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Formation of Dielectric Layers and Charge Regulation in Protein Adsorption at Biomimetic Interfaces
journal contribution
posted on 2012-01-24, 00:00 authored by Rune A. Hartvig, Marco van de Weert, Jesper Østergaard, Lene Jorgensen, Henrik JensenProtein charge is an important parameter in the understanding
of
protein interactions and function. Proteins are subject to dynamic
charge regulation, that is, the influence of the local environment
(such as charged interfaces and biopolymers) on protein charge. Charge
regulation is governed by differences in the dielectric and electrostatic
environment between adsorbed protein and the free protein in bulk
solution. In this work protein charge regulation is addressed experimentally
by employing electrochemistry at interfaces between two immiscible
electrolyte solutions (ITIES) as well as theoretically by developing
a new protein adsorption model at ITIES. Electrochemistry at ITIES
is shown to be particularly well suited to study protein charge regulation
as the adsorbed protein experiences a different dielectric environment
compared to the bulk phase and the external control of the water/oil
potential difference allows systematic studies on how potential induced
ion gradients affect protein charge. The theoretical model incorporates
all the features of the experimental system and specifically takes
into account protein charge regulation at ITIES as well as the impact
of the formation of dielectric layers on the experimentally observed
impedance. The model parameters include the protein charge–pH
profile, bulk pH, and the overall potential difference. It is shown
that the formation of a dielectric layer and the associated charge
regulation are the main factors dictating the observed experimental
behavior. Finally, the theoretical model is used to interpret literature
results, and the consistency between the model and the relatively
large data set suggests that the model may be used more generally
for understanding and predicting protein adsorption.