[The low-molecular weight antioxidants of microorganisms].

PubMed

Skorokhod, I O; Kurdysh, I K

2014-01-01

Support of optimum redox-homeostasis in the cells of microorganisms plays a substantial role in the processes of DNA synthesis, respiration, providing of immune and protective reactions, activity of enzymes, etc. The changes of the redox-status can be accompanied by the increase of the level of reactive oxygen species (ROS) which predetermine the damage of biologically active molecules. Adjusting of ROS concentrations is a very important process in development of microorganisms. Low-molecular antioxidants are effective inhibitors of free-radical processes. The authors of the review present the description of oxidants and consider the ways of origin and consequences of their influence on the living cells. An accent is done on phenomenological description of low-molecular antioxidants. The basic mechanisms of their action are considered. Special attention is given to the question of synergism between these protectors. The detailed study of mechanisms of functioning of low-molecular antioxidants in the cells of microorganisms will allow using these living objects in different spheres of human activity.

Species-Specific Standard Redox Potential of Thiol-Disulfide Systems: A Key Parameter to Develop Agents against Oxidative Stress

NASA Astrophysics Data System (ADS)

Mirzahosseini, Arash; Noszál, Béla

2016-11-01

Microscopic standard redox potential, a new physico-chemical parameter was introduced and determined to quantify thiol-disulfide equilibria of biological significance. The highly composite, codependent acid-base and redox equilibria of thiols could so far be converted into pH-dependent, apparent redox potentials (E’°) only. Since the formation of stable metal-thiolate complexes precludes the direct thiol-disulfide redox potential measurements by usual electrochemical techniques, an indirect method had to be elaborated. In this work, the species-specific, pH-independent standard redox potentials of glutathione were determined primarily by comparing it to 1-methylnicotinamide, the simplest NAD+ analogue. Secondarily, the species-specific standard redox potentials of the two-electron redox transitions of cysteamine, cysteine, homocysteine, penicillamine, and ovothiol were determined using their microscopic redox equilibrium constants with glutathione. The 30 different, microscopic standard redox potential values show close correlation with the respective thiolate basicities and provide sound means for the development of potent agents against oxidative stress.

Redox signaling in skeletal muscle: role of aging and exercise.

PubMed

Ji, Li Li

2015-12-01

Skeletal muscle contraction is associated with the production of ROS due to altered O2 distribution and flux in the cell. Despite a highly efficient antioxidant defense, a small surplus of ROS, such as hydrogen peroxide and nitric oxide, may serve as signaling molecules to stimulate cellular adaptation to reach new homeostasis largely due to the activation of redox-sensitive signaling pathways. Recent research has highlighted the important role of NF-κB, MAPK, and peroxisome proliferator-activated receptor-γ coactivator-1α, along with other newly discovered signaling pathways, in some of the most vital biological functions, such as mitochondrial biogenesis, antioxidant defense, inflammation, protein turnover, apoptosis, and autophagy. There is evidence that the inability of the cell to maintain proper redox signaling underlies some basic mechanisms of biological aging, during which inflammatory and catabolic pathways eventually predominate. Physical exercise has been shown to activate various redox signaling pathways that control the adaptation and remodeling process. Although this stimulatory effect of exercise declines with aging, it is not completed abolished. Thus, aged people can still benefit from regular physical activity in the appropriate forms and at proper intensity to preserve muscle function. Copyright © 2015 The American Physiological Society.

Applying the Nernst equation to simulate redox potential variations for biological nitrification and denitrification processes.

PubMed

Chang, Cheng-Nan; Cheng, Hong-Bang; Chao, Allen C

2004-03-15

In this paper, various forms of Nernst equations have been developed based on the real stoichiometric relationship of biological nitrification and denitrification reactions. Instead of using the Nernst equation based on a one-to-one stoichiometric relation for the oxidizing and the reducing species, the basic Nernst equation is modified into slightly different forms. Each is suitable for simulating the redox potential (ORP) variation of a specific biological nitrification or denitrification process. Using the data published in the literature, the validity of these developed Nernst equations has been verified by close fits of the measured ORP data with the calculated ORP curve. The simulation results also indicate that if the biological process is simulated using an incorrect form of Nernst equation, the calculated ORP curve will not fit the measured data. Using these Nernst equations, the ORP value that corresponds to a predetermined degree of completion for the biochemical reaction can be calculated. Thus, these Nernst equations will enable a more efficient on-line control of the biological process.

Species-Specific Thiol-Disulfide Equilibrium Constant: A Tool To Characterize Redox Transitions of Biological Importance.

PubMed

Mirzahosseini, Arash; Somlyay, Máté; Noszál, Béla

2015-08-13

Microscopic redox equilibrium constants, a new species-specific type of physicochemical parameters, were introduced and determined to quantify thiol-disulfide equilibria of biological significance. The thiol-disulfide redox equilibria of glutathione with cysteamine, cysteine, and homocysteine were approached from both sides, and the equilibrium mixtures were analyzed by quantitative NMR methods to characterize the highly composite, co-dependent acid-base and redox equilibria. The directly obtained, pH-dependent, conditional constants were then decomposed by a new evaluation method, resulting in pH-independent, microscopic redox equilibrium constants for the first time. The 80 different, microscopic redox equilibrium constant values show close correlation with the respective thiolate basicities and provide sound means for the development of potent agents against oxidative stress.

Combination of Lewis Basic Selenium Catalysis and Redox Selenium Chemistry: Synthesis of Trifluoromethylthiolated Tertiary Alcohols with Alkenes.

PubMed

Zhu, Zechen; Luo, Jie; Zhao, Xiaodan

2017-09-15

A new and efficient method for diaryl selenide catalyzed vicinal CF 3 S hydroxylation of 1,1-multisubstitued alkenes has been developed. Various trifluoromethylthiolated tertiary alcohols could be readily synthesized under mild conditions. This method is also effective for the intramolecular cyclization of alkenes tethered by carboxylic acid, hydroxy, sulfamide, or ester groups and is associated with the introduction of a CF 3 S group. Mechanistic studies have revealed that the pathway involves a redox cycle between Se(II) and Se(IV) and Lewis basic selenium catalysis.

Peripheral artery disease, redox signaling, oxidative stress - Basic and clinical aspects.

PubMed

Steven, Sebastian; Daiber, Andreas; Dopheide, Jörn F; Münzel, Thomas; Espinola-Klein, Christine

2017-08-01

Reactive oxygen and nitrogen species (ROS and RNS, e.g. H 2 O 2 , nitric oxide) confer redox regulation of essential cellular signaling pathways such as cell differentiation, proliferation, migration and apoptosis. At higher concentrations, ROS and RNS lead to oxidative stress and oxidative damage of biomolecules (e.g. via formation of peroxynitrite, fenton chemistry). Peripheral artery disease (PAD) is characterized by severe ischemic conditions in the periphery leading to intermittent claudication and critical limb ischemia (end stage). It is well known that redox biology and oxidative stress play an important role in this setting. We here discuss the major pathways of oxidative stress and redox signaling underlying the disease progression with special emphasis on the contribution of inflammatory processes. We also highlight therapeutic strategies comprising pharmacological (e.g. statins, angiotensin-converting enzyme inhibitors, phosphodiesterase inhibition) and non-pharmacological (e.g. exercise) interventions. Both of these strategies induce potent indirect antioxidant and anti-inflammatory mechanisms that may contribute to an improvement of PAD associated complications and disease progression by removing excess formation of ROS and RNS (e.g. by ameliorating primary complications such as hyperlipidemia and hypertension) as well as the normalization of the inflammatory phenotype suppressing the progression of atherosclerosis. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Biogeochemical redox processes and their impact on contaminant dynamics

USGS Publications Warehouse

Borch, Thomas; Kretzschmar, Ruben; Kappler, Andreas; Van Cappellen, Philippe; Ginder-Vogel, Matthew; Campbell, Kate M.

2010-01-01

Life and element cycling on Earth is directly related to electron transfer (or redox) reactions. An understanding of biogeochemical redox processes is crucial for predicting and protecting environmental health and can provide new opportunities for engineered remediation strategies. Energy can be released and stored by means of redox reactions via the oxidation of labile organic carbon or inorganic compounds (electron donors) by microorganisms coupled to the reduction of electron acceptors including humic substances, iron-bearing minerals, transition metals, metalloids, and actinides. Environmental redox processes play key roles in the formation and dissolution of mineral phases. Redox cycling of naturally occurring trace elements and their host minerals often controls the release or sequestration of inorganic contaminants. Redox processes control the chemical speciation, bioavailability, toxicity, and mobility of many major and trace elements including Fe, Mn, C, P, N, S, Cr, Cu, Co, As, Sb, Se, Hg, Tc, and U. Redox-active humic substances and mineral surfaces can catalyze the redox transformation and degradation of organic contaminants. In this review article, we highlight recent advances in our understanding of biogeochemical redox processes and their impact on contaminant fate and transport, including future research needs.

Redox Regulation of Protein Kinases

PubMed Central

Truong, Thu H.; Carroll, Kate S.

2015-01-01

Protein kinases represent one of the largest families of genes found in eukaryotes. Kinases mediate distinct cellular processes ranging from proliferation, differentiation, survival, and apoptosis. Ligand-mediated activation of receptor kinases can lead to the production of endogenous H2O2 by membrane-bound NADPH oxidases. In turn, H2O2 can be utilized as a secondary messenger in signal transduction pathways. This review presents an overview of the molecular mechanisms involved in redox regulation of protein kinases and its effects on signaling cascades. In the first half, we will focus primarily on receptor tyrosine kinases (RTKs), whereas the latter will concentrate on downstream non-receptor kinases involved in relaying stimulant response. Select examples from the literature are used to highlight the functional role of H2O2 regarding kinase activity, as well as the components involved in H2O2 production and regulation during cellular signaling. In addition, studies demonstrating direct modulation of protein kinases by H2O2 through cysteine oxidation will be emphasized. Identification of these redox-sensitive residues may help uncover signaling mechanisms conserved within kinase subfamilies. In some cases, these residues can even be exploited as targets for the development of new therapeutics. Continued efforts in this field will further basic understanding of kinase redox regulation, and delineate the mechanisms involved in physiologic and pathological H2O2 responses. PMID:23639002

Lipid Raft Redox Signaling: Molecular Mechanisms in Health and Disease

PubMed Central

Zhou, Fan; Katirai, Foad

2011-01-01

Abstract Lipid rafts, the sphingolipid and cholesterol-enriched membrane microdomains, are able to form different membrane macrodomains or platforms upon stimulations, including redox signaling platforms, which serve as a critical signaling mechanism to mediate or regulate cellular activities or functions. In particular, this raft platform formation provides an important driving force for the assembling of NADPH oxidase subunits and the recruitment of other related receptors, effectors, and regulatory components, resulting, in turn, in the activation of NADPH oxidase and downstream redox regulation of cell functions. This comprehensive review attempts to summarize all basic and advanced information about the formation, regulation, and functions of lipid raft redox signaling platforms as well as their physiological and pathophysiological relevance. Several molecular mechanisms involving the formation of lipid raft redox signaling platforms and the related therapeutic strategies targeting them are discussed. It is hoped that all information and thoughts included in this review could provide more comprehensive insights into the understanding of lipid raft redox signaling, in particular, of their molecular mechanisms, spatial-temporal regulations, and physiological, pathophysiological relevances to human health and diseases. Antioxid. Redox Signal. 15, 1043–1083. PMID:21294649

Extremes in Oxidizing Power, Acidity, and Basicity

DTIC Science & Technology

2013-10-01

and extremely difficult to oxidize, with reversible redox potentials calculated up to 5 V above ferrocene /ferricenium. In liquid sulfur dioxide, the...ol, the undecafluorinated anion is oxidized reversibly at 2.43 V above ferrocene /ferricenium (calculated 2.40 V) but the radical is too unstable for...unusually weakly nucleophilic and extremely difficult to oxidize, with reversible redox potentials calculated up to 5 V above ferrocene /ferricenium. In

Redox Regulation of Cell Survival

PubMed Central

Trachootham, Dunyaporn; Lu, Weiqin; Ogasawara, Marcia A.; Valle, Nilsa Rivera-Del

2008-01-01

Abstract Reactive oxygen species (ROS) and reactive nitrogen species (RNS) play important roles in regulation of cell survival. In general, moderate levels of ROS/RNS may function as signals to promote cell proliferation and survival, whereas severe increase of ROS/RNS can induce cell death. Under physiologic conditions, the balance between generation and elimination of ROS/RNS maintains the proper function of redox-sensitive signaling proteins. Normally, the redox homeostasis ensures that the cells respond properly to endogenous and exogenous stimuli. However, when the redox homeostasis is disturbed, oxidative stress may lead to aberrant cell death and contribute to disease development. This review focuses on the roles of key transcription factors, signal-transduction pathways, and cell-death regulators in affecting cell survival, and how the redox systems regulate the functions of these molecules. The current understanding of how disturbance in redox homeostasis may affect cell death and contribute to the development of diseases such as cancer and degenerative disorders is reviewed. We also discuss how the basic knowledge on redox regulation of cell survival can be used to develop strategies for the treatment or prevention of those diseases. Antioxid. Redox Signal. 10, 1343–1374. PMID:18522489

Co3O4-based honeycombs as compact redox reactors/heat exchangers for thermochemical storage in the next generation CSP plants

NASA Astrophysics Data System (ADS)

Pagkoura, Chrysoula; Karagiannakis, George; Halevas, Eleftherios; Konstandopoulos, Athanasios G.

