Globular proteins exhibit dielectrophoresis (DEP) responses in experiments where the applied field gradient factor ∇E² appears far too small, according to standard DEP theory, to overcome dispersive forces associated with the thermal energy kT of disorder. To address this a DEP force equation is proposed that replaces a previous empirical relationship between the macroscopic and microscopic forms of the Clausius–Mossotti factor. This equation relates the DEP response of a protein directly to the dielectric increment δε⁺ and decrement δε⁻ that characterize its β‐dispersion at radio frequencies, and also indirectly to its intrinsic dipole moment by way of providing a measure of the protein's effective volume. A parameter Γ_pw, taken as a measure of cross‐correlated dipole interactions between the protein and its water molecules of hydration, is included in this equation. For 9 of the 12 proteins, for which an evaluation can presently be made, Γ_pw has a value of ≈4600 ± 120. These conclusions follow an analysis of the failure of macroscopic dielectric mixture (effective medium) theories to predict the dielectric properties of solvated proteins. The implication of a polarizability greatly exceeding the intrinsic value for a protein might reflect the formation of relaxor ferroelectric nanodomains in its hydration shell.

中文翻译：

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蛋白质介电泳：关键介电参数和进化理论

根据标准 DEP 理论，球状蛋白质在实验中表现出介电泳 (DEP) 响应，其中外加场梯度因子 ∇ E ²显得太小，无法克服与无序热能kT相关的色散力。为了解决这个问题，提出了一个 DEP 力方程，它取代了克劳修斯-莫索蒂因子的宏观和微观形式之间先前的经验关系。该方程将蛋白质的 DEP 响应直接与介电增量 δε ⁺和减量 δε ^{- 相关联}，后者表征其在射频下的 β 色散，并通过提供蛋白质有效体积的度量间接与其固有偶极矩相关。参数Γ_pw被视为蛋白质与其水合水分子之间互相关偶极相互作用的量度，包含在该方程中。对于目前可以对其进行评估的 12 种蛋白质中的 9 种，Γ _pw的值为 ≈4600 ± 120。这些结论是根据宏观介电混合物（有效介质）理论无法预测溶剂化蛋白质。极化率大大超过蛋白质的内在价值的含义可能反映了其水合壳中弛豫铁电纳米域的形成。