Calix[n]arenes are macrocylic compounds derivated from the synthesis of phenols and aldehydes, where [n] refers to the number of the macrocyclic cycles. The characteristic feature of calix[n]arenes is the presence of the hydrophobic cavity lending them ability to recognize metal ions, organic molecules, proteins and other ligands^1-3. Herein we present the results of the study of the physical properties  of monolayers formed by calix[4]resorcinarenes and their mixtures with dipalmitoyl phosphatidylcholine (DPPC) formed at the air/water interface. We also studied the mechanisms of interaction of calixarenes with neurotransmitter dopamine.  For this purpose we applied the methods of measurement  surface-pressure area isotherms, surface potential and Maxwell displacement currents (MDC).^4,5 Due to their amphiphilic nature both calix[4]arene and DPPC form stable monolayers. For mixed monolayers, increase of the content of calixarenes in the monolayers resulted in increase of the mean molecular area and decrease of the compressibility modulus. We also observed immiscibility of both components in the mixed monolayers at all the molar ratios studies, mainly at the higher surface pressure when the monolayers were in the solid state.  Presence of dopamine in the subphase resulted in the increase of the mean molecular area and in decrease of the monolayer compressibility modulus, which suggest destabilization of the calixarene monolayers. This could be due to the binding of the dopamine inside the hydrophobic cavities of calix[4]resorcinarenes, weakening thus the strength of the lateral forces acting between the adjacent molecules in the monolayer. Moreover, MDC was used for the first time to study changes in the charge state of the monolayers. Dipole moment of calix[4]resorcinarene in the presence of dopamine, as analyzed by MDC, reached the maximum value in the phase transition from liquid to solid phase, which suggests the binding of dopamine depends on the surface pressure, and hence on the orientation of the calix[4]arene in the monolayer. However, quantification of the excess of Gibbs free energy of the mutual calix[4]resorcinarene-dopamine bond implies weak interactions.

Acknowlegements: This work was supported by Agency for Promotion Research and Development under the contracts No. APVV-0362-07 and APVV-LPP-0341-09.

¹      Gutsche, C. D., Muthukrishnan, R. J. Org. Chem. 43 (1978), 4905-4906

²      Nikolelis, D. P., Petropoulou, S. S. E., Pergel, E., Toth, K. Electroanalysis 14 (2002), 783-789

³     Oshima, T., Ishii, T., Baba, Y., Higuchi, H., Ohto, K., Inoue, K. Solv. Extr. Res. Dev. Japan 15 (2008), 89-98

⁴    Vitovič, P., Nikolelis, D. P., Hianik, T.  Biochim. Biophys. Acta 1758 (2006), 1852-1861

⁵      Weis, M., Janíček, R., Cirák, J., Hianik, T. J. Phys. Chem. B 111 (2007), 10626-10632

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