Journal articles on the topic 'Redox des particules'
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1
Peña, Fernando J., Cristian O’Flaherty, José M. Ortiz Rodríguez, Francisco E. Martín Cano, Gemma L. Gaitskell-Phillips, María C. Gil, and Cristina Ortega Ferrusola. "Redox Regulation and Oxidative Stress: The Particular Case of the Stallion Spermatozoa." Antioxidants 8, no. 11 (November 19, 2019): 567. http://dx.doi.org/10.3390/antiox8110567.
Abstract:
Redox regulation and oxidative stress have become areas of major interest in spermatology. Alteration of redox homeostasis is recognized as a significant cause of male factor infertility and is behind the damage that spermatozoa experience after freezing and thawing or conservation in a liquid state. While for a long time, oxidative stress was just considered an overproduction of reactive oxygen species, nowadays it is considered as a consequence of redox deregulation. Many essential aspects of spermatozoa functionality are redox regulated, with reversible oxidation of thiols in cysteine residues of key proteins acting as an “on–off” switch controlling sperm function. However, if deregulation occurs, these residues may experience irreversible oxidation and oxidative stress, leading to malfunction and ultimately death of the spermatozoa. Stallion spermatozoa are “professional producers” of reactive oxygen species due to their intense mitochondrial activity, and thus sophisticated systems to control redox homeostasis are also characteristic of the spermatozoa in the horse. As a result, and combined with the fact that embryos can easily be collected in this species, horses are a good model for the study of redox biology in the spermatozoa and its impact on the embryo.
2
Reyhani, Amin, Thomas G. McKenzie, Qiang Fu, and Greg G. Qiao. "Redox-Initiated Reversible Addition–Fragmentation Chain Transfer (RAFT) Polymerization." Australian Journal of Chemistry 72, no. 7 (2019): 479. http://dx.doi.org/10.1071/ch19109.
Abstract:
Reversible addition–fragmentation chain transfer (RAFT) polymerization initiated by a radical-forming redox reaction between a reducing and an oxidizing agent (i.e. ‘redox RAFT’) represents a simple, versatile, and highly useful platform for controlled polymer synthesis. Herein, the potency of a wide range of redox initiation systems including enzyme-mediated redox reactions, the Fenton reaction, peroxide-based reactions, and metal-catalyzed redox reactions, and their application in initiating RAFT polymerization, are reviewed. These redox-RAFT polymerization methods have been widely studied for synthesizing a broad range of homo- and co-polymers with tailored molecular weights, compositions, and (macro)molecular structures. It has been demonstrated that redox-RAFT polymerization holds particular promise due to its excellent performance under mild conditions, typically operating at room temperature. Redox-RAFT polymerization is therefore an important and core part of the RAFT methodology handbook and may be of particular importance going forward for the fabrication of polymeric biomaterials under biologically relevant conditions or in biological systems, in which naturally occurring redox reactions are prevalent.
3
Godoi, Marco Antônio Abrantes de Barros. "MITOLOGIA DO MUNDO VEGETAL GRECO-ROMANO: ALGUNS EXEMPLOS PARTICULARES." PRINCIPIA, no. 40 (December 8, 2020): 119–25. http://dx.doi.org/10.12957/principia.2020.55873.
Abstract:
Desde os tempos primitivos, o animismo vem sendo uma característica universal da visão que o ser humano tem sobre a sua experiência com seu ambiente, sendo uma perspectiva holística do universo, este ser humano encara-o como um universo vivo, seja uma pedra, seja um rio, ou a vegetação ao redor, todos possuem um espírito que se manifesta e se conecta com todos ao redor. A partir desta visão de mundo primevo, as sociedades posteriores construíram uma visão do mundo vegetal complexa que leva a representações de cada elemento da natureza. Aqui pretendemos observar, na primeira parte um aspecto geral desta perspectiva sobre uma visão do mito e da forma como o homem veio construindo esta percepção do mundo vegetal e seu elo com sua vida. Na segunda parte estudaremos algumas particularidades do mito do carvalho, do narciso, da oliveira e da videira.
4
Albrecht, Simone C., Mirko C. Sobotta, Daniela Bausewein, Isabel Aller, Rüdiger Hell, Tobias P. Dick, and Andreas J. Meyer. "Redesign of Genetically Encoded Biosensors for Monitoring Mitochondrial Redox Status in a Broad Range of Model Eukaryotes." Journal of Biomolecular Screening 19, no. 3 (August 16, 2013): 379–86. http://dx.doi.org/10.1177/1087057113499634.
Abstract:
The development of genetically encoded redox biosensors has paved the way toward chemically specific, quantitative, dynamic, and compartment-specific redox measurements in cells and organisms. In particular, redox-sensitive green fluorescent proteins (roGFPs) have attracted major interest as tools to monitor biological redox changes in real time and in vivo. Most recently, the engineering of a redox relay that combines glutaredoxin (Grx) with roGFP2 as a translational fusion (Grx1-roGFP2) led to a biosensor for the glutathione redox potential ( EGSH). The expression of this probe in mitochondria is of particular interest as mitochondria are the major source of oxidants, and their redox status is closely connected to cell fate decisions. While Grx1-roGFP2 can be expressed in mammalian mitochondria, it fails to enter mitochondria in various nonmammalian model organisms. Here we report that inversion of domain order from Grx1-roGFP2 to roGFP2-Grx1 yields a biosensor with perfect mitochondrial targeting while fully maintaining its biosensor capabilities. The redesigned probe thus allows extending in vivo observations of mitochondrial redox homeostasis to important nonmammalian model organisms, particularly plants and insects.
5
Paffen, Alina, Christopher Cremer, and Frederic W. Patureau. "Phenotellurazine redox catalysts: elements of design for radical cross-dehydrogenative coupling reactions." Beilstein Journal of Organic Chemistry 20 (June 4, 2024): 1292–97. http://dx.doi.org/10.3762/bjoc.20.112.
Abstract:
Redox active phenotellurazine catalysts have been recently utilized in two different cross-dehydrogenative coupling reactions. In this study, we revisit the design of the phenotellurazine redox catalysts. In particular, we investigate the level of cooperativity between the Te- and N-centers, the effect of secondary versus tertiary N-centers, the effect of heterocyclic versus non-heterocyclic structures, and the effect of substitution patterns on the redox catalytic activity.
6
Evtugyn, Gennady A., Anna V. Porfireva, and Ivan I. Stoikov. "Electrochemical DNA sensors based on spatially distributed redox mediators: challenges and promises." Pure and Applied Chemistry 89, no. 10 (September 26, 2017): 1471–90. http://dx.doi.org/10.1515/pac-2016-1124.
Abstract:
AbstractDNA and aptasensors are widely used for fast and reliable detection of disease biomarkers, pharmaceuticals, toxins, metabolites and other species necessary for biomedical diagnostics. In the overview, the concept of spatially distributed redox mediators is considered with particular emphasis to the signal generation and biospecific layer assembling. The application of non-conductive polymers bearing redox labels, supramolecular carriers with attached DNA aptamers and redox active dyes and E-sensor concept are considered as examples of the approach announced.
7
Barbosa, Milena Cristian do Nascimento, Márcia Taynara Machado Almeida, Mayrhon José Abrantes Farias, and Adriano Lopes de Souza. "DESAFIOS E POSSIBILIDADES DO ESTÁGIO SUPERVISIONADO EM EDUCAÇÃO FÍSICA: A EXPERIÊNCIA COM O ENSINO HÍBRIDO." Revista Docência e Cibercultura 6, no. 5 (October 6, 2022): 252–66. http://dx.doi.org/10.12957/redoc.2022.66371.
Abstract:
O presente artigo objetiva relatar as experiências vividas por acadêmicas do curso de Licenciatura em Educação Física durante o do Estágio Supervisionado em uma escola pública no município de Tocantinópolis-TO. Nesse trabalho utilizamos a narrativa autobiográfica para abordar os desafios e as possibilidades vivenciadas no modelo de Ensino Híbrido, problematizando a didática utilizada nos portfólios e propondo reflexões quanto ao papel da Educação Física em meio a um contexto de ensino fragilizado, incluindo os respectivos impactos nas práticas corporais/atividades realizadas na escola. A partir dessa experiência, foi possível perceber a importância do uso de outras linguagens, para além da escrita, na apropriação dos conhecimentos que cerceiam o cotidiano escolar, de forma geral, e os momentos das aulas de Educação Física, de forma particular.
8
Jacob, Claus. "Redox signalling via the cellular thiolstat." Biochemical Society Transactions 39, no. 5 (September 21, 2011): 1247–53. http://dx.doi.org/10.1042/bst0391247.
