New metal ion binding mode of valinomycin, incorporating the whole hexaaqua complex
What is it about?
The antibiotic macrocycle valinomycin gulps up a large hexaaquamagnesium complex [Mg(H2O)6]2+. This reveals yet another cation-binding mode of valinomycin, which is known to selective K+ carrier. A beautiful three-fold crystal network, including the counter-ion trifluoromethanesulfonate, is exhibited in the crystal structure.
Why is it important?
This work reveals valinomycin's versatile ability to bind cations, including a fully hydrated cation through hydrogen-bonding, not by direct coordination, as showcased in this work. Valinomycin has been known since 1960's, and the most crystal structures were published in the 60's to 80's. Then the structural investigation seemed to have stopped for a while. This is our 3rd publication in the last 5 years regarding new ion-binding modes exhibited by valinomycin.