Conformational studies of A23187 with mono-, di- and trivalent metal ions by circular dichroism spectroscopy

Divakar, S and Easwaran, KRK (1987) Conformational studies of A23187 with mono-, di- and trivalent metal ions by circular dichroism spectroscopy. In: Biophysical Chemistry, 27 (2). pp. 139-147.

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Abstract

CD studies carried out on A 23187 (calcimycin) indicate a solvent-dependent conformation for the free acid. Alkali metal ions bound to the ionophore weakly. Divalent metal ions such as $Mg^{2+}$, $Ca^{2+}$, $Sr^{2+}$, $Ba^{2+}$, and $Co^{2+}$ and trivalent lanthanide metal ions such as $La^{3+}$ formed predominantly 2:1 (ionophore-metal ion) complexes at low concentrations of metal ions, but both 2:1 and 1:1 complexes were formed with increasing salt concentration. $Mg^{2+}$ and $Co^{2+}$ exhibited similar CD behavior that differed from that observed for the other divalent and lanthanide metal ions. The structure of 2:1 complexes involved two ligand molecules coordinated to the metal ion through the carboxylate oxygen, benzoxazole nitrogen, and keto-pyrrole oxygen from each ligand molecule along with one or more solvent molecules. Values of the binding constants were determined for 2:1 complexes of the ionophore with divalent and lanthanide metal ions.

Item Type:	Journal Article
Publication:	Biophysical Chemistry
Publisher:	Elsevier Science B.V.
Additional Information:	Copyright of this article belongs to Elsevier Science B.V.
Keywords:	CD;Ionophore-metal ion complex;Conformational analysis;Coordination structure
Department/Centre:	Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited:	12 Mar 2008
Last Modified:	19 Sep 2010 04:43
URI:	http://eprints.iisc.ac.in/id/eprint/13273

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