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Oxidative Medicine and Cellular... 2020Free radicals are chemical species (atoms, molecules, or ions) containing one or more unpaired electrons in their external orbitals and generally display a remarkable... (Review)
Review
Free radicals are chemical species (atoms, molecules, or ions) containing one or more unpaired electrons in their external orbitals and generally display a remarkable reactivity. The evidence of their existence was obtained only at the beginning of the 20th century. Chemists gradually ascertained the involvement of free radicals in organic reactions and, in the middle of the 20th century, their production in biological systems. For several decades, free radicals were thought to cause exclusively damaging effects . This idea was mainly supported by the finding that oxygen free radicals readily react with all biological macromolecules inducing their oxidative modification and loss of function. Moreover, evidence was obtained that when, in the living organism, free radicals are not neutralized by systems of biochemical defences, many pathological conditions develop. However, after some time, it became clear that the living systems not only had adapted to the coexistence with free radicals but also developed methods to turn these toxic substances to their advantage by using them in critical physiological processes. Therefore, free radicals play a dual role in living systems: they are toxic by-products of aerobic metabolism, causing oxidative damage and tissue dysfunction, and serve as molecular signals activating beneficial stress responses. This discovery also changed the way we consider antioxidants. Their use is usually regarded as helpful to counteract the damaging effects of free radicals but sometimes is harmful as it can block adaptive responses induced by low levels of radicals.
Topics: Animals; Antioxidants; Free Radicals; Humans; Oxidants; Oxidative Stress; Reactive Oxygen Species; Superoxide Dismutase
PubMed: 32411336
DOI: 10.1155/2020/9829176 -
Chemical Reviews Feb 2022The nervous system poses a grand challenge for integration with modern electronics and the subsequent advances in neurobiology, neuroprosthetics, and therapy which would... (Review)
Review
The nervous system poses a grand challenge for integration with modern electronics and the subsequent advances in neurobiology, neuroprosthetics, and therapy which would become possible upon such integration. Due to its extreme complexity, multifaceted signaling pathways, and ∼1 kHz operating frequency, modern complementary metal oxide semiconductor (CMOS) based electronics appear to be the only technology platform at hand for such integration. However, conventional CMOS-based electronics rely exclusively on electronic signaling and therefore require an additional technology platform to translate electronic signals into the language of neurobiology. Organic electronics are just such a technology platform, capable of converting electronic addressing into a variety of signals matching the endogenous signaling of the nervous system while simultaneously possessing favorable material similarities with nervous tissue. In this review, we introduce a variety of organic material platforms and signaling modalities specifically designed for this role as "translator", focusing especially on recent implementation in neuromodulation. We hope that this review serves both as an informational resource and as an encouragement and challenge to the field.
Topics: Electronics; Oxides; Semiconductors
PubMed: 35050623
DOI: 10.1021/acs.chemrev.1c00390 -
International Journal of Molecular... Aug 2023In the last few decades, reticular chemistry has grown significantly as a field of porous crystalline molecular materials. Scientists have attempted to create the ideal... (Review)
Review
In the last few decades, reticular chemistry has grown significantly as a field of porous crystalline molecular materials. Scientists have attempted to create the ideal platform for analyzing distinct anions based on optical sensing techniques (chromogenic and fluorogenic) by assembling different metal-containing units with suitable organic linking molecules and different organic molecules to produce crystalline porous materials. This study presents novel platforms for anion recognition based on reticular chemistry with high selectivity, sensitivity, electronic tunability, structural recognition, strong emission, and thermal and chemical stability. The key materials for reticular chemistry, Metal-Organic Frameworks (MOFs), Zeolitic Imidazolate Frameworks (ZIFs), and Covalent-Organic Frameworks (COFs), and the pre- and post-synthetic modification of the linkers and the metal oxide clusters for the selective detection of the anions, have been discussed. The mechanisms involved in sensing are also discussed.
