Raman Spectroscopy of Phospholipid Black Films

Single planar bilayers of DMPC free-standing in air (black films) have been studied by confocal micro Raman spectroscopy in the 600−4000 cm -1 spectral range. The DMPC vibrational bands are well-defined. This allows the derivation of two parameters associated with the packing and mobility and with the fluidity of the alkyl chains and to quantify the rigidity enhancement accompanying the L α liquid crystalline to gel phase transition ( T m = 24 °C). The intensity of the water band allows to evaluate the thickness of the interstitial aqueous core which is 22 ± 4 Å in the L α phase. This water band exhibits a spectral change relative to bulk liquid water which is significant of the confinement of water molecules in the aqueous core.