CD spectra of MBI-Cu/ZnSOD system.

<p>Conditions: Cu/ZnSOD: 5.0×10⁻⁷ molL⁻¹; pH 7.4; <i>T</i> = 293 K.</p

Stern-Volmer quenching constants for the interaction of MBI with Cu/ZnSOD at 293 K and 310 K.

a<p><i>R</i> is the correlation coefficient.</p>b<p><i>S.D.</i> is the standard deviation for the <i>K</i>_SV values.</p><p>Stern-Volmer quenching constants for the interaction of MBI with Cu/ZnSOD at 293 K and 310 K.</p

Effect of MBI on Cu/ZnSOD fluorescence.

<p>Conditions: Cu/ZnSOD: 3.0×10⁻⁶ molL⁻¹; MBI/(×10⁻⁵ molL⁻¹): (a) 0, (b) 1, (c) 2, (d) 3, (e) 4, (f) 5; (g): MBI (1×10⁻⁵ molL⁻¹) + buffer (0.02 molL⁻¹); pH 7.4; <i>T</i> = 293 K.</p

Molecular Interaction Mechanism between 2-Mercaptobenzimidazole and Copper-Zinc Superoxide Dismutase

<div><p>2-Mercaptobenzimidazole (MBI) is widely utilized as a corrosion inhibitor, copper-plating brightener and rubber accelerator. The residue of MBI in the environment is potentially harmful. In the present work, the toxic interaction of MBI with the important antioxidant enzyme copper-zinc superoxide dismutase (Cu/ZnSOD) was investigated using spectroscopic and molecular docking methods. MBI can interact with Cu/ZnSOD to form an MBI-Cu/ZnSOD complex. The binding constant, number of binding sites and thermodynamic parameters were measured, which indicated that MBI could spontaneously bind with Cu/ZnSOD with one binding site through hydrogen bonds and van der Waals forces. MBI bound into the Cu/ZnSOD interface of two subdomains, which caused some microenvironmental and secondary structure changes of Cu/ZnSOD and further resulted in the inhibition of Cu/ZnSOD activity. This work provides direct evidence at a molecular level to show that exposure to MBI could induce changes in the structure and function of the enzyme Cu/ZnSOD. The estimated methods in this work may be applied to probe molecular interactions of biomacromolecules and other pollutants and drugs.</p></div

Synchronous fluorescence spectra of Cu/ZnSOD (A) Δ<i>λ</i> = 15 nm and (B) Δ<i>λ</i> = 60 nm.

<p>Conditions: Cu/ZnSOD: 3.0×10⁻⁶ molL⁻¹; MBI/(×10⁻⁵ molL⁻¹): (a) 0, (b) 1, (c) 2, (d) 3, (e) 4, (f) 5; pH 7.4; <i>T</i> = 293 K.</p

Distance between MBI and the neighboring residues (6 Å involved).

<p>Distance between MBI and the neighboring residues (6 Å involved).</p

Binding constants and relative thermodynamic parameters of the MBI-Cu/ZnSOD system.

a<p><i>R</i> is the correlation coefficient for the <i>K</i>_a values.</p><p>Binding constants and relative thermodynamic parameters of the MBI-Cu/ZnSOD system.</p

Quenching of Cu/ZnSOD synchronous fluorescence by MBI.

<p>Conditions: Cu/ZnSOD: 3.0×10⁻⁶ molL⁻¹; (○)Δ<i>λ</i> = 15 nm and (▪) Δ<i>λ</i> = 60 nm.</p

Docking results of the MBI and Cu/ZnSOD system.

<p>(A) Binding site of MBI to Cu/ZnSOD. Two subdomains of Cu/ZnSOD are in different colors. (B) 2D structure of MBI with atom numbers. (C) Detailed illustration of the binding between MBI and Cu/ZnSOD. Hydrogen bonds are depicted as red dashed lines. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of the article).</p

Effect of MBI on Cu/ZnSOD activity.

<p>Cu/ZnSOD was exposed to graded concentrations of MBI for 60, 120 or 240 min. Conditions: Cu/ZnSOD: 3 nM. Data were pooled from at least three independent experiments and analyzed with one-way ANOVA. Error bars indicate SD.</p