Abstract:
Research conducted during the last two decades has provided evidence for the existence of an extensive intracellular redox signalling, control and feedback network based on different cysteine-containing proteins and enzymes. Together, these proteins enable the living cell to sense and respond towards external and internal redox changes in a measured, gradual, appropriate and mostly reversible manner. The (bio)chemical basis of this regulatory ‘thiolstat’ is provided by the complex redox chemistry of the amino acid cysteine, which occurs in vivo in various sulfur chemotypes and is able to participate in different redox processes. Although our knowledge of the biological redox behaviour of sulfur (i.e. cysteine or methionine) is expanding, numerous questions still remain. Future research will need to focus on the individual proteins involved in this redox system, their particular properties and specific roles in cellular defence and survival. Once it is more fully understood, the cellular thiolstat and its individual components are likely to form prominent targets for drug design.
9
Yang, Kylie, Jacek L. Kolanowski, and Elizabeth J. New. "Mitochondrially targeted fluorescent redox sensors." Interface Focus 7, no. 2 (April 6, 2017): 20160105. http://dx.doi.org/10.1098/rsfs.2016.0105.
Abstract:
The balance of oxidants and antioxidants within the cell is crucial for maintaining health, and regulating physiological processes such as signalling. Consequently, imbalances between oxidants and antioxidants are now understood to lead to oxidative stress, a physiological feature that underlies many diseases. These processes have spurred the field of chemical biology to develop a plethora of sensors, both small-molecule and fluorescent protein-based, for the detection of specific oxidizing species and general redox balances within cells. The mitochondrion, in particular, is the site of many vital redox reactions. There is therefore a need to target redox sensors to this particular organelle. It has been well established that targeting mitochondria can be achieved by the use of a lipophilic cation-targeting group, or by utilizing natural peptidic mitochondrial localization sequences. Here, we review how these two approaches have been used by a number of researchers to develop mitochondrially localized fluorescent redox sensors that are already proving useful in providing insights into the roles of reactive oxygen species in the mitochondria.
10
Cicconi, Maria Rita, Charles Le Losq, Roberto Moretti, and Daniel R. Neuville. "Magmas are the Largest Repositories and Carriers of Earth’s Redox Processes." Elements 16, no. 3 (June 1, 2020): 173–78. http://dx.doi.org/10.2138/gselements.16.3.173.
Abstract:
Magma is the most important chemical transport agent throughout our planet. This paper provides an overview of the interplay between magma redox, major element chemistry, and crystal and volatile content, and of the influence of redox on the factors that drive igneous system dynamics. Given the almost infinite combinations of temperature, pressure, and chemical compositions relevant to igneous petrology, we focus on the concepts and methods that redox geochemistry provides to understand magma formation, ascent, evolution and crystallization. Particular attention is paid to the strong and complex interplay between melt structure and chemistry, and to the influence that redox conditions have on melt properties, crystallization mechanisms and the solubility of volatile components.
11
McLean, K. J., M. Sabri, K. R. Marshall, R. J. Lawson, D. G. Lewis, D. Clift, P. R. Balding, et al. "Biodiversity of cytochrome P450 redox systems." Biochemical Society Transactions 33, no. 4 (August 1, 2005): 796–801. http://dx.doi.org/10.1042/bst0330796.
Abstract:
P450s (cytochrome P450 mono-oxygenases) are a superfamily of haem-containing mono-oxygenase enzymes that participate in a wide range of biochemical pathways in different organisms from all of the domains of life. To facilitate their activity, P450s require sequential delivery of two electrons passed from one or more redox partner enzymes. Although the P450 enzymes themselves show remarkable similarity in overall structure, it is increasingly apparent that there is enormous diversity in the redox partner systems that drive the P450 enzymes. This paper examines some of the recent advances in our understanding of the biodiversity of the P450 redox apparatus, with a particular emphasis on the redox systems in the pathogen Mycobacterium tuberculosis.
12
Feng, Yunxiao, Fengli Gao, Xinyao Yi, and Ming La. "Optical Bioassays Based on the Signal Amplification of Redox Cycling." Biosensors 14, no. 6 (May 24, 2024): 269. http://dx.doi.org/10.3390/bios14060269.
Abstract:
Optical bioassays are challenged by the growing requirements of sensitivity and simplicity. Recent developments in the combination of redox cycling with different optical methods for signal amplification have proven to have tremendous potential for improving analytical performances. In this review, we summarized the advances in optical bioassays based on the signal amplification of redox cycling, including colorimetry, fluorescence, surface-enhanced Raman scattering, chemiluminescence, and electrochemiluminescence. Furthermore, this review highlighted the general principles to effectively couple redox cycling with optical bioassays, and particular attention was focused on current challenges and future opportunities.
13
Attene-Ramos, Matias S., Kajorn Kitiphongspattana, Katrin Ishii-Schrade, and H. Rex Gaskins. "Temporal changes of multiple redox couples from proliferation to growth arrest in IEC-6 intestinal epithelial cells." American Journal of Physiology-Cell Physiology 289, no. 5 (November 2005): C1220—C1228. http://dx.doi.org/10.1152/ajpcell.00164.2005.
Abstract:
Changes in intracellular redox couples and redox reactive molecules have been implicated in the regulation of a variety of cellular processes, including cell proliferation and growth arrest by contact inhibition. However, the magnitude, direction, and temporal relationship of redox changes to cellular responses are incompletely defined. The present work sought to characterize redox and metabolic changes associated with proliferative stages to contact inhibition of growth in rat IEC-6 intestinal epithelial cells. From the first day of culture until 1 day before confluence, an increase in GSH concentrations and a significant reduction in the redox potential of the GSSG/2GSH couple were observed. These changes were accompanied by a decrease in relative reactive oxygen species (ROS) and nitric oxide (NO) concentrations and oxidation of the redox potential of the NADP+/reduced NADP and NAD+/NADH couples. Postconfluent cells exhibited a significant decrease in GSH concentrations and a significant oxidation of the GSSG/2GSH couple. When cell proliferation decreased, relative ROS concentrations increased ( P < 0.01), whereas NO concentrations remained unchanged, and the NAD+/NADH couple became more reduced. Together, these data indicate that the redox potential of distinct couples varies differentially in both magnitude and direction during successive stages of IEC-6 growth. This finding points out the difficulty of defining intracellular redox status at particular stages of cell growth by examining only one redox species. In addition, the data provide a numerical framework for future research of regulatory mechanisms governed by distinct intracellular redox couples.
14
Timoshnikov, Viktor A., Olga Yu Selyutina, Nikolay E. Polyakov, Victoria Didichenko, and George J. Kontoghiorghes. "Mechanistic Insights of Chelator Complexes with Essential Transition Metals: Antioxidant/Pro-Oxidant Activity and Applications in Medicine." International Journal of Molecular Sciences 23, no. 3 (January 23, 2022): 1247. http://dx.doi.org/10.3390/ijms23031247.
Abstract:
The antioxidant/pro-oxidant activity of drugs and dietary molecules and their role in the maintenance of redox homeostasis, as well as the implications in health and different diseases, have not yet been fully evaluated. In particular, the redox activity and other interactions of drugs with essential redox metal ions, such as iron and copper, need further investigation. These metal ions are ubiquitous in human nutrition but also widely found in dietary supplements and appear to exert major effects on redox homeostasis in health, but also on many diseases of free radical pathology. In this context, the redox mechanistic insights of mainly three prototype groups of drugs, namely alpha-ketohydroxypyridines (alpha-hydroxypyridones), e.g., deferiprone, anthraquinones, e.g., doxorubicin and thiosemicarbazones, e.g., triapine and their metal complexes were examined; details of the mechanisms of their redox activity were reviewed, with emphasis on the biological implications and potential clinical applications, including anticancer activity. Furthermore, the redox properties of these three classes of chelators were compared to those of the iron chelating drugs and also to vitamin C, with an emphasis on their potential clinical interactions and future clinical application prospects in cancer, neurodegenerative and other diseases.
15
Nagahara, Noriyuki. "Catalytic Site Cysteines of Thiol Enzyme: Sulfurtransferases." Journal of Amino Acids 2011 (December 28, 2011): 1–7. http://dx.doi.org/10.4061/2011/709404.
Abstract:
Thiol enzymes have single- or double-catalytic site cysteine residues and are redox active. Oxidoreductases and isomerases contain double-catalytic site cysteine residues, which are oxidized to a disulfide via a sulfenyl intermediate and reduced to a thiol or a thiolate. The redox changes of these enzymes are involved in their catalytic processes. On the other hand, transferases, and also some phosphatases and hydrolases, have a single-catalytic site cysteine residue. The cysteines are redox active, but their sulfenyl forms, which are inactive, are not well explained biologically. In particular, oxidized forms of sulfurtransferases, such as mercaptopyruvate sulfurtransferase and thiosulfate sulfurtransferase, are not reduced by reduced glutathione but by reduced thioredoxin. This paper focuses on why the catalytic site cysteine of sulfurtransferase is redox active.
