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NMR evidence of a valinomycin-proton complex.

Kríz J, Makrlík E, Vanura P

Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic.

In addition to the well-known complexes of valinomycin with alkali metal cations, an equimolar complex of the same compound with proton was found to be formed in nitrobenzene. Hydrogen bis(1,2-dicarbollylide) cobaltate (HDCC) was used as a proton source. According to NMR spectra, the complex formation is quantitative at proton/valinomycin molar ratios up to 1:1 but there is fast exchange of protons between coordinated and uncoordinated valinomycin molecules at lower ratios. 1H and 13C NMR spectra show a dramatic change in the valinomycin conformation during its coordination with protons, probably from a propeller-like to a bracelet-like form. As valinomycin is one of the well-known ion-carrying ionophores facilitating especially the K+ ion transport across a biological membrane, the existence of the valinomycin-proton complex could be important in biochemistry and biology.

Published 9 January 2006 in Biopolymers, 81(2): 104-9.
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