2016-05-01

Over the last years, several research groups have focused on developing efficient thermochemical heat storage (THS) systems, in-principle capable of being coupled with next generation high temperature Concentrated Solar Power plants. Among systems studied, the Co3O4/CoO redox system is a promising candidate. Currently, research efforts extend beyond basic level identification of promising materials to more application-oriented approaches aiming at validation of THS performance at pilot scale reactors. The present work focuses on the investigation of cobalt oxide based honeycomb structures as candidate reactors/heat exchangers to be employed for such purposes. In the evaluation conducted and presented here, cobalt oxide-based structures with different composition and geometrical characteristics were subjected to redox cycles in the temperature window between 800 and 1000°C under air flow. Basic aspects related to redox performance of each system are briefly discussed but the main focus lies on the evaluation of the segments structural stability after multi-cyclic operation. The latter is based on macroscopic visual observation and also supplemented by pre- (i.e. fresh samples) and post-characterization (i.e. after long term exposure) of extruded honeycombs via combined mercury porosimetry and SEM analysis.

Insights.

ERIC Educational Resources Information Center

Bogner, Donna, Ed.

1990-01-01

Presented is an approach to solving oxidation-reduction reactions. The advantage of this procedure for both acidic and basic equations is stressed and emphasizes the electrical nature of redox equations. (KR)

Strategies for "wiring" redox-active proteins to electrodes and applications in biosensors, biofuel cells, and nanotechnology.

PubMed

Nöll, Tanja; Nöll, Gilbert

2011-07-01

In this tutorial review the basic approaches to establish electrochemical communication between redox-active proteins and electrodes are elucidated and examples for applications in electrochemical biosensors, biofuel cells and nanotechnology are presented. The early stage of protein electrochemistry is described giving a short overview over electron transfer (ET) between electrodes and proteins, followed by a brief introduction into experimental procedures for studying proteins at electrodes and possible applications arising thereof. The article starts with discussing the electrochemistry of cytochrome c, the first redox-active protein, for which direct reversible ET was obtained, under diffusion controlled conditions and after adsorption to electrodes. Next, examples for the electrochemical study of redox enzymes adsorbed on electrodes and modes of immobilization are discussed. Shortly the experimental approach for investigating redox-active proteins adsorbed on electrodes is outlined. Possible applications of redox enzymes in electrochemical biosensors and biofuel cells working by direct ET (DET) and mediated ET (MET) are presented. Furthermore, the reconstitution of redox active proteins at electrodes using molecular wire-like units in order to "wire" the proteins to the electrode surface and possible applications in nanotechnology are discussed.

ROS-mediated redox signaling during cell differentiation in plants.

PubMed

Schmidt, Romy; Schippers, Jos H M

2015-08-01

Reactive oxygen species (ROS) have emerged in recent years as important regulators of cell division and differentiation. The cellular redox state has a major impact on cell fate and multicellular organism development. However, the exact molecular mechanisms through which ROS manifest their regulation over cellular development are only starting to be understood in plants. ROS levels are constantly monitored and any change in the redox pool is rapidly sensed and responded upon. Different types of ROS cause specific oxidative modifications, providing the basic characteristics of a signaling molecule. Here we provide an overview of ROS sensors and signaling cascades that regulate transcriptional responses in plants to guide cellular differentiation and organ development. Although several redox sensors and cascades have been identified, they represent only a first glimpse on the impact that redox signaling has on plant development and growth. We provide an initial evaluation of ROS signaling cascades involved in cell differentiation in plants and identify potential avenues for future studies. This article is part of a Special Issue entitled Redox regulation of differentiation and de-differentiation. Copyright © 2015 Elsevier B.V. All rights reserved.

Redox-signals and macrophage biology (for the upcoming issue of molecular aspects of medicine on signaling by reactive oxygen species).

PubMed

Weigert, Andreas; von Knethen, Andreas; Fuhrmann, Dominik; Dehne, Nathalie; Brüne, Bernhard

2018-01-11

Macrophages are known for their versatile role in biology. They sense and clear structures that contain exogenous or endogenous pathogen-associated molecular patterns. This process is tightly linked to the production of a mixture of potentially harmful oxidants and cytokines. Their inherent destructive behavior is directed against foreign material or structures of 'altered self', which explains the role of macrophages during innate immune reactions and inflammation. However, there is also another side of macrophages when they turn into a tissue regenerative, pro-resolving, and healing phenotype. Phenotype changes of macrophages are termed macrophage polarization, representing a continuum between classical and alternative activation. Macrophages as the dominating producers of superoxide/hydrogen peroxide and nitric oxide are not only prone to oxidative modifications but also to more subtle signaling properties of redox-active molecules conveying redox regulation. We review basic concepts of the enzymatic nitric oxide and superoxide production within macrophages, refer to their unique chemical reactions and outline biological consequences not only for macrophage biology but also for their communication with cells in the microenvironment. These considerations link hypoxia to the NO system, addressing feedforward as well as feedback circuits. Moreover, we summarize the role of redox-signaling affecting epigenetics and reflect the central role of mitochondrial-derived oxygen species in inflammation. To better understand the diverse functions of macrophages during initiation as well as resolution of inflammation and to decode their versatile roles during innate and adaptive immunity with the entire spectrum of cell protective towards cell destructive activities we need to appreciate the signaling properties of redox-active species. Herein we discuss macrophage responses in terms of nitric oxide and superoxide formation with the modulating impact of hypoxia. Copyright © 2018. Published by Elsevier Ltd.

Redox Regulation of Mitochondrial Function

PubMed Central

Handy, Diane E.

2012-01-01

Abstract Redox-dependent processes influence most cellular functions, such as differentiation, proliferation, and apoptosis. Mitochondria are at the center of these processes, as mitochondria both generate reactive oxygen species (ROS) that drive redox-sensitive events and respond to ROS-mediated changes in the cellular redox state. In this review, we examine the regulation of cellular ROS, their modes of production and removal, and the redox-sensitive targets that are modified by their flux. In particular, we focus on the actions of redox-sensitive targets that alter mitochondrial function and the role of these redox modifications on metabolism, mitochondrial biogenesis, receptor-mediated signaling, and apoptotic pathways. We also consider the role of mitochondria in modulating these pathways, and discuss how redox-dependent events may contribute to pathobiology by altering mitochondrial function. Antioxid. Redox Signal. 16, 1323–1367. PMID:22146081

Multiple-membrane multiple-electrolyte redox flow battery design

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, Yushan; Gu, Shuang; Gong, Ke

A redox flow battery is provided. The redox flow battery involves multiple-membrane (at least one cation exchange membrane and at least one anion exchange membrane), multiple-electrolyte (one electrolyte in contact with the negative electrode, one electrolyte in contact with the positive electrode, and at least one electrolyte disposed between the two membranes) as the basic characteristic, such as a double-membrane, triple electrolyte (DMTE) configuration or a triple-membrane, quadruple electrolyte (TMQE) configuration. The cation exchange membrane is used to separate the negative or positive electrolyte and the middle electrolyte, and the anion exchange membrane is used to separate the middle electrolytemore » and the positive or negative electrolyte.« less

Imaging dynamic redox processes with genetically encoded probes.

PubMed

Ezeriņa, Daria; Morgan, Bruce; Dick, Tobias P

2014-08-01

Redox signalling plays an important role in many aspects of physiology, including that of the cardiovascular system. Perturbed redox regulation has been associated with numerous pathological conditions; nevertheless, the causal relationships between redox changes and pathology often remain unclear. Redox signalling involves the production of specific redox species at specific times in specific locations. However, until recently, the study of these processes has been impeded by a lack of appropriate tools and methodologies that afford the necessary redox species specificity and spatiotemporal resolution. Recently developed genetically encoded fluorescent redox probes now allow dynamic real-time measurements, of defined redox species, with subcellular compartment resolution, in intact living cells. Here we discuss the available genetically encoded redox probes in terms of their sensitivity and specificity and highlight where uncertainties or controversies currently exist. Furthermore, we outline major goals for future probe development and describe how progress in imaging methodologies will improve our ability to employ genetically encoded redox probes in a wide range of situations. This article is part of a special issue entitled "Redox Signalling in the Cardiovascular System." Copyright © 2014 Elsevier Ltd. All rights reserved.

Feasibility of assessing health state by detecting redox state of human body based on Chinese medicine constitution.

PubMed

Li, Ling-Ru; Wang, Qi; Wang, Ji; Wang, Qian-Fei; Yang, Ling-Ling; Zheng, Lu-Yu; Zhang, Yan

2016-08-01

This article discussed the feasibility of assessing health state by detecting redox state of human body. Firstly, the balance of redox state is the basis of homeostasis, and the balance ability of redox can reflflect health state of human body. Secondly, the redox state of human body is a sensitive index of multiple risk factors of health such as age, external environment and psychological factors. It participates in the occurrence and development of multiple diseases involving metabolic diseases and nervous system diseases, and can serve as a cut-in point for treatment of these diseases. Detecting the redox state of high risk people is signifificantly important for early detection and treatment of disease. The blood plasma and urine could be selected to detect, which is convenient. It is pointed that the indexes not only involve oxidation product and antioxidant enzyme but also redox couple. Chinese medicine constitution reflflects the state of body itself and the ability of adapting to external environment, which is consistent with the connotation of health. It is found that there are nine basic types of constitution in Chinese population, which provides a theoretical basis of health preservation, preventive treatment of disease and personalized treatment. With the combination of redox state detection and the Chinese medicine constitution theory, the heath state can be systemically assessed by conducting large-scale epidemiological survey with classifified detection on redox state of human body.

Using the Chemistry of Fireworks to Engage Students in Learning Basic Chemical Principles: A Lesson in Eco-Friendly Pyrotechnics

ERIC Educational Resources Information Center

Steinhauser, Georg; Klapotke, Thomas M.

2010-01-01

Fascination with fireworks and pyrotechnics can be used for educational purposes. Several aspects of pyrochemistry such as redox reactions, flame colors, or the theory of combustion can be incorporated in the curriculum to illustrate some basic chemical principles, guaranteeing a lesson that will be engaging and memorable. Beyond classic…

Vegetarian diets and public health: biomarker and redox connections.

PubMed

Benzie, Iris F F; Wachtel-Galor, Sissi

2010-11-15

Vegetarian diets are rich in antioxidant phytochemicals. However, they may not act as antioxidants in vivo, and yet still have important signaling and regulatory functions. Some may act as pro-oxidants, modulating cellular redox tone and oxidizing redox sensitive sites. In this review, evidence for health benefits of vegetarian diets is presented from different perspectives: epidemiological, biomarker, evolutionary, and public health, as well as antioxidant. From the perspective of molecular connections between diet and health, evidence of a role for plasma ascorbic acid as a biomarker for future disease risk is presented. Basic concepts of redox-based cell signaling are presented, and effects of antioxidant phytochemicals on signaling, especially via redox tone, sulfur switches and the Antioxidant Response Element (ARE), are explored. Sufficient scientific evidence exists for public health policy to promote a plant-rich diet for health promotion. This does not need to wait for science to provide all the answers as to why and how. However, action and interplay of dietary antioxidants in the nonequilibrium systems that control redox balance, cell signaling, and cell function provide rich ground for research to advance understanding of orthomolecular nutrition and provide science-based evidence to advance public health in our aging population.

Mitochondrial respiratory chain complexes as sources and targets of thiol-based redox-regulation.

PubMed

Dröse, Stefan; Brandt, Ulrich; Wittig, Ilka

2014-08-01

The respiratory chain of the inner mitochondrial membrane is a unique assembly of protein complexes that transfers the electrons of reducing equivalents extracted from foodstuff to molecular oxygen to generate a proton-motive force as the primary energy source for cellular ATP-synthesis. Recent evidence indicates that redox reactions are also involved in regulating mitochondrial function via redox-modification of specific cysteine-thiol groups in subunits of respiratory chain complexes. Vice versa the generation of reactive oxygen species (ROS) by respiratory chain complexes may have an impact on the mitochondrial redox balance through reversible and irreversible thiol-modification of specific target proteins involved in redox signaling, but also pathophysiological processes. Recent evidence indicates that thiol-based redox regulation of the respiratory chain activity and especially S-nitrosylation of complex I could be a strategy to prevent elevated ROS production, oxidative damage and tissue necrosis during ischemia-reperfusion injury. This review focuses on the thiol-based redox processes involving the respiratory chain as a source as well as a target, including a general overview on mitochondria as highly compartmentalized redox organelles and on methods to investigate the redox state of mitochondrial proteins. This article is part of a Special Issue entitled: Thiol-Based Redox Processes. Copyright © 2014 Elsevier B.V. All rights reserved.