Topics: Anions; Oxides; Electronics; Metal-Organic Frameworks; Porosity
PubMed: 37685850
DOI: 10.3390/ijms241713045 -
Water Research Apr 2024This publication summarizes my journey in the field of chemical oxidation processes for water treatment over the last 30+ years. Initially, the efficiency of the... (Review)
Review
This publication summarizes my journey in the field of chemical oxidation processes for water treatment over the last 30+ years. Initially, the efficiency of the application of chemical oxidants for micropollutant abatement was assessed by the abatement of the target compounds only. This is controlled by reaction kinetics and therefore, second-order rate constant for these reactions are the pre-requisite to assess the efficiency and feasibility of such processes. Due to the tremendous efforts in this area, we currently have a good experimental data base for second-order rate constants for many chemical oxidants, including radicals. Based on this, predictions can be made for compounds without experimental data with Quantitative Structure Activity Relationships with Hammet/Taft constants or energies of highest occupied molecular orbitals from quantum chemical computations. Chemical oxidation in water treatment has to be economically feasible and therefore, the extent of transformation of micropollutants is often limited and mineralization of target compounds cannot be achieved under realistic conditions. The formation of transformation products from the reactions of the target compounds with chemical oxidants is inherent to oxidation processes and the following questions have evolved over the years: Are the formed transformation products biologically less active than the target compounds? Is there a new toxicity associated with transformation products? Are transformation products more biodegradable than the corresponding target compounds? In addition to the positive effects on water quality related to abatement of micropollutants, chemical oxidants react mainly with water matrix components such as the dissolved organic matter (DOM), bromide and iodide. As a matter of fact, the fraction of oxidants consumed by the DOM is typically > 99%, which makes such processes inherently inefficient. The consequences are loss of oxidation capacity and the formation of organic and inorganic disinfection byproducts also involving bromide and iodide, which can be oxidized to reactive bromine and iodine with their ensuing reactions with DOM. Overall, it has turned out in the last three decades, that chemical oxidation processes are complex to understand and to manage. However, the tremendous research efforts have led to a good understanding of the underlying processes and allow a widespread and optimized application of such processes in water treatment practice such as drinking water, municipal and industrial wastewater and water reuse systems.
Topics: Bromides; Iodides; Water Pollutants, Chemical; Oxidation-Reduction; Oxidants; Water Purification
PubMed: 38387263
DOI: 10.1016/j.watres.2024.121148 -
Molecules (Basel, Switzerland) Jul 2019Oxidation of sulfide to sulfate is known to consist of several steps. Key intermediates in this process are the so-called small oxoacids of sulfur (SOS)-sulfenic HSOH... (Review)
Review
Oxidation of sulfide to sulfate is known to consist of several steps. Key intermediates in this process are the so-called small oxoacids of sulfur (SOS)-sulfenic HSOH (hydrogen thioperoxide, oxadisulfane, or sulfur hydride hydroxide) and sulfoxylic S(OH) acids. Sulfur monoxide can be considered as a dehydrated form of sulfoxylic acid. Although all of these species play an important role in atmospheric chemistry and in organic synthesis, and are also invoked in biochemical processes, they are quite unstable compounds so much so that their physical and chemical properties are still subject to intense studies. It is well-established that sulfoxylic acid has very strong reducing properties, while sulfenic acid is capable of both oxidizing and reducing various substrates. Here, in this review, the mechanisms of sulfide oxidation as well as data on the structure and reactivity of small sulfur-containing oxoacids, sulfur monoxide, and its precursors are discussed.
Topics: Free Radicals; Hydrogen Sulfide; Kinetics; Oxidation-Reduction; Oxides; Peroxides; Safrole; Sulfates; Sulfenic Acids; Sulfides; Sulfur Compounds
PubMed: 31366103
DOI: 10.3390/molecules24152768 -
Molecules (Basel, Switzerland) Jul 2023The chemistry of hypervalent iodine reagents has now become quite valuable due to the reactivity of these compounds under mild reaction conditions and their resemblance... (Review)
Review
The chemistry of hypervalent iodine reagents has now become quite valuable due to the reactivity of these compounds under mild reaction conditions and their resemblance in chemical properties to transition metals. The environmentally friendly nature of these reagents makes them suitable for Green Chemistry. Reagents with a dual nature, such as iodine(III) reagents, are capable electrophiles, while iodine(V) reagents are known for their strong oxidant behavior. Various iodine(V) reagents including IBX and DMP have been used as oxidants in organic synthesis either in stoichiometric or in catalytic amounts. In this review article, we describe various oxidation reactions induced by iodine(V) reagents reported in the past decade.
Topics: Iodine; Oxidants; Oxidation-Reduction; Indicators and Reagents; Catalysis
PubMed: 37446912
DOI: 10.3390/molecules28135250 -
International Journal of Molecular... May 2023In recent years, organic pollutants have become a global problem due to their negative impact on human health and the environment. Photocatalysis is one of the most... (Review)
Review
In recent years, organic pollutants have become a global problem due to their negative impact on human health and the environment. Photocatalysis is one of the most promising methods for the removal of organic pollutants from wastewater, and oxide semiconductor materials have proven to be among the best in this regard. This paper presents the evolution of the development of metal oxide nanostructures (MONs) as photocatalysts for ciprofloxacin degradation. It begins with an overview of the role of these materials in photocatalysis; then, it discusses methods of obtaining them. Then, a detailed review of the most important oxide semiconductors (ZnO, TiO, CuO, etc.) and alternatives for improving their photocatalytic performance is provided. Finally, a study of the degradation of ciprofloxacin in the presence of oxide semiconductor materials and the main factors affecting photocatalytic degradation is carried out. It is well known that antibiotics (in this case, ciprofloxacin) are toxic and non-biodegradable, which can pose a threat to the environment and human health. Antibiotic residues have several negative impacts, including antibiotic resistance and disruption of photosynthetic processes.
