Title
The adsorption and unfolding kinetics determines the folding state of proteins at the air-water interface and thereby the equation of state
Author
Wierenga, P.A.
Egmond, M.R.
Voragen, A.G.J.
de Jongh, H.H.J.
TNO Kwaliteit van Leven
Publication year
2006
Abstract
Unfolding of proteins has often been mentioned as an important factor during the adsorption process at air-water interfaces and in the increase of surface pressure at later stages of the adsorption process. This work focuses on the question whether the folding state of the adsorbed protein depends on the rate of adsorption to the interface, which can be controlled by bulk concentration. Therefore, the adsorption of proteins with varying structural stabilities at several protein concentrations was studied using ellipsometry and surface tensiometry. For β-lactoglobulin the adsorbed amount (Γ) needed to reach a certain surface pressure (Π) decreased with decreasing bulk concentration. Ovalbumin showed no such dependence. To verify whether this difference in behavior is caused by the difference in structural stability, similar experiments were performed with cytochrome c and a destabilized variant of this protein. Both proteins showed identical Π - Γ, and no dependence on bulk concentration. From this work it was concluded that unfolding will only take place if the kinetics of adsorption is similar or slower than the kinetics of unfolding. The latter depends on the activation energy of unfolding (which is in the order of 100-300 kJ/mol), rather than the free energy of unfolding (typically 10-50 kJ/mol). © 2006 Elsevier Inc. All rights reserved.
Subject
Nutrition
Food technology
Air-water interface
Protein adsorption
Surface denaturation
Surface equation of state
Adsorption
Cytology
Equations of state
Interfaces (materials)
Molecules
Surface properties
Air-water interface
Protein adsorption
Surface denaturation
Surface equation of state
Proteins
beta lactoglobulin
cytochrome c
ovalbumin
water
adsorption
air
article
ellipsometry
kinetics
mathematical analysis
pressure
priority journal
protein folding
protein processing
protein stability
protein structure
surface property
Adsorption
Air
Calorimetry
Cytochromes c
Drug Stability
Kinetics
Lactoglobulins
Ovalbumin
Pressure
Protein Conformation
Protein Denaturation
Protein Folding
Proteins
Surface Properties
Urea
Water
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DOI
https://doi.org/10.1016/j.jcis.2006.03.016
TNO identifier
239372
ISSN
0021-9797
Source
Journal of Colloid and Interface Science, 299 (2), 850-857
Document type
article