Anaerobic microbial redox processes in a landfill leachate contaminated aquifer (Grindsted, Denmark)

NASA Astrophysics Data System (ADS)

Ludvigsen, L.; Albrechtsen, H.-J.; Heron, G.; Bjerg, P. L.; Christensen, T. H.

1998-10-01

The distribution of anaerobic microbial redox processes was investigated along a 305 m long transect of a shallow landfill-leachate polluted aquifer. By unamended bioassays containing sediment and groundwater, 37 samples were investigated with respect to methane production, sulfate, iron, and manganese reduction, and denitrification. Methane production was restricted to the most reduced part of the plume with rates of 0.003-0.055 nmol CH 4/g dry weight/day. Sulfate reduction was observed at rates of maximum 1.8 nmol SO 42-/g dry weight/day along with methane production in the plume, but sulfate reduction was also observed further downgradient of the landfill. Iron reduction at rates of 5-19 nmol Fe(II)/g dry weight/day was observed in only a few samples, but this may be related to a high detection limit for the iron reducing bioassay. Manganese reduction at rates of maximum 2.4 nmol Mn(II)/g dry weight/day and denitrification at rates of 0.2-37 nmol N 2O-N/g dry weight/day were observed in the less reduced part of the plume. All the redox processes were microbial processes. In many cases, several redox processes took place simultaneously, but in all samples one process dominated accounting for more than 70% of the equivalent carbon conversion. The bioassays showed that the redox zones in the plume identified from the groundwater composition (e.g. as methanogenic and sulfate reducing) locally hosted also other redox processes (e.g. iron reduction). This may have implications for the potential of the redox zone to degrade trace amounts of organic chemicals and suggests that unamended bioassays may be an important supplement to other approaches in characterizing the redox processes in an anaerobic plume.

Redox-capacitor to connect electrochemistry to redox-biology.

PubMed

Kim, Eunkyoung; Leverage, W Taylor; Liu, Yi; White, Ian M; Bentley, William E; Payne, Gregory F

2014-01-07

It is well-established that redox-reactions are integral to biology for energy harvesting (oxidative phosphorylation), immune defense (oxidative burst) and drug metabolism (phase I reactions), yet there is emerging evidence that redox may play broader roles in biology (e.g., redox signaling). A critical challenge is the need for tools that can probe biologically-relevant redox interactions simply, rapidly and without the need for a comprehensive suite of analytical methods. We propose that electrochemistry may provide such a tool. In this tutorial review, we describe recent studies with a redox-capacitor film that can serve as a bio-electrode interface that can accept, store and donate electrons from mediators commonly used in electrochemistry and also in biology. Specifically, we (i) describe the fabrication of this redox-capacitor from catechols and the polysaccharide chitosan, (ii) discuss the mechanistic basis for electron exchange, (iii) illustrate the properties of this redox-capacitor and its capabilities for promoting redox-communication between biology and electrodes, and (iv) suggest the potential for enlisting signal processing strategies to "extract" redox information. We believe these initial studies indicate broad possibilities for enlisting electrochemistry and signal processing to acquire "systems level" redox information from biology.

Efficient green methanol synthesis from glycerol

NASA Astrophysics Data System (ADS)

Haider, Muhammad H.; Dummer, Nicholas F.; Knight, David W.; Jenkins, Robert L.; Howard, Mark; Moulijn, Jacob; Taylor, Stuart H.; Hutchings, Graham J.

2015-12-01

The production of biodiesel from the transesterification of plant-derived triglycerides with methanol has been commercialized extensively. Impure glycerol is obtained as a by-product at roughly one-tenth the mass of the biodiesel. Utilization of this crude glycerol is important in improving the viability of the overall process. Here we show that crude glycerol can be reacted with water over very simple basic or redox oxide catalysts to produce methanol in high yields, together with other useful chemicals, in a one-step low-pressure process. Our discovery opens up the possibility of recycling the crude glycerol produced during biodiesel manufacture. Furthermore, we show that molecules containing at least two hydroxyl groups can be converted into methanol, which demonstrates some aspects of the generality of this new chemistry.

Quantitative proteomic characterization of redox-dependent post-translational modifications on protein cysteines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duan, Jicheng; Gaffrey, Matthew J.; Qian, Wei-Jun

Protein cysteine thiols play a crucial role in redox signaling, regulation of enzymatic activity and protein function, and maintaining redox homeostasis in living systems. The unique chemical reactivity of thiol groups makes cysteine susceptible to oxidative modifications by reactive oxygen and nitrogen species to form a broad array of reversible and irreversible protein post-translational modifications (PTMs). The reversible modifications in particular are one of the major components of redox signaling and are involved in regulation of various cellular processes under physiological and pathological conditions. The biological significance of these redox PTMs in health and diseases has been increasingly recognized. Herein,more » we review the recent advances of quantitative proteomic approaches for investigating redox PTMs in complex biological systems, including the general considerations of sample processing, various chemical or affinity enrichment strategies, and quantitative approaches. We also highlight a number of redox proteomic approaches that enable effective profiling of redox PTMs for addressing specific biological questions. Although some technological limitations remain, redox proteomics is paving the way towards a better understanding of redox signaling and regulation in human health and diseases.« less

Method for characterization of the redox condition of cementitious materials

DOEpatents

Almond, Philip M.; Langton, Christine A.; Stefanko, David B.

2015-12-22

Disclosed are methods for determining the redox condition of cementitious materials. The methods are leaching methods that utilize an in situ redox indicator that is present in the cementitious materials as formed. The in situ redox indicator leaches from cementitious material and, when the leaching process is carried out under anaerobic conditions can be utilized to determine the redox condition of the material. The in situ redox indicator can exhibit distinct characteristics in the leachate depending upon the redox condition of the indicator.

Mechanisms and consequences of oxidative stress in lung disease: therapeutic implications for an aging populace.

PubMed

Hecker, Louise

2018-04-01

The rapid expansion of the elderly population has led to the recent epidemic of age-related diseases, including increased incidence and mortality of chronic and acute lung diseases. Numerous studies have implicated aging and oxidative stress in the pathogenesis of various pulmonary diseases; however, despite recent advances in these fields, the specific contributions of aging and oxidative stress remain elusive. This review will discuss the consequences of aging on lung morphology and physiology, and how redox imbalance with aging contributes to lung disease susceptibility. Here, we focus on three lung diseases for which aging is a significant risk factor: acute respiratory distress syndrome (ARDS), chronic obstructive pulmonary disease (COPD), and idiopathic pulmonary fibrosis (IPF). Preclinical and clinical development for redox- and senescence-altering therapeutic strategies are discussed, as well as scientific advancements that may direct current and future therapeutic development. A deeper understanding of how aging impacts normal lung function, redox balance, and injury-repair processes will inspire the development of new therapies to prevent and/or reverse age-associated pulmonary diseases, and ultimately increase health span and longevity. This review is intended to encourage basic, clinical, and translational research that will bridge knowledge gaps at the intersection of aging, oxidative stress, and lung disease to fuel the development of more effective therapeutic strategies for lung diseases that disproportionately afflict the elderly.

Protein Electrochemistry: Questions and Answers.

PubMed

Fourmond, V; Léger, C

This chapter presents the fundamentals of electrochemistry in the context of protein electrochemistry. We discuss redox proteins and enzymes that are not photoactive. Of course, the principles described herein also apply to photobioelectrochemistry, as discussed in later chapters of this book. Depending on which experiment is considered, electron transfer between proteins and electrodes can be either direct or mediated, and achieved in a variety of configurations: with the protein and/or the mediator free to diffuse in solution, immobilized in a thick, hydrated film, or adsorbed as a sub-monolayer on the electrode. The experiments can be performed with the goal to study the protein or to use it. Here emphasis is on mechanistic studies, which are easier in the configuration where the protein is adsorbed and electron transfer is direct, but we also explain the interpretation of signals obtained when diffusion processes affect the response.This chapter is organized as a series of responses to questions. Questions 1-5 are related to the basics of electrochemistry: what does "potential" or "current" mean, what does an electrochemical set-up look like? Questions 6-9 are related to the distinction between adsorbed and diffusive redox species. The answers to questions 10-13 explain the interpretation of slow and fast scan voltammetry with redox proteins. Questions 14-19 deal with catalytic electrochemistry, when the protein studied is actually an enzyme. Questions 20, 21 and 22 are general.

Principles in redox signaling: from chemistry to functional significance.

PubMed

Bindoli, Alberto; Rigobello, Maria Pia

2013-05-01

Reactive oxygen and nitrogen species are currently considered not only harmful byproducts of aerobic respiration but also critical mediators of redox signaling. The molecules and the chemical principles sustaining the network of cellular redox regulated processes are described. Special emphasis is placed on hydrogen peroxide (H(2)O(2)), now considered as acting as a second messenger, and on sulfhydryl groups, which are the direct targets of the oxidant signal. Cysteine residues of some proteins, therefore, act as sensors of redox conditions and are oxidized in a reversible reaction. In particular, the formation of sulfenic acid and disulfide, the initial steps of thiol oxidation, are described in detail. The many cell pathways involved in reactive oxygen species formation are reported. Central to redox signaling processes are the glutathione and thioredoxin systems controlling H(2)O(2) levels and, hence, the thiol/disulfide balance. Lastly, some of the most important redox-regulated processes involving specific enzymes and organelles are described. The redox signaling area of research is rapidly expanding, and future work will examine new pathways and clarify their importance in cellular pathophysiology.

Redox biology of the intestine

PubMed Central

Circu, Magdalena L.; Aw, Tak Yee

2011-01-01

The intestinal tract, known for its capability for self-renew, represents the first barrier of defense between the organism and its luminal environment. The thiol/disulfide redox systems comprising the glutathione/glutathione disulfide (GSH/GSSG), cysteine/cystine (Cys/CySS) and reduced and oxidized thioredoxin (Trx/TrxSS) redox couples play important roles in preserving tissue redox homeostasis, metabolic functions, and cellular integrity. Control of the thiol-disulfide status at the luminal surface is essential for maintaining mucus fluidity and absorption of nutrients, and protection against chemical-induced oxidant injury. Within intestinal cells, these redox couples preserve an environment that supports physiological processes and orchestrates networks of enzymatic reactions against oxidative stress. In this review, we focus on the intestinal redox and antioxidant systems, their subcellular compartmentation, redox signaling and epithelial turnover, and contribution of luminal microbiota, key aspects that are relevant to understanding redox-dependent processes in gut biology with implications for degenerative digestive disorders, such as inflammation and cancer. PMID:21831010

New tools for redox biology: From imaging to manipulation.

PubMed

Bilan, Dmitry S; Belousov, Vsevolod V

2017-08-01

Redox reactions play a key role in maintaining essential biological processes. Deviations in redox pathways result in the development of various pathologies at cellular and organismal levels. Until recently, studies on transformations in the intracellular redox state have been significantly hampered in living systems. The genetically encoded indicators, based on fluorescent proteins, have provided new opportunities in biomedical research. The existing indicators already enable monitoring of cellular redox parameters in different processes including embryogenesis, aging, inflammation, tissue regeneration, and pathogenesis of various diseases. In this review, we summarize information about all genetically encoded redox indicators developed to date. We provide the description of each indicator and discuss its advantages and limitations, as well as points that need to be considered when choosing an indicator for a particular experiment. One chapter is devoted to the important discoveries that have been made by using genetically encoded redox indicators. Copyright © 2016 Elsevier Inc. All rights reserved.

Rab7-a novel redox target that modulates inflammatory pain processing.

PubMed

Kallenborn-Gerhardt, Wiebke; Möser, Christine V; Lorenz, Jana E; Steger, Mirco; Heidler, Juliana; Scheving, Reynir; Petersen, Jonas; Kennel, Lea; Flauaus, Cathrin; Lu, Ruirui; Edinger, Aimee L; Tegeder, Irmgard; Geisslinger, Gerd; Heide, Heinrich; Wittig, Ilka; Schmidtko, Achim

2017-07-01

Chronic pain is accompanied by production of reactive oxygen species (ROS) in various cells that are important for nociceptive processing. Recent data indicate that ROS can trigger specific redox-dependent signaling processes, but the molecular targets of ROS signaling in the nociceptive system remain largely elusive. Here, we performed a proteome screen for pain-dependent redox regulation using an OxICAT approach, thereby identifying the small GTPase Rab7 as a redox-modified target during inflammatory pain in mice. Prevention of Rab7 oxidation by replacement of the redox-sensing thiols modulates its GTPase activity. Immunofluorescence studies revealed Rab7 expression to be enriched in central terminals of sensory neurons. Knockout mice lacking Rab7 in sensory neurons showed normal responses to noxious thermal and mechanical stimuli; however, their pain behavior during inflammatory pain and in response to ROS donors was reduced. The data suggest that redox-dependent changes in Rab7 activity modulate inflammatory pain sensitivity.

