Catalytic spectrofluorimetric determination of superoxide anion radical and superoxide dismutase activity using N,N-dimethylaniline as the substrate for horseradish peroxidase (HRP)

Photochemical reaction of superoxide radicals with 1-naphthol

The photochemical reactions between 1-naphthol (1-NP) and the superoxide anion radical (O2•–) were investigated in detail by using 365 nm UV irradiation. The results showed that the conversion rate of 1-NP decreased with the increase of the initial concentration of 1-NP, whereas by increasing the pH and riboflavin concentration, the photochemical reaction was accelerated. The second-order reaction rate constant was estimated to be (3.64 ± 0.17) × 108 L mol−1 s−1. The major photolysis products identified by using gas chromatography – mass spectrometry (GC–MS) were 1,4-naphquinone and 2,3-epoxyresin-2,3-dihydro-1,4-naphquinone, and their reaction pathways were also discussed. An atmospheric model showed that both the bulk water reaction and the heterogeneous surface reaction deserve attention in atmospheric aqueous chemistry.

Etching of AuNPs Through Superoxide Radical Dismutation by Cu-Zn Superoxide Dismutase Resulted in Remarkable Changes of its Localized Surface Plasmon Resonance

BACKGROUND

Superoxide dismutases (SODs) are categorized as antioxidant enzymes that are involved in many processes such as stress signalling responses and cell protection against free radical species. The primary function of SOD is the removal of produced radical species like superoxide ions in different physiological processes. There are various isozymes of SODs which are classified according to the metal cofactor in their active sites into four general types of Fe-SOD, Mn-SOD, Cu/Zn-SOD and Ni-SOD. Among metal nanoparticles, gold nanoparticles (AuNPs) are useful for biological purposes as sensing probe for determining critical analysis based on surface plasmon resonance and colorimetric method. In this study, the human Cu-Zn SOD expressed, purified, and its interaction with AuNPs based on a new colorimetric method was investigated.

OBJECTIVES

In this approach, a colorimetric detection method for SOD activity was developed based on the carboxylic stabilized AuNPs.

MATERIAL AND METHODS

The Ni-NTA Sepharose affinity column was performed for the purification process of enzyme. Following SOD purification, the enzyme activity in presence of AuNPs due to the possible etching in the presence of free radicals which are produced by riboflavin, methionine, Na₂CO₃ and potassium phosphate buffer, have been performed. In addition, Fluorescence spectroscopy analysis toward SOD and gold nanoparticle were performed.

RESULTS

Superoxide radicals generated from the enzymatic reaction would preferentially etch AuNPs and resulted in remarkable changes of localized surface plasmon resonance of AuNPs, which is reduced in the presence of SOD. Under the optimized experimental conditions assay (pH~7.8 and 25 ˚C), better selectivity and sensitivity toward SOD activity was shown.

CONCLUSIONS

In this context, an indirect new colorimetric method for determining of SOD activity based on gold nanoparticles (AuNPs) was evaluated. According to the presented result, it may be concluded that by scavenging of free superoxide radicals in the presence of SOD, the amount of AuNP absorbance can be replenished.

Photochemical reactions between 1,4-benzoquinone and O2•

The superoxide anion radical (O2•-) is one of the most predominant reactive oxygen species (ROS), which is also involved in diverse chemical and biological processes. In this study, O2•- was generated by irradiating riboflavin in an O2-saturated solution using an ultraviolet lamp (λem = 365 nm) as the light source. The photochemical reduction of 1,4-benzoquinone (p-BQ) by O2•- was explored by 355-nm laser flash photolysis (LFP) and 365-nm UV light steady irradiation. The results showed that the photodecomposition efficiency of p-BQ was influenced by the riboflavin concentration, p-BQ initial concentration, and pH values. The superoxide anion radical originating from riboflavin photolysis served as a reductant to react with p-BQ, forming reduced BQ radicals (BQ•-) with a second-order rate constant of 1.1 × 109 L mol-1 s-1. The main product of the photochemical reaction between p-BQ and O2•- was hydroquinone (H2Q). The present work suggests that the reaction with O2•- is a potential transformation pathway of 1, 4-benzoquinone in atmospheric aqueous environments.