16
Dos Santos, Jorge Luís Rodrigues, and Matheus Motta dos Santos. "Fé e resistência: por uma teologia do respeito." Revista Docência e Cibercultura 5, no. 2 (July 12, 2021): 262–58. http://dx.doi.org/10.12957/redoc.2021.57183.
Abstract:
A ocorrência de casos de intolerância religiosa aumentam significativamente em todas as partes do mundo. No caso particular do Brasil, episódios de intolerância religiosa multiplicam-se e destacam-se as violências e agressões sofridas por praticantes e estabelecimentos de cultos afro-brasileiros – perpetrados inclusive por religiosos de outras afiliações religiosas. Acreditamos ser urgente e necessária a reflexão sobre a construção de uma sociedade que tenha a diversidade e a pluralidade como valores inalienáveis, e o respeito em relação ao direito de expressar uma religiosidade com liberdade e sem restrições. O apelo pela tolerância, enquanto uma forma de promoção do entendimento, mostra-se insuficiente. Tolerar é de certo modo, suportar, e não reconhecer o direito à diversidade e a diferença. O que se deve exigir é o respeito, enquanto um dever como cidadão da comunidade planetária humana. Respeito, que garanta a existência, o reconhecimento, e até a valorização do outro em todas as suas dimensões. Isento de qualquer tipo de agressão ou violência, e que permita a dignidade de sua humanidade plena, segura e saudável.
17
Wu, X., N. H. Bishopric, D. J. Discher, B. J. Murphy, and K. A. Webster. "Physical and functional sensitivity of zinc finger transcription factors to redox change." Molecular and Cellular Biology 16, no. 3 (March 1996): 1035–46. http://dx.doi.org/10.1128/mcb.16.3.1035.
Abstract:
Redox regulation of DNA-binding proteins through the reversible oxidation of key cysteine sulfhydryl groups has been demonstrated to occur in vitro for a range of transcription factors. The direct redox regulation of DNA binding has not been described in vivo, possibly because most protein thiol groups are strongly buffered against oxidation by the highly reduced intracellular environment mediated by glutathione, thioredoxin, and associated pathways. For this reason, only accessible protein thiol groups with high thiol-disulfide oxidation potentials are likely to be responsive to intracellular redox changes. In this article, we demonstrate that zinc finger DNA-binding proteins, in particular members of the Sp-1 family, appear to contain such redox-sensitive -SH groups. These proteins displayed a higher sensitivity to redox regulation than other redox-responsive factors both in vitro and in vivo. This effect was reflected in the hyperoxidative repression of transcription from promoters with essential Sp-1 binding sites, including the simian virus 40 early region, glycolytic enzyme, and dihydrofolate reductase genes. Promoter analyses implicated the Sp-1 sites in this repression. Non-Sp-1-dependent redox-regulated genes including metallothionein and heme oxygenase were induced by the same hyperoxic stress. The studies demonstrate that cellular redox changes can directly regulate gene expression in vivo by determining the level of occupancy of strategically positioned GC-binding sites.
18
Xie, Dong-Ling, Xue-Lian Zheng, Can-Yu Zhou, Mukesh Kumar Kanwar, and Jie Zhou. "Functions of Redox Signaling in Pollen Development and Stress Response." Antioxidants 11, no. 2 (January 30, 2022): 287. http://dx.doi.org/10.3390/antiox11020287.
Abstract:
Cellular redox homeostasis is crucial for normal plant growth and development. Each developmental stage of plants has a specific redox mode and is maintained by various environmental cues, oxidants, and antioxidants. Reactive oxygen species (ROS) and reactive nitrogen species are the chief oxidants in plant cells and participate in cell signal transduction and redox balance. The production and removal of oxidants are in a dynamic balance, which is necessary for plant growth. Especially during reproductive development, pollen development depends on ROS-mediated tapetal programmed cell death to provide nutrients and other essential substances. The deviation of the redox state in any period will lead to microspore abortion and pollen sterility. Meanwhile, pollens are highly sensitive to environmental stress, in particular to cell oxidative burst due to its peculiar structure and function. In this regard, plants have evolved a series of complex mechanisms to deal with redox imbalance and oxidative stress damage. This review summarizes the functions of the main redox components in different stages of pollen development, and highlights various redox protection mechanisms of pollen in response to environmental stimuli. In continuation, we also discuss the potential applications of plant growth regulators and antioxidants for improving pollen vigor and fertility in sustaining better agriculture practices.
19
Khonde, Peguy Lutete, and Anwar Jardine. "Improved synthesis of the super antioxidant, ergothioneine, and its biosynthetic pathway intermediates." Organic & Biomolecular Chemistry 13, no. 5 (2015): 1415–19. http://dx.doi.org/10.1039/c4ob02023e.
20
Pereira, Daise Santos, Marcia Guerra Pereira, Alana Alves Pereira, and Maria Cecília Ribeiro Paixão. "Luta antirracista na educação infantil em tempos de pandemia: o que as táticas docentes revelam?" Revista Docência e Cibercultura 5, no. 2 (July 12, 2021): 259–78. http://dx.doi.org/10.12957/redoc.2021.57270.
Abstract:
A opção pela continuidade do ano letivo de 2020, na forma remota emergencial no Estado do Rio de Janeiro, resultou de deliberação político-administrativa exclusiva das instâncias de governo, cuja aplicação não foi acompanhada de um debate amplo e participativo na sociedade e, em particular, entre os profissionais de ensino, responsáveis pelos discentes e comunidade acadêmica. O objetivo deste artigo é apresentar táticas usadas por professores da educação infantil para uma educação antirracista, em meio às inadequações das instituições, realidades locais e as limitações de atendimento mínimo dos objetivos previstos na legislação brasileira relativos a cada nível de ensino. Tais astúcias dos praticantes do cotidiano são apontadas como decisivas, no sentido de evitar que a acentuada desigualdade social no interior da sociedade seja agravada pelas precárias condições de inclusão digital presentes nos lares brasileiros. Como demonstração do resultado da pesquisa, alicerçada em narrativas de docentes atuantes na educação infantil do município de Magé e interpretadas por meio da combinação dos conceitos de Boaventura de Souza Santos, Michel de Certeau e de Paulo Freire, são apresentadas três experiências do emprego de táticas que subvertem às funções atribuídas ao ensino remoto pelos gestores educacionais.
21
Burke, L. Declan, and Lisa M. Hurley. "Redox behaviour of thermally activated platinum electrodes with particular reference to operation at elevated temperature." Journal of Solid State Electrochemistry 4, no. 6 (July 4, 2000): 353–62. http://dx.doi.org/10.1007/s100080000127.
22
Costa, Cláudio F., Celien Lismont, Serhii Chornyi, Hongli Li, Mohamed A. F. Hussein, Hans R. Waterham, and Marc Fransen. "Functional Analysis of GSTK1 in Peroxisomal Redox Homeostasis in HEK-293 Cells." Antioxidants 12, no. 6 (June 7, 2023): 1236. http://dx.doi.org/10.3390/antiox12061236.
Abstract:
Peroxisomes serve as important centers for cellular redox metabolism and communication. However, fundamental gaps remain in our understanding of how the peroxisomal redox equilibrium is maintained. In particular, very little is known about the function of the nonenzymatic antioxidant glutathione in the peroxisome interior and how the glutathione antioxidant system balances with peroxisomal protein thiols. So far, only one human peroxisomal glutathione-consuming enzyme has been identified: glutathione S-transferase 1 kappa (GSTK1). To study the role of this enzyme in peroxisomal glutathione regulation and function, a GSTK1-deficient HEK-293 cell line was generated and fluorescent redox sensors were used to monitor the intraperoxisomal GSSG/GSH and NAD+/NADH redox couples and NADPH levels. We provide evidence that ablation of GSTK1 does not change the basal intraperoxisomal redox state but significantly extends the recovery period of the peroxisomal glutathione redox sensor po-roGFP2 upon treatment of the cells with thiol-specific oxidants. Given that this delay (i) can be rescued by reintroduction of GSTK1, but not its S16A active site mutant, and (ii) is not observed with a glutaredoxin-tagged version of po-roGFP2, our findings demonstrate that GSTK1 contains GSH-dependent disulfide bond oxidoreductase activity.
