Adsorption of pepsin in octadecylamine matrix at air–water interface Original Research Article

The incorporation/entrapment of water-soluble surface-active enzyme, pepsin (PEP) within an insoluble cationic octadecylamine (ODA) monolayer is studied by Langmuir–Blodgett technique. The observation suggests that the incorporation of PEP is less preferable at compressed region (~ 30 mN/m). The electrostatic interaction plays a significant role for the greater incorporation of PEP in cationic ODA monolayer. The surface pressure–area isotherms along with FE-SEM analysis indicates the squeezing out of PEP from the monolayer at higher surface pressure. This will assist to select the optimum surface pressure to obtain a good quality and well-ordered Langmuir monolayer. FTIR study of amide bands together with FE-SEM imaging of ODA–PEP mixed film indicates that ODA perturbs the PEP by the increment of β-structure resulting into larger unfolding, intra, and intermolecular aggregates.