Experimental Evidence for a Valinomycin – Proton Complex

Summary. From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium H⁺ (aq) + NaL⁺ (nb) = HL⁺ (nb) + Na⁺ (aq) taking place in the two-phase water-nitrobenzene system (L = valinomycin, aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log K_ex (H⁺, NaL⁺) = −1.1 ± 0.1. Further, the stability constant of the valinomycin-proton complex in nitrobenzene saturated with water was calculated as log β_nb(HL⁺) = 5.3 ± 0.1. Finally, the stability constants of complexes of some univalent cations with valinomycin were summarized and discussed.