The basic biology of redoxosomes in cytokine-mediated signal transduction and implications for disease-specific therapies.

PubMed

Spencer, Netanya Y; Engelhardt, John F

2014-03-18

Redox reactions have been established as major biological players in many cellular signaling pathways. Here we review mechanisms of redox signaling with an emphasis on redox-active signaling endosomes. Signals are transduced by relatively few reactive oxygen species (ROS), through very specific redox modifications of numerous proteins and enzymes. Although ROS signals are typically associated with cellular injury, these signaling pathways are also critical for maintaining cellular health at homeostasis. An important component of ROS signaling pertains to localization and tightly regulated signal transduction events within discrete microenvironments of the cell. One major aspect of this specificity is ROS compartmentalization within membrane-enclosed organelles such as redoxosomes (redox-active endosomes) and the nuclear envelope. Among the cellular proteins that produce superoxide are the NADPH oxidases (NOXes), transmembrane proteins that are implicated in many types of redox signaling. NOXes produce superoxide on only one side of a lipid bilayer; as such, their orientation dictates the compartmentalization of ROS and the local control of signaling events limited by ROS diffusion and/or movement through channels associated with the signaling membrane. NOX-dependent ROS signaling pathways can also be self-regulating, with molecular redox sensors that limit the local production of ROS required for effective signaling. ROS regulation of the Rac-GTPase, a required co-activator of many NOXes, is an example of this type of sensor. A deeper understanding of redox signaling pathways and the mechanisms that control their specificity will provide unique therapeutic opportunities for aging, cancer, ischemia-reperfusion injury, and neurodegenerative diseases.

The Basic Biology of Redoxosomes in Cytokine-Mediated Signal Transduction and Implications for Disease-Specific Therapies

PubMed Central

2015-01-01

Redox reactions have been established as major biological players in many cellular signaling pathways. Here we review mechanisms of redox signaling with an emphasis on redox-active signaling endosomes. Signals are transduced by relatively few reactive oxygen species (ROS), through very specific redox modifications of numerous proteins and enzymes. Although ROS signals are typically associated with cellular injury, these signaling pathways are also critical for maintaining cellular health at homeostasis. An important component of ROS signaling pertains to localization and tightly regulated signal transduction events within discrete microenvironments of the cell. One major aspect of this specificity is ROS compartmentalization within membrane-enclosed organelles such as redoxosomes (redox-active endosomes) and the nuclear envelope. Among the cellular proteins that produce superoxide are the NADPH oxidases (NOXes), transmembrane proteins that are implicated in many types of redox signaling. NOXes produce superoxide on only one side of a lipid bilayer; as such, their orientation dictates the compartmentalization of ROS and the local control of signaling events limited by ROS diffusion and/or movement through channels associated with the signaling membrane. NOX-dependent ROS signaling pathways can also be self-regulating, with molecular redox sensors that limit the local production of ROS required for effective signaling. ROS regulation of the Rac-GTPase, a required co-activator of many NOXes, is an example of this type of sensor. A deeper understanding of redox signaling pathways and the mechanisms that control their specificity will provide unique therapeutic opportunities for aging, cancer, ischemia-reperfusion injury, and neurodegenerative diseases. PMID:24555469

Kynurenine pathway metabolites and enzymes involved in redox reactions.

PubMed

González Esquivel, D; Ramírez-Ortega, D; Pineda, B; Castro, N; Ríos, C; Pérez de la Cruz, V

2017-01-01

Oxido-reduction reactions are a fundamental part of the life due to support many vital biological processes as cellular respiration and glucose oxidation. In the redox reactions, one substance transfers one or more electrons to another substance. An important electron carrier is the coenzyme NAD + , which is involved in many metabolic pathways. De novo biosynthesis of NAD + is through the kynurenine pathway, the major route of tryptophan catabolism, which is sensitive to redox environment and produces metabolites with redox capacity, able to alter biological functions that are controlled by redox-responsive signaling pathways. Kynurenine pathway metabolites have been implicated in the physiology process and in the physiopathology of many diseases; processes that also share others factors as dysregulation of calcium homeostasis, mitochondrial dysfunction, oxidative stress, inflammation and cell death, which impact the redox environment. This review examines in detail the available evidence in which kynurenine pathway metabolites participate in redox reactions and their effect on cellular redox homeostasis, since the knowledge of the main factors and mechanisms that lead to cell death in many neurodegenative disorders and other pathologies, such as mitochondrial dysfunction, oxidative stress and kynurenines imbalance, will allow to develop therapies using them as targets. This article is part of the Special Issue entitled 'The Kynurenine Pathway in Health and Disease'. Copyright © 2016 Elsevier Ltd. All rights reserved.

An Unconventional Redox Cross Claisen Condensation-Aromatization of 4-Hydroxyprolines with Ketones.

PubMed

Tang, Mi; Sun, Rengwei; Li, Hao; Yu, Xinhong; Wang, Wei

2017-08-18

Reaction of α-amino acids, particularly prolines and their derivatives with carbonyl compounds via decarboxylative redox process, is a viable strategy for synthesis of structurally diverse nitrogen centered heterocyclics. In these processes, the decarboxylation is the essential driving force for the processes. The realization of the redox process without decarboxylation may offer an opportunity to explore new reactions. Herein, we report the discovery of an unprecedented redox Claisen-type condensation aromatization cascade reaction of 4-substituted 4-hydroxyproline and its esters with unreactive ketones. We found that the use of propionic acid as a catalyst and a co-solvent can change the reaction course. The commonly observed redox decarboxylation and aldol condensation reactions are significantly minimized. Moreover, unreactive ketones can effectively participate in the Claisen condensation reaction. The new reactivity enables a redox cyclization via an unconventional Claisen-type condensation reaction of in situ formed enamine intermediates from ketone precursors with 4-substituted 4-hydroxyproline and its esters as electrophilic acylation partners. Under the reaction conditions, the cascade process proceeds highly regio- and stereoselectively to afford highly synthetically and biologically valued cis-2,3-dihydro-1H-pyrrolizin-1-ones with a broad substrate scope in efficient 'one-pot' operation, whereas such structures generally require multiple steps.

Study to establish cost projections for production of Redox chemicals

NASA Technical Reports Server (NTRS)

Walther, J. F.; Greco, C. C.; Rusinko, R. N.; Wadsworth, A. L., III

1982-01-01

A cost study of four proposed manufacturing processes for redox chemicals for the NASA REDOX Energy Storage System yielded favorable selling prices in the range $0.99 to $1.91/kg of chromic chloride, anhydrous basis, including ferrous chloride. The prices corresponded to specific energy storage costs from under $9 to $17/kWh. A refined and expanded cost analysis of the most favored process yielded a price estimate corresponding to a storage cost of $11/kWh. The findings supported the potential economic viability of the NASA REDOX system.

Determining Li+-Coupled Redox Targeting Reaction Kinetics of Battery Materials with Scanning Electrochemical Microscopy.

PubMed

Yan, Ruiting; Ghilane, Jalal; Phuah, Kia Chai; Pham Truong, Thuan Nguyen; Adams, Stefan; Randriamahazaka, Hyacinthe; Wang, Qing

2018-02-01

The redox targeting reaction of Li + -storage materials with redox mediators is the key process in redox flow lithium batteries, a promising technology for next-generation large-scale energy storage. The kinetics of the Li + -coupled heterogeneous charge transfer between the energy storage material and redox mediator dictates the performance of the device, while as a new type of charge transfer process it has been rarely studied. Here, scanning electrochemical microscopy (SECM) was employed for the first time to determine the interfacial charge transfer kinetics of LiFePO 4 /FePO 4 upon delithiation and lithiation by a pair of redox shuttle molecules FcBr 2 + and Fc. The effective rate constant k eff was determined to be around 3.70-6.57 × 10 -3 cm/s for the two-way pseudo-first-order reactions, which feature a linear dependence on the composition of LiFePO 4 , validating the kinetic process of interfacial charge transfer rather than bulk solid diffusion. In addition, in conjunction with chronoamperometry measurement, the SECM study disproves the conventional "shrinking-core" model for the delithiation of LiFePO 4 and presents an intriguing way of probing the phase boundary propagations induced by interfacial redox reactions. This study demonstrates a reliable method for the kinetics of redox targeting reactions, and the results provide useful guidance for the optimization of redox targeting systems for large-scale energy storage.

Glutathione redox potential in the mitochondrial intermembrane space is linked to the cytosol and impacts the Mia40 redox state

PubMed Central

Kojer, Kerstin; Bien, Melanie; Gangel, Heike; Morgan, Bruce; Dick, Tobias P; Riemer, Jan

2012-01-01

Glutathione is an important mediator and regulator of cellular redox processes. Detailed knowledge of local glutathione redox potential (EGSH) dynamics is critical to understand the network of redox processes and their influence on cellular function. Using dynamic oxidant recovery assays together with EGSH-specific fluorescent reporters, we investigate the glutathione pools of the cytosol, mitochondrial matrix and intermembrane space (IMS). We demonstrate that the glutathione pools of IMS and cytosol are dynamically interconnected via porins. In contrast, no appreciable communication was observed between the glutathione pools of the IMS and matrix. By modulating redox pathways in the cytosol and IMS, we find that the cytosolic glutathione reductase system is the major determinant of EGSH in the IMS, thus explaining a steady-state EGSH in the IMS which is similar to the cytosol. Moreover, we show that the local EGSH contributes to the partially reduced redox state of the IMS oxidoreductase Mia40 in vivo. Taken together, we provide a comprehensive mechanistic picture of the IMS redox milieu and define the redox influences on Mia40 in living cells. PMID:22705944

Redox Flow Batteries, a Review

DOE Office of Scientific and Technical Information (OSTI.GOV)

Knoxville, U. Tennessee; U. Texas Austin; U, McGill

2011-07-15

Redox flow batteries are enjoying a renaissance due to their ability to store large amounts of electrical energy relatively cheaply and efficiently. In this review, we examine the components of redox flow batteries with a focus on understanding the underlying physical processes. The various transport and kinetic phenomena are discussed along with the most common redox couples.

Characteristics and Kinetic Analysis of AQS Transformation and Microbial Goethite Reduction:Insight into "Redox mediator-Microbe-Iron oxide" Interaction Process.

PubMed

Zhu, Weihuang; Shi, Mengran; Yu, Dan; Liu, Chongxuan; Huang, Tinglin; Wu, Fengchang

2016-03-29

The characteristics and kinetics of redox transformation of a redox mediator, anthraquinone-2-sulfonate (AQS), during microbial goethite reduction by Shewanella decolorationis S12, a dissimilatory iron reduction bacterium (DIRB), were investigated to provide insights into "redox mediator-iron oxide" interaction in the presence of DIRB. Two pre-incubation reaction systems of the "strain S12- goethite" and the "strain S12-AQS" were used to investigate the dynamics of goethite reduction and AQS redox transformation. Results show that the concentrations of goethite and redox mediator, and the inoculation cell density all affect the characteristics of microbial goethite reduction, kinetic transformation between oxidized and reduced species of the redox mediator. Both abiotic and biotic reactions and their coupling regulate the kinetic process for "Quinone-Iron" interaction in the presence of DIRB. Our results provide some new insights into the characteristics and mechanisms of interaction among "quinone-DIRB- goethite" under biotic/abiotic driven.

Involvement of Redox State in the Aging of Drosophila melanogaster

PubMed Central

Radyuk, Svetlana N.; Sohal, Rajindar S.

2013-01-01

Abstract Significance: The main objective of this review was to provide an exposition of investigations, conducted in Drosophila melanogaster, on the role of reactive oxygen species and redox state in the aging process. While early transgenic studies did not clearly support the validity of the oxidative stress hypothesis of aging, predicated on the accumulation of structural damage, they spawned a broader search for redox-related effects that might impact the aging process. Recent Advances: Initial evidence implicating the thiol redox state as a possible causative factor in aging has been obtained in Drosophila. Overexpression of genes, such as GCL, G6PD, Prx2, and Prx5, which are involved in the maintenance of thiol redox homeostasis, has strong positive effects on longevity. Further, the depletion of peroxiredoxin activity in the mitochondria through the double knockdown of Prx5 and Prx3 not only results in a redox crisis but also elicits a rapid aging phenotype. Critical Issues: Herein, we summarize the present status of knowledge about the main components of the machinery controlling thiol redox homeostasis and describe how age-related redox fluctuations might impact aging more acutely through disruption of the redox-sensitive signaling mechanisms rather than via the simple accumulation of structural damage. Future Directions: Based on these initial insights into the plausible impact of redox fluctuations on redox signaling, future studies should focus on the pathways that have been explicitly implicated in aging, such as insulin signaling, TOR, and JNK/FOXO, with particular attention to elements that are redox sensitive. Antioxid. Redox Signal. 19, 788–803. PMID:23458359

Novel insights into redox system and the mechanism of redox regulation.

