The Study of  Physical Properties of Lipid Monolayers Composed of Amphiphilic Carotenoids

Jana Šandorová 1Zuzana Garaiova 1Christer L. Øpstad 2Vassilia Partali 2Hans R. Sliwka 2Tibor Hianik 1

1. Comenius University, Department of Biophysics and Chemical Physics, Mlynská dolina F1, Bratislava 842 48, Slovakia (Slovak Rep.)
2. Department of Chemistry, Norwegian University of Science and Technology (NTNU), Trondheim N - 7491, Norway

Abstract

We studied physical properties of mixed monolayers composed of dipalmitoyl-phosphatidylcholine (DPPC) and specially designed amphiphilic carotenoid (C2) containing glycerophosphocholine group. The carotenoids formed stable monolayers at an air-water interface. Using Langmuir method we obtained series of π-A isotherms  and determined the mean area per molecule of pure carotenoids  (76.1 ± 2.5 Ǻ2), DPPC (57.5 ± 4.4Ǻ2) and for their mixtures. The C2 does not affect the shape of the isotherm and collaps pressure, but caused slight shift of the isotherm toward larger molecular area. The analysis of mixing properties showed that at the surface pressure above 10 mN/m the aggregates composed of pure carotenoids apeared, while at lower surface pressures the complexes of lipids and carotenoids were formed at relatively low molecular fraction of C2 (0.2-0.5 mol%). The compressibility modulus of the monolayers composed of DPPC was larger in comparison with those of carotenoids. However, already at low molar content of carotenoids (0,2 mol%) the elastic modulus increased suggesting high ordered structures due to van der Waals interactions between the hydrophobic chains of DPPC and polyene chain of C2. Measurement of dipole potential evidences on possibility of parallel and perpendicular orientation of C2 relatively to the subphase in the mixed monolayers.

Acknowlegements: This work was supported by Slovak Research and Development Agency (Contracts No. APVV-0410-10, LPP-0250-09 and SK-PL-0034-09) and Grant Agency VEGA (Project No.1/0794/10).

 

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Presentation: Poster at SMCBS'2011 International Workshop, by Zuzana Garaiova
See On-line Journal of SMCBS'2011 International Workshop

Submitted: 2011-08-31 14:01
Revised:   2011-08-31 14:01