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Carboxylic ionophore (lasalocid A and A23187)-mediated lanthanide ion transport across phospholipid vesicles

Shastri, Bhamidipati P and Sankaram, Mantripragada B and Easwaran, Kalpathy RK (1987) Carboxylic ionophore (lasalocid A and A23187)-mediated lanthanide ion transport across phospholipid vesicles. In: Biochemistry, 26 (16). pp. 4925-4930.

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Abstract

The transport kinetics of three lanthanide ions {(Pr^{3+}, Nd^{3+}, and {Eu^{3+}})} across dimyristoylphosphatidylcholine and dipalmitoylphosphatidylcholine unilamellar vesicles mediated by the 2 carboxylic ionophores lasalocid A and A23187 were studied by proton NMR spectroscopy. Time-dependent changes in the chemical shifts of head group choline signals were measured to calculate apparent rate conststants of transport. These experiments were done at different ionophore concentrations to determine the stoichiometry of the transporting species. The rates of transport were faster in the absence of intravesicular {La^{3+}} compared to those obsserved in its presence. The stoichiometry of the transporting species was 2:1 (ionophore:cation) for both lasalocid A and A23187 in dimyristoylphosphatidylcholine vesicles. However, stoichiometries of >2 were obtained for lasalocid A-mediated lanthanide ion transport across dipalmitoylphosphatidylcholine vesicles. Possible reasons for the observation of such noninteger stoichiometries are discussed. Also, A23187 is a more efficient carrier ionophore than lasalocid A.

Item Type: Journal Article
Additional Information: Copyright for this article belongs to the American Chemical Society
Department/Centre: Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited: 13 May 2008
Last Modified: 19 Sep 2010 04:44
URI: http://eprints.iisc.ernet.in/id/eprint/13950

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