Conformational characterisation of valinomycin complexation with barium salts-a nuclear magnetic resonance spectroscopic study

Devarajan, S. ; Easwaran, K. R. K. (1984) Conformational characterisation of valinomycin complexation with barium salts-a nuclear magnetic resonance spectroscopic study Journal of Biosciences, 6 (1). pp. 1-16. ISSN 0250-5991

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Official URL: http://www.ias.ac.in/jarch/jbiosci/6/1-16.pdf

Related URL: http://dx.doi.org/10.1007/BF02702853

Abstract

Conformations of valinomycin and its complexes with Perchlorate and thiocyanate salts of barium, in a medium polar solvent acetonitrile, were studied using nuclear magnetic resonance spectroscopic techniques. Valinomycin was shown to have a bracelet conformation in acetonitrile. With the doubly charged barium ion, the molecule, at lower concentrations, predominantly formed a 1:1 complex. At higher concentrations, however, apart from the 1:1, peptide as well as ion sandwich complexes were formed in addition to a 'final complex'. Unlike the standard 1:1 potassium complex, where the ion was centrally located in a bracelet conformation, the 1:1 barium complex contained the barium ion at the periphery. The 'final complex' appeared to be an open conformation with no internal hydrogen bonds and has two bound barium ions. This complex was probably made of average of many closely related conformations that were exchanging very fast (on nuclear magnetic resonance time scale) among them. The conformation of the 'final complex' resembled the conformation obtained in the solid state. Unlike the Perchlorate anion, the thiocyanate anion seemed to have a definite role in stabilising the various complexes. While the conformation of the 1:1 complex indicated a mechanism of ion capture at the membrane interface, the sandwich complexes might explain the transport process by a relay mechanism.

Item Type:Article
Source:Copyright of this article belongs to Indian Academy of Sciences.
Keywords:NMR Study; Conformation; Ionophores; Valinomycin-barium Complex; Transmembrane Ion-transport
ID Code:11192
Deposited On:09 Nov 2010 03:50
Last Modified:16 May 2016 20:40

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