NMR evidence of a valinomycin–proton complex

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 þ ion transport across a biological membrane, the existence of the valinomycin-proton complex could be important in biochemistry and biology. #

A Proton Complex of p-tert-Butylcalix[4]arene-tetrakis(N,N-dimethylthioacetamide): NMR Evidence and Probable Structure

“…In the following NMR spectra, the signal assignment (which was checked by means of 2D COSY-LR and NOESY NMR spectra for 1 H and HSQC and HMBC spectra for 13 NMR spectra [15,19]. The average spectral shape is caused by a rapid interconversion between two identical structures (pinched cone).…”

Theoretical and experimental study of the complexation of valinomycin with ammonium cation

“…Besides K + and Na + ions, other both metal and nonmetal ions, including ammonium cation, bind to valinomycin as well 1, 2, 8–11. Moreover, a formation of equimolar complex of valinomycin with proton in two‐phase system, nitrobenzene (NB) saturated with water, was recently confirmed by NMR measurements 12. However, to the best of our knowledge, the detailed structure of the complex of valinomycin ligand (L) with ammonium as central ion, L‐NH 4 + , has not been solved up to now.…”

Capillary affinity electrophoresis and ab initio calculation studies of valinomycin complexation with Na+ ion

“…Besides K + and Na + ions, Val also binds several other metal and nonmetal ions [1, 2, 9 -12]. Moreover, a formation of equimolar complex of Val with proton in two-phase system, nitrobenzene saturated with water, was recently confirmed by NMR measurements [13].…”