Hepatoprotective effect of Arctium lappa root extract on cadmium toxicity in adult Wistar rats

This study was performed to determine the effects of Arctium lappa (Al) to protect against cadmium damage in the rat liver. Male rats received a single i.p. dose of CdCl2 (1.2 mg/kg body weight (BW)) with or without Al extract administered daily by gavage (300 mg/kg BW) for 7 or 56 days. After 7 days, Al caused plasma transaminase activity to diminish in groups Al (glutamic oxaloacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT)) and CdAl (GPT). After 56 days, GOT and GPT plasma activities were reduced in the Cd group. No alteration in plasma levels of creatinine, total bilirubin, and total protein were observed. GOT liver activity increased in the Cd group. No alteration was observed in superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST), and malondialdehyde (MDA) dosage. In the Cd group, hepatocyte proportion decreased and sinusoid capillary proportion increased. In the Al and CdAl groups, the nuclear proportion increased and the cytoplasmic proportion decreased. The hepatocyte nucleus density reduced in Cd and increased in the Al group. After 56 days, there was no alteration in the Cd group. In Al and CdAl groups, the nuclear proportion increased without cytoplasmic proportion variation, but the sinusoid capillary proportion was reduced. The hepatocyte nucleus density decreased in the Cd group and increased in the Al and CdAl groups. In conclusion, the liver function indicators showed that A. lappa protected the liver against cadmium toxicity damage.

Antioxidant defense and apoptotic effectors in ascorbic acid and β-glycerophosphate-induced osteoblastic differentiation

MC3T3-E1 cells grown in the presence of ascorbic acid and β-glycerophosphate (AA/β-GP) express alkaline phosphatase and produce an extensive collagenous extracellular matrix. Differentiated MC3T3-E1 cells are more sensitive to hydrogen peroxide-induced oxidative stress than undifferentiated cells. In this study, we compared the profile of antioxidant enzymes and molecular markers of apoptosis in undifferentiated and differentiated MC3T3-E1 cells (cell differentiation was induced by treatment with AA/β-GP). Differentiated osteoblasts showed lower expression and activity of catalase, glutathione S-transferase and glutathione peroxidase. The total superoxide dismutase activity and the expression of Cu/Zn superoxide dismutase were also lower, while the expression of Mn superoxide dismutase was higher in differentiated osteoblasts. The level of malondialdehyde, a widely used marker for oxidative stress, was lower in the AA/β-GP group compared with control cells, but this difference was not significant. Western blotting showed that treatment with AA/β-GP increased the Bax/Bcl-2 ratio used as an index of cellular vulnerability to apoptosis. In addition, the activities of caspases 3, 8 and 9 and cleaved poly (ADP) ribose polymerase were significantly higher in differentiated cells. These findings provide new insights into how changes in the activities of major antioxidant enzymes and in the signaling pathways associated with apoptosis may influence the susceptibility of bone cells to oxidative stress.

Third-generation superoxide anion sensor based on superoxide dismutase directly immobilized by sol–gel thin film on gold electrode

A third-generation biosensor for superoxide anion (O(2)*-) was developed based on superoxide dismutase (SOD) immobilized by thin silica-PVA sol-gel film on gold electrode surface. A rapid and direct electron transfer of SOD in the thin sol-gel film at the gold electrode was realized without any mediators or promoters. The characterization of the SOD electrodes showed a quasi-reversible electrochemical redox behavior with a formal potential of 80 + 5 mV (versus SCE) in 50 mmol l(-1) phosphate buffer solution (PBS), pH 7.0. The heterogeneous electron transfer rate constant was evaluated to be about 2.1s(-1). The anodic and cathodic transfer coefficients are 0.6 and 0.4, respectively. Based on biomolecular recognition for specific reactivity of SOD toward O(2)*- the SOD electrode was applied to a sensitive and selective measurement of O(2)*- with the low operation potential (-0.15 V versus SCE) in phosphate buffer solution, pH 7.0. The amperometric response was proportional to O(2)*- concentration in the range of 0.2-1.6 micromol l(-1) and the detection limit was 0.1 micromol l(-1) at a signal-to-noise ration of 3. The preparation of SOD electrode is easy and simple. The uniform porous structure of the silica-PVA sol-gel matrix results in a fast response rate of immobilized SOD and is very efficient for stabilizing the enzyme activity.