Oxidation Of Catechol Research Articles

Effects of the modification of bacterial cellulose as a template for the in situ enzyme-catalyzed polymerization of catechol

In this study, we investigated the effects of the modification of bacterial cellulose used as a template on the in situ polymerization of catechol by laccase. The bacterial cellulose was modified by sulfonation and the entrapment of carboxymethyl cellulose. The catechol polymerization was optimized at a pH of 5.5, catechol concentration of 50 mM, and synthesis time of 24 h. After the in situ polymerization, conductive and colored bacterial cellulose composites were obtained. The bacterial cellulose composites containing oligomers/polymers were analyzed using Fourier-transform infrared spectroscopy, scanning electron microscopy, and color strength measurements, and the conductivity of the bacterial cellulose composites was evaluated using a four-probe method. The results revealed that the modification of bacterial cellulose as a template for catechol oxidation resulted in the production of fibers with enhanced coloration and conductive properties owing to the presence of the enzymatically-obtained polymers. The results suggest the promising potential of both sulfonated bacterial cellulose and carboxymethyl cellulose-bacterial cellulose as templates for the formation of other functional polymers and composite materials.

Bimetallic MOF synergy molecularly imprinted ratiometric electrochemical sensor based on MXene decorated with polythionine for ultra-sensitive sensing of catechol

Dual-signal ratiometric molecularly imprinted polymer (MIP) electrochemical sensors with bimetallic active sites and high-efficiency catalytic activity were fabricated for the sensing of catechol (CC) with high selectivity and sensitivity. The amino-functionalization bimetallic organic framework materials (Fe@Ti-MOF-NH2), coupled with two-dimensional layered titanium carbide (MXene) co-modified glassy carbon electrode provides an expanded surface while amplifying the output signal through the electropolymerization immobilization of polythionine (pTHi) and MIP. The oxidation of CC and pTHi were presented as the response signal and the internal reference signal. The oxidation peak current at +0.42 V rose with increased concentration of CC, while the peak currents of pTHi at −0.20 V remained constant. Compared to the common single-signal sensing system, this one (MIP/pTHi/MXene/Fe@Ti-MOF-NH2/GCE), a novel ratiometric MIP electrochemical sensor exhibited two segments wide dynamic range of 1.0–300 μM (R2 = 0.9924) and 300–4000 μM (R2 = 0.9912), as well as an ultralow detection limit of 0.54 μM (S/N = 3). Due to the specific recognition function of MIPs and the advantages of built-in correction of pTHi, the prepared surface imprinting sensor presented an excellent performance in selectivity and reproducibility. Besides, this sensor possessed superior anti-interference ability with ions and biomolecules, excellent reproducibility, repeatability, and acceptable stability. Furthermore, the proposed sensing system exhibits high specific recognition in the determination of environmental matrices and biological fluids in real samples with satisfactory results. Therefore, this signal-enhanced ratiometric MIP electrochemical sensing strategy can accurately and selectively analyze and detect other substances.

New In Situ Catalysts Based on Nitro Functional Pyrazole Derivatives and Copper (II) Salts for Promoting Oxidation of Catechol to o-Quinone

Herein, new substituted ligands based on pyrazole (L1–L4) were synthesized via a one-step by condensing (1H-pyrazole-1-yl) methanol with different primary amine compounds. The present work utilized the catalytic properties of the in situ complexes formed by these ligands with various copper (II) salts viz. Cu(CH3COO)2, CuSO4, CuCl2, and Cu(NO3)2 for the oxidation of catechol to o-quinone. The studies showed that the catalytic activities depend on the nature and concentration of the ligand, the nature of the counterion, and the solvent. It was observed that the complex formed by L2 and Cu(CH3COO)2 exhibited good catalytic activity in methanol with Vmax of 41.67 µmol L−1 min−1 and Km of 0.02 mol L−1.

Structural and bio-catalytic aspects of nano crystallite iron(iii) complexes containing triazole-based ligands

Stopped-follow kinetic study of the aerobic oxidation of catechol and 2-aminophenol by new Fe(iii) complexes as oxidase functional models.

A dinuclear copper(II) complex with photoswitchable catechol oxidation activity.

In this study, we report the first example of a photoswitchable copper complex with catechol oxidase activity. The distance between the two copper centres is optimal for catalytic catechol oxidation in the Z-configuration. Thus, the activity of the catalyst is increased compared to its E-configuration.

