Interaction and incorporation of ovalbumin with stearic acid monolayer: Langmuir-Blodgett film formation and deposition

In this communication, the surface activity of the ovalbumin (OVA) at the air/water interface was studied to establish the nature of the interaction with the stearic acid (SA) monolayer, based on Langmuir-Blodgett (LB) technique. The interaction was monitored by studying the time (t) variation of surface pressure (π) at constant area (A). The growth of π with time indicates a positive association between the SA and the OVA molecules. The surface compressibility analysis has been performed to specify the phase transition of OVA-SA mixed monolayer. Incorporation/association of OVA within the SA monolayer led to noteworthy changes in surface compressibility and was surface pressure as well as protein concentration dependent. Both the hydrophobic and the Vander wall type interactions are found to be responsible for the association. The quenching of tyrosine band in tryptophan excitation spectrum is observed in steady-state fluorescence spectroscopy. This suggests that the tyrosine is the probable binding site with SA. Due to incorporation of SA, the energy transfer from tyrosine to tryptophan is hindered. At higher pressure, OVA tend to squeeze out from the SA monolayer. The high-resolution field emission scanning electron microscope (FE-SEM) image confirms this observation. Aggregated protein structure observed at high pressure indicates unfolding of protein.