed in the solid state.76 Interestingly, T1 ,... 

Another type of compound with potential ionophoric activity contains a single carboxylic acid group which can neutralize the charge on the metal ion. As the structures of some of these show (23-28), they have an abundance of potential O donor atoms. 

Trypsin hydrolysis of SR vesicles cleaves the (Ca2, Mg2+)-ATPase into three fragments, NH2-20 000, 30 000 and 45 OOO-COOH. The phosphorylation site is associated with an aspartic acid residue in the 30 000 fragment and ionophoric activity with the 20 000 fragment. The amino terminus of the enzyme is located on the cytoplasmic side of the membrane.143... 

Regen58 used amphotericin B as a design basis for the structural requirements of an ion channel. Composed of a rigid, hydrophobic sterol nucleus and flexible hydrophilic chains, 50 was expected to function via self-assembly in a membrane bilayer. Cation flux was assessed using Lehn s NMR method and comparisons were made with the bouquet molecules. Ionophoric activity was similar to the more sophisticated bouquet molecules (maximum entry achieved in ca. 60 h), but Na+ transport was significantly less than recorded with amphotericin B. 

Figure 10.4 (a) Resistance of bovine tracheai mucosa to injury eiicited by ionophore activated human neutrophils, and (b) susceptibility of bronchial mucosa under identical conditions. Injury, In this case cell detachment, was measured indirectly by measuring the permeability of the airway mucosa to serum albumin. Cells were applied to the basolateral surface and the vector of solute movement was basolateral-apical. 

In order to examine the ionophoric activities of crownophanes, their extraction of solid alkali metal thiocyanates into CHjClj was carried out. As shown in Table 2, crownophanes 34 (s. Scheme 1) efficiently and selectively extracted LiSCN under anhydrous conditions. The linear oligo(oxyethylene) compounds also extracted the salt sufficiently. Their alkali metal affinity seems to result in... 

Mitani, M. Otake, N. Studies on the ionophorous antibiotics. XV. The monovalent cation selective ionophorous activities of carriomycin. lonomycin. and etheromycin. J. Antibiot. 1978, 31. 750-755. 

Neutral macrocyclic ethers have been used to facilitate the transport of cations across liquid membranes. It has been found that the anion desolvation energy barrier is one of the more important factors in controlling the rate of transfer across the membrane. a-Carboxy-a>-hydroxypolyethers containing ethylene and 1,2-phenylene units can transport metal-ions from aqueous alkali metal hydroxide to an aqueous solution of hydrochloric add through a liquid membrane of hexan-l-ol. However, unlike natural carboxylic ionophores, active transport against the alkali metal-ion concentration gradient could not be observed. ... 

Lee, T. H., Mencia-Huerta, J.-M., Shih, C., Corey, E. J., Lewis, R. A., and Austen, K. F. (1984). Effects of exogenous arachidonic, eicosapentaenoic, and docosahexaenoic acids on the generation of 5-lipoxygenase pathway products by ionophore-activated human neutrophils. J. Clin. Invest. 74, 1922 1933. 

Shai, Y, Fox, J., Caratsch, C., Shih, Y.L., Edwards, C., and Lazarovid, P. (1988) Sequencing and synthesis of pardaxin, a polypeptide from the Red Sea Moses sole with ionophore activity. FEES Lett., 242, 161-166. 

Historically, enzyme catalysis has played a highly prominent role, with the first enzyme-catalyzed asymmetric addition of HCN to aldehydes dating back to 1908 [167]. A wide range of both aromatic and aliphatic ketones are suitable substrates and produce cyanohydrins of high optical purity. The most readily available and hence most commonly employed enzyme for asymmetric cyanohydrin formation is (R)-hydroxynitrile lyase isolated from almonds. Recent cloning and over-expression techniques have also made a number of (S)-hydroxynitrile lyases available for organic synthesis [164, 165]. This was utilized in Griengl s synthesis of coriolic acid (255), a natural product that displays calcium ionophoric activity and acts as a prostacyclin mimic (Scheme 2.32) [168]. Thus, an (S)-hydroxynitrile lyase was cloned from rubber trees (Hevea brasiliensis), overexpressed in Pichia pastoris, and used to provide cyanohydrin 254 in 99 % ee. 

Lee TH, Menica-Huerta JM, Shih C, Corey EJ, Lewis RA, Austen KF (1984) Effects of exogouMis arachidonic, dcosapentaenoic, and docosahexaenoic adds on the generaticm of 5-lipoxygenase pathway products by ionophore-activated human neutrophils. J Clin Invest 74 1922-1933... 

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