Topics: Humans; Ciprofloxacin; Zinc Oxide; Nanostructures; Anti-Bacterial Agents; Oxides; Environmental Pollutants; Catalysis
PubMed: 37298517
DOI: 10.3390/ijms24119564 -
Sensors (Basel, Switzerland) Jun 2022During recent decades, metal oxide semiconductors (MOS) have sparked more attention in various applications and industries due to their excellent sensing... (Review)
Review
During recent decades, metal oxide semiconductors (MOS) have sparked more attention in various applications and industries due to their excellent sensing characteristics, thermal stability, abundance, and ease of synthesis. They are reliable and accurate for measuring and monitoring environmentally important toxic gases, such as NO, NO, NO, HS, CO, NH, CH, SO, and CO. Compared to other sensing technologies, MOS sensors are lightweight, relatively inexpensive, robust, and have high material sensitivity with fast response times. Green nanotechnology is a developing branch of nanotechnology and aims to decrease the negative effects of the production and application of nanomaterials. For this purpose, organic solvents and chemical reagents are not used to prepare metal nanoparticles. On the contrary, the synthesis of metal or metal oxide nanoparticles is done by microorganisms, either from plant extracts or fungi, yeast, algae, and bacteria. Thus, this review aims at illustrating the possible green synthesis of different metal oxides such as ZnO, TiO, CeO, SnO, InO, CuO, NiO, WO and FeO, as well as metallic nanoparticles doping.
Topics: Gases; Metal Nanoparticles; Nanotechnology; Oxides; Semiconductors
PubMed: 35808164
DOI: 10.3390/s22134669 -
Yakugaku Zasshi : Journal of the... 2023Organic nitroxyl radicals represented by 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) are known to be compounds that catalyze alcohol oxidation reactions. These... (Review)
Review
Organic nitroxyl radicals represented by 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) are known to be compounds that catalyze alcohol oxidation reactions. These catalytic reactions can be applied to a wide range of compounds with hydroxy and amino groups. It is also possible to selectively oxidize primary alcohols by designing the skeleton around the nitroxyl radical moiety for use in organic synthesis. Reactions can also be carried out by electrochemical methods, and the electrical current measured during the reaction can be used to quantify the substrates. Therefore, the combination of reactions catalyzed by nitroxyl radicals and electrochemical techniques is expected to be applied as a new analytical method. However, since the reaction does not proceed rapidly in neutral aqueous solutions, it has mostly been applied in basic aqueous solutions or organic solvents, and there have been no reports on sensor applications under physiological conditions. Herein, we have developed a novel catalyst, nortropine N-oxyl (NNO), which is highly active even in neutral aqueous solutions, and have found that it can be used for the analysis of biological components and drugs under physiological conditions. The combination of this method with enzymatic reactions made it possible to specifically detect certain compounds. In this review, we describe a novel analytical method that combines these nitroxyl radicals with electrochemical methods.
Topics: Oxidation-Reduction; Nitrogen Oxides; Catalysis; Water; Free Radicals
PubMed: 36724933
DOI: 10.1248/yakushi.22-00143 -
Chemical Reviews Feb 2016The review summarizes current trends and developments in the polymerization of alkylene oxides in the last two decades since 1995, with a particular focus on the most... (Review)
Review
The review summarizes current trends and developments in the polymerization of alkylene oxides in the last two decades since 1995, with a particular focus on the most important epoxide monomers ethylene oxide (EO), propylene oxide (PO), and butylene oxide (BO). Classical synthetic pathways, i.e., anionic polymerization, coordination polymerization, and cationic polymerization of epoxides (oxiranes), are briefly reviewed. The main focus of the review lies on more recent and in some cases metal-free methods for epoxide polymerization, i.e., the activated monomer strategy, the use of organocatalysts, such as N-heterocyclic carbenes (NHCs) and N-heterocyclic olefins (NHOs) as well as phosphazene bases. In addition, the commercially relevant double-metal cyanide (DMC) catalyst systems are discussed. Besides the synthetic progress, new types of multifunctional linear PEG (mf-PEG) and PPO structures accessible by copolymerization of EO or PO with functional epoxide comonomers are presented as well as complex branched, hyperbranched, and dendrimer like polyethers. Amphiphilic block copolymers based on PEO and PPO (Poloxamers and Pluronics) and advances in the area of PEGylation as the most important bioconjugation strategy are also summarized. With the ever growing toolbox for epoxide polymerization, a "polyether universe" may be envisaged that in its structural diversity parallels the immense variety of structural options available for polymers based on vinyl monomers with a purely carbon-based backbone.
Topics: Alkynes; Epoxy Compounds; Ethylene Oxide; Molecular Structure; Oxides; Polymerization; Polymers
PubMed: 26713458
DOI: 10.1021/acs.chemrev.5b00441