1 4 benzoquinone bq

Copper(II) acetate hydrate (Sigma-Aldrich, St. Louis, MO, USA, 98% purity), SWCNTs possessing an outward diameter of 1–2 nm, (US Research Nanomaterials, Inc., Houston, TX, USA, >90% purity), ethanol (Sigma-Aldrich, 99.5%), and MB (Alfa Aesar, Heysham, Lancashire, UK, high purity), potassium iodide (KI, Sigma-Aldrich, 99.99% purity), isopropyl alcohol (IPA, Sigma-Aldrich, 99.7% purity), 1,4-benzoquinone (BQ, Sigma-Aldrich, 99.99% purity) were employed with no additional purification; working MB solutions with the required concentrations were solubilized using distilled water.

where I_contr and I_MNP are the maximum bioluminescence intensities in the absence and presence of MNPs, respectively.
Values of I^rel were determined at different concentrations of MNPs. The dependence of I^rel vs. MNP concentrations was studied and plotted.
Additionally, to characterize the toxic effects of MNPs on the bacteria, their effective concentrations that inhibited the luminescence intensity by 50% (I^rel = 0.5), EC₅₀, were determined and compared.
To create conditions of the model oxidative stress, we used an organic oxidizer, 1,4-benzoquinone (Bq) (Sigma-Aldrich, St. Louis, MO, USA). The Bq was prepared in 3% NaCl solutions and in distilled water for bacterial and enzymatic assays, respectively. The Bq concentrations that inhibited the bioluminescence intensity of bacterial and enzymatic systems by 50% were applied in the experiments (10⁻⁷ M and 5 × 10⁻⁷ M, respectively). To study and compare changes in the toxicity in the Bq solutions with the addition of MNPs, the antioxidant coefficients I^rel_Bq were determined as follows:
where, I_MNP + _Bq and I_Bq are the maximum bioluminescence intensities in the Bq solutions in the presence and absence of MNPs, respectively.
A higher MNP concentration range inhibiting the bioluminescence intensity (I^rel < 1) was not used in the experiments to determine I^rel_Bq. The dependence of I_MNP + _Bq vs. MNP concentrations was studied and plotted.