23
Silva, Jeanny Meiry Sombra, Juliana Caetano Neto, Thiago Henrique Valério Pereira, and Francielle Aparecida Miquilini Arcega. "Integração entre os multiletramentos e a educação midiática: saberes e práticas docentes na educação básica." Revista Docência e Cibercultura 5, no. 4 (December 17, 2021): 97–120. http://dx.doi.org/10.12957/redoc.2021.59471.
Abstract:
Este artigo apresenta o relato de uma prática didática desenvolvida na perspectiva da pedagogia dos multiletramentos e da integração curricular das tecnologias digitais. Os participantes foram 39 alunos do Ensino Fundamental II de uma escola particular da capital de São Paulo que, num período de pouco mais de três meses, se envolveram num projeto integrado coordenado por professores de diferentes componentes curriculares. Este texto tem por objetivos relatar a percepção dos professores ao participarem dessa experiência didática; identificar quais foram os sentidos atribuídos pelos alunos e observar o que a produção deles revela sobre suas aprendizagens. Os dados foram coletados por meio de depoimentos em vídeos, questionário, produções discentes e diário de observação docente. Neste artigo analisamos os depoimentos dos alunos. O referencial teórico que fundamentou a prática e análise dos dados baseou-se na Pedagogia dos Multiletramentos e Educação Midiática. Os resultados apontam para as potencialidades da pedagogia dos multiletramentos e da educação midiática, de forma integrada ao conteúdo curricular, pois proporcionaram aos professores formas significativas de trabalhar conteúdos e, aos alunos, o desenvolvimento da autonomia e da criatividade, o aprendizado advindo do trabalho em equipe, o desenvolvimento de pesquisas, seleções de informações, produção de conteúdo e tomada de decisões.
24
Fernandes, Nathan Moretto Guzzo, Vilmar José Borges, Rebeca Soterio Martins, Shirlliney Virginio de Sousa, and Tiago Cardoso Melo. "NO CONTEXTO DE CIBERCULTURA, O QUE PODE A FOTOGRAFIA NO ENSINO DE GEOGRAFIA?" Revista Docência e Cibercultura 8, no. 3 (April 19, 2024): 01–23. http://dx.doi.org/10.12957/redoc.2023.74551.
Abstract:
O presente artigo objetiva pensar a fotografia como alternativa aos métodos convencionais no ensino de geografia, considerando-a uma linguagem criadora de conhecimentos e produtora de saberes que permite aos estudantes serem participantes do processo de criação, produção e pensamento sobre o espaço geográfico em que estão inseridos. Para tal finalidade, dialoga com autores que trabalham conceitos fundamentais para a disciplina de geografia bem como com autores que estudam fotografia e sua contribuição à educação. Utiliza, como aportes metodológicos, o levantamento bibliográfico e o uso de oficinas pedagógicas como ferramenta de produção coletiva e de registro de informações. O trabalho justifica-se pela ampliação do uso de artefatos tecnológicos em geral e, em particular, da fotografia na educação no contexto de cibercultura. Aposta no cotidiano escolar como lugar privilegiado para criações curriculares. E, assim, deriva deste trabalho a realização de uma oficina de fotografias com estudantes do 9º ano de uma escola pública de ensino fundamental. Como reverberações da oficina, os estudantes puderam repensar seus cotidianos e espaços de vivências dentro de múltiplos e contínuos mundos a partir das imagens fotográficas registradas por eles e ainda compreender conceitos geográficos. Conclui que diferentes linguagens, como a fotografia, têm grande potencial pedagógico no ensino de geografia.
25
Martinovich, G. G., I. V. Martinovich, V. V. Voinarouski, D. V. Grigorieva, I. V. Gorudko, and O. M. Panasenko. "Free radicals and signal transduction in cells." Биофизика 68, no. 4 (August 15, 2023): 667–84. http://dx.doi.org/10.31857/s0006302923040063.
Abstract:
This review provides an overview of molecular mechanisms of intracellular signal transduction involving free radicals. The structure and functions of enzymes that can form superoxide anion-radical and hydrogen peroxide are considered in detail. The mechanisms of regulation of cell properties with the participation of specialized redox chains formed by a group of proteins interacting through electron transport processes are discussed. Genetically mediated mechanisms of regulation of redox cell homeostasis are analyzed. Particular attention is paid to the issue concerning quantitative characterization of the network of interactions of oxidizing and reducing agents, which determines the species and individual characteristics of redox homeostasis and the stress response of cells.
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Witherspoon, Erin, and Zhe Wang. "Fundamental Understanding of Water's Role in the Oxygen Redox Process in Ionic Liquids." ECS Meeting Abstracts MA2022-02, no. 55 (October 9, 2022): 2123. http://dx.doi.org/10.1149/ma2022-02552123mtgabs.
Abstract:
The O2/O2 •- redox couple is of particular interest for use in energy storage technology due to its abundance, sustainability, and potentially high energy density. Conversely, in the presence of a proton source, such as water, the O2/O2 •- redox couple may become unstable and irreversible. However, the fundamental understanding of this process is still not clear. In this work, O2/O2 •- redox process has been investigated in the presence of water using electrochemistry combined with in-situ spectroscopic methods in ionic liquid media. The findings for the redox reaction of oxygen in ionic liquids reported here indicate a complex mechanism on different electrode surfaces. This study is to elucidate the mechanism and reaction intermediates; it will also provide a fundamental understanding of oxygen chemistry and ionic liquid green chemistry for future emphasis on batteries, fuel cells, and gas sensor applications.
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Wiyoto, Wiyoto, Sukenda Sukenda, Enang Harris, Kukuh Nirmala, and Daniel Djokosetiyanto. "Water Quality and Sediment Profile in Shrimp Culture with Different Sediment Redox Potential and Stocking Densities Under Laboratory Condition." ILMU KELAUTAN: Indonesian Journal of Marine Sciences 21, no. 2 (June 2, 2016): 65. http://dx.doi.org/10.14710/ik.ijms.21.2.65-76.
Abstract:
Sediment quality has been considered as one of the prime factors influencing the environment quality that support maximum shrimp production.The aim of the study was toevaluate the effects of sediment redox potential and shrimp stocking density on the profile of some sediment and water quality parameters. Two factors randomized factorial design was applied, with stocking density (60 and 120 shrimps.m-2) as the first variable and sediment redox potential (-65 mV, -108 mV and -206 mV) as the second variable. Some significant changes in TP, total Mn, and total S concentrations in the sediment were observed after the experimentation (P<0.05). Sediment redox potential significantly affected the dissolved oxygen, TAN, NO2, NO3, and H2S concentrations in the water. Whereas shrimp stocking density affected all water quality parameters except H2S concentration. Significant interactions between redox potential and stocking densities were observed in the nitrite and alkalinity concentrations. The significant effects of both shrimp density and redox potential on the sediment and water parameters in particular those that are known to directly affect the shrimp welfare (e.g. oxygen, ammonia, nitrite and H2S) indicate that these variables are of important aspects in shrimp pond management. Furthermore, the results clearly showed that -206mV redox potential significantly reduced the dissolved oxygen concentration in the sediment-water interface and increased the generation of H2S in water column. Thereby, this redox potential level is not advisable for shrimp culture system. Keywords: redox potential, stocking density.
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Hillion, Melanie, and Haike Antelmann. "Thiol-based redox switches in prokaryotes." Biological Chemistry 396, no. 5 (May 1, 2015): 415–44. http://dx.doi.org/10.1515/hsz-2015-0102.
Abstract:
Abstract Bacteria encounter reactive oxygen species (ROS) as a consequence of the aerobic life or as an oxidative burst of activated neutrophils during infections. In addition, bacteria are exposed to other redox-active compounds, including hypochloric acid (HOCl) and reactive electrophilic species (RES) such as quinones and aldehydes. These reactive species often target the thiol groups of cysteines in proteins and lead to thiol-disulfide switches in redox-sensing regulators to activate specific detoxification pathways and to restore the redox balance. Here, we review bacterial thiol-based redox sensors that specifically sense ROS, RES and HOCl via thiol-based mechanisms and regulate gene transcription in Gram-positive model bacteria and in human pathogens, such as Staphylococcus aureus and Mycobacterium tuberculosis. We also pay particular attention to emerging widely conserved HOCl-specific redox regulators that have been recently characterized in Escherichia coli. Different mechanisms are used to sense and respond to ROS, RES and HOCl by 1-Cys-type and 2-Cys-type thiol-based redox sensors that include versatile thiol-disulfide switches (OxyR, OhrR, HypR, YodB, NemR, RclR, Spx, RsrA/RshA) or alternative Cys phosphorylations (SarZ, MgrA, SarA), thiol-S-alkylation (QsrR), His-oxidation (PerR) and methionine oxidation (HypT). In pathogenic bacteria, these redox-sensing regulators are often important virulence regulators and required for adapation to the host immune defense.
