scholarly journals The Kinetic and Analytical Aspects of Enzyme Competitive Inhibition: Sensing of Tyrosinase Inhibitors

Biosensors ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 322
Author(s):  
Raouia Attaallah ◽  
Aziz Amine
Keyword(s):  
Competitive Inhibition ◽  
Kojic Acid ◽  
Amperometric Response ◽  
Competitive Inhibitors ◽  
Tyrosinase Inhibitors ◽  
Carbon Black Paste ◽  
Optimized Conditions ◽  
Paste Electrode ◽  
Substrate Concentrations

An amperometric biosensor based on tyrosinase, immobilized onto a carbon black paste electrode using glutaraldehyde and BSA was constructed to detect competitive inhibitors. Three inhibitors were used in this study: benzoic acid, sodium azide, and kojic acid, and the obtained values for fifty percent of inhibition (IC50) were 119 µM, 1480 µM, and 30 µM, respectively. The type of inhibition can also be determined from the curve of the degree of inhibition by considering the shift of the inhibition curves. Amperometric experiments were performed with a biosensor polarized at the potential −0.15 V vs. Ag/AgCl and using 0.1 M phosphate buffer (pH 6.8) as an electrolyte. Under optimized conditions, the proposed biosensor showed a linear amperometric response toward catechol detection from 0.5 µM to 38 µM with a detection limit of 0.35 µM (S/N = 3), and its sensitivity was 66.5 mA M−1 cm−2. Moreover, the biosensor exhibited a good storage stability. Conversely, a novel graphical plot for the determination of reversible competitive inhibition was represented for free tyrosinase. The graph consisted of plotting the half-time reaction (t1/2) as a function of the inhibitor concentration at various substrate concentrations. This innovative method relevance was demonstrated in the case of kojic acid using a colorimetric bioassay relying on tyrosinase inhibition. The results showed that the t1/2 provides an extended linear range of tyrosinase inhibitors.

Isoprenylated Phenolic Compounds from Morus macroura as Potent Tyrosinase Inhibitors

Planta Medica ◽  
2017 ◽  
Vol 84 (05) ◽  
pp. 336-343 ◽  
Author(s):  
Yifan Wang ◽  
Liangjin Xu ◽  
Wen Gao ◽  
Lixin Niu ◽  
Chunyue Huang ◽  
...  
Keyword(s):  
Kojic Acid ◽  
Positive Control ◽  
Diels Alder ◽  
Extensive Analysis ◽  
Ic50 Value ◽  
Ic50 Values ◽  
Tyrosinase Inhibitors ◽  
Inhibitory Activities ◽  
New Compounds

AbstractThree new Diels-Alder adducts, macrourins E – G (1–3), one new 2-arylbenzofuran, macrourin H (4), and eight known Diels-Alder adducts (5–12) were isolated from Morus macroura. Their structures were elucidated through extensive analysis of spectroscopic data. The 1H NMR and ECD trends in the determination of the configurations of these Diels-Alder adducts were summarized. The tyrosinase inhibitory activities of all compounds isolated were evaluated, and the new compounds (1–4) as well as the eight known compounds (5–12) were found to be potent with IC50 values ranging from 0.39 to 4.54 µM. Among them, 1 showed the best tyrosinase inhibitory activity with an IC50 value of 0.39 µM, approximately 50 times stronger than the positive control, kojic acid.

Synthesis of Co/TiO2 Nanocomposite and its Use in Construction of a Sensitive and Selective Sensor for Determination of Ciprofloxacin

2013 ◽  
Vol 829 ◽  
pp. 563-567 ◽  
Author(s):  
Mojtaba Shamsipur ◽  
Mohammad Bagher Gholivand ◽  
Sara Dehdashtian ◽  
Mostafa Feyzi ◽  
Fataneh Jafari
Keyword(s):  
Sol Gel ◽  
Differential Pulse ◽  
Gravimetric Analysis ◽  
Carbon Paste ◽  
Ftir Spectrometry ◽  
Pulse Voltammetry ◽  
Optimized Conditions ◽  
Paste Electrode ◽  
Selective Sensor

The Co/TiO2 nanocomposite was synthesized by a modified sol-gel method. The surface structure and composition of nanoparticles were characterized by scanning electron microscopy (SEM), X-ray powder diffraction analysis (XRD), Fourier transform infrared (FTIR) spectrometry, thermal gravimetric analysis (TGA) and N2 physisorption. A carbon paste electrode (CPE) modified with Co/TiO2 nanocomposite was prepared and used for low level determination of antibiotic ciprofloxacin (CF) using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Under optimized conditions, the modified electrode exhibited a linear response over the concentration range of 0.1 to 70 μM CF, with a detection limit of 0.03 μM. The proposed sensor was applied to the CF determination in serum and urine samples.

scholarly journals Regulatory proteins (inhibitors or activators) affect estimates of Mr of enzymes and receptors by radiation inactivation. A theoretical model

1985 ◽  
Vol 226 (3) ◽  
pp. 797-801 ◽  
Author(s):  
M Potier ◽  
S Giroux
Keyword(s):  
Biological Activity ◽  
Theoretical Model ◽  
Absorbed Dose ◽  
Effector Proteins ◽  
Regulatory Proteins ◽  
Radiation Inactivation ◽  
Effector System ◽  
Competitive Inhibitors ◽  
Substrate Concentrations

The radiation-inactivation method allows the determination of the Mr of enzymes and receptors by monitoring the decay of biological activity as a function of absorbed dose. The presence of regulatory or effector proteins (inhibitors or activators) associated with an enzyme or receptor, or released in the preparation after tissue homogenization, may affect the decay of biological activity. How the activity is affected, however, will depend on the type of inhibition (competitive or non-competitive), the inhibitor or activator concentration, the dissociation constant of the enzyme-effector system, and the effector Mr relative to that of the enzyme. Since little is known on how effector proteins influence radiation inactivation of enzymes and receptors, we have considered a theoretical model in an effort to provide a framework for the interpretation of experimentally obtained data. Our model predicts that competitive and non-competitive inhibitors of enzymes could be distinguished by analysing irradiated samples with various substrate concentrations. Inhibitors will decrease whereas activators will increase the apparent target size of enzymes or receptors.

