pH and Solvent H/D Isotope Effects on the Thermodynamics and Kinetics of Electron Transfer for Electrode-Immobilized Native and Urea-Unfolded Stellacyanin

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• 作者：Antonio Ranieri ; Gianantonio Battistuzzi ; Marco Borsari ; Carlo Augusto Bortolotti ; Giulia Di Rocco ; Marco Sola
• 刊名：Langmuir
• 出版年：2012
• 出版时间：October 23, 2012
• 年：2012
• 卷：28
• 期：42
• 页码：15087-15094
• 全文大小：303K
• 年卷期：v.28,no.42(October 23, 2012)
• ISSN：1520-5827

文摘

The thermodynamics of Cu(II) to Cu(I) reduction and the kinetics of the electron transfer (ET) process for Rhus vernicifera stellacyanin (STC) immobilized on a decane-1-thiol coated gold electrode have been measured through cyclic voltammetry at varying pH and temperature, in the presence of urea and in D₂O. Immobilized STC undergoes a limited conformational change that mainly results in an enhanced exposure of one or both copper binding histidines to solvent which slightly stabilizes the cupric state and increases histidine basicity. The large immobilization-induced increase in the pK_a for the acid transition (from 4.5 to 6.3) makes this electrode鈥揝AM鈥損rotein construct an attractive candidate as a biomolecular ET switch operating near neutral pH in molecular electronics. Such a potential interest is increased by the robustness of this interface against chemical unfolding as it undergoes only moderate changes in the reduction thermodynamics and in the ET rate in the presence of up to 8 M urea. The sensitivity of these parameters to solvent H/D isotope effects testifies to the role of protein solvation as effector of the thermodynamics and kinetics of ET.