Green electro-organic synthesis of a novel catechol derivative based on o-benzoquinone nucleophilic addition

In this work, a green-electrochemical synthesis was applied to catechol oxidation (1) to o-benzoquinone (2) using cyclic voltammetry and potential controlled coulometry.

Diarylation of thiazolopyrimidines by laccase and their in vitro evaluation as antitumor agents

A mild and efficient method was developed for the synthesis of new derivatives of thiazolo[3,2-a] pyrimidin-3(2H)-ones from available starting materials based on the oxidation of catechols to ortho-quinone by Myceliophthora thermophila laccase (Novozym 51,003) and 1,4-addition of active methylene carbon to these in situ generated intermediates in moderate to good yields (35–93%). The structure of the products was confirmed through 1H NMR, 13C NMR, HMBC, HSQC, DEPT-135, and mass spectroscopy techniques. These novel compounds were evaluated as active antitumor agents against human colorectal adenocarcinoma and liver adenocarcinoma cell lines. All compounds displayed potent inhibition activities against the HT-29 cell line with IC50 values of 9.8–35.9 µM, superior to the positive control doxorubicin, and most showed potent anticancer activities against the HepG2 cell line.

Aerial Oxidation of Phenol/Catechol in the Presence of Catalytic Amounts of [(Cl)2Mn(RCOOET)], RCOOET= Ethyl-5-Methyl-1-(((6-Methyl-3-Nitropyridin-2-yl)Amino)Methyl)-1H-Pyrazole-3-Carboxylate

In this work, we report on the catalytic activity of a manganese complex [(Cl)2Mn(RCOOET)], where RCOOET is ethyl-5-methyl-1-(((6-methyl-3-nitropyridin-2-yl)amino)methyl)-1H-pyrazole-3-carboxylate, in the oxidation of phenol or catechol by atmospheric oxygen to form o-quinone. The [(Cl)2Mn(RCOOET)] catalyzes the oxidation of catechol at a rate of 3.74 µmol L−1 min−1 in tetrahydrofuran (THF), in a similar manner to catecholase or tyrosinase.

A De Novo‐Designed Type 3 Copper Protein Tunes Catechol Substrate Recognition and Reactivity

AbstractDe novo metalloprotein design is a remarkable approach to shape protein scaffolds toward specific functions. Here, we report the design and characterization of Due Rame 1 (DR1), a de novo designed protein housing a di‐copper site and mimicking the Type 3 (T3) copper‐containing polyphenol oxidases (PPOs). To achieve this goal, we hierarchically designed the first and the second di‐metal coordination spheres to engineer the di‐copper site into a simple four‐helix bundle scaffold. Spectroscopic, thermodynamic, and functional characterization revealed that DR1 recapitulates the T3 copper site, supporting different copper redox states, and being active in the O2‐dependent oxidation of catechols to o‐quinones. Careful design of the residues lining the substrate access site endows DR1 with substrate recognition, as revealed by Hammet analysis and computational studies on substituted catechols. This study represents a premier example in the construction of a functional T3 copper site into a designed four‐helix bundle protein.

A De Novo-Designed Type 3 Copper Protein Tunes Catechol Substrate Recognition and Reactivity.

De novo metalloprotein design is a remarkable approach to shape protein scaffolds toward specific functions. Here, we report the design and characterization of Due Rame 1 (DR1), a de novo designed protein housing a di-copper site and mimicking the Type 3 (T3) copper-containing polyphenol oxidases (PPOs). To achieve this goal, we hierarchically designed the first and the second di-metal coordination spheres to engineer the di-copper site into a simple four-helix bundle scaffold. Spectroscopic, thermodynamic, and functional characterization revealed that DR1 recapitulates the T3 copper site, supporting different copper redox states, and being active in the O2 -dependent oxidation of catechols to o-quinones. Careful design of the residues lining the substrate access site endows DR1 with substrate recognition, as revealed by Hammet analysis and computational studies on substituted catechols. This study represents a premier example in the construction of a functional T3 copper site into a designed four-helix bundle protein.

