scholarly journals Laccases: Versatile Biocatalysts for the Synthesis of Heterocyclic Cores

Molecules ◽  
2021 ◽  
Vol 26 (12) ◽  
pp. 3719
Author(s):  
Ana Catarina Sousa ◽  
Lígia O. Martins ◽  
M. Paula Robalo
Keyword(s):  
Membered Ring ◽  
Low Molecular Weight ◽  
Redox Potentials ◽  
Redox Mediators ◽  
Multicopper Oxidases ◽  
Phenothiazine Derivatives ◽  
Ph Values ◽  
Electron Shuttles ◽  
Specific Oxidation ◽  
Optimal Ph

Laccases are multicopper oxidases that have shown a great potential in various biotechnological and green chemistry processes mainly due to their high relative non-specific oxidation of phenols, arylamines and some inorganic metals, and their high redox potentials that can span from 500 to 800 mV vs. SHE. Other advantages of laccases include the use of readily available oxygen as a second substrate, the formation of water as a side-product and no requirement for cofactors. Importantly, addition of low-molecular-weight redox mediators that act as electron shuttles, promoting the oxidation of complex bulky substrates and/or of higher redox potential than the enzymes themselves, can further expand their substrate scope, in the so-called laccase-mediated systems (LMS). Laccase bioprocesses can be designed for efficiency at both acidic and basic conditions since it is known that fungal and bacterial laccases exhibit distinct optimal pH values for the similar phenolic and aromatic amines. This review covers studies on the synthesis of five- and six-membered ring heterocyclic cores, such as benzimidazoles, benzofurans, benzothiazoles, quinazoline and quinazolinone, phenazine, phenoxazine, phenoxazinone and phenothiazine derivatives. The enzymes used and the reaction protocols are briefly outlined, and the mechanistic pathways described.

scholarly journals Effect of alkaline pH on photosynthetic water oxidation and the association of extrinsic proteins with Photosystem Two

1989 ◽  
Vol 258 (2) ◽  
pp. 357-362 ◽  
Author(s):  
D J Chapman ◽  
J De Felice ◽  
K Davis ◽  
J Barber
Keyword(s):  
Water Splitting ◽  
Water Oxidation ◽  
Binding Sites ◽  
Partial Recovery ◽  
Alkaline Ph ◽  
Ph Values ◽  
Extrinsic Proteins ◽  
Reversible Phase ◽  
Photosynthetic Water Oxidation ◽  
Optimal Ph

Incubation of a membrane preparation enriched in Photosystem Two (PSII) at alkaline pH inhibited the water-splitting reactions in two distinct steps. Up to pH 8.5 the inhibition was reversible, whereas at higher alkalinities it was irreversible. It was shown that the reversible phase correlated with loss and rebinding of the 23 kDa extrinsic polypeptide. However, after mild alkaline treatments a partial recovery was possible without the binding of the 23 kDa polypeptide when the assay was at the optimal pH of 6.5 and in a medium containing excess Cl-. The irreversible phase was found to be closely linked with the removal of the 33 kDa extrinsic protein of PSII. Treatments with pH values above 8.5 not only caused the 33 kDa protein to be displaced from the PSII-enriched membranes, but also resulted in an irreversible modification of the binding sites such that the extrinsic 33 kDa protein could not reassociate with PSII when the pH was lowered to 6.5. The results obtained with these more extreme alkaline pH treatments support the notion that the 23 kDa protein cannot bind to PSII unless the 33 kDa protein is already bound. The differential effect of pH on the removal of the 23 kDa and 33 kDa proteins contrasted with the data of Kuwabara & Murata [(1983) Plant Cell Physiol. 24, 741-747], but this discrepancy was accounted for by the use of glycerol in the incubation media.

scholarly journals Optimal pH in chlorinated swimming pools – balancing formation of by-products

2013 ◽  
Vol 11 (3) ◽  
pp. 465-472 ◽  
Author(s):  
Kamilla M. S. Hansen ◽  
Hans-Jørgen Albrechtsen ◽  
Henrik R. Andersen
Keyword(s):  
Body Fluid ◽  
Product Formation ◽  
Swimming Pools ◽  
Batch Experiments ◽  
Ph Values ◽  
Precursor Ratio ◽  
Decreasing Ph ◽  
Ph Range ◽  
By Products ◽  
Optimal Ph

