Albumin-fatty acid interactions at monolayer interface
1 Department of Biological Sciences, Faculty of Science and Technology, Sunway University, No. 5, Jalan Universiti, Bandar Sunway, Petaling Jaya, Selangor 46150, Malaysia
2 Department of Chemistry, Faculty of Science, University of Malaya, Kuala Lumpur 50603, Malaysia
Nanoscale Research Letters 2014, 9:218 doi:10.1186/1556-276X-9-218Published: 7 May 2014
The fluid mosaic model of Singer and Nicolson in 1972 shows how proteins are embedded in membranes. To elucidate the interactions between proteins and the surrounding lipids, stearic acid (SA) and bovine serum albumin (BSA) were used as lipid-protein components to mimic the normal membrane bilayer environment using the Langmuir-Blodgett technique. Surface pressure (π)-molecular area (A) isotherms were recorded for the SA monolayer in the presence of BSA on water. The mixed monolayer was successfully transferred onto an oxidized silicon wafer and imaged by tapping mode atomic force microscopy (AFM). Miscibility, compressibility and thermodynamic stability of the mixed system were examined. A large negative deviation of Aex, together with the minimum value of ΔGex, was observed when the mole fraction of BSA (XBSA) was 0.8, indicating this to be the most stable mixture. In a compressibility analysis, XBSA was observed at below 50 mN m-1, denoting a liquid-expanded phase and showing the occurrence of a strong interaction of SA with BSA molecules in this phase. AFM observations supported the quantitative data indicating that BSA was strongly attracted onto the membrane surface as predicted.