Abstract
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. ^1^H and ^13^C 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. © 2005 Wiley Periodicals, Inc. Biopolymers 81: 104–109, 2006
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