Ion Pairing between Cl~- or ClO_4~- and Alkali Metal Complexes of Ionophore Antibiotics inOrganic Solvents: A Multinuclear NMR and FT-IR Study

摘要

The extent of ion pairing in chloride and perchiorate salts was studied by measurement of the CV and a resonances and the observation of the perchiorate stretching frequency by use of nuclear magnetic res~ (NMR) spectroscopy and Fourier transform infrared spectroscopy (FT-IR), respectively, for a variety of iom~ in various solutions and in large unilaminar vesicles (LUVs). The NMR line widths of chloride and perd~ were larger in solutions containing the neutral ionophores valinomycin (Val) and nonactin (Non) than in socontaining the negatively charged ionophores nigericin (Nig). lasalocid (Las), and monensin (Mon), The x isci~ corrected perchiorate NMR line widths in solutions containing Val and Las were sign ficantfy’negatively con~ (r23 0.99) with the dielectric constant of the solvent. Solvents~ with low dielectric constants favoredformation. From methanolic solutions containing the Lit, Na~, K~, and Cs+ salts of Cl— and C104. determined that the c~ition with the highest selectivity for the ionophore affords the most ion pairing. A in pH from 7 to 3 had no significant effect on the NMR line widths of chloride and perchlorate insolutions containing Val, whereas a similar decrease in p1-I in a methanolic solution containing Mon 2-fold increase in the line widths. The FT-IR difference spectrum of KCLO4 in a methanolic solution c Val showed splitting at the perchlorate stretching frequency. No band splitting was observed in the ET-IRspectrum of KCIO4 in methanolic solutions containing Las. The efflux of 35C1 in LUVs containing the ionophore Val followed first-order kinetics with an efflux constant of 1.70 x iO’-~ min’, as determined NMR spectroscopy. The induction of increased membrane permeability in LUVs by the ionophore was de to be negligible for Val and Nig by fluorescence spectroscopy.