PubMed

Wang, Xin; Hai, Chunxu

2016-07-01

In view of the critical role of redox system in numerous physiological and pathophysiological processes, it is important to clearly understand the family members and regulatory mechanism of redox system. In this work, we will systematically review the current data detailing the reactive oxygen species (ROS), enzymatic and non-enzymatic antioxidants and redox sensitive transcription factors and we give a brief description of redox-mediated epigenetic and post-translational regulation. We propose that the redox system functions as a "Redox Chain", consisting of "ROS-generating Enzyme Chain", "Combined Antioxidant Chain" and "Transcription Factor Chain". We suggest that an individualized assessment of the redox status in the body should be conducted for the redox intervention of a patient. The strategy of intervention is to maintain redox homeostasis via either facilitation of ROS signaling or enhancement of antioxidant defense. These findings provide valuable new insights into redox system and open up new paths for the control of redox-related disorders.

An UV-vis spectroelectrochemical approach for rapid detection of phenazines and exploration of their redox characteristics.

PubMed

Chen, Wei; Liu, Xiao-Yang; Qian, Chen; Song, Xiang-Ning; Li, Wen-Wei; Yu, Han-Qing

2015-02-15

Phenazines are widely distributed in the environment and play an important role in various biological processes to facilitate microbial metabolism and electron transfer. In this work, an efficient and reliable spectroelectrochemical method is developed to quantitatively detect 1-hydroxyphenazine (1-OHPZ), a representative phenazine, and explore its redox characteristics. This approach is based on the sensitive absorption change of 1-OHPZ in response to its changes under redox state in rapid electrochemical reduction. The redox reaction of 1-OHPZ in aqueous solution is a proton-coupled electron transfer process, with a reversible one-step 2e(-)/2H(+) transfer reaction. This spectroelectrochemical approach exhibits good linear response covering two magnitudes to 1-OHPZ with a detection limit of 0.48µM, and is successfully applied to detect 1-OHPZ from a mixture of phenazines produced by Pseudomonas aeruginosa cultures. This method might also be applicable in exploring the abundance and redox processes of a wide range of other redox-active molecules in natural and engineered environments. Copyright © 2014 Elsevier B.V. All rights reserved.

Redox proteomics and drug development.

PubMed

D'Alessandro, Angelo; Rinalducci, Sara; Zolla, Lello

2011-11-18

As alterations of the redox homeostasis lie at the root of many pathophysiological processes in human health, redox proteomics holds the promise to shed further light on fundamental biological processes. In this review, the mechanisms of reactive oxygen species (ROS) and reactive nitrogen species (RNS) production are reviewed, mainly addressing those chemical phenomena which have already been associated with pathological conditions (of the central nervous system, cardiovascular system, or simply related to aging and altered-cell cycle regulation). From Alzheimer's to Parkinson's and Hungtinton's disease, from ageing to cancer, oxidative stress (OS) appears to represent a common trait in so many relevant biological aspects of human health, that further investments in the field of redox proteomics ought to be mandatory. For the foreseeable future, redox proteomics will likely play a pivotal role in the quest for new therapeutical targets and their validation, in the process of determining OS-triggered cellular alteration upon drug treatments and thus in the very heart of the design and testing of new drugs and their metabolites against those pathologies relying on altered redox homeostasis. Copyright © 2011 Elsevier B.V. All rights reserved.

Simultaneous anionic and cationic redox

NASA Astrophysics Data System (ADS)

Jung, Sung-Kyun; Kang, Kisuk

2017-12-01

It is challenging to unlock anionic redox activity, accompanied by full utilization of available cationic redox process, to boost capacity of battery cathodes. Now, material design by tuning the metal-oxygen interaction is shown to be a promising solution.

Conditions affecting the release of phosphorus from surface lake sediments.

PubMed

Christophoridis, Christophoros; Fytianos, Konstantinos

2006-01-01

Laboratory studies were conducted to determine the effect of pH and redox conditions, as well as the effect of Fe, Mn, Ca, Al, and organic matter, on the release of ortho-phosphates in lake sediments taken from Lakes Koronia and Volvi (Northern Greece). Results were evaluated in combination with experiments to determine P fractionation in the sediment. The study revealed the major effect of redox potential and pH on the release of P from lake sediments. Both lakes showed increased release rates under reductive conditions and high pH values. The fractionation experiments revealed increased mobility of the reductive P fraction as well as of the NaOH-P fraction, indicating participation of both fractions in the overall release of sediment-bound P, depending on the prevailing environmental conditions. The results were assessed in combination with the release patterns of Fe, Mn, Ca, Al, and organic matter, enabling the identification of more specific processes of P release for each lake. The basic release patterns included the redox induced reductive dissolution of P-bearing metal oxides and the competitive exchange of phosphate anions with OH- at high pH values. The formation of an oxidized surface microlayer under oxic conditions acted as a protective film, preventing further P release from the sediments of Lake Volvi, while sediments from Lake Koronia exhibited a continuous and increased tendency to release P under various physicochemical conditions, acting as a constant source of internal P loading.

Timing of developmental reduction in epithelial glutathione redox potential is associated with increased epithelial proliferation in the immature murine intestine.

PubMed

Reid, Graham K; Berardinelli, Andrew J; Ray, Laurie; Jackson, Arena R; Neish, Andrew S; Hansen, Jason M; Denning, Patricia W

2017-08-01

BackgroundThe intracellular redox potential of the glutathione (GSH)/glutathione disulfide (GSSG) couple regulates cellular processes. In vitro studies indicate that a reduced GSH/GSSG redox potential favors proliferation, whereas a more oxidized redox potential favors differentiation. Intestinal growth depends upon an appropriate balance between the two. However, how the ontogeny of intestinal epithelial cellular (IEC) GSH/GSSG redox regulates these processes in the developing intestine has not been fully characterized in vivo.MethodsOntogeny of intestinal GSH redox potential and growth were measured in neonatal mice.ResultsWe show that IEC GSH/GSSG redox potential becomes increasingly reduced (primarily driven by increased GSH concentration) over the first 3 weeks of life. Increased intracellular GSH has been shown to drive proliferation through increased poly-ADP-ribose polymerase (PARP) activity. We show that increasing IEC poly-ADP-ribose chains can be measured over the first 3 weeks of life, indicating an increase in IEC PARP activity. These changes are accompanied by increased intestinal growth and IEC proliferation as assessed by villus height/crypt depth, intestinal length, and Ki67 staining.ConclusionUnderstanding how IEC GSH/GSSG redox potential is developmentally regulated may provide insight into how premature human intestinal redox states can be manipulated to optimize intestinal growth and adaptation.

Redox Proteomics: A Key Tool for New Insights into Protein Modification with Relevance to Disease.

PubMed

Butterfield, D Allan; Perluigi, Marzia

2017-03-01

Oxidatively modified proteins are characterized by elevations in protein-resident carbonyls or 3-nitrotyrosine, measures of protein oxidation, or protein bound reactive alkenals such as 4-hydroxy-2-nonenal, a measure of lipid peroxidation. Oxidatively modified proteins nearly always have altered structure and function. Redox proteomics is that branch of proteomics used to identify oxidized proteins and determine the extent and location of oxidative modifications in the proteomes of interest. This technique nearly always employs mass spectrometry as the major platform to achieve the goals of identifying the target proteins. Once identified, oxidatively modified proteins can be placed in specific molecular pathways to provide insights into protein oxidation and human disease. Both original research and review articles are included in this Forum on Redox Proteomics. The topics related to redox proteomics range from basic chemistry of sulfur radical-induced redox modifications in proteins, to the thiol secretome and inflammatory network, to reversible thiol oxidation in proteomes, to the role of glutamine synthetase in peripheral and central environments on inflammation and insulin resistance, to bioanalytical aspects of tyrosine nitrated proteins, to protein oxidation in human smokers and models thereof, and to Alzheimer disease, including articles on the brain ubiquitinylome and the "triangle of death" composed of oxidatively modified proteins involved in energy metabolism, mammalian target of rampamycin activation, and the proteostasis network. This Forum on Redox Proteomics is both timely and a critically important resource to highlight one of the key tools needed to better understand protein structure and function in oxidative environments in health and disease. Antioxid. Redox Signal. 26, 277-279.

Metabolic control of redox and redox control of metabolism in plants.

PubMed

Geigenberger, Peter; Fernie, Alisdair R

2014-09-20

Reduction-oxidation (Redox) status operates as a major integrator of subcellular and extracellular metabolism and is simultaneously itself regulated by metabolic processes. Redox status not only dominates cellular metabolism due to the prominence of NAD(H) and NADP(H) couples in myriad metabolic reactions but also acts as an effective signal that informs the cell of the prevailing environmental conditions. After relay of this information, the cell is able to appropriately respond via a range of mechanisms, including directly affecting cellular functioning and reprogramming nuclear gene expression. The facile accession of Arabidopsis knockout mutants alongside the adoption of broad-scale post-genomic approaches, which are able to provide transcriptomic-, proteomic-, and metabolomic-level information alongside traditional biochemical and emerging cell biological techniques, has dramatically advanced our understanding of redox status control. This review summarizes redox status control of metabolism and the metabolic control of redox status at both cellular and subcellular levels. It is becoming apparent that plastid, mitochondria, and peroxisome functions influence a wide range of processes outside of the organelles themselves. While knowledge of the network of metabolic pathways and their intraorganellar redox status regulation has increased in the last years, little is known about the interorganellar redox signals coordinating these networks. A current challenge is, therefore, synthesizing our knowledge and planning experiments that tackle redox status regulation at both inter- and intracellular levels. Emerging tools are enabling ever-increasing spatiotemporal resolution of metabolism and imaging of redox status components. Broader application of these tools will likely greatly enhance our understanding of the interplay of redox status and metabolism as well as elucidating and characterizing signaling features thereof. We propose that such information will enable us to dissect the regulatory hierarchies that mediate the strict coupling of metabolism and redox status which, ultimately, determine plant growth and development.

Electrochemical analyses of redox-active iron minerals: a review of nonmediated and mediated approaches.

PubMed

Sander, Michael; Hofstetter, Thomas B; Gorski, Christopher A

2015-05-19

Redox-active minerals are ubiquitous in the environment and are involved in numerous electron transfer reactions that significantly affect biogeochemical processes and cycles as well as pollutant dynamics. As a consequence, research in different scientific disciplines is devoted to elucidating the redox properties and reactivities of minerals. This review focuses on the characterization of mineral redox properties using electrochemical approaches from an applied (bio)geochemical and environmental analytical chemistry perspective. Establishing redox equilibria between the minerals and working electrodes is a major challenge in electrochemical measurements, which we discuss in an overview of traditional electrochemical techniques. These issues can be overcome with mediated electrochemical analyses in which dissolved redox mediators are used to increase the rate of electron transfer and to facilitate redox equilibration between working electrodes and minerals in both amperometric and potentiometric measurements. Using experimental data on an iron-bearing clay mineral, we illustrate how mediated electrochemical analyses can be employed to derive important thermodynamic and kinetic data on electron transfer to and from structural iron. We summarize anticipated methodological advancements that will further contribute to advance an improved understanding of electron transfer to and from minerals in environmentally relevant redox processes.

Arteriovenous oscillations of the redox potential: Is the redox state influencing blood flow?

PubMed

Poznanski, Jaroslaw; Szczesny, Pawel; Pawlinski, Bartosz; Mazurek, Tomasz; Zielenkiewicz, Piotr; Gajewski, Zdzislaw; Paczek, Leszek

2017-09-01

Studies on the regulation of human blood flow revealed several modes of oscillations with frequencies ranging from 0.005 to 1 Hz. Several mechanisms were proposed that might influence these oscillations, such as the activity of vascular endothelium, the neurogenic activity of vessel wall, the intrinsic activity of vascular smooth muscle, respiration, and heartbeat. These studies relied typically on non-invasive techniques, for example, laser Doppler flowmetry. Oscillations of biochemical markers were rarely coupled to blood flow. The redox potential difference between the artery and the vein was measured by platinum electrodes placed in the parallel homonymous femoral artery and the femoral vein of ventilated anesthetized pigs. Continuous measurement at 5 Hz sampling rate using a digital nanovoltmeter revealed fluctuating signals with three basic modes of oscillations: ∼ 1, ∼ 0.1 and ∼ 0.01 Hz. These signals clearly overlap with reported modes of oscillations in blood flow, suggesting coupling of the redox potential and blood flow. The amplitude of the oscillations associated with heart action was significantly smaller than for the other two modes, despite the fact that heart action has the greatest influence on blood flow. This finding suggests that redox potential in blood might be not a derivative but either a mediator or an effector of the blood flow control system.

