Ionomycin is an ionophore and an antibiotic that binds calcium ions (Ca2+) in a ratio 1:1.

Its β-diketone and carboxylic acid group form a chelate with calcium.

[3] Ionomycin is often sold as a free acid, or as a Ca2+ salt.

Both are insoluble in water, but soluble in fats and DMSO.

Because of their fat solubility, they bind to proteins like albumin, which may interfere with their use in studies involving blood.