Title
Quantitative description of the relation between protein net charge and protein adsorption to air-water interfaces
Author
Wierenga, P.A.
Meinders, M.B.J.
Egmond, M.R.
Voragen, A.G.J.
de Jongh, H.H.J.
TNO Kwaliteit van Leven
Publication year
2005
Abstract
In this study a set of chemically engineered variants of ovalbumin was produced to study the effects of electrostatic charge on the adsorption kinetics and resulting surface pressure at the air-water interface. The modification itself was based on the coupling of succinic anhydride to lysine residues on the protein surface. After purification of the modified proteins, five homogeneous batches were obtained with increasing degrees of modification and ζ-potentials ranging from -19 to -26 mV (-17 mV for native ovalbumin). These batches showed no changes in secondary, tertiary, or quaternary structure compared to the native protein. However, the rate of adsorption as measured with ellipsometry was found to decrease with increasing net charge, even at the initial stages of adsorption. This indicates an energy barrier to adsorption. With the use of a model based on the random sequential adsorption model, the energy barrier for adsorption was calculated and found to increase from 4.1 kT to 6.1 kT when the protein net charge was increased from -12 to -26. A second effect was that the increased electrostatic repulsion resulted in a larger apparent size of the adsorbed proteins, which went from 19 to 31 nm2 (native and highest modification, respectively), corresponding to similar interaction energies at saturation. The interaction energy was found to determine not only the saturation surface load but also the surface pressure as a function of the surface load. This work shows that, in order to describe the functionality of proteins at interfaces, they can be described as hard colloidal particles. Further, it is shown that the build-up of protein surface layers can be described by the coulombic interactions, exposed protein hydrophobicity, and size. © 2005 American Chemical Society.
Subject
Nutrition
Food technology
Adsorption
Air
Chemical analysis
Colloids
Electric charge
Electrostatics
Hydrophobicity
Interfaces (materials)
Saturation (materials composition)
Water
Adsorption kinetics
Air-water interface
Electrostatic charge
Energy barrier
Surface pressure
Proteins
ovalbumin
water
adsorption
air
article
chemistry
flow kinetics
kinetics
protein secondary structure
protein tertiary structure
Adsorption
Air
Kinetics
Ovalbumin
Protein Structure, Secondary
Protein Structure, Tertiary
Rheology
Water
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http://resolver.tudelft.nl/uuid:2c29a06c-098a-4044-ae8b-137dd65d4dca
DOI
https://doi.org/10.1021/jp050990g
TNO identifier
238707
ISSN
1520-6106
Source
Journal of Physical Chemistry B, 109 (35), 16946-16952
Document type
article