Lipid organization in liposomes can be evaluated by measuring
the vibrational symmetric stretching energy of CH2 at 2850 cm1
using FTIR. Peak wavenumber value increases with fluidity. Experiments
were performed with an IFS vector V22 spectrophotometer
(Bruker Optics, Wissenbourg, France) equipped with a Bio
ATR II in silicon crystal. Measurements were taken at every 4 C
from 4 C to 40 C, with equilibrium time of 120 s for each measurement
temperature. Temperature of the crystal was controlled
by Bio-ATR II cells (Bruker Optics, Wissenbourg, France) with a
double coat to allow liquid circulation and a cryostat to regulate
temperature. Between 10 and 20 mg of dry lipids was diluted in
100 ml of chloroform. 50 ml were deposited on the crystal and
evaporated at room temperature. After evaporation, 100 ml of
deuterium oxide was deposited on the film to hydrate the lipids.
Data were processed using OPUS software (Bruker, USA).