Voltammetric determination of 1,2-diaminoanthraquinone using carbon paste electrode

2011 ◽  
Vol 76 (8) ◽  
pp. 1033-1041
Author(s):  
Jiří Zima ◽  
Veronika Tinková ◽  
Joseph Wang ◽  
Jiří Barek
Keyword(s):  
River Water ◽  
Direct Current ◽  
Carbon Paste Electrode ◽  
Differential Pulse ◽  
Voltammetric Determination ◽  
Carbon Paste ◽  
Limit Of Determination ◽  
Optimized Conditions ◽  
Paste Electrode

Direct current (DC) voltammetry and differential pulse (DP) voltammetry using a carbon paste electrode (CPE) have been used for the determination of trace amounts of ecotoxic 1,2-diaminoanthraquinone (DAAQ). The limit of determination (LD) of DAAQ for DC voltammetry was 2 × 10–6 mol l–1, and for DP voltammetry 2 × 10–7 mol l–1 under the optimized conditions in a mixed Britton–Robinson buffer pH 12 and methanol (1:9) medium. Adsorptive accummulation of the analyte on the surface of CPE decreased the limit of determination to 2 × 10–8 mol l–1 for DP voltammetry. Practical applicability of these newly developed methods was verified on model samples of river water.

scholarly journals Detection of mercury by a new sensor based CPE modified with extract of takaout plant

2016 ◽  
Vol 5 (4) ◽  
pp. 514-520
Author(s):  
Abdelaziz Ait sidi mou ◽  
Aicha Ouarzane ◽  
Mama El Rhazi
Keyword(s):  
Carbon Paste Electrode ◽  
Tap Water ◽  
Pulse Amplitude ◽  
Carbon Paste ◽  
Accumulation Time ◽  
Wave Voltammetry ◽  
Anodic Peak Current ◽  
Optimized Conditions ◽  
Paste Electrode

A new carbon paste electrode (CPE) modified with extract takaout was developed for the determination of mercury using square wave voltammetry (SWV).  Compared with carbon paste electrode, the anodic peak current had a significant increase at the modified electrode. Under the optimized conditions (amount of modifier 3%, 0.1 M acetate buffer pH 2, accumulation potential -0.6 V, accumulation time 300 s, resting time 10 s, frequency 25 Hz, pulse amplitude 0.050 V, step height 2 mV), a linear response was obtained in the concentration range from 3.1 to 11 µM Hg(II) and the detection limit was 0.42 µM. The results indicate that this electrode is sensitive and effective for determination of Hg2+ in the tap water sample.

Feasibility of a Nano‐Carbon Black Paste Electrode for Simultaneous Voltammetric Determination of Antioxidants in Food Samples and Biodiesel in the Presence of Surfactant

2020 ◽  
Vol 32 (6) ◽  
pp. 1198-1207
Author(s):  
Pedro Nunes Angelis ◽  
Jhessica Cássia Mendonça ◽  
Luana Rianne da Rocha ◽  
Tainara Boareto Capelari ◽  
Maiyara Carolyne Prete ◽  
...  
Keyword(s):  
Carbon Black ◽  
Food Samples ◽  
Voltammetric Determination ◽  
Nano Carbon ◽  
Carbon Black Paste ◽  
Simultaneous Voltammetric Determination ◽  
Paste Electrode

scholarly journals Modified Carbon Nanotube Paste Electrode for Voltammetric Determination of Carbidopa, Folic Acid, and Tryptophan

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Sakineh Esfandiari Baghbamidi ◽  
Hadi Beitollahi ◽  
Hassan Karimi-Maleh ◽  
Somayeh Soltani-Nejad ◽  
Vahhab Soltani-Nejad ◽  
...  
Keyword(s):  
Folic Acid ◽  
Carbon Nanotube ◽  
Voltammetric Determination ◽  
Multiwall Carbon Nanotube ◽  
Wave Voltammetry ◽  
Carbon Nanotube Paste Electrode ◽  
Optimized Conditions ◽  
Paste Electrode ◽  
Multiwall Carbon

A simple and convenient method is described for voltammetric determination of carbidopa (CD), based on its electrochemical oxidation at a modified multiwall carbon nanotube paste electrode. Under optimized conditions, the proposed method exhibited acceptable analytical performances in terms of linearity (over the concentration range from 0.1 to 700.0 μM), detection limit (65.0 nM), and reproducibility (RSD=2.5%) for a solution containing CD. Also, square wave voltammetry (SWV) was used for simultaneous determination of CD, folic acid (FA), and tryptophan (TRP) at the modified electrode. To further validate its possible application, the method was used for the quantification of CD, FA, and TRP in urine samples.

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