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Surai, Peter F., Ivan I. Kochish, and Michael T. Kidd. "Redox Homeostasis in Poultry: Regulatory Roles of NF-κB." Antioxidants 10, no. 2 (January 28, 2021): 186. http://dx.doi.org/10.3390/antiox10020186.
Abstract:
Redox biology is a very quickly developing area of modern biological sciences, and roles of redox homeostasis in health and disease have recently received tremendous attention. There are a range of redox pairs in the cells/tissues responsible for redox homeostasis maintenance/regulation. In general, all redox elements are interconnected and regulated by various means, including antioxidant and vitagene networks. The redox status is responsible for maintenance of cell signaling and cell stress adaptation. Physiological roles of redox homeostasis maintenance in avian species, including poultry, have received limited attention and are poorly characterized. However, for the last 5 years, this topic attracted much attention, and a range of publications covered some related aspects. In fact, transcription factor Nrf2 was shown to be a master regulator of antioxidant defenses via activation of various vitagenes and other protective molecules to maintain redox homeostasis in cells/tissues. It was shown that Nrf2 is closely related to another transcription factor, namely, NF-κB, responsible for control of inflammation; however, its roles in poultry have not yet been characterized. Therefore, the aim of this review is to describe a current view on NF-κB functioning in poultry with a specific emphasis to its nutritional modulation under various stress conditions. In particular, on the one hand, it has been shown that, in many stress conditions in poultry, NF-κB activation can lead to increased synthesis of proinflammatory cytokines leading to systemic inflammation. On the other hand, there are a range of nutrients/supplements that can downregulate NF-κB and decrease the negative consequences of stress-related disturbances in redox homeostasis. In general, vitagene–NF-κB interactions in relation to redox balance homeostasis, immunity, and gut health in poultry production await further research.
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Sarandy, Mariáurea Matias, Reggiani Vilela Gonçalves, and Giuseppe Valacchi. "Cutaneous Redox Senescence." Biomedicines 12, no. 2 (February 1, 2024): 348. http://dx.doi.org/10.3390/biomedicines12020348.
Abstract:
Our current understanding of skin cell senescence involves the role of environmental stressors (UV, O3, cigarette smoke, particulate matter, etc.), lifestyle (diet, exercise, etc.) as well as genetic factors (metabolic changes, hormonal, etc.). The common mechanism of action of these stressors is the disturbance of cellular redox balance characterized by increased free radicals and reactive oxygen species (ROS), and when these overload the intrinsic antioxidant defense system, it can lead to an oxidative stress cellular condition. The main redox mechanisms that activate cellular senescence in the skin involve (1) the oxidative damage of telomeres causing their shortening; (2) the oxidation of proteomes and DNA damage; (3) an a in lysosomal mass through the increased activity of resident enzymes such as senescence-associated β-galactosidase (SA-β-gal) as well as other proteins that are products of lysosomal activity; (4) and the increased expression of SASP, in particular pro-inflammatory cytokines transcriptionally regulated by NF-κB. However, the main targets of ROS on the skin are the proteome (oxi-proteome), followed by telomeres, nucleic acids (DNAs), lipids, proteins, and cytoplasmic organelles. As a result, cell cycle arrest pathways, lipid peroxidation, increased lysosomal content and dysfunctional mitochondria, and SASP synthesis occur. Furthermore, oxidative stress in skin cells increases the activity of p16INK4A and p53 as inhibitors of Rb and CDks, which are important for maintaining the cell cycle. p53 also promotes the inactivation of mTOR-mediated autophagic and apoptotic pathways, leading to senescence. However, these markers alone cannot establish the state of cellular senescence, and multiple analyses are encouraged for confirmation. An updated and more comprehensive approach to investigating skin senescence should include further assays of ox-inflammatory molecular pathways that can consolidate the understanding of cutaneous redox senescence.
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Amante, Lúcia. "Cultura da Avaliação e Contextos Digitais de Aprendizagem: O modelo PrACT." Revista Docência e Cibercultura 1, no. 1 (November 4, 2017): 135–50. http://dx.doi.org/10.12957/redoc.2017.30912.
Abstract:
Com os novos cenários de aprendizagem decorrentes do desenvolvimento tecnológico e em particular da Web 2.0, torna-se necessário repensar o processo de ensino-aprendizagem e as práticas docentes, designadamente ao nível de estratégias de avaliação alinhadas com paradigmas mais recentes, onde novos conceitos e perspetivas dão lugar a uma nova cultura de avaliação. Esta nova perspetiva, opõe-se à “cultura psicométrica do teste” e tem por base o construtivismo social, encarando o estudante como um participante ativo que partilha a responsabilidade pelo processo de aprendizagem, que se envolve na avaliação que, por sua vez, deve assumir múltiplas e diversificadas formas. Que novos conceitos emergem nesta abordagem? Que modelos podem ancorar esta nova cultura de avaliação? Como desenhar um sistema de avaliação que garanta a qualidade desta nova abordagem? Como podem os novos media digitais contribuir para uma avaliação mais relevante? Partindo do trabalho empírico desenvolvido em pesquisas neste âmbito e do quadro conceptual do modelo PrACT (Praticabilidade, Consistência, Autenticidade e Transparência) (PEREIRA, OLIVEIRA & TINOCA, 2011; PEREIRA, OLIVEIRA & AMANTE, 2015) assume-se a cultura da avaliação como contraponto à cultura do teste e propõe-se uma abordagem edumétrica na análise da qualidade das novas formas de avaliação. Neste texto argumentamos sobre a importância de desenvolver e aplicar um quadro conceptual, com base no conceito de avaliação digital alternativa, que enquadre as práticas de avaliação e contribua para a sustentabilidade dessas práticas designadamente nos novos contextos de aprendizagem.
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Michalowska-Kaczmarczyk, Anna M., and Tadeusz Michalowski. "Physicochemical and Analytical Implications of GATES/GEB Principles." Journal of Biomedical Research & Environmental Sciences 2, no. 12 (December 2021): 1202–10. http://dx.doi.org/10.37871/jbres1373.
Abstract:
The fundamental property of electrolytic systems involved with linear combination f12 = 2∙f(O) – f(H) of elemental balances: f1 = f(H) for Y1 = H, and f2 = f(O) for Y2 = O, is presented. The dependency/independency of the f12 on Charge Balance (f0 = ChB) and other elemental and/or core balances fk = f(Yk) (k = 3,…,K) is the general criterion distinguishing between non-redox and redox systems. The f12 related to a redox system is the primary form of a Generalized Electron Balance (GEB), formulated for redox systems within the Generalized Approach to Electrolytic System (GATES) as GATES/GEB ⊂ GATES. The set of K balances f0,f12,f3,…,fK is necessary/ sufficient/needed to solve an electrolytic redox system, while the K-1 balances f0,f3,…,fK are the set applied to solve an electrolytic non-redox system. The identity (0 = 0) procedure of checking the linear independency/ dependency property of f12 within the set f0,f12,f3,…,fK (i) provides the criterion distinguishing between the redox and non-redox systems and (ii) specifies Oxidation Numbers (ONs) of elements in particular components of the system, and in the species formed in the system. Some chemical concepts, such as oxidant, reductant, oxidation number, equivalent mass, stoichiometry, perceived as derivative within GATES, are indicated. All the information is gained on the basis of the titration Ce(SO4)2 (C) + H2SO4 (C1) + CO2 (C2) ⇨ FeSO4 (C0) + H2SO4 (C01) + CO2 (C02), simulated with use of the iterative computer program MATLAB.
33
Jesse, Kate Ashley, Sergio Diaz-Abad, Sandip Maurya, and Benjamin L. Davis. "Sterically Bulky Asymmetric Benzophenone Derivatives as Negolytes in a Non-Aqueous Redox Flow Battery." ECS Meeting Abstracts MA2023-01, no. 3 (August 28, 2023): 773. http://dx.doi.org/10.1149/ma2023-013773mtgabs.
Abstract:
To increase renewable energy generation to the electrical grid, intermittent energy sources, such as wind and solar energy, need a long-term, large scale energy storage method. Redox flow batteries (RFB) are an attractive solution as they allow for long term storage in various redox states of an organic or inorganic compound. The ideal redox-active compound for a RFB should have a high energy density, which can be achieved through a large potential difference in redox events, high concentration of charge carrier, or by increasing the number of electrons transferred during a given redox event. In particular, nonaqueous RFB (NRFB) are promising for building a system with a large potential difference for redox events due the large electrochemical solvent window (~5 V for acetonitrile) as compared to water (~2 V). While metal complexes featuring redox active ligands have been thoroughly investigated as carriers in NRFBs, they are often too expensive for widespread use. This has led to increasing interest in organic carriers. Benzophenone is a promising candidate for an organic negolyte due to its high solubility in acetonitrile and the presence of a reversible reduction at -2.1 V vs. Ag/Ag+. Unfortunately, the durability of benzophenone during cycling is low. Here, we discuss the degradation products of benzophenone during cycling and show how the incorporation of sterically bulky groups ortho to the benzophenone carbonyl improves durability. We then evaluate the utility of these benzophenone derivatives as negolytes in a NRFB flow cell.
