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Monolayers and bilayers are useful models of natural membranes, in this paper we report some investigations either on membrane components or their model analogs, in two-dimensional state. In particular we studied mixed monolayers of two polypeptides to deduce the interfacial orientation and the bidimensional miscibility of the two macromolecules. The properties of lipids in monolayers, Black Lipid Membranes (BLM) and vesicles were then compared. We obtained the conditions of molecular structure and of interfacial distribution for the formation and the stability of each model system. We also modeled photoprocesses occurring in natural membranes studying charge transfer in mono and multilayers between an excited donor implanted in the lipid portion of the system and an appropriate water soluble acceptor. Finally we describe the construction of a mimetic membrane containing an ioncarrier, namely valinomycin, by means of Langmuir-Blodgett technique that proved to be selective to potassium ions.En considtrant que le monocouches et bicouches sont des modkles de membrane trks utiles, on report des investigations men& soit sur des composants modtles soit sur des constituants des membranes elles-mCme. En particulier on etudie des monocouches melange de deux polypeptides et l'on dauit leur orientation ?I l'interface ainsi que leur miscibilitt bidimensionnelle. On compare ensuite le proprietts des lipides dans le monocouches, le BLM et le vtsicules et l'on deduit les conditions de structure molkulaire et de distribution interfasale nhessaires ?I la formation et 3 la stabilitk de chaque systeme bidimensionnel.On ttudie aussi le processes de transferement de charge et de masse dans le monocouches et multicouches. Enfin on reporte la rMization d'une membrane mimetique contenante un transportateur ionique (Valinomicine) par le moyen de multicouches de L-B, qui se rkvkle selective aux ions K f .

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Electron spin resonance spectroscopy of doxylstearic acids with the paramagnetic unit inserted in the 5,6,7,9,12, and 16 carbon position was used to analyze the dynamic and structural features of dioleoylphosphatidylcholine (DOPC) vesicles in the presence and in the absence of ceramide (CER) and as a function of temperature. The sizes and the homogeneity of these lipid aggregates were checked by electron microscopy and turbidimetry. The order parameter, as calculated from the ESR line shapes, indicated that near room temperature the vesicles had a relatively high orientational organization from the polar surface down to the system of the double bonds of the oleoyl residues of DOPC, whereas the double-layer region beyond the double bond was increasingly fluid. At temperatures lower than the gel-liquid crystal phase transition of CER, T,, the presence of the sphingolipid did not alter significantly the motional properties of the hydrocarbon chains. At T 2 T,, the addition of CER affected only the lipid layer region from the surface down to the oleoyl double bonds with resulting increased fluidity. The double-bond region acted therefore as a boundary for the effect of CER. No definitive evidence of lipid interdigitation was given by the results reported in this work.

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