Enhancing laccase-assisted polymerization reactions with perfluorinated compounds

The catalysis of reactions by laccases are oxygen-dependent. Perfluorinated compounds (PFCs) are known to increase the solubility of oxygen when compared with water being applied in several fields as gas-dissolving agents. Herein, PFCs like Zonyl, perfluorohexane (C6F14), and perfluorodecalin(C10F18) were explored as promising agents to increase the rate of oxygen available on laccase-assisted oxidation of catechol. The oxidation of catechol was performed with and without aeration, using reactors with different agitation regimens (orbital shaker water bath and vertical rotating reactor). The enzymatic reactions and the level of oxygen were monitored by UV-Visible spectroscopy and oxygen quantification, respectively. The polymerization yield was estimated in terms of polymer weight gain after laccase-assisted oxidation and the products of reaction were analyzed by 1H NMR,MALDI-TOF and particle size measurements. After laccase oxidation, the poly(catechol) was successfully synthesized with a polymerization degree (DP) of 7 and a mean size of 115 nm, independently on the PFCs and aeration conditions. The findings showed that all PFCs examined, particularly perfluorodecalin, had the ability to dissolve oxygen, increasing its rate during oxidation reaction. The yield of poly(catechol) is 1.25 times higher using perfluorodecalin, under aeration, compared to the reaction carried out only with laccase. We provide the first evidence that PFCs significantly increase the oxidation of phenols by laccase.

Dual Responsive Optical Sensor for The Detection of Zn2+and Al3+: Supportive Single‐Crystal X‐ray Structure of its Ni(II) Complex and DFT Studies

AbstractA tripodal pentadentate mono‐imine derivative, 2‐({2‐[bis‐(2‐amino‐ethyl)‐amino]‐ethylimino}‐methyl)‐phenol (L2) is employed for ‘turn on’ fluorescence recognition of Zn2+and Al3+at two different wavelengths. Chelation‐enhanced fluorescence (CHEF) assisted inhibition of excited‐state intramolecular proton transfer (ESIPT) is proposed as the sensing mechanism. The1HNMR, mass, IR spectral data, Jobs experiment and single crystal X‐ray structure of the [Ni(II)‐L2] complex (N1) strongly support the structure of L2 and its interaction with Zn2+and Al3+. Density functional theoretical (DFT) studies indicate higher stability of the Zn2+and Al3+adducts over free L2. The recognition of Zn2+and Al3+at two different emission wavelengths allows to construct a binary logic gate. Moreover, L2 is useful for determination unknown concentration of Al3+in real water samples. The complex N1 catalyses the catechol oxidation reaction.

Quinoline Derivatives with Different Functional Groups: Evaluation of Their Catecholase Activity

In this work, we are interested in finding new catalysts for catecholase, whose principle is based on the oxidation reaction of catechol to o-quinone. In this context, we have studied a series of seven quinoline-based compounds. The present work indicates that the complexes formed between seven selected quinoline compounds and the copper salts viz. Cu(OAc)2, CuSO4, Cu(NO3)2, and CuCl2 elicit catalytic activities for the oxidation of catechol to o-quinone. The complexes formed with the Cu(OAc)2 salt show a much higher catalytic activity than the others, whereas the Cu(NO3)2 and CuCl2 salts formed complexes with low catalytic activity. This study also shows that the oxidation rate depends on two factors, namely the chemical structure of the ligands and the nature of the ions coordinated with the copper.

Oxidation of Catechols at the Air-Water Interface by Nitrate Radicals.

Abundant substituted catechols are emitted to, and created in, the atmosphere during wildfires and anthropogenic combustion and agro-industrial processes. While ozone (O3) and hydroxyl radicals (HO•) efficiently react in a 1 μs contact time with catechols at the air-water interface, the nighttime reactivity dominated by nitrate radicals (NO3) remains unexplored. Herein, online electrospray ionization mass spectrometry (OESI-MS) is used to explore the reaction of NO3(g) with a series of representative catechols (catechol, pyrogallol, 3-methylcatechol, 4-methylcatechol, and 3-methoxycatechol) on the surface of aqueous microdroplets. The work detects the ultrafast generation of nitrocatechol (aromatic) compounds, which are major constituents of atmospheric brown carbon. Two mechanisms are proposed to produce nitrocatechols, one (equivalent to H atom abstraction) following fast electron transfer from the catechols (QH2) to NO3, forming NO3- and QH2•+ that quickly deprotonates into a semiquinone radical (QH•). The second mechanism proceeds via cyclohexadienyl radical intermediates from NO3 attack to the ring. Experiments in the pH range from 4 to 8 showed that the production of nitrocatechols was favored under the most acidic conditions. Mechanistically, the results explain the interfacial production of chromophoric nitrocatechols that modify the absorption properties of tropospheric particles, making them more susceptible to photooxidation, and alter the Earth's radiative forcing.

