Study of the interfacial properties of calixarenes and their interaction with dopamine in mixed phospholipid monolayers
|Pavol Vitovic 1, Tibor Hianik 1, Dimitrios P. Nikolelis 2, Martin Weis 3, Julius Cirák 3|
1. Comenius University, Department of Biophysics and Chemical Physics, Mlynská dolina F1, Bratislava 842 48, Slovakia (Slovak Rep.)
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 ligands1-3. Herein we present the results of the study of the physical properties of monolayers formed by calixresorcinarenes 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 calixarene 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 calixresorcinarenes, 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 calixresorcinarene 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 calixarene in the monolayer. However, quantification of the excess of Gibbs free energy of the mutual calixresorcinarene-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.
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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
Presentation: Short communication at SMCBS'2009 International Workshop, by Pavol Vitovic
See On-line Journal of SMCBS'2009 International Workshop
Submitted: 2009-08-31 11:43 Revised: 2009-10-28 12:13