Mixed monomolecular films

Using an automated film balance the behavior of mixed monomolecular films exhibiting deviations from ideality was studied. Particular attention was paid to condensation effects obtained when cholesterol is mixed with a more expanded component. The deviations at various film pressures are discussed in terms of the partial molecular areas of the film components. Slope changes in these plots are caused by phase transitions of the expanded monolayer component and do not indicate the formation of surface complexes. In addition, the excess free energies, entropies, and enthalpies of mixing were evaluated, but these parameters could be interpreted only for systems involving pure expanded components, for which it is clear that the observed condensation effects must involve molecular interactions. 

The monolayer technique was also used to study the covalent inhibition of lipases using mixed monomolecular films of substrate containing amphiphilic inhibitor molecules and using a zero order trough with a reaction compartment containing the mixed substrate/inhibitor film whereas the reservoir compartment was covered with a film of pure substrate [44, 57]. 

Pieroni, G. and Verger, R. (1979) Hydrolysis of mixed monomolecular films of triglyceride/lecithin by pancreatic lipase. ). Biol. Chem. 254, 10090-10094... 

Spratte, K. and Riegler, H., Steady-state morphology and composition of mixed monomolecular films at the air-water interface in the vicinity of the three-phase line Model calculations and experiments, Langmuir, 10, 3161-3173 (1994). 

In mixed bilayer vesicles diacetylenic and natural lipids exhibit the same miscibility behavior as in monomolecular films. This can be demonstrated using differential scanning calorimetry (DSC). The neutral lipid (23) is immiscible with DSPC or DOPC as indicated by the two phase transitions of the mixed liposomes which occur at the same temperatures as those of the pure components (Fig. 33 a). 

Formation of lamellar liquid crystalline phases at the O/W interface This mechanism, as suggested by Friberg and coworkers [37], proposed that surfactant or mixed surfactant film can produce several bilayers that wrap the droplets. As a result of these multilayer structures, the potential drop is shifted to longer distances, thus reducing the van der Waals attractions. A schematic representation of the role of Hquid crystals is shown in Figure 10.32, which illustrates the difference between having a monomolecular layer and a multilayer, as is the case with hquid crystals. 

An ordered arrangement of GOD and ferrocene on a platinum electrode has been obtained by using the Langmuir-Blodgett (LB) technique (Moriizumi et al., 1988). Monomolecular films on electrodes were made by mixing the mediator with lipid followed by adsorption of GOD on the film at the trough surface. The quantity of GOD could be flexibly controlled by the number of LB films, thus giving sensors of different sensitivity. 

Since the 1960s natural surface films ( sea slicks ), that tend to exhibit thicknesses of one molecule only, have been in the focus of interdisciplinary research that required input by various disciplines such as oceanography, meteorology, physics and chemistry. Albeit the thickness of such monomolecular surface films is small compared to that of mineral oil films their wave damping capability and, thus, their influence on air-sea interactions is comparable. Consequently, they are still often mixed up with mineral oil films ( oil spills ), particularly in the Same of remote sensing applications. It is the aim of the present book to provide a scientific basis that allows avoiding such misinterpretation in the future. 

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