Abstract
In this article, the interaction between bovine serum albumin (BSA) and the cationic 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) at the air-buffer interface was investigated at different subphase’s pH values (pH = 3, 5 and 10). Surface pressure measurements (π − A) and penetration kinetics process (π − t) were carried out to reveal the interaction mechanism and the dynamical behavior. The data showed that π − A isotherms moved towards larger mean molecular area when the concentration of BSA ([BSA]) increased, the amount of BSA adsorbed onto DOTAP monolayer reached a threshold value at a [BSA] of 5 × 10−8 M, and BSA desorbed from the lipid monolayer as time goes by. The results revealed that the association of BSA with DOTAP at the air-buffer interface was affected by the subphase’s pH value. When pH = 10, the interaction mechanism between them was a combination of hydrophobic interaction and electrostatic attraction, so BSA molecules could be well separated and purified from complex mixtures. AFM images demonstrated that pH value and [BSA] could affect the morphology feature of DOTAP monolayer and the adsorption and desorption processes of BSA. So the study provides an important experimental basis and theoretical support for learning the interaction mechanism among biomolecules in separation and purification of biomolecules and biosensor.
Highlights
In recent years, the research of the separation and purification of proteins has aroused extensive concern due to its increasing significance in diagnostics and therapeutics[1]
Electrostatic interaction existed between the charged molecules of Bovine serum albumin (BSA) and the polar head of dioleoyl-3-trimethy- lammonium-propane (DOTAP) at pH = 3 and 10, and non-electrostatic interaction existed at pH = 5, when BSA moved to the interface
If the binding of DOTAP to BSA was dominated by electrostatic interaction, the π − A isotherms of DOTAP monolayer would not shift to the larger mean molecular area with the addition of BSA at pH = 3
Summary
The research of the separation and purification of proteins has aroused extensive concern due to its increasing significance in diagnostics and therapeutics[1]. The combination of molecular recognition and LB technique is a very efficient method for the separation and purification of proteins[2]. The study of the interaction between protein and ligand provides an important experimental basis and theoretical support for learning the interaction mechanism among biomolecules in the fields of separation and purification of biomolecules and biosensor. Bovine serum albumin (BSA) is one of the main proteins in bovine serum. It involves many biological functions, such as transporting metal ions, nutrients and drugs, maintaining osmotic pressure and buffering pH value[2,6]. The separation and purification of BSA from complex mixtures are important for health care and pharmaceutical applications. The morphology changes of DOTAP monolayer at different pHs can be observed from AFM images
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