@article {3061,
	title = {BINDING AND TRANSPORT OF CALCIUM-IONS BY SYNTHETIC ANALOGS OF IONOMYCIN},
	journal = {Canadian Journal of Chemistry-Revue Canadienne De Chimie},
	volume = {72},
	number = {6},
	year = {1994},
	note = {ISI Document Delivery No.: NV309Times Cited: 4Cited Reference Count: 66},
	month = {Jun},
	pages = {1512-1524},
	type = {Article},
	abstract = {The transport of calcium ions across an organic barrier by a series of synthetic analogues of ionomycin was measured in a cylindrical glass cell using chloroform as the artificial membrane. The presence of a beta-diketone and carboxyl group in the same molecule and a sufficient Lipid solubility of the compounds were shown to be necessary and sufficient conditions for Ca2+ transport. Small and no transport of Ca2+ were found for analogues 5 and 6, respectively, due to the low lipid solubility of these compounds. The Ca2+ transport rate for analogues 8 and 13-15 followed the order of 8 > 13 > 14 > 15, which demonstrated that optimal Ca2+ transport was achieved when the beta-diketone was separated from the carboxyl group by seven methylene units, identical to that found in ionomycin. Analogues 8-10 were comparable to ionomycin and calcimycin in terms of Ca2+ transport. Ca2+ transport by the analogues was found to be a saturable process that obeyed Michaelis-Menten kinetics. It was dependent on the pH in the aqueous source phase and independent of the pH in the receiving phase. Both the carboxyl and the beta-diketo groups were ionized in the transport of Ca2+, indicating that the stoichiometry of Ca2+ complex in transport was 1:1. The pK(a) of the beta-diketone of the analogues was determined to be in the range of 10.90-11.16 in 80\% MeOH-H2O. The pK(a) values were related to the lipid solubility of the compounds and the hydrocarbon chain length between the beta-diketone and the carboxyl group. The binding constants of the analogues with Ca2+ and Mg2+ in 80\% MeOH-H2O were determined to be in the order of 10(2) M(-1) and 10(3) M(-1), respectively, using the pK(a) method. The stoichiometry of Mg2+ binding was found to be 1:1 by the mole ratio method. The selectivity in binding and in transport followed the same order, being Mg2+ > Ca2+ >> Na+, K+.},
	keywords = {A23187, ACETYLACETONE, ALKALINE-EARTH CATIONS, COMPLEXATION, COUNTERTRANSPORT, COUPLED, DIVALENT-CATION IONOPHORE, FORMATION-CONSTANTS, MEMBRANE, METAL-IONS, SYSTEMS},
	isbn = {0008-4042},
	url = {<Go to ISI>://A1994NV30900011},
	author = {Hu, Thomas Q. and Weiler, L.}
}