In order to identify the optimal pH range for chlorinated swimming pools, the formation of trihalomethanes, haloacetonitriles and trichloramine was investigated in the pH-range 6.5–7.5 in batch experiments. An artificial body fluid analogue was used to simulate bather load as the precursor for by-products. The chlorine-to-precursor ratio used in the batch experiments influenced the amounts of by-products formed, but regardless of the ratio the same trends in the effect of pH were observed. Trihalomethane formation was reduced by decreasing pH, but haloacetonitrile and trichloramine formation increased. To evaluate the significance of the increase and decrease of the investigated organic by-products at the different pH values, the genotoxicity was calculated based on literature values. The calculated genotoxicity was approximately at the same level in the pH range 6.8–7.5 and increased when pH was 6.7 or lower. An optimal pH range for by-products formation in swimming pools was identified at pH 7.0–7.2. In the wider pH range (pH 6.8–7.5), the effect on by-product formation was negligible. Swimming pools should never be maintained at lower pH than 6.8 since formation of both haloacetonitriles and trichloramine increase significantly below this value.

scholarly journals Electrolyte Composition in Li/O2 Batteries with LiI Redox Mediators: Solvation Effects on Redox Potentials and Implications for Redox Shuttling

2018 ◽  
Vol 122 (3) ◽  
pp. 1522-1534 ◽  
Author(s):  
Azusa Nakanishi ◽  
Morgan L. Thomas ◽  
Hoi-Min Kwon ◽  
Yuki Kobayashi ◽  
Ryoichi Tatara ◽  
...  
Keyword(s):  
Electrolyte Composition ◽  
Redox Potentials ◽  
Redox Mediators ◽  
Solvation Effects

Comparative characterization of digestive proteases in redhead cichlid (Vieja melanurus) and twoband cichlid (Vieja bifasciata) (Percoidei: Cichlidae)

2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Carlos Alfonso Frías-Quintana ◽  
Emyr Saul Peña-Marín ◽  
Carlos David Ramírez-Custodio ◽  
Rafael Martínez-García ◽  
Luis Daniel Jiménez-Martínez ◽  
...  
Keyword(s):  
Meat Quality ◽  
Alkaline Proteases ◽  
Optimal Temperature ◽  
Digestive Capacity ◽  
Digestive Proteases ◽  
Ph Values ◽  
Specific Diet ◽  
Specific Inhibitors ◽  
Optimal Ph

ABSTRACT In the Southeast of Mexico, there are many native cichlids with commercial interest such as redhead cichlid (Vieja melanurus) and twoband cichlid (V. bifasciata), which have a great local demand and excellent meat quality. However, it is necessary to implement their culture based on nutrition studies and digestive biochemistry. This study’s objective was to characterize these two cichlids’ digestive proteases (pH, temperature, and inhibitors) through biochemistry techniques. Results showed that V. melanurus and V. bifasciata have a digestive capacity analogous to other omnivore fishes, where the optimal pH values of stomach proteases (4 and 2, respectively) and intestinal proteases (6 and 12, respectively), the optimal temperature of acid (35°C and 55°C, respectively) and alkaline proteases (45°C and 55°C, respectively) are quite similar. Both species presented high thermal and pH stabilities. Inhibition showed that V. melanurus is more sensitive to specific inhibitors for alkaline proteases than V. bifasciata. In conclusion, V. bisfasciata and V. melanurus have different digestive protease patterns. Both species can hydrolyze different protein ingredients to formulate a specific diet. Nevertheless, V. bifasciata is more resistant to the presence of inhibitors, which allow it to include vegetable proteins in its diet.

A new software of calculating the pH values of coastal seawater: Considering the effects of low molecular weight organic acids

2019 ◽  
Vol 211 ◽  
pp. 108-116 ◽  
Author(s):  
Li-Na Lyu ◽  
Daoming Lu ◽  
Chengjun Sun ◽  
Haibing Ding ◽  
Liang-Min Yu ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Organic Acids ◽  
Low Molecular Weight ◽  
Coastal Seawater ◽  
Ph Values

Optimizing electron transfer from CdSe QDs to hydrogenase for photocatalytic H2 production

2019 ◽  
Vol 55 (39) ◽  
pp. 5579-5582 ◽  
Author(s):  
Monica L. K. Sanchez ◽  
Chang-Hao Wu ◽  
Michael W. W. Adams ◽  
R. Brian Dyer
Keyword(s):  
Quantum Dots ◽  
Electron Transfer ◽  
Reduction Potential ◽  
H2 Production ◽  
Cdse Quantum Dots ◽  
Redox Mediators ◽  
Cdse Qds ◽  
Electron Shuttles ◽  
Hydrogenase Enzyme