Square-Wave and Cyclic Voltammetry of Native Proanthocyanidins Extracted from Grapevine (Vitis vinifera) on the Glassy Carbon Electrode

Condensed tannins are short polymers of flavan-3-ols found in grapes (also known as proanthocyanidins). An investigation on the electrochemical oxidation of grapevine proanthocyanidins (PAs) on glassy carbon electrodes under various conditions was conducted for the first time. To study how the proanthocyanidins were oxidized, square-wave and cyclic voltammetry were used. There is a predominant oxidation peak associated with the extract of proanthocyanidins, and this can be attributed to the oxidation of catechol 3′,4′-dihydroxyl groups, which can form their oxidation peak. There are two electrons and two protons involved in the oxidation of the catechol group, which must be kept in mind when considering the oxidation of the catechol group. On the glassy carbon electrode (GCE), the PAs extracted from grapevine are oxidized by an adsorption-dependent mechanism as they interact with the GCE surface. As a result, it was found that the anodic peak current varied linearly with PAs’ concentrations in the range of 4 to 50 ppm, with a detection limit of 3.07 ppm (S/N = 3). There was a development in the surface concentration of the oxidation products at the GC electrode; as the scans progressed, the surface concentration of oxidation products at the electrode remained at 4.83 × 10−11 mol cm−2, indicating that they were immobilized on the GCE as oxidation products adsorbed on the electrode.

Mesoporogen free synthesis of CuO/TiO2 heterojunction for ultra-trace detection of catechol in water samples

Creating mesoporous architecture on the surface of metal oxides without using pore creating agent is significant interest in electrochemical sensors because these materials act as an efficient electron transfer process between the electrode interface and the analytes. Recent advances in mesoporous titanium dioxide (TiO2)-based materials have acquired extraordinary opportunities because of their interconnected porous structure could act as a host for doping with various transition metals or heteroatoms to form a new type of heterojunction. Herein, a simple method is developed to synthesize mesoporous copper oxide (CuO) decorated on TiO2 nanostructures in which homogenous shaped CuO nanocrystals act as dopants decorated on the mesoporous structure of TiO2, resulting in p-n heterojunction nanocomposite. The TiO2 particles exhibit a mesoporous structure with a pore volume of about 0.117 cm3/g is capable to load CuO nanocrystals on the surface. As a result, large pore volume 0.304 cm³/g is obtained for CuO–TiO2 heterojunction nanocomposite with the loading of uniform-shaped CuO nanocrystals on the mesoporous TiO2. The resulting CuO–TiO2 nanocomposite on modified glassy carbon (GC) electrode exhibits good electrochemical performance for oxidation of catechol with the observation of strong enhancement in the anodic peak potential at +0.36 V. The decrease in the overpotential for the oxidation of catechol when compared to TiO2/GC is attributed to the presence of CuO nanocrystals providing a large surface area, resulting in wide linear range 10 nM to 0.57 μM. Moreover, the resultant modified electrode exhibited good sensitivity, selectivity and reproducibility and the sensor could able to determine the presence of catechol in real samples such as lake and river water. Therefore, the obtained CuO–TiO2 nanocomposite on the modified GC delivered good electrochemical sensing performance and which could be able to perform a promising strategy for designing various metal oxide doped nanocomposites for various photochemical and electrocatalytic applications.

Even allocation of benefits stabilizes microbial community engaged in metabolic division of labor.

Microbial communities execute metabolic pathways to drive global nutrient cycles. Within a community, functionally specialized strains can perform different yet complementary steps within a linear pathway, a phenomenon termed metabolic division of labor (MDOL). However, little is known about how such metabolic behaviors shape microbial communities. Here, we derive a theoretical framework to define the assembly of a community that degrades an organic compound through MDOL. The framework indicates that to ensure community stability, the strains performing the initial steps should hold a growth advantage (m) over the "private benefit" (n) of the strain performing the last step. The steady-state frequency of the last strain is then determined by the quotient of n and m. Our experiments show that the framework accurately predicts the assembly of our synthetic consortia that degrade naphthalene through MDOL. Our results provide insights for designing and managing stable microbial systems for metabolic pathway optimization.

