ionofore

An ionophore, a term more commonly spelled ionophore (and less frequently seen as ionofore), is a chemical compound that increases the permeability of a biological membrane to specific ions. Ionophores act by either binding and shuttling ions through the lipid bilayer in a carrier mechanism or by forming transmembrane channels that allow ions to diffuse down their electrochemical gradients. Transport can be electrogenic or electroneutral, and ion selectivity varies by compound.

There are two main classes. Carrier ionophores bind a particular ion in a lipophilic complex and diffuse across the membrane, releasing the ion on the other side. Channel-forming ionophores assemble into pores that permit ions to pass through. Examples include valinomycin (highly selective for K+), nonactin and ionomycin as carriers, and gramicidin A, alamethicin, and related peptides as channels. Some agents such as monensin and nigericin operate as ion exchangers (Na+/H+ or K+/H+), influencing ion gradients through coupled transport.

Most natural ionophores are secondary metabolites produced by microorganisms such as Streptomyces species or certain fungi, though synthetic variants exist. They play roles in microbial competition and ion homeostasis and can disrupt cellular ion balance in target organisms.

In research and medicine, ionophores are used to manipulate membrane potential and study ion transport mechanisms. Their ability to collapse ion gradients makes them useful tools in cell biology, physiology, and pharmacology, but also raises concerns about toxicity and specificity when considered for therapeutic use.