Selective membrane transport of amino acids by functionalised calix[4]arenes

Calix[n]arenes as cyclic oligomers are important receptors of supramolecular hosts involved in host-guest molecular recognition of various compounds as well as in analytical applications such as separation of chemical or biochemical compounds. Derivatisation of calix[n]arenes at the upper and lower rim in order to introduce various functional groups has led to new compounds with desired properties. The synthesis of efficient receptors for molecular recognition of bioactive molecules contribute to understanding of the molecular recognition in biological processes. In the present contribution, we reported aspects of complex formation, solvent extraction and transport through liquid membrane assisted by the pH gradient of amino acid methylesters by using a series of calix[4]arenes substituted by acid and amido functions, glycolic chains and hydroxyl groups. All these receptors have been found to act as extractants in liquid-liquid extraction or carriers for transport trough liquid membrane of aromatic amino acid methylesters aiming at their separation. The complexation properties of calix[n]arenes towards amino acids have been evaluated by UV-Vis spectrometry. The effects of physicochemical parameters that might influence the separation of amino acids by extraction process, and transport trough liquid membrane using functionalized calix[4]arenes have been investigated.