34
Wiederkehr, Nadir Ana. "REDOX REACTIONS INVOLVING N-ALKYL-DIHYDRONICOTINAMIDES." SOUTHERN BRAZILIAN JOURNAL OF CHEMISTRY 2, no. 2 (December 20, 1994): 121–35. http://dx.doi.org/10.48141/sbjchem.v2.n2.1994.122_1994.pdf.
Abstract:
Electron transfer reactions involving a series of N-alkyl-dihydronicotinamides (R-NAH) as donors were studied in homogenous solvents and in micellar media. In particular, the redox chemistry and kinetics of the reduction of methylene blue and cytochrome-C, by varying the alkyl chain length (R = C4, C8, C12) were investigated The schemes proposed for functionalized surfactants of nicotinamide suggest photochemical conversion based on light-induced electron-transfer reactions.
35
Leonard, Jeffrey, Nichole Reyes, Kyle M. Allen, Kelvin Randhir, Like Li, Nick AuYeung, Jeremy Grunewald, Nathan Rhodes, Michael Bobek, and James F. Klausner. "Effects of Dopant Metal Variation and Material Synthesis Method on the Material Properties of Mixed Metal Ferrites in Yttria Stabilized Zirconia for Solar Thermochemical Fuel Production." International Journal of Photoenergy 2015 (2015): 1–10. http://dx.doi.org/10.1155/2015/856385.
Abstract:
Mixed metal ferrites have shown much promise in two-step solar-thermochemical fuel production. Previous work has typically focused on evaluating a particular metal ferrite produced by a particular synthesis process, which makes comparisons between studies performed by independent researchers difficult. A comparative study was undertaken to explore the effects different synthesis methods have on the performance of a particular material during redox cycling using thermogravimetry. This study revealed that materials made via wet chemistry methods and extended periods of high temperature calcination yield better redox performance. Differences in redox performance between materials made via wet chemistry methods were minimal and these demonstrated much better performance than those synthesized via the solid state method. Subsequently, various metal ferrite samples (NiFe2O4, MgFe2O4, CoFe2O4, and MnFe2O4) in yttria stabilized zirconia (8YSZ) were synthesized via coprecipitation and tested to determine the most promising metal ferrite combination. It was determined that 10 wt.% CoFe2O4in 8YSZ produced the highest and most consistent yields of O2and CO. By testing the effects of synthesis methods and dopants in a consistent fashion, those aspects of ferrite preparation which are most significant can be revealed. More importantly, these insights can guide future efforts in developing the next generation of thermochemical fuel production materials.
36
Morgado, Leonor, Joana M. Dantas, Marta Bruix, Yuri Y. Londer, and Carlos A. Salgueiro. "Fine Tuning of Redox Networks on Multiheme Cytochromes fromGeobacter sulfurreducensDrives Physiological Electron/Proton Energy Transduction." Bioinorganic Chemistry and Applications 2012 (2012): 1–9. http://dx.doi.org/10.1155/2012/298739.
Abstract:
The bacteriumGeobacter sulfurreducens (Gs)can grow in the presence of extracellular terminal acceptors, a property that is currently explored to harvest electricity from aquatic sediments and waste organic matter into microbial fuel cells. A family composed of five triheme cytochromes (PpcA-E) was identified inGs. These cytochromes play a crucial role by bridging the electron transfer from oxidation of cytoplasmic donors to the cell exterior and assisting the reduction of extracellular terminal acceptors. The detailed thermodynamic characterization of such proteins showed that PpcA and PpcD have an important redox-Bohr effect that might implicate these proteins in the e−/H+coupling mechanisms to sustain cellular growth. The physiological relevance of the redox-Bohr effect in these proteins was studied by determining the fractional contribution of each individual redox-microstate at different pH values. For both proteins, oxidation progresses from a particular protonated microstate to a particular deprotonated one, over specific pH ranges. The preferred e−/H+transfer pathway established by the selected microstates indicates that both proteins are functionally designed to couple e−/H+transfer at the physiological pH range for cellular growth.
37
Kuczyńska, Monika, Patrycja Jakubek, and Agnieszka Bartoszek. "More than Just Antioxidants: Redox-Active Components and Mechanisms Shaping Redox Signalling Network." Antioxidants 11, no. 12 (December 4, 2022): 2403. http://dx.doi.org/10.3390/antiox11122403.
Abstract:
The concept of oxidative stress as a condition underlying a multitude of human diseases has led to immense interest in the search for antioxidant-based remedies. The simple and intuitive story of “the bad” reactive oxygen species (ROS) and “the good” antioxidants quickly (and unsurprisingly) lead to the commercial success of products tagged “beneficial to health” based solely on the presence of antioxidants. The commercial success of antioxidants by far preceded the research aimed at understanding the exact redox-related mechanisms that are in control of shaping the states of health and disease. This review describes the redox network formed by the interplay of ROS with cellular molecules and the resulting regulation of processes at the genomic and proteomic levels. Key players of this network are presented, both involved in redox signalling and control of cellular metabolism linked to most, if not all, physiological processes. In particular, this review focuses on the concept of reductive stress, which still remains less well-established compared to oxidative stress.
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Fukuzumi, Shunichi, Yong-Min Lee, and Wonwoo Nam. "Photocatalytic redox reactions with metalloporphyrins." Journal of Porphyrins and Phthalocyanines 24, no. 01n03 (January 2020): 21–32. http://dx.doi.org/10.1142/s1088424619300131.
Abstract:
Metalloporphyrinoids are utilized as efficient sensitizers and catalysts in photosynthesis and the reverse reaction that is respiration. Because metalloporphyrinoids show strong absorption in the visible region and redox active, metalloporphyrinoids are also suited as photoredox catalysts for photo-driven redox reactions using solar energy. In particular, metalloporphyrins are utilized as pivotal components to mimic the structure and function of the photosynthetic reaction center. Metalloporphyrins are used as photoredox catalysts for hydrogen evolution from electron and proton sources combining hydrogen evolution catalysts. Metalloporphyrins also act as thermal redox catalysts for photocatalytic reduction of CO2 with photoredox catalysts. Metalloporphyrins are also used as dual catalysts for a photoredox catalyst for oxygenation of substrates with H2O and a redox catalyst for O2 reduction when dioxygen is used as a two-electron oxidant and H2O as an oxygen source, both of which are the greenest reactants. Free base porphyrins can also be employed as promising photoredox catalysts for C–C bond formation reactions.
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Kosmambetova, G. R. "Active centers of redox catalysts." Catalysis and Petrochemistry, no. 32 (2021): 9–31. http://dx.doi.org/10.15407/kataliz2021.32.009.
Abstract:
The development of representations about the active site structure of solid-phase catalysts, ranging from the work of H. Taylor to a modern understanding of the complex and multi-level structure of catalytic systems, is considered. The main types of active centers of catalysts for redox processes of deep, selective, and preferential conversion are analyzed. It is shown that for each type of reaction, regardless of the chemical nature of the catalyst components, the structure of the active center is characterized by certain common features and determines the direction of conversion. Particular attention is paid to the structure of active sites formed by the type of an isolated active center ("Single Site Isolation"), which allows achieving high selectivity of catalytic processes in the direction of target products obtaining and implementation of new reactions. In particular, the reaction of methane oxidative carbonylation to acetic acid was first carried out in a gas phase using molecular oxygen as an oxidant and catalysts whose active centers were presented by isolated Rh3+ ions in the composition of rhodium selenochloride. A separate type of active center is presented by atoms located on the grain boundaries of crystallites, which arise as a result of interfacing interaction between catalyst components: support, active component, modificator, as well as grain boundaries between homogeneous nanocrystallites in agglomerated systems. It is shown that an important role in the manifestation of catalytic properties plays the availability of an active center for reagents, caused by the spatial structure of catalysts. Zeolites, organometallic compounds (MOF), mesostructural oxides in which active centers are located inside the cavity channels are examples of such catalytic systems. The main strategy of research in the field of advanced catalysts is aimed at developing methods for the synthesis of catalytic materials, which provide formation as the maximum number of active centers, so their availability for reagents and subsequent conversion to target products. Designing such systems is a complex task, based on establishing a correlation between composition, structure, and size characteristics of catalytic materials.
