DIFFERENCES IN THE PHYSICAL-PROPERTIES OF LIPID MONOLAYERS AND BILAYERS ON A SPHERICAL SOLID SUPPORT

A monolayer of 1,2-dipalmitoyl-d(62)-glycero-3-phosphocholine (DPPC-d( 62)) coated onto silanized silica beads (spherical supported monolayer : SSM) is studied by H-2-NMR and DSC, The results are compared with th ose obtained from a single bilayer on the same solid support (spherica l supported vesicles: SSV) and from multilamellar vesicles (MLV). The phase transition temperature (T-m) of the SSMs is significantly higher than that of the bilayer systems and the extent of this difference de pends on the lipid density in the monolayer that is determined during its preparation, H-2-NMR reveals a gel and fluid phase coexistence in the SSM transition region. A comparison of the H-2-NMR line shapes sug gests the presence of highly curved structures for the fluid phase of the SSM samples, From a comparison of SSM and SSV transverse relaxatio n in the fluid phase we can conclude that the lateral diffusion coeffi cient D-1 in supported monolayers is similar to that in bilayers.