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-alpha liquid crystalline to gel phase transition (T-m = 24 degreesC). The intensity of the water band allows to evaluate the thickness of the interstitial aqueous con which is 22 +/- 4 Angstrom in the L-alpha 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.