The thermodynamics of pyrochemical processes for liquid metal reactor fuel cycles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, I.

1987-01-01

The thermodynamic basis for pyrochemical processes for the recovery and purification of fuel for the liquid metal reactor fuel cycle is described. These processes involve the transport of the uranium and plutonium from one liquid alloy to another through a molten salt. The processes discussed use liquid alloys of cadmium, zinc, and magnesium and molten chloride salts. The oxidation-reduction steps are done either chemically by the use of an auxiliary redox couple or electrochemically by the use of an external electrical supply. The same basic thermodynamics apply to both the salt transport and the electrotransport processes. Large deviations from idealmore » solution behavior of the actinides and lanthanides in the liquid alloys have a major influence on the solubilities and the performance of both the salt transport and electrotransport processes. Separation of plutonium and uranium from each other and decontamination from the more noble fission product elements can be achieved using both transport processes. The thermodynamic analysis is used to make process design computations for different process conditions.« less

Characteristics and kinetic analysis of AQS transformation and microbial goethite reduction: Insight into “redox mediator-microbe-iron oxide” interaction process

DOE PAGES

Zhu, Weihuang; Shi, Mengran; Yu, Dan; ...

2016-03-29

Here, the characteristics and kinetics of redox transformation of a redox mediator, anthraquinone-2-sulfonate (AQS), during microbial goethite reduction by Shewanella decolorationis S12, a dissimilatory iron reduction bacterium (DIRB), were investigated to provide insights into “redox mediator-iron oxide” interaction in the presence of DIRB. Two pre-incubation reaction systems of the “strain S12-goethite” and the “strain S12-AQS” were used to investigate the dynamics of goethite reduction and AQS redox transformation. Results show that the concentrations of goethite and redox mediator, and the inoculation cell density all affect the characteristics of microbial goethite reduction, kinetic transformation between oxidized and reduced species of themore » redox mediator. Both abiotic and biotic reactions and their coupling regulate the kinetic process for “Quinone-Iron” interaction in the presence of DIRB. Our results provide some new insights into the characteristics and mechanisms of interaction among “quinone-DIRB- goethite” under biotic/abiotic driven.« less

Dissecting Redox Biology Using Fluorescent Protein Sensors.

PubMed

Schwarzländer, Markus; Dick, Tobias P; Meyer, Andreas J; Morgan, Bruce

2016-05-01

Fluorescent protein sensors have revitalized the field of redox biology by revolutionizing the study of redox processes in living cells and organisms. Within one decade, a set of fundamental new insights has been gained, driven by the rapid technical development of in vivo redox sensing. Redox-sensitive yellow and green fluorescent protein variants (rxYFP and roGFPs) have been the central players. Although widely used as an established standard tool, important questions remain surrounding their meaningful use in vivo. We review the growing range of thiol redox sensor variants and their application in different cells, tissues, and organisms. We highlight five key findings where in vivo sensing has been instrumental in changing our understanding of redox biology, critically assess the interpretation of in vivo redox data, and discuss technical and biological limitations of current redox sensors and sensing approaches. We explore how novel sensor variants may further add to the current momentum toward a novel mechanistic and integrated understanding of redox biology in vivo. Antioxid. Redox Signal. 24, 680-712.

Redox reaction characteristics of riboflavin: a fluorescence spectroelectrochemical analysis and density functional theory calculation.

PubMed

Chen, Wei; Chen, Jie-Jie; Lu, Rui; Qian, Chen; Li, Wen-Wei; Yu, Han-Qing

2014-08-01

Riboflavin (RF), the primary redox active component of flavin, is involved in many redox processes in biogeochemical systems. Despite of its wide distribution and important roles in environmental remediation, its redox behaviors and reaction mechanisms in hydrophobic sites remain unclear yet. In this study, spectroelectrochemical analysis and density functional theory (DFT) calculation were integrated to explore the redox behaviors of RF in dimethyl sulfoxide (DMSO), which was used to create a hydrophobic environment. Specifically, cyclic voltafluorometry (CVF) and derivative cyclic voltafluorometry (DCVF) were employed to track the RF concentration changing profiles. It was found that the reduction contained a series of proton-coupled electron transfers dependent of potential driving force. In addition to the electron transfer-chemical reaction-electron transfer process, a disproportionation (DISP1) process was also identified to be involved in the reduction. The redox potential and free energy of each step obtained from the DFT calculations further confirmed the mechanisms proposed based on the experimental results. The combination of experimental and theoretical approaches yields a deep insight into the characteristics of RF in environmental remediation and better understanding about the proton-coupled electron transfer mechanisms. Copyright © 2014 Elsevier B.V. All rights reserved.

Visualizing redox orbitals and their potentials in advanced lithium-ion battery materials using high-resolution x-ray Compton scattering

PubMed Central

Hafiz, Hasnain; Suzuki, Kosuke; Barbiellini, Bernardo; Orikasa, Yuki; Callewaert, Vincent; Kaprzyk, Staszek; Itou, Masayoshi; Yamamoto, Kentaro; Yamada, Ryota; Uchimoto, Yoshiharu; Sakurai, Yoshiharu; Sakurai, Hiroshi; Bansil, Arun

2017-01-01

Reduction-oxidation (redox) reactions are the key processes that underlie the batteries powering smartphones, laptops, and electric cars. A redox process involves transfer of electrons between two species. For example, in a lithium-ion battery, current is generated when conduction electrons from the lithium anode are transferred to the redox orbitals of the cathode material. The ability to visualize or image the redox orbitals and how these orbitals evolve under lithiation and delithiation processes is thus of great fundamental and practical interest for understanding the workings of battery materials. We show that inelastic scattering spectroscopy using high-energy x-ray photons (Compton scattering) can yield faithful momentum space images of the redox orbitals by considering lithium iron phosphate (LiFePO4 or LFP) as an exemplar cathode battery material. Our analysis reveals a new link between voltage and the localization of transition metal 3d orbitals and provides insight into the puzzling mechanism of potential shift and how it is connected to the modification of the bond between the transition metal and oxygen atoms. Our study thus opens a novel spectroscopic pathway for improving the performance of battery materials. PMID:28845452

Visualizing redox orbitals and their potentials in advanced lithium-ion battery materials using high-resolution x-ray Compton scattering.

PubMed

Hafiz, Hasnain; Suzuki, Kosuke; Barbiellini, Bernardo; Orikasa, Yuki; Callewaert, Vincent; Kaprzyk, Staszek; Itou, Masayoshi; Yamamoto, Kentaro; Yamada, Ryota; Uchimoto, Yoshiharu; Sakurai, Yoshiharu; Sakurai, Hiroshi; Bansil, Arun

2017-08-01

Reduction-oxidation (redox) reactions are the key processes that underlie the batteries powering smartphones, laptops, and electric cars. A redox process involves transfer of electrons between two species. For example, in a lithium-ion battery, current is generated when conduction electrons from the lithium anode are transferred to the redox orbitals of the cathode material. The ability to visualize or image the redox orbitals and how these orbitals evolve under lithiation and delithiation processes is thus of great fundamental and practical interest for understanding the workings of battery materials. We show that inelastic scattering spectroscopy using high-energy x-ray photons (Compton scattering) can yield faithful momentum space images of the redox orbitals by considering lithium iron phosphate (LiFePO 4 or LFP) as an exemplar cathode battery material. Our analysis reveals a new link between voltage and the localization of transition metal 3d orbitals and provides insight into the puzzling mechanism of potential shift and how it is connected to the modification of the bond between the transition metal and oxygen atoms. Our study thus opens a novel spectroscopic pathway for improving the performance of battery materials.

Antioxidants as therapeutics in the intensive care unit: Have we ticked the redox boxes?

PubMed

Margaritelis, Nikos V

2016-09-01

Critically ill patients are under oxidative stress and antioxidant administration reasonably emerged as a promising approach to combat the aberrant redox homeostasis in this patient cohort. However, the results of the antioxidant treatments in the intensive care unit are conflicting and inconclusive. The main objective of the present review is to highlight some inherent, yet widely overlooked redox-related issues about the equivocal effectiveness of antioxidants in the intensive care unit, beyond methodological considerations. In particular, the discrepancy in the literature partially stems from: (1) the largely unspecified role of reactive species in disease onset and progression, (2) our fragmentary understanding on the interplay between inflammation and oxidative stress, (3) the complex spatiotemporal specificity of in vivo redox biology, (4) the pleiotropic effects of antioxidants and (5) the divergent effects of antioxidants according to the temporal administration pattern. In addition, two novel and sophisticated practices with promising pre-clinical results are presented: (1) the selective neutralization of reactive species in key organelles after they are formed (i.e., in mitochondria) and (2) the targeted complete inhibition of dominant reactive species sources (i.e., NADPH oxidases). Finally, the reductive potential of NADPH as a key pharmacological target for redox therapies is rationalized. In light of the above, the recontextualization of knowledge from basic redox biology to translational medicine seems imperative to perform more realistic in vivo studies in the fast-growing field of critical care pharmacology. Copyright © 2016 Elsevier Ltd. All rights reserved.

Redox equilibria in hydroxylamine oxidoreductase. Electrostatic control of electron redistribution in multielectron oxidative processes.

PubMed

Kurnikov, Igor V; Ratner, Mark A; Pacheco, A Andrew

2005-02-15

We report results of continuum electrostatics calculations of the cofactor redox potentials, and of the titratable group pK(a) values, in hydroxylamine oxidoreductase (HAO). A picture of a sophisticated multicomponent control of electron flow in the protein emerged from the studies. First, we found that neighboring heme cofactors strongly interact electrostatically, with energies of 50-100 mV. Thus, cofactor redox potentials depend on the oxidation state of other cofactors, and cofactor redox potentials in the active (partially oxidized) enzyme differ substantially from the values obtained in electrochemical redox titration experiments. We found that, together, solvent-exposed heme 1 (having a large negative redox potential) and heme 2 (having a large positive redox potential) form a lock for electrons generated during the oxidation reaction The attachment of HAO's physiological electron transfer partner cytochrome c(554) results in a positive shift in the redox potential of heme 1, and "opens the electron gate". Electrons generated as a result of hydroxylamine oxidation travel to heme 3 and heme 8, which have redox potentials close to 0 mV versus NHE (this result is in partial disagreement with an existing experimental redox potential assignment). The closeness of hemes 3 and 8 from different enzyme subunits allows redistribution of the four electrons generated as a result of hydroxylamine oxidation, among the three enzyme subunits. For the multielectron oxidation process to be maximally efficient, the redox potentials of the electron-accepting cofactors should be roughly equal, and electrostatic interactions between extra electrons on these cofactors should be minimal. The redox potential assignments presented in the paper satisfy this general rule.

Redox Signaling Mechanisms in Nervous System Development.

PubMed

Olguín-Albuerne, Mauricio; Morán, Julio

2018-06-20

Numerous studies have demonstrated the actions of reactive oxygen species (ROS) as regulators of several physiological processes. In this study, we discuss how redox signaling mechanisms operate to control different processes such as neuronal differentiation, oligodendrocyte differentiation, dendritic growth, and axonal growth. Recent Advances: Redox homeostasis regulates the physiology of neural stem cells (NSCs). Notably, the neuronal differentiation process of NSCs is determined by a change toward oxidative metabolism, increased levels of mitochondrial ROS, increased activity of NADPH oxidase (NOX) enzymes, decreased levels of Nrf2, and differential regulation of different redoxins. Furthermore, during the neuronal maturation processes, NOX and MICAL produce ROS to regulate cytoskeletal dynamics, which control the dendritic and axonal growth, as well as the axonal guidance. The redox homeostasis changes are, in part, attributed to cell metabolism and compartmentalized production of ROS, which is regulated, sensed, and transduced by different molecules such as thioredoxins, glutaredoxins, peroxiredoxins, and nucleoredoxin to control different signaling pathways in different subcellular regions. The study of how these elements cooperatively act is essential for the understanding of nervous system development, as well as the application of regenerative therapies that recapitulate these processes. The information about these topics in the last two decades leads us to the conclusion that the role of ROS signaling in development of the nervous system is more important than it was previously believed and makes clear the importance of exploring in more detail the mechanisms of redox signaling. Antioxid. Redox Signal. 28, 1603-1625.

The fairytale of the GSSG/GSH redox potential.

