Phospholipid monolayers chiral discrimination

The ability of a chiral molecule to distinguish between the enantiomers of a second (different) chiral molecule was defined in Sect. II as a diastereomer discrimination. This phenomenon may be observed in a mixed monolayer of two chiral surfactants and may also occur when a chiral substance is dissolved in the aqueous subphase under the monolayer of a second chiral substance. As before, examples of such chiral discrimination would not include those whose difference in monolayer behavior results only from the gross structural differences of diastereomers such as the different force-area characteristics exhibited by mixed monolayers of l-oleoyl-2-stearoyl-3-s -phospha-tidylcholine with epimeric steroids (120). The relevant experiment, that of comparing the monolayer behavior of mixed monolayers of cholesterol with enantiomeric phospholipids, has been reported (121). As might be anticipated from our previous discussion of... 

Both the N- (a-methylbenzy 1) stearamide and phospholipid systems as detailed above proved to be difficult systems with which to work. The inability of N- a-methylbenzy 1)stearamide to form stable monolayers or even to spread from the crystal on anything but very acidic subphases presents a significant technical challenge despite the presence of a chiral headgroup that is unobstructed by other molecular features. On the other hand, the phospholipid surfactants that spread to form stable films both from solution and from their bulk crystals on pure water subphases at ambient temperatures displayed no discernible enantiomeric discrimination in any film property. The chiral functionality on these biomolecules is apparently shielded from intermolecular interactions with other chiral centers to the extent... 

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