Transmembrane Migration Molecular Shuttles

Organic ligands that bind to alkali metal and alkaline earth cations are known as ionophores, literally ion carrying compounds. Valinomycin, a cyclic natural antibiotic consisting of alternating d- and L-valine separated by D-hydroxyisovalerate and L-lactate groups shown in Fig. 5.2, binds K+ one thousand times better than 

Anions can also be transported across membranes. In Nature, Cl- is transported by prodigiosins which comprise three conjugated pyrrole groups and a lipophilic alkyl 

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