PubMed

Flohé, Leopold

2013-05-01

The term GSSG/GSH redox potential is frequently used to explain redox regulation and other biological processes. The relevance of the GSSG/GSH redox potential as driving force of biological processes is critically discussed. It is recalled that the concentration ratio of GSSG and GSH reflects little else than a steady state, which overwhelmingly results from fast enzymatic processes utilizing, degrading or regenerating GSH. A biological GSSG/GSH redox potential, as calculated by the Nernst equation, is a deduced electrochemical parameter based on direct measurements of GSH and GSSG that are often complicated by poorly substantiated assumptions. It is considered irrelevant to the steering of any biological process. GSH-utilizing enzymes depend on the concentration of GSH, not on [GSH](2), as is predicted by the Nernst equation, and are typically not affected by GSSG. Regulatory processes involving oxidants and GSH are considered to make use of mechanistic principles known for thiol peroxidases which catalyze the oxidation of hydroperoxides by GSH by means of an enzyme substitution mechanism involving only bimolecular reaction steps. The negligibly small rate constants of related spontaneous reactions as compared with enzyme-catalyzed ones underscore the superiority of kinetic parameters over electrochemical or thermodynamic ones for an in-depth understanding of GSH-dependent biological phenomena. At best, the GSSG/GSH potential might be useful as an analytical tool to disclose disturbances in redox metabolism. This article is part of a Special Issue entitled Cellular Functions of Glutathione. Copyright © 2012 Elsevier B.V. All rights reserved.

Redox Regulation of Neuronal Voltage-Gated Calcium Channels

PubMed Central

Jevtovic-Todorovic, Vesna

2014-01-01

Abstract Significance: Voltage-gated calcium channels are ubiquitously expressed in neurons and are key regulators of cellular excitability and synaptic transmitter release. There is accumulating evidence that multiple subtypes of voltage-gated calcium channels may be regulated by oxidation and reduction. However, the redox mechanisms involved in the regulation of channel function are not well understood. Recent Advances: Several studies have established that both T-type and high-voltage-activated subtypes of voltage-gated calcium channel can be redox-regulated. This article reviews different mechanisms that can be involved in redox regulation of calcium channel function and their implication in neuronal function, particularly in pain pathways and thalamic oscillation. Critical Issues: A current critical issue in the field is to decipher precise mechanisms of calcium channel modulation via redox reactions. In this review we discuss covalent post-translational modification via oxidation of cysteine molecules and chelation of trace metals, and reactions involving nitric oxide-related molecules and free radicals. Improved understanding of the roles of redox-based reactions in regulation of voltage-gated calcium channels may lead to improved understanding of novel redox mechanisms in physiological and pathological processes. Future Directions: Identification of redox mechanisms and sites on voltage-gated calcium channel may allow development of novel and specific ion channel therapies for unmet medical needs. Thus, it may be possible to regulate the redox state of these channels in treatment of pathological process such as epilepsy and neuropathic pain. Antioxid. Redox Signal. 21, 880–891. PMID:24161125

Metabolic Control of Redox and Redox Control of Metabolism in Plants

PubMed Central

Fernie, Alisdair R.

2014-01-01

Abstract Significance: Reduction-oxidation (Redox) status operates as a major integrator of subcellular and extracellular metabolism and is simultaneously itself regulated by metabolic processes. Redox status not only dominates cellular metabolism due to the prominence of NAD(H) and NADP(H) couples in myriad metabolic reactions but also acts as an effective signal that informs the cell of the prevailing environmental conditions. After relay of this information, the cell is able to appropriately respond via a range of mechanisms, including directly affecting cellular functioning and reprogramming nuclear gene expression. Recent Advances: The facile accession of Arabidopsis knockout mutants alongside the adoption of broad-scale post-genomic approaches, which are able to provide transcriptomic-, proteomic-, and metabolomic-level information alongside traditional biochemical and emerging cell biological techniques, has dramatically advanced our understanding of redox status control. This review summarizes redox status control of metabolism and the metabolic control of redox status at both cellular and subcellular levels. Critical Issues: It is becoming apparent that plastid, mitochondria, and peroxisome functions influence a wide range of processes outside of the organelles themselves. While knowledge of the network of metabolic pathways and their intraorganellar redox status regulation has increased in the last years, little is known about the interorganellar redox signals coordinating these networks. A current challenge is, therefore, synthesizing our knowledge and planning experiments that tackle redox status regulation at both inter- and intracellular levels. Future Directions: Emerging tools are enabling ever-increasing spatiotemporal resolution of metabolism and imaging of redox status components. Broader application of these tools will likely greatly enhance our understanding of the interplay of redox status and metabolism as well as elucidating and characterizing signaling features thereof. We propose that such information will enable us to dissect the regulatory hierarchies that mediate the strict coupling of metabolism and redox status which, ultimately, determine plant growth and development. Antioxid. Redox Signal. 21, 1389–1421. PMID:24960279

Redox regulation of neuronal voltage-gated calcium channels.

PubMed

Todorovic, Slobodan M; Jevtovic-Todorovic, Vesna

2014-08-20

Voltage-gated calcium channels are ubiquitously expressed in neurons and are key regulators of cellular excitability and synaptic transmitter release. There is accumulating evidence that multiple subtypes of voltage-gated calcium channels may be regulated by oxidation and reduction. However, the redox mechanisms involved in the regulation of channel function are not well understood. Several studies have established that both T-type and high-voltage-activated subtypes of voltage-gated calcium channel can be redox-regulated. This article reviews different mechanisms that can be involved in redox regulation of calcium channel function and their implication in neuronal function, particularly in pain pathways and thalamic oscillation. A current critical issue in the field is to decipher precise mechanisms of calcium channel modulation via redox reactions. In this review we discuss covalent post-translational modification via oxidation of cysteine molecules and chelation of trace metals, and reactions involving nitric oxide-related molecules and free radicals. Improved understanding of the roles of redox-based reactions in regulation of voltage-gated calcium channels may lead to improved understanding of novel redox mechanisms in physiological and pathological processes. Identification of redox mechanisms and sites on voltage-gated calcium channel may allow development of novel and specific ion channel therapies for unmet medical needs. Thus, it may be possible to regulate the redox state of these channels in treatment of pathological process such as epilepsy and neuropathic pain.

Mitochondrial redox and pH signaling occurs in axonal and synaptic organelle clusters.

PubMed

Breckwoldt, Michael O; Armoundas, Antonis A; Aon, Miguel A; Bendszus, Martin; O'Rourke, Brian; Schwarzländer, Markus; Dick, Tobias P; Kurz, Felix T

2016-03-22

Redox switches are important mediators in neoplastic, cardiovascular and neurological disorders. We recently identified spontaneous redox signals in neurons at the single mitochondrion level where transients of glutathione oxidation go along with shortening and re-elongation of the organelle. We now have developed advanced image and signal-processing methods to re-assess and extend previously obtained data. Here we analyze redox and pH signals of entire mitochondrial populations. In total, we quantified the effects of 628 redox and pH events in 1797 mitochondria from intercostal axons and neuromuscular synapses using optical sensors (mito-Grx1-roGFP2; mito-SypHer). We show that neuronal mitochondria can undergo multiple redox cycles exhibiting markedly different signal characteristics compared to single redox events. Redox and pH events occur more often in mitochondrial clusters (medium cluster size: 34.1 ± 4.8 μm(2)). Local clusters possess higher mitochondrial densities than the rest of the axon, suggesting morphological and functional inter-mitochondrial coupling. We find that cluster formation is redox sensitive and can be blocked by the antioxidant MitoQ. In a nerve crush paradigm, mitochondrial clusters form sequentially adjacent to the lesion site and oxidation spreads between mitochondria. Our methodology combines optical bioenergetics and advanced signal processing and allows quantitative assessment of entire mitochondrial populations.

Kinetics of steel slag leaching: Batch tests and modeling

DOE Office of Scientific and Technical Information (OSTI.GOV)

De Windt, Laurent, E-mail: laurent.dewindt@mines-paristech.fr; Chaurand, Perrine; Rose, Jerome

2011-02-15

Reusing steel slag as an aggregate for road construction requires to characterize the leaching kinetics and metal releases. In this study, basic oxygen furnace (BOF) steel slag were subjected to batch leaching tests at liquid to solid ratios (L/S) of 10 and 100 over 30 days; the leachate chemistry being regularly sampled in time. A geochemical model of the steel slag is developed and validated from experimental data, particularly the evolution with leaching of mineralogical composition of the slag and trace element speciation. Kinetics is necessary for modeling the primary phase leaching, whereas a simple thermodynamic equilibrium approach can bemore » used for secondary phase precipitation. The proposed model simulates the kinetically-controlled dissolution (hydrolysis) of primary phases, the precipitation of secondary phases (C-S-H, hydroxide and spinel), the pH and redox conditions, and the progressive release of major elements as well as the metals Cr and V. Modeling indicates that the dilution effect of the L/S ratio is often coupled to solubility-controlled processes, which are sensitive to both the pH and the redox potential. A sensitivity analysis of kinetic uncertainties on the modeling of element releases is performed.« less

Understanding performance limitation and suppression of leakage current or self-discharge in electrochemical capacitors: a review.

PubMed

Ike, Innocent S; Sigalas, Iakovos; Iyuke, Sunny

2016-01-14

Self-discharge is known to have considerable adverse effects on the performance and application of electrochemical capacitors (ECs). Thus, obtaining an understanding of EC self-discharge mechanism(s) and subsequent derivation and solution of EC models, subject to a particular mechanism or combination of mechanisms during charging, discharging and storage of the device, is the only way to solve problems associated with EC self-discharge. In this review, we summarize recent progress with respect to EC self-discharge by considering the two basic types, electric double-layer capacitors (EDLC) and pseudocapacitors, and their hybrids with their respective charge storage mechanisms, distinguishable self-discharge mechanisms, charge redistribution and charge/energy loss during self-discharge. It was clearly observed that most of the voltage reduction is not purely due to the self-discharge effect but is basically due to redistribution of charge carriers deep inside pores and can therefore be retrieved from a capacitor during long-time discharging. Tuning the self-discharge rate is therefore feasible for single-walled carbon nanotube (SWNT) ECs and can be achieved by simply adjusting the surface chemistry of the nanotubes. The effects of surface chemistry modification on EC self-discharge are very important in studying and suppressing the self-discharge process and will benefit potential applications of ECs with respect to energy retention. Self-discharge can be averted by the use of redox couples that are transformed to insoluble species via electrolysis and adsorbed onto the activated carbon electrode in redox-couple EDLCs, thus transforming the EDLC electrolyte into a material that can store charge. Self-discharge in ECs can also be successfully suppressed by utilizing an ion-interchange layer (ion-exchange membrane), separator or CuSO4 mobile electrolyte that can be converted into an insoluble species by electrolysis during the charge/discharge process. This will help in producing a modern-day blueprint for ECs with high capacitance and improved energy sustainability.

Information processing through a bio-based redox capacitor: signatures for redox-cycling.

PubMed

Liu, Yi; Kim, Eunkyoung; White, Ian M; Bentley, William E; Payne, Gregory F

2014-08-01

Redox-cycling compounds can significantly impact biological systems and can be responsible for activities that range from pathogen virulence and contaminant toxicities, to therapeutic drug mechanisms. Current methods to identify redox-cycling activities rely on the generation of reactive oxygen species (ROS), and employ enzymatic or chemical methods to detect ROS. Here, we couple the speed and sensitivity of electrochemistry with the molecular-electronic properties of a bio-based redox-capacitor to generate signatures of redox-cycling. The redox capacitor film is electrochemically-fabricated at the electrode surface and is composed of a polysaccharide hydrogel with grafted catechol moieties. This capacitor film is redox-active but non-conducting and can engage diffusible compounds in either oxidative or reductive redox-cycling. Using standard electrochemical mediators ferrocene dimethanol (Fc) and Ru(NH3)6Cl3 (Ru(3+)) as model redox-cyclers, we observed signal amplifications and rectifications that serve as signatures of redox-cycling. Three bio-relevant compounds were then probed for these signatures: (i) ascorbate, a redox-active compound that does not redox-cycle; (ii) pyocyanin, a virulence factor well-known for its reductive redox-cycling; and (iii) acetaminophen, an analgesic that oxidatively redox-cycles but also undergoes conjugation reactions. These studies demonstrate that the redox-capacitor can enlist the capabilities of electrochemistry to generate rapid and sensitive signatures of biologically-relevant chemical activities (i.e., redox-cycling). Published by Elsevier B.V.

Fundamental Chemical Kinetic And Thermodynamic Data For Purex Process Models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taylor, R.J.; Fox, O.D.; Sarsfield, M.J.

