Congresos y reuniones científicas
Título:
Thermotropic phase behavior of isolated myelin membranes under different ionic content as observed by SAXS/SANS combination.
Autor/es:
RAFAEL GUSTAVO OLIVEIRA; SCHNECK, E.; FUNARI, S. S.; DEMÉ, B.; TANAKA, M.; MAGGIO, B.
Reunión:
Workshop; BILL 2011 (Bilayers at Institute Laue Langevin); 2011
Institución organizadora:
Institute Laue Langevin
Resumen:
The purified myelin membrane
is the starting material for the biochemical studies such as isolation
of detergent resistant membrane fractions. Normally, the last procedure
involves the extraction of lipids on non-ionic detergents under
cooling. The thermotropic behavior of purified myelin membranes is
examined in the 5-46 ºC for a series of different solvent systems by
SAXS/WAXS and DSC. Additionally we succeeded in producing planar
multilayers of myelin on Si/SiO2 wafers by testing different
spreading techniques. The objective here is to take advantage of
planar scattering geometry in SANS experiments, controlling the ionic
content of the aqueous media. The results with SAXS and SANS are
consistent in showing that, regardless of the aqueous media, the myelin
membrane becomes heterogeneous below room temperature. The
heterogeneous state is further stabilized by ionic media like
physiological solution, then phase coexistence persists up to the
border of the physiological temperature. The extreme case is the one of
Ca2+ at high concentration (over 20 mM), then the phase
coexistence is permanent at least up to 46 ºC. Nevertheless, the
relative proportion of the phases, and thus probably the phase
composition, markedly changes with temperature. From a general point of
view, it has been suggested by multiple authors that cell membranes
are set at the border of phase transition or critical points for phase
mixing. The results showed appear to fit into this general framework.