Nonlinear dielectric response of dilute protein solutions

Abstract

The nonlinear dielectric response of proteins in solution far exceeds that of surrounding water. This high nonlinear contrast can be used to monitor protein conformational activity altering its dipole moment.

Linear and Nonlinear Dielectric Response of Intrinsically Disordered Proteins

“…When dipolar correlations are screened, one obtains g K − 1 ≪ 1 and a ∝ c p ⟨M p 2 ⟩ 2 . A positive contribution from g K − 1 becomes dominant with decreasing ionic strength, and the NDE gains a strong, ∝ c p 3 ⟨M p 2 ⟩ 4 , scaling with the protein concentration 11 (Figure 3B). This result is based on the perturbation expansion for g K (eq 17).…”

“…The dipole moment of the sample fluctuates due to conformational changes of individual proteins, their density fluctuations, and their rotations producing non-Gaussian statistics of M z even in the limit of infinite dilution. 19 The NDE was shown 11 to be highly sensitive to protein dipole interactions responsible for the scaling a ∝ M p 8 in the regime dominated by dipolar correlations. Because of this strong scaling, nonlinear dielectric spectroscopy can be used to monitor protein conformations and, potentially, physiological activity.…”

“…The NDE was shown to be highly sensitive to protein dipole interactions responsible for the scaling a ∝ M p 8 in the regime dominated by dipolar correlations. Because of this strong scaling, nonlinear dielectric spectroscopy can be used to monitor protein conformations and, potentially, physiological activity.…”

“…The previous theoretical study of the NDE of protein solutions has shown that the first summand in eq , arising from interactions between the protein dipoles, dominates for most practical conditions unless at very low protein concentrations. Electrolyte screening was not considered in that work, and here we add ionic screening to evaluate conditions allowing to extract χ B from the Piekara coefficient.…”

“…The first exploration of this possibility 11 has indeed shown that the nonlinear dielectric effect (NDE) arising from proteins far exceeds that of the solvent. The NDE arises from correlations of protein dipoles if they are not screened by electrolyte.…”