Molecular recognition based on membrane potential changes induced by host-guest complexation with inorganic and organic guests

Guest-induced changes in membrane potentials are one of the representative modes of electrochemical signal transduction by molecular recognition at th e interface of an organic membrane and an aqueous solution. Recent approach es based on synthetic hosts capable of effecting membrane potential changes by host-guest complexation with inorganic and organic guests are described . Although the studies in this area have mainly been aimed at inorganic cat ions as the target guests, recent approaches for recognition of inorganic a nions and further organic guests are also documented. Highly selective chan ges in membrane potentials can be achieved for inorganic cations by sophist icated design of crown ethers and related compounds. Hosts with complementa ry charge(s) or multiple hydrogen bonding sites are effective for the recog nition of inorganic anions and also of the polar moieties of organic ions. On the other hand, the recognition of nonpolar moieties of organic guests c an be achieved by inclusion into well-defined cavities of host molecules. Q uaternary onium and protonated amine salts are recently found to be capable of effecting membrane potential changes by complexation with neutral pheno lic guests.