Electrochemistry of Eu(III) Binding to N-terminal of Euplotes Octocarinatus Centrin

抄録

Ciliate Euplotes octocarinatus centrin (EoCen) is a member of the EF-hand super family of calcium-binding proteins, which is associated with the centrosomes. In this work, the interaction between N-terminal of EoCen (N-EoCen) and Eu³⁺ was investigated by cyclic voltammetry and UV-Vis spectroscopies. The result shows that a 2:1 of Eu³⁺ to N-EoCen complex (Eu₂-N-EoCen) is formed. The electrochemical characteristics of Eu₂-N-EoCen at a multi-wall carbon nanotube/Nafion composite film modified glassy carbon electrode (MWNT/Nafion/GCE) were then investigated in detail, from which a direct, quasi reversible electron transfer of Eu₂-N-EoCen had been obtained. According to the Laviron diffusionless-controled equations, the electron transfer rate constant k_s, was calculated to be 2.33 ± 0.14 s⁻¹. The pH dependence of the formal potential of Eu₂-N-EoCen suggests that protonation accompanies electron transfer between pH 5.5–7.4. The electrochemical redox and quantitative analysis of Eu₂-N-EoCen are therefore of great significance not only studying the physiological processes of Eu₂-N-EoCen in organisms but also the interaction mechanism with target protein.