Mobile carrier ionophores for Fe(II).

A23187 and certain other carboxylate ionophores are capable of transferring Fe(II) but not Fe(III) across phospholipid bilayers (liposomes) and red cell membranes. A23187 is able to transfer Fe(II) from ferritin loaded liposomes when allied with a suitable redox couple and sink. The affinity of A23187 for Fe(II) is approximately five orders of magnitude greater than for Ca2+, as judged by two phase extraction techniques.