Conformational characterisation of valinomycin complexation with barium salts—A nuclear magnetic resonance spectroscopic study.
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Date
1984-03
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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.
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NMR study, conformation, ionophores, valinomycin-barium complex, transmembrane ion-transport
Citation
Devarajan S, Easwaran K R K. Conformational characterisation of valinomycin complexation with barium salts—A nuclear magnetic resonance spectroscopic study. Journal of Biosciences. 1984 Mar; 6(1): 1-16.