A series of viologen related redox mediators of varying reduction potential has been characterized and their utility as electron shuttles between CdSe quantum dots and hydrogenase enzyme has been demonstrated.

scholarly journals Sharp kinetic acceleration potentials during mediated redox catalysis of insulators

2021 ◽  
Author(s):  
Deqing Cao ◽  
Xiaoxiao Shen ◽  
Aiping Wang ◽  
Fengjiao Yu ◽  
Yuping Wu ◽  
...  
Keyword(s):  
Redox Potentials ◽  
Redox Catalysis ◽  
Redox Mediators ◽  
Fast Kinetics ◽  
Surface Conditions ◽  
Storage Materials ◽  
Surface Facets

Abstract Redox mediators could catalyse otherwise slow and energy-inefficient cycling of Li-S and Li-O2 batteries by shuttling electrons/holes between the electrode and the solid insulating storage materials. For mediators to work efficiently they need to oxidize the solid with fast kinetics yet the lowest possible overpotential. Here, we found that when the redox potentials of mediators are tuned via, e.g., Li+ concentration in the electrolyte, they exhibit distinct threshold potentials, where the kinetics accelerate several-fold within a range as small as 10 mV. This phenomenon is independent of types of mediators and electrolyte. The acceleration originates from the overpotentials required to activate fast Li+/e– extraction and the following chemical step at specific abundant surface facets. Efficient redox catalysis at insulating solids requires therefore carefully considering the surface conditions of the storage materials and electrolyte-dependent redox potentials, which may be tuned by salt concentrations or solvents.

scholarly journals Palette of Luciferases: Natural Biotools for New Applications in Biomedicine

Acta Naturae ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 15-27
Author(s):  
A. A. Kotlobay ◽  
Z. M. Kaskova ◽  
I. V. Yampolsky
Keyword(s):  
Atmospheric Oxygen ◽  
Biochemical Properties ◽  
Quantum Yields ◽  
External Irradiation ◽  
Low Molecular Weight ◽  
Non Invasive ◽  
Enzyme Thermostability ◽  
Highly Sensitive ◽  
New Applications ◽  
Optimal Ph

Optoanalytical methods based on using genetically encoded bioluminescent enzymes,luciferases, allow one to obtain highly sensitive signals, are non-invasive, and require no external irradiation. Bioluminescence is based on the chemical reaction of oxidation of a low-molecular-weight substrate (luciferin) by atmospheric oxygen, which is catalyzed by an enzyme (luciferase). Relaxation of the luciferin oxidation product from its excited state is accompanied by a release of a quantum of light, which can be detected as an analytical signal.The ability to express luciferase genes in various heterological systems and high quantum yields of luminescence reactions have made these tools rather popular in biology and medicine. Amongseveral naturally available luciferases, a few have been found to be useful for practicalapplication. Luciferase size, the wavelength of its luminescence maximum, enzyme thermostability, optimal pH of the reaction, and the need for cofactors areparameters that may differ for luciferases from different groups of organisms, and this fact directly affects the choice of the application area for each enzyme. It is quite important to overview the whole range of currently available luciferases based ontheir biochemical properties before choosing one bioluminescent probe suitable for a specific application.

scholarly journals Effects of pH and Magnetic Material on Immunomagnetic Separation of Cryptosporidium Oocysts from Concentrated Water Samples

2002 ◽  
Vol 68 (4) ◽  
pp. 2066-2070 ◽  
Author(s):  
Ryan C. Kuhn ◽  
Channah M. Rock ◽  
Kevin H. Oshima
Keyword(s):  
Magnetic Material ◽  
Water Samples ◽  
Environmental Water ◽  
Immunomagnetic Separation ◽  
Deionized Water ◽  
Ph Values ◽  
Cryptosporidium Oocysts ◽  
Optimum Ph ◽  
Effects Of Ph ◽  
Optimal Ph

ABSTRACT In this study, we examined the effect that magnetic materials and pH have on the recoveries of Cryptosporidium oocysts by immunomagnetic separation (IMS). We determined that particles that were concentrated on a magnet during bead separation have no influence on oocyst recovery; however, removal of these particles did influence pH values. The optimal pH of the IMS was determined to be 7.0. The numbers of oocysts recovered from deionized water at pH 7.0 were 26.3% higher than those recovered from samples that were not at optimal pH. The results indicate that the buffers in the IMS kit did not adequately maintain an optimum pH in some water samples. By adjusting the pH of concentrated environmental water samples to 7.0, recoveries of oocysts increased by 26.4% compared to recoveries from samples where the pH was not adjusted.

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