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Issue 19, 2005
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Proteinlipid interactions at the air/water interface

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Abstract

Surface pressure measurements and external reflection FTIR spectroscopy have been used to probe proteinlipid interactions at the air/water interface. Spread monomolecular layers of stearic acid and phosphocholine were prepared and held at different compressed phase states prior to the introduction of protein to the buffered subphase. Contrasting interfacial behaviour of the proteins, albumin and lysozyme, was observed and revealed the role of both electrostatic and hydrophobic interactions in protein adsorption. The rate of adsorption of lysozyme to the air/water interface increased dramatically in the presence of stearic acid, due to strong electrostatic interactions between the negatively charged stearic acid head group and lysozyme, whose net charge at pH 7 is positive. Introduction of albumin to the subphase resulted in solubilisation of the stearic acid via the formation of an albumin–stearic acid complex and subsequent adsorption of albumin. This observation held for both human and bovine serum albumin. Protein adsorption to a PC layer held at low surface pressure revealed adsorption rates similar to adsorption to the bare air/water interface and suggested very little interaction between the protein and the lipid. For PC layers in their compressed phase state some adsorption of protein occurred after long adsorption times. Structural changes of both lysozyme and albumin were observed during adsorption, but these were dramatically reduced in the presence of a lipid layer compared to that of adsorption to the pure air/water interface.

Graphical abstract: Protein–lipid interactions at the air/water interface

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Publication details

The article was received on 09 May 2005, accepted on 02 Aug 2005 and first published on 19 Aug 2005


Article type: Paper
DOI: 10.1039/B506558P
Citation: Phys. Chem. Chem. Phys., 2005,7, 3478-3485
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    Proteinlipid interactions at the air/water interface

    M. D. Lad, F. Birembaut, R. A. Frazier and R. J. Green, Phys. Chem. Chem. Phys., 2005, 7, 3478
    DOI: 10.1039/B506558P

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