Deutsche Tagung f ¨ur Forschung mit ... - SNI-Portal

Biologische Systeme und Medizin Poster: Mi., 14:00–16:30 M-P192
Interaction of long side chains Quinones and Hydroquinones with Model
Membranes.
Sérgio S. Funari 1 , Maria Hanulova 1 , Claudio di Vitta 2
1 HASYLAB at DESY, Notkestrase 85, 22603 Hamburg, Germany – 2 Institute of Chemistry,
University of Sao Paulo, Sao Paulo, Brasil
Quinones and hydroquinones present some biological activity. Generally speaking not
much is known about and it is still not clear the relationship between doses and their
effects. Moreover, the mechanism of action also is still speculative. Here we present
the initial part of our study, i.e. the interaction of these compounds with model
membranes. Two compounds were synthesized with side chains matching the acyl
chain lenght of lipids forming model membranes. We present results from mixtures of
these compounds with POPC, a zwitterionic lipid, using polarizing optical microscopy
(POM) and X-ray scattering obtained simultaneously from small and wide angles at the
soft condensed matter beam line A2 from HASYLAB at DESY. For each sample studied
a temperature scan was carried out at typically 1-2 ◦ C/min. Due to the hydrophobicity
of these compounds, they remain crystalline (needles) in water. Therefore mixtures
of them with lipids could not be prepared by direct missing, but rather requiring a
chloroform solution of both components, followed by solvent evaporation and posterior
direct hydration. X-ray scattering near room temperature show patterns containing
characteristics of lipid bilayers superimposed to typical patterns from crystals. It seems
that at room temperature we have two phases, a solid crystal (quinone or hydroquinone)
and a lipid liquid crystalline. Interestingly, they do not separate easily. Heating these
samples to relatively high temperatures causes the melting of the crystals (above ca.
50 ◦ C, but depending on the sample composition). Cooling at 1-2 ◦ C/min does not
produce an X-ray pattern of a two mixed phases system. However the pattern can be
seen in the following day. The phase transitions and the mixing of phases are being
investigated in more detail and shall be reported.