40
Schweiss, Ruediger, Christian Meiser, and Fu Wei Thomas Goh. "Steady-State Measurements of Vanadium Redox-Flow Batteries to Study Particular Influences of Carbon Felt Properties." ChemElectroChem 4, no. 8 (May 9, 2017): 1969–74. http://dx.doi.org/10.1002/celc.201700280.
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Freeman, Christopher J., Borkat Ullah, Md Shafiul Islam, and Maryanne M. Collinson. "Potentiometric Biosensing of Ascorbic Acid, Uric Acid, and Cysteine in Microliter Volumes Using Miniaturized Nanoporous Gold Electrodes." Biosensors 11, no. 1 (December 28, 2020): 10. http://dx.doi.org/10.3390/bios11010010.
Abstract:
Potentiometric redox sensing is a relatively inexpensive and passive approach to evaluate the overall redox state of complex biological and environmental solutions. The ability to make such measurements in ultra-small volumes using high surface area, nanoporous electrodes is of particular importance as such electrodes can improve the rates of electron transfer and reduce the effects of biofouling on the electrochemical signal. This work focuses on the fabrication of miniaturized nanoporous gold (NPG) electrodes with a high surface area and a small footprint for the potentiometric redox sensing of three biologically relevant redox molecules (ascorbic acid, uric acid, and cysteine) in microliter volumes. The NPG electrodes were inexpensively made by attaching a nanoporous gold leaf prepared by dealloying 12K gold in nitric acid to a modified glass capillary (1.5 mm id) and establishing an electrode connection with copper tape. The surface area of the electrodes was ~1.5 cm2, providing a roughness factor of ~16 relative to the geometric area of 0.09 cm2. Scanning electron microscopy confirmed the nanoporous framework. A linear dependence between the open-circuit potential (OCP) and the logarithm of concentration (e.g., Nernstian-like behavior) was obtained for all three redox molecules in 100 μL buffered solutions. As a first step towards understanding a real system, the response associated with changing the concentration of one redox species in the presence of the other two was examined. These results show that at NPG, the redox potential of a solution containing biologically relevant concentrations of ascorbic acid, uric acid, and cysteine is strongly influenced by ascorbic acid. Such information is important for the measurement of redox potentials in complex biological solutions.
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Kappler, Andreas, Aaron Thompson, and Muammar Mansor. "Impact of Biogenic Magnetite Formation and Transformation on Biogeochemical Cycles." Elements 19, no. 4 (August 1, 2023): 222–27. http://dx.doi.org/10.2138/gselements.19.4.222.
Abstract:
Magnetite is a redox-active mineral that can form from both abiotic and biotic processes, and plays an active role in different biogeochemical cycles. Biogenic magnetite particles have properties that differ from their abiogenic counterparts in a variety of ways, including their size, chemical purity, magnetic properties, and association with biomass-derived organic matter. These properties directly influence magnetite reactivity—in particular its sorbent and redox behavior—affecting its association with metals, oxyanions, and other compounds in the environment. Biogenic (and abiogenic) magnetite particles are involved in redox processes by storing electrons, functioning as biogeobatteries, and by transferring electrons between microbial cells or between cells and inorganic constituents. Thus, magnetite influences the fate of contaminants and nutrients in the environment.
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Mantle, David, Mollie Dewsbury, and Iain P. Hargreaves. "The Ubiquinone-Ubiquinol Redox Cycle and Its Clinical Consequences: An Overview." International Journal of Molecular Sciences 25, no. 12 (June 20, 2024): 6765. http://dx.doi.org/10.3390/ijms25126765.
Abstract:
Coenzyme Q10 (CoQ10) plays a key role in many aspects of cellular metabolism. For CoQ10 to function normally, continual interconversion between its oxidised (ubiquinone) and reduced (ubiquinol) forms is required. Given the central importance of this ubiquinone–ubiquinol redox cycle, this article reviews what is currently known about this process and the implications for clinical practice. In mitochondria, ubiquinone is reduced to ubiquinol by Complex I or II, Complex III (the Q cycle) re-oxidises ubiquinol to ubiquinone, and extra-mitochondrial oxidoreductase enzymes participate in the ubiquinone–ubiquinol redox cycle. In clinical terms, the outcome of deficiencies in various components associated with the ubiquinone–ubiquinol redox cycle is reviewed, with a particular focus on the potential clinical benefits of CoQ10 and selenium co-supplementation.
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Rutkowska, Iwona A., Claudia Janiszewska, Keti Vezzu, Enrico Negro, Vito Di Noto, and Pawel J. Kulesza. "(Invited) Microelectrode-Based Diagnosis of Charge Propagation and Redox Transitions in Concentrated Polyoxometallate Electrolyte of Potential Utility for Redox Flow Battery." ECS Meeting Abstracts MA2023-01, no. 49 (August 28, 2023): 2564. http://dx.doi.org/10.1149/ma2023-01492564mtgabs.
Abstract:
Concentrated solutions of Keggin-type silicotungstic acid, as well as the system’s single crystals (H4SiW12O40*31H2O) and their colloidal suspensions have been tested using the microelectrode methodology to determine mass-transport, electron self-exchange and apparent (effective) diffusion-type coefficients for charge propagation and homogeneous (electron self-exchange) rates of electron transfers. Silicotungstic acid facilitates proton conductivity, and undergoes fast, reversible, multi-electron electron transfers leading to the formation of highly conducting, mixed-valence (tungsten(VI,V) heteropoly blue) compounds. To develop useful electroanalytical diagnostic criteria, electroanalytical approaches utilizing microdisk electrodes have been adapted to characterize redox transitions of the system and to determine kinetic parameters. Combination of micoroelectrode-based experiments performed in two distinct diffusional regimes: radial (long-term experiment; e.g., slow scan rate voltammetry or long-pulse chronoamperometry) and linear (short-term experiment; e.g., fast scan rate voltammetry or short-pulse chronocoulometry) permits absolute determination of such parameters as effective concentration of redox centers (C0 ) and apparent transport (diffusion) coefficient (Dapp ). The knowledge of these parameters, in particular of [Dapp 1/2 C0 ] seems to be of importance to the evaluation of utility of redox electrolytes for charge storage. While current densities which reflect dynamics of electrochemical processes have an influence on the systems’ current densities, the viscosity of the electrolyte and the mass transport dynamics are also affected by the nature of the redox-active material and its concentration. Trying to develop useful electroanalytical diagnostic approaches, we have successfully utilized microelectrode-based probes, as well as the historical concepts of charge propagation in semi-solid or semi-liquid systems developed for mixed-valence polynuclear materials in order to characterize concentrated redox electrolytes. Among important parameters are concentration of redox centers (C0 ) and apparent transport (diffusion) coefficient (Dapp ). The knowledge of these parameters and, in particular of [Dapp 1/2 C0 ], are crucial when it comes to evaluation of the diffusional-type charge propagation dynamics in the concentrated electrolyte which may reflect both physical mass transport and electron self-exchange (electron-hopping) contributions. Both potential-step (chronocoulometry, chronoamperometry) and cyclic voltammetric experiments utilizing microdisk electrodes have been adapted to characterization (identification of redox transitions and determination of kinetic parameters) of model inorganic redox electrolytes, namely highly-concentrated solutions or colloidal suspensions of Keggin-type polyoxometallate, silicotungstic acid.
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Markelova, Ekaterina, Christopher T. Parsons, Raoul-Marie Couture, Christina M. Smeaton, Benoit Madé, Laurent Charlet, and Philippe Van Cappellen. "Deconstructing the redox cascade: what role do microbial exudates (flavins) play?" Environmental Chemistry 14, no. 8 (2017): 515. http://dx.doi.org/10.1071/en17158.
