scholarly journals Novel Enzyme-Free Multifunctional Bentonite/Polypyrrole/Silver Nanocomposite Sensor for Hydrogen Peroxide Detection over a Wide pH Range

Sensors ◽  
2019 ◽  
Vol 19 (20) ◽  
pp. 4442 ◽  
Author(s):  
Khouloud Jlassi ◽  
Mostafa H. Sliem ◽  
Kamel Eid ◽  
Igor Krupa ◽  
Mohamed M. Chehimi ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Ag Nanoparticles ◽  
Rational Design ◽  
Uv Light ◽  
Low Cost ◽  
Current Response ◽  
Ag Nps ◽  
Hydrogen Peroxide Detection ◽  
Wide Ph Range ◽  
Ph Range

Precise designs of low-cost and efficient catalysts for the detection of hydrogen peroxide (H2O2) over wide ranges of pH are important in various environmental applications. Herein, a versatile and ecofriendly approach is presented for the rational design of ternary bentonite-silylpropyl-polypyrrole/silver nanoarchitectures (denoted as BP-PS-PPy/Ag) via the in-situ photo polymerization of pyrrole with salinized bentonite (BP-PS) in the presence of silver nitrate. The Pyrrolyl-functionalized silane (PS) is used as a coupling agent for tailoring the formation of highly exfoliated BP-PS-PPy sheet-like nanostructures ornamented with monodispersed Ag nanoparticles (NPs). Taking advantage of the combination between the unique physicochemical properties of BP-PS-PPy and the outstanding catalytic merits of Ag nanoparticles (NPs), the as-synthesized BP-PS-PPy/Ag shows a superior electrocatalytic reduction and high-detection activity towards H2O2 under different pH conditions (from 3 to 10). Intriguingly, the UV-light irradiation significantly enhances the electroreduction activity of H2O2 substantially, compared with the dark conditions, due to the high photoelectric response properties of Ag NPs. Moreover, BP-PS-PPy/Ag achived a quick current response with a detection limit at 1 μM within only 1 s. Our present approach is green, facile, scalable and renewable.

scholarly journals Improvement in Thermostability of an Achaetomium sp. Strain Xz8 Endopolygalacturonase via the Optimization of Charge-Charge Interactions

2015 ◽  
Vol 81 (19) ◽  
pp. 6938-6944 ◽  
Author(s):  
Tao Tu ◽  
Huiying Luo ◽  
Kun Meng ◽  
Yanli Cheng ◽  
Rui Ma ◽  
...  
Keyword(s):  
Rational Design ◽  
Residual Activity ◽  
Maximal Activity ◽  
Wild Type ◽  
Content Type ◽  
Highly Active ◽  
Wide Ph Range ◽  
Enzyme Thermal Stability ◽  
Ph Range ◽  
Charge Interactions

ABSTRACTImproving enzyme thermostability is of importance for widening the spectrum of application of enzymes. In this study, a structure-based rational design approach was used to improve the thermostability of a highly active, wide-pH-range-adaptable, and stable endopolygalacturonase (PG8fn) fromAchaetomiumsp. strain Xz8 via the optimization of charge-charge interactions. By using the enzyme thermal stability system (ETSS), two residues—D244 and D299—were inferred to be crucial contributors to thermostability. Single (D244A and D299R) and double (D244A/D299R) mutants were then generated and compared with the wild type. All mutants showed improved thermal properties, in the order D244A < D299R < D244A/D299R. In comparison with PG8fn, D244A/D299R showed the most pronounced shifts in temperature of maximum enzymatic activity (Tmax), temperature at which 50% of the maximal activity of an enzyme is retained (T50), and melting temperature (Tm), of about 10, 17, and 10.2°C upward, respectively, with the half-life (t1/2) extended by 8.4 h at 50°C and 45 min at 55°C. Another distinguishing characteristic of the D244A/D299R mutant was its catalytic activity, which was comparable to that of the wild type (23,000 ± 130 U/mg versus 28,000 ± 293 U/mg); on the other hand, it showed more residual activity (8,400 ± 83 U/mg versus 1,400 ± 57 U/mg) after the feed pelleting process (80°C and 30 min). Molecular dynamics (MD) simulation studies indicated that mutations at sites D244 and D299 lowered the overall root mean square deviation (RMSD) and consequently increased the protein rigidity. This study reveals the importance of charge-charge interactions in protein conformation and provides a viable strategy for enhancing protein stability.

scholarly journals Ultrasonic synthesized Konjac gum/PEG-silver nanoparticles for colorimetric detection of hydrogen peroxide