Catecholase, phenoxazinone synthase and copper (CuII) complex based on pyrazolic ligand: Preparation and characterization

The high catalytic activity of catechol oxidation in atmospheric oxygen signified the selectivity and efficiency of the metalloenzyme [CuSO4L], with L is 5 chloro-N-((3,5-dimethyl-1H-pyrazol-1-yl)methyl)pyridin-2-amine. In this study, two parameters influencing the catecholase activity were examined: the nature of solvent and the nature of the complex. The best activity of catechol oxidation is given by the synthesized complex in methanol solvent with the rate of 1.7 μmol/L min−1. In the contrary, the prepared complex in situ (weak catalyst) showed weak value in the oxidation rate (0.14 μmol/L min−1) in DMSO.However, our complex synthesized in good yield was subjected to several spectral and thermal analyses to verify the results obtained.

Single and multiple site Cu(II) catalysts for benzyl alcohol and catechol oxidation reactions

Cu(II) catalysts both in homogeneous and heterogeneous form were synthesized to bring the distinction between the single and multiple site catalysis. The single site mononuclear complexes with axial occupancy of Cl- and CH3COO- ligand and the acetate, imidazolate bridged dinuclear Cu(II) complexes were tested for selective oxidation of benzyl alcohol and catechol oxidation. The reactivity of the complexes was compared with the multiple site copper oxide (CuO) nanocatalyst derived from the metal complex precursor. The single site Cu(II) catalyst showed much superior activity in the selective oxidation of BA compared to the dinuclear and the CuO-nanocatalyst. The oxidation of catechol to o-benzoquinone was however found to be catalyzed more preferably by the di-nuclear systems. The high lability of Cl- and -OOCH3 groups in the mononuclear complexes allowed the incoming oxidant, substrate as well as the solvent (acetonitrile, CH3CN) molecules to interact with the active Cu-centre and thereby favoured the benzyl alcohol oxidation. Both the experimental and theoretical studies provided a conclusive idea about the reaction mechanism of benzyl alcohol and catechol oxidation. UV–vis, cyclic voltammetric study and density functional theory (DFT) calculations provided the strong evidence for the formation of Cu-CH3CN complex during benzyl alcohol oxidation. FTIR and Raman study substantiated by the theoretical calculations indicated for the formation of Cu- hydroperoxo species during the catalytic studies. The kinetics study revealed for the 1st order kinetic for the catechol oxidation and the DFT study predicted for the exothermic nature of the catechol oxidation process.

Transformation of L-DOPA and Dopamine on the Surface of Gold Nanoparticles: An NMR and Computational Study.

Gold nanoparticles (AuNPs) have found applications in biomedicine as diagnostic tools, but extensive research efforts have been also directed toward their development as more efficient drug delivery agents. The high specific surface area of AuNPs may provide dense loading of molecules like catechols (L-DOPA and dopamine) on nanosurfaces, enabling functionalization strategies for advancing conventional therapy and diagnostic approaches of neurodegenerative diseases. Despite numerous well-described procedures in the literature for preparation of different AuNPs, possible transformation and structural changes of surface functionalization agents have not been considered thoroughly. As a case in point, the catechols L-DOPA and dopamine were selected because of their susceptibility to oxidation, cyclization, and polymerization. To assess the fate of coating and functionalization agents during the preparation of AuNPs or interaction at the nano-bio interface, a combination of spectroscopy, light scattering, and microscopy techniques was used while structural information and reaction mechanism were obtained by NMR in combination with computational tools. The results revealed that the final form of catechol on the AuNP nanosurface depends on the molar ratio of Au used for AuNP preparation. A large molar excess of L-DOPA or dopamine is needed to prepare AuNPs funtionalized with fully reduced catechols. In the case of molar excess of Au, the oxidation of catechols to dopamine quinone and dopaquinone was promoted, and dopaquinone underwent intramolecular cyclization in which additional oxidation products, leukodopachrome, dopachrome, or its tautomer, were formed because of the larger intrinsic acidity of the more nucleophilic amino group in dopaquinone. MD simulations showed that, of the oxidation products, dopachrome had the highest affinity for binding to the AuNPs surface. The results highlight how a more versatile methodological approach, combining experimental and in silico techniques, allows more reliable characterization of binding events at the surface of AuNPs for possible applications in biomedicine.