Synthesis and Application of Ion Recognition Compounds with High Sensitivities for Medical Science

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Purpose of our study is to develop the method for measurements of sodium and potassium ion concentrations in cells using new fluorescent ion probes based on calixarenes. Calixarenes are known as new class of ion-binding compounds prepared from the phenol-aldehyde condensation. In comparison with polyether ionophores such as crown ethres and cryptands, the lipophilicities of calixarenes are very high. Thus it is expected that the calixarenes can be easily incorporated into biological membanes. In order to use calixarens as ion probes, it is nessesarry to investigate their ionophoric properties in biological membranes. We investigated the ionophoric propeties of ester derivatives of p-tert-butylcalix[4,6, or8]arenes using a planarbilayr membrane system. Through this investigation, we found that the calix[4]arene ester has a ability of a sodiumion probe with a high Na^+/K^+ selectivity. Further, we found that a fluorescentsodium probe derived from the calix[4]arene ester derivative exhibits a high Na^+/K selectivity : the value of the Na^+/K^+ selectivity of the synthesized sodium probe was found to be ca. 40.For the calix[6]arene ester, we also found the utility of the potassium ion probe. However, for the calix[8]arene ester, we could not the ionophoric activity in phospholipd bilayr membranes. From this study, we conclude that ester derivatives of the calix[4]arene and calix[6]arene have potentials for use as sodium and potassium fluorescent probe in biological membranes. Applications of these calixarenes in biologicalsystems are in progress.