Miscibility of an acylated hepatitis A synthetic antigen derivative [palmitoyl VP3(110-121)] with lipids: a monolayer study

Mixed monolayers of an acylated derivative of hepatitis A synthetic peptide VP3(110-121) with neutral, cationic or anionic lipids were spread at the a ir/water interface. Deviations from ideality as well as thermodynamic value s were calculated at different surface pressures using the free-excess ener gy, the interaction parameter and the enthalpy. The miscibility at the coll apse point was also checked. Maximum deviations from ideality were found fo r mixtures containing the anionic lipid phosphatidylglycerol (PG), and it s eems that the monolayer composition is not stable through compression, as t he peptide is ejected from the film. Films containing neutral [dipalmitoylp hosphatidylcholine (DPPC)] or cationic [stearyl-amine (SA)] lipids showed m ore regular behaviour. As the peptide has a net negative charge it is proba ble that electrostatic interactions are in part responsible of the good mis cibility of palmitoyl VP3(110-121) with SA. In order to prepare liposomes c ontaining palmitoyl VP3(110-121), lipids such as SA or DPPC/SA will be a mo re suitable choice than anionic lipids such as PG.