Abstract:
Environmental contextRedox potential is a controlling variable in aquatic chemistry. Through time series data, we show that microbial exudates released by bacteria may control trends in redox potential observed in natural waters. In particular, electron transfer between these exudates and the electrode could explain the values measured in the presence of abundant oxidants such as oxygen and nitrate. AbstractRedox electrodes are commonly used to measure redox potentials (EH) of natural waters. The recorded EH values are usually interpreted in terms of the dominant inorganic redox couples. To further advance the interpretation of measured EH distributions along temporal and spatial redox gradients, we performed a series of reactor experiments in which oxidising and reducing conditions were alternated by switching between sparging with air and N2. Starting from a simple electrolyte solution and ending with a complex biogeochemical system, common groundwater solutes, metabolic substrates (NO3− and C3H5O3−), bacteria (Shewanella oneidensis MR-1) and goethite (α-FeOOH(s)) were tested by increasing the system complexity with each subsequent experiment. This systematic approach yielded a redox cascade ranging from +500 to −350 mV (pH ~7.4). The highest and lowest EH values registered by the platinum (Pt) electrode agreed with Nernstian redox potentials predicted for the O2/H2O2 and FeOOH/Fe2+(aq) couples respectively. Electrode poisoning by the organic pH buffer (MOPS) and addition of bacteria to the aerated solutions resulted in marked decreases in measured EH values. The latter effect is attributed to the release of flavins by Shewanella oneidensis MR-1 to the medium. As expected, equilibrium with the non-electroactive NO3−/NO2−/NH4+ redox couples could not account for the EH values recorded during dissimilatory nitrate reduction to ammonium (DNRA). However, the observed EH range for DNRA coincided with that bracketed by EH values measured in separate abiotic solutions containing either the oxidised (+324 ± 29 mV) or reduced (−229 ± 40 mV) forms of flavins. The results therefore suggest that the Pt electrode detected the presence of the electroactive flavins, even at submicromolar concentrations. In particular, flavins help explain the fairly low EH values measured in the presence of strong oxidants, such as O2 and NO3−.
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Stepovaya, E. A., E. V. Shakhristova, O. L. Nosareva, E. V. Rudikov, M. Y. Egorova, D. Y. Egorova, and V. V. Novitsky. "Redox-dependent mechanisms of regulation of breast epithelial cell proliferation." Biomeditsinskaya Khimiya 63, no. 2 (2017): 159–64. http://dx.doi.org/10.18097/pbmc20176302159.
Abstract:
Activation of free radical oxidation in different cell types, including breast epithelial cells, may result in damage to macromolecules, in particular, proteins taking part in regulation of cell proliferation and apoptosis. The glutathione, glutaredoxin and thioredoxin systems play an essential role in maintaining intracellular redox homeostasis. Due to this fact, modulation of cellular redox status under the effect of an SH group inhibitor and an SH group protector may be used as a model for studying the role of redox proteins and glutathione in regulating cell proliferation in different pathological processes. In this study we have evaluated the state of the thioredoxin, glutaredoxin and glutathione systems as well as their role in regulating proliferation of HBL-100 breast epithelial cells under redox status modulation with N-ethylmaleimide (NEM) and 1,4-dithioerythriol (DTE). Modulating the redox status of breast epithelial cells under the effect of NEM and DTE influences the functional activity of glutathione-dependent enzymes, glutaredoxin, thioredoxin, and thioredoxin reductase through changes in the GSH and GSSG concentrations. In HBL-100 cells under redox-status modulation, we have found an increase in the number of cells in the S-phase of the cell cycle and a decrease in the number of cells in the G0/G1 and G2/М phases, as opposed to the values in the intact culture. The proposed model of proliferative activity of cells under redox status modulation may be used for development of new therapeutic approaches for treatment of diseases accompanied by oxidative stress generation.
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Yoshida, Keisuke, and Toru Hisabori. "Determining the Rate-Limiting Step for Light-Responsive Redox Regulation in Chloroplasts." Antioxidants 7, no. 11 (October 31, 2018): 153. http://dx.doi.org/10.3390/antiox7110153.
Abstract:
Thiol-based redox regulation ensures light-responsive control of chloroplast functions. Light-derived signal is transferred in the form of reducing power from the photosynthetic electron transport chain to several redox-sensitive target proteins. Two types of protein, ferredoxin-thioredoxin reductase (FTR) and thioredoxin (Trx), are well recognized as the mediators of reducing power. However, it remains unclear which step in a series of redox-relay reactions is the critical bottleneck for determining the rate of target protein reduction. To address this, the redox behaviors of FTR, Trx, and target proteins were extensively characterized in vitro and in vivo. The FTR/Trx redox cascade was reconstituted in vitro using recombinant proteins from Arabidopsis. On the basis of this assay, we found that the FTR catalytic subunit and f-type Trx are rapidly reduced after the drive of reducing power transfer, irrespective of the presence or absence of their downstream target proteins. By contrast, three target proteins, fructose 1,6-bisphosphatase (FBPase), sedoheptulose 1,7-bisphosphatase (SBPase), and Rubisco activase (RCA) showed different reduction patterns; in particular, SBPase was reduced at a low rate. The in vivo study using Arabidopsis plants showed that the Trx family is commonly and rapidly reduced upon high light irradiation, whereas FBPase, SBPase, and RCA are differentially and slowly reduced. Both of these biochemical and physiological findings suggest that reducing power transfer from Trx to its target proteins is a rate-limiting step for chloroplast redox regulation, conferring distinct light-responsive redox behaviors on each of the targets.
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Briehl, Margaret M., Margaret E. Tome, Sarah T. Wilkinson, Melba C. Jaramillo, and Kristy Lee. "Mitochondria and redox homoeostasis as chemotherapeutic targets." Biochemical Society Transactions 42, no. 4 (August 1, 2014): 939–44. http://dx.doi.org/10.1042/bst20140087.
Abstract:
Characteristics of cancer cells include a more oxidized redox environment, metabolic reprogramming and apoptosis resistance. Our studies with a lymphoma model have explored connections between the cellular redox environment and cancer cell phenotypes. Alterations seen in lymphoma cells made resistant to oxidative stress include: a more oxidized redox environment despite increased expression of antioxidant enzymes, enhanced net tumour growth, metabolic changes involving the mitochondria and resistance to the mitochondrial pathway to apoptosis. Of particular importance, the cells show cross-resistance to multiple chemotherapeutic agents used to treat aggressive lymphomas. Analyses of clinical and tumour data reveal the worst prognosis when patients’ lymphomas have gene expression patterns consistent with the most oxidized redox environment. Lymphomas from patients with the worst survival outcomes express increased levels of proteins involved in oxidative phosphorylation, including cytochrome c. This is consistent with these cells functioning as metabolic opportunists. Using lymphoma cell models and primary lymphoma cultures, we observed enhanced killing using genetic and drug approaches which further oxidize the cellular redox environment. These approaches include increased expression of SOD2 (superoxide dismutase 2), treatment with a manganoporphyrin that oxidizes the glutathione redox couple, or treatment with a copper chelator that inhibits SOD1 and leads to peroxynitrite-dependent cell death. The latter approach effectively kills lymphoma cells that overexpress the anti-apoptotic protein Bcl-2. Given the central role of mitochondria in redox homoeostasis, metabolism and the intrinsic pathway to apoptosis, our studies support the development of new anti-cancer drugs to target this organelle.
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Downs, Charles A., and My N. Helms. "Regulation of ion transport by oxidants." American Journal of Physiology-Lung Cellular and Molecular Physiology 305, no. 9 (November 1, 2013): L595—L603. http://dx.doi.org/10.1152/ajplung.00212.2013.
Abstract:
Ion channels perform a variety of cellular functions in lung epithelia. Oxidant- and antioxidant-mediated mechanisms (that is, redox regulation) of ion channels are areas of intense research. Significant progress has been made in our understanding of redox regulation of ion channels since the last Experimental Biology report in 2003. Advancements include: 1) identification of nonphagocytic NADPH oxidases as sources of regulated reactive species (RS) production in epithelia, 2) an understanding that excessive treatment with antioxidants can result in greater oxidative stress, and 3) characterization of novel RS signaling pathways that converge upon ion channel regulation. These advancements, as discussed at the 2013 Experimental Biology Meeting in Boston, MA, impact our understanding of oxidative stress in the lung, and, in particular, illustrate that the redox state has profound effects on ion channel and cellular function.
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Park, Jinah, Sunmi Lee, Sanghyuk Lee, and Sang Won Kang. "2-Cys Peroxiredoxins: Emerging Hubs Determining Redox Dependency of Mammalian Signaling Networks." International Journal of Cell Biology 2014 (2014): 1–10. http://dx.doi.org/10.1155/2014/715867.
Abstract:
Mammalian cells have a well-defined set of antioxidant enzymes, which includes superoxide dismutases, catalase, glutathione peroxidases, and peroxiredoxins. Peroxiredoxins are the most recently identified family of antioxidant enzymes that catalyze the reduction reaction of peroxides, such as H2O2. In particular, typical 2-Cys peroxiredoxins are the featured peroxidase enzymes that receive the electrons from NADPH by coupling with thioredoxin and thioredoxin reductase. These enzymes distribute throughout the cellular compartments and, therefore, are thought to be broad-range antioxidant defenders. However, recent evidence demonstrates that typical 2-Cys peroxiredoxins play key signal regulatory roles in the various signaling networks by interacting with or residing near a specific redox-sensitive molecule. These discoveries help reveal the redox signaling landscape in mammalian cells and may further provide a new paradigm of therapeutic approaches based on redox signaling.