2021 ◽  
Author(s):  
SELCAN KARAKUŞ ◽  
Nevin Taşaltın ◽  
Cihat Taşaltın ◽  
Nuray Bekoz Üllen
Keyword(s):  
Hydrogen Peroxide ◽  
Silver Nanoparticles ◽  
Biomedical Applications ◽  
Limit Of Detection ◽  
Low Cost ◽  
Colorimetric Detection ◽  
Rheological Parameters ◽  
Ag Nps ◽  
Synthesis Strategy ◽  
Konjac Gum

Abstract Green and low-cost synthesis strategy for ultrasonic preparation of polymer blend matrix based silver nanoparticles (Ag NPs) and the development of rapid and high sensitive detection route have a great attention in biomedical applications. Therefore, in this study, we investigated the hydrogen peroxide detection performance of Konjac gum (KG)/PEG-Ag NPs. The KG/PEG-Ag NPs was synthesized via an ultrasonic process and characterized by different techniques such as ultraviolet–visible spectroscopy (UV–Vis), Fourier-Transform Infrared spectroscopy (FT-IR), Scanning Electron Microscope (SEM) and Energy Dispersive X-ray spectroscopy (EDX). Furthermore, we determined the experimental optimization on the effect of the rheological parameters of nanostructure with the highest correlation constant (R 2 : 0.989-0.996), and the intrinsic viscosity (14.71-26.77 dl/g). To provide the miscible polymer blends and homogeneous dispersion of the nanostructure, we compared the rheological parameters with the experimental results. The response time was less than 5 s and the lower limit of detection was 0.071 μM. This novel highly sensitive, rapid, and naked-eye colorimetric biosensor based Ag NPs which are prepared ultrasonic manufacturing approach, opens up a green approach of development facile and rapid detection of hydrogen peroxide in practical biomedical applications.

Synthesis of Highly Dispersed Ag Nanoparticles under Microwave Irradiation with PAMAM Dendrimer as Reductant and Stabilizer for Nonenzymatic Detecting Hydrogen Peroxide

2013 ◽  
Vol 726-731 ◽  
pp. 1387-1390
Author(s):  
Xiao Ping Fan ◽  
Zhi Min Luo ◽  
Li Qun Xue ◽  
Xiu Ling Ma ◽  
Sheng Chen
Keyword(s):  
Hydrogen Peroxide ◽  
Microwave Irradiation ◽  
Ag Nanoparticles ◽  
Electrochemical Method ◽  
Fast Response ◽  
Pamam Dendrimer ◽  
Carbon Electrode ◽  
Nonenzymatic Sensor ◽  
Ag Nps ◽  
Highly Dispersed

A simple and sensitive electrochemical method for the nonenzymatic detection of hydrogen peroxide (H2O2) has been proposed. Highly dispersed Ag nanoparticles (NPs) were synthesized under microwave irradiation with PAMAM dendrimer as reductant and stabilizer. The formation of Ag NPs decorated with PAMAM dendrimer (Ag-G3.5-PAMAM) was confirmed by ultraviolet visible spectrophotometer (UV-vis). The as-prepared Ag-G3.5-PAMAM was used to modify the glassy carbon electrode (GCE) for nonenzymatic detection of hydrogen peroxide. It is showed that the fabricated electrochemical sensor based on Ag-G3.5-PAMAM exhibits fast response to hydrogen peroxide.The result indicates that Ag-G3.5-PAMAM may have promising applications in the development of nonenzymatic sensor for hydrogen peroxide in the future.

Preparation and Properties of a Cholesterol Oxidase from Nocardia sp. and Its Application to the Enzymatic Assay of Total Cholesterol in Serum

1973 ◽  
Vol 19 (12) ◽  
pp. 1350-1356 ◽  
Author(s):  
W Richmond
Keyword(s):  
Hydrogen Peroxide ◽  
Total Cholesterol ◽  
Enzyme Assay ◽  
Cholesterol Oxidase ◽  
Xylenol Orange ◽  
Extraction And Purification ◽  
Production Of Hydrogen ◽  
Nocardia Sp ◽  
Wide Ph Range ◽  
Ph Range

Abstract I describe the characterization, extraction, and purification of a cholesterol:oxygen oxidoreductase (EC 1.1.3.6) from Nocardia sp. This enzyme catalyzes oxidation of cholesterol to Δ4-choIestenone, with production of hydrogen peroxide. It is very stable, active over a wide pH range, and has a Km of 1.4 x 10-5 mol/ liter. It is highly specific for Δ4- or Δ5-3β-hydroxycholestanes, and may be applied to the assay of serum total cholesterol. In the procedure presented here, hydrogen peroxide is measured by reaction with quadrivalent titanium and xylenol orange. This constitutes a one-enzyme assay with stable reagents, which does not require protein precipitation and is not subject to interference from hemoglobin or bilirubin.

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