2007-07-01

To support either the continued operations of current reprocessing plants or the development of future fuel processing using hydrometallurgical processes, such as Advanced Purex or UREX type flowsheets, the accurate simulation of Purex solvent extraction is required. In recent years we have developed advanced process modeling capabilities that utilize modern software platforms such as Aspen Custom Modeler and can be run in steady state and dynamic simulations. However, such advanced models of the Purex process require a wide range of fundamental data including all relevant basic chemical kinetic and thermodynamic data for the major species present in the process. Thismore » paper will summarize some of these recent process chemistry studies that underpin our simulation, design and testing of Purex solvent extraction flowsheets. Whilst much kinetic data for actinide redox reactions in nitric acid exists in the literature, the data on reactions in the diluted TBP solvent phase is much rarer. This inhibits the accurate modelization of the Purex process particularly when species show a significant extractability in to the solvent phase or when cycling between solvent and aqueous phases occurs, for example in the reductive stripping of Pu(IV) by ferrous sulfamate in the Magnox reprocessing plant. To support current oxide reprocessing, we have investigated a range of solvent phase reactions: - U(IV)+HNO{sub 3}; - U(IV)+HNO{sub 2}; - U(IV)+HNO{sub 3} (Pu catalysis); - U(IV)+HNO{sub 3} (Tc catalysis); - U(IV)+ Np(VI); - U(IV)+Np(V); - Np(IV)+HNO{sub 3}; - Np(V)+Np(V); Rate equations have been determined for all these reactions and kinetic rate constants and activation energies are now available. Specific features of these reactions in the TBP phase include the roles of water and hydrolyzed intermediates in the reaction mechanisms. In reactions involving Np(V), cation-cation complex formation, which is much more favourable in TBP than in HNO{sub 3}, also occurs and complicates the redox chemistry. Whilst some features of the redox chemistry in TBP appear similar to the corresponding reactions in aqueous HNO{sub 3}, there are notable differences in rates, the forms of the rate equations and mechanisms. Secondly, to underpin the development of advanced single cycle flowsheets using the complexant aceto-hydroxamic acid, we have also characterised in some detail its redox chemistry and solvent extraction behaviour with both Np and Pu ions. We find that simple hydroxamic acids are remarkably rapid reducing agents for Np(VI). They also reduce Pu(VI) and cause a much slower reduction of Pu(IV) through a complex mechanism involving acid hydrolysis of the ligand. AHA is a strong hydrophilic and selective complexant for the tetravalent actinide ions as evidenced by stability constant and solvent extraction data for An(IV), M(III) and U(VI) ions. This has allowed the successful design of U/Pu+Np separation flowsheets suitable for advanced fuel cycles. (authors)« less

Managing the cellular redox hub in photosynthetic organisms.

PubMed

Foyer, Christine H; Noctor, Graham

2012-02-01

Light-driven redox chemistry is a powerful source of redox signals that has a decisive input into transcriptional control within the cell nucleus. Like photosynthetic electron transport pathways, the respiratory electron transport chain exerts a profound control over gene function, in order to balance energy (reductant and ATP) supply with demand, while preventing excessive over-reduction or over-oxidation that would be adversely affect metabolism. Photosynthetic and respiratory redox chemistries are not merely housekeeping processes but they exert a controlling influence over every aspect of plant biology, participating in the control of gene transcription and translation, post-translational modifications and the regulation of assimilatory reactions, assimilate partitioning and export. The number of processes influenced by redox controls and signals continues to increase as do the components that are recognized participants in the associated signalling pathways. A step change in our understanding of the overall importance of the cellular redox hub to plant cells has occurred in recent years as the complexity of the management of the cellular redox hub in relation to metabolic triggers and environmental cues has been elucidated. This special issue describes aspects of redox regulation and signalling at the cutting edge of current research in this dynamic and rapidly expanding field. © 2011 Blackwell Publishing Ltd.

[Redox Molecular Imaging Using ReMI].

PubMed

Hyodo, Fuminori; Ito, Shinji; Utsumi, Hideo

2015-01-01

Tissue redox status is one of the most important parameters to maintain homeostasis in the living body. Numerous redox reactions are involved in metabolic processes, such as energy production in the mitochondrial electron transfer system. A variety of intracellular molecules such as reactive oxygen species, glutathione, thioredoxins, NADPH, flavins, and ascorbic acid may contribute to the overall redox status in tissues. Breakdown of redox balance may lead to oxidative stress and can induce many pathological conditions such as cancer, neurological disorders, and aging. Therefore imaging of tissue redox status and monitoring antioxidant levels in living organisms can be useful in the diagnosis of disease states and assessment of treatment response. In vivo redox molecular imaging technology such as electron spin resonance imaging (ESRI), magnetic resonance imaging (MRI), and dynamic nuclear polarization (DNP)-MRI (redox molecular imaging; ReMI) is emerging as a viable redox status imaging modality. This review focuses on the application of magnetic resonance technologies using MRI or DNP-MRI and redox-sensitive contrast agents.

Redox Proteomics in Selected Neurodegenerative Disorders: From Its Infancy to Future Applications

PubMed Central

Perluigi, Marzia; Reed, Tanea; Muharib, Tasneem; Hughes, Christopher P.; Robinson, Renã A.S.; Sultana, Rukhsana

2012-01-01

Abstract Several studies demonstrated that oxidative damage is a characteristic feature of many neurodegenerative diseases. The accumulation of oxidatively modified proteins may disrupt cellular functions by affecting protein expression, protein turnover, cell signaling, and induction of apoptosis and necrosis, suggesting that protein oxidation could have both physiological and pathological significance. For nearly two decades, our laboratory focused particular attention on studying oxidative damage of proteins and how their chemical modifications induced by reactive oxygen species/reactive nitrogen species correlate with pathology, biochemical alterations, and clinical presentations of Alzheimer's disease. This comprehensive article outlines basic knowledge of oxidative modification of proteins and lipids, followed by the principles of redox proteomics analysis, which also involve recent advances of mass spectrometry technology, and its application to selected age-related neurodegenerative diseases. Redox proteomics results obtained in different diseases and animal models thereof may provide new insights into the main mechanisms involved in the pathogenesis and progression of oxidative-stress-related neurodegenerative disorders. Redox proteomics can be considered a multifaceted approach that has the potential to provide insights into the molecular mechanisms of a disease, to find disease markers, as well as to identify potential targets for drug therapy. Considering the importance of a better understanding of the cause/effect of protein dysfunction in the pathogenesis and progression of neurodegenerative disorders, this article provides an overview of the intrinsic power of the redox proteomics approach together with the most significant results obtained by our laboratory and others during almost 10 years of research on neurodegenerative disorders since we initiated the field of redox proteomics. Antioxid. Redox Signal. 17, 1610–1655. PMID:22115501

Acetylacetone as an efficient electron shuttle for concerted redox conversion of arsenite and nitrate in the opposite direction.

PubMed

Chen, Zhihao; Song, Xiaojie; Zhang, Shujuan; Wu, Bingdang; Zhang, Guoyang; Pan, Bingcai

2017-11-01

The redox conversion of arsenite and nitrate has direct effects on their potential environment risks. Due to the similar reduction potentials, there are few technologies that can simultaneously oxidize arsenite and reduce nitrate in one process. Here, we demonstrate that a diketone-mediated photochemical process could efficiently do this. A combined experimental and theoretical investigation was conducted to elucidate the mechanisms behind the redox conversion in the UV/acetylacetone (AA) process. Our key finding is that UV irradiation significantly changed the redox potential of AA. The excited AA, 3 (AA)*, acted as a semiquinone radical-like electron shuttle. For arsenite oxidation, the efficiency of 3 (AA)* was 1-2 orders of magnitude higher than those of quinone-type electron shuttles, whereas the consumption of AA was 2-4 orders of magnitude less than those of benzonquinones. The oxidation of arsenite and reduction of nitrate could be both accelerated when they existed together in UV/AA process. The results indicate that small diketones are some neglected but potent electron shuttles of great application potential in regulating aquatic redox reactions with the combination of UV irradiation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Electrochemical Study and Determination of Electroactive Species with Screen-Printed Electrodes

ERIC Educational Resources Information Center

Martín-Yerga, Daniel; Costa Rama, Estefanía; Costa García, Agustín

2016-01-01

A lab appropriate to introduce voltammetric techniques and basic electrochemical parameters is described in this work. It is suitable to study theoretical concepts of electrochemistry in an applied way for analytical undergraduate courses. Two electroactive species, hexaammineruthenium and dopamine, are used as simple redox systems. Screen-printed…

Insights into the redox components of dissolved organic matters during stabilization process.

PubMed

Yuan, Ying; Xi, Bei-Dou; He, Xiao-Song; Ma, Yan; Zhang, Hui; Li, Dan; Zhao, Xin-Yu

2018-05-01

The changes of dissolved organic matter (DOM) components during stabilization process play significant effects on its redox properties but are little reported. Composting is a stabilization process of DOM, during which both the components and electron transfer capacities (ETCs) of DOM change. The redox components within compost-derived DOM during the stabilization process are investigated in this study. The results show that compost-derived DOM contained protein-like, fulvic-like, and humic-like components. The protein-like component decreases during composting, whereas the fulvic- and humic-like components increase during the process. The electron-donating capacity (EDC), electron-accepting capacity (EAC), and ETC of compost-derived DOM all increase during composting but their correlations with the components presented significant difference. The humic-like components were the main functional component responsible for both EDC and ETC, whereas the protein- and fluvic-like components show negative effects with the EAC, EDC, and ETC, suggesting that the components within DOM have specific redox properties during the stabilization process. These findings are very meaningful for better understanding the geochemical behaviors of DOM in the environment.

Concise Redox Deracemization of Secondary and Tertiary Amines with a Tetrahydroisoquinoline Core via a Nonenzymatic Process.

PubMed

Ji, Yue; Shi, Lei; Chen, Mu-Wang; Feng, Guang-Shou; Zhou, Yong-Gui

2015-08-26

A concise deracemization of racemic secondary and tertiary amines with a tetrahydroisoquinoline core has been successfully realized by orchestrating a redox process consisted of N-bromosuccinimide oxidation and iridum-catalyzed asymmetric hydrogenation. This compatible redox combination enables one-pot, single-operation deracemization to generate chiral 1-substituted 1,2,3,4-tetrahydroisoquinolines with up to 98% ee in 93% yield, offering a simple and scalable synthetic technique for chiral amines directly from racemic starting materials.

Probing biological redox chemistry with large amplitude Fourier transformed ac voltammetry

PubMed Central

Adamson, Hope

2017-01-01

Biological electron-exchange reactions are fundamental to life on earth. Redox reactions underpin respiration, photosynthesis, molecular biosynthesis, cell signalling and protein folding. Chemical, biomedical and future energy technology developments are also inspired by these natural electron transfer processes. Further developments in techniques and data analysis are required to gain a deeper understanding of the redox biochemistry processes that power Nature. This review outlines the new insights gained from developing Fourier transformed ac voltammetry as a tool for protein film electrochemistry. PMID:28804798

ARSENIC TRANSPORT AND FATE IN SULFIDIC ENVIRONMENTS: AS(III) - FES INTERACTIONS

EPA Science Inventory

Arsenic mobility in groundwater and retention in aquifer materials at contaminated sites is often linked to redox processes, especially iron and sulfur cycling at redox boundaries. Important processes include adsorption or co-precipitation reactions of arsenate, arsenite, or th...

Review on anionic redox for high-capacity lithium- and sodium-ion batteries

NASA Astrophysics Data System (ADS)

Zhao, Chenglong; Wang, Qidi; Lu, Yaxiang; Hu, Yong-Sheng; Li, Baohua; Chen, Liquan

2017-05-01

Rechargeable batteries, especially lithium-ion batteries, are now widely used as power sources for portable electronics and electric vehicles, but material innovations are still needed to satisfy the increasing demand for larger energy density. Recently, lithium- and sodium-rich electrode materials, including the A2MO3-family layered compounds (A  =  Li, Na; M  =  Mn4+, Ru4+, etc), have been extensively studied as potential high-capacity electrode materials for a cumulative cationic and anionic redox activity. Negatively charged oxide ions can potentially donate electrons to compensate for the absence of oxidable transition metals as a redox center to further increase the reversible capacity. Understanding and controlling the state-of-the-art anionic redox processes is pivotal for the design of advanced energy materials, highlighted in rechargeable batteries. Hence, experimental and theoretical approaches have been developed to consecutively study the diverting processes, states, and structures involved. In this review, we attempt to present a literature overview and provide insight into the reaction mechanism with respect to the anionic redox processes, proposing some opinions as target oriented. It is hoped that, through this discussion, the search for anionic redox electrode materials with high-capacity rechargeable batteries can be advanced, and practical applications realized as soon as possible.

Visualizing redox orbitals and their potentials in advanced lithium-ion battery materials using high-resolution x-ray Compton scattering

DOE PAGES

Hafiz, Hasnain; Suzuki, Kosuke; Barbiellini, Bernardo; ...

2017-08-02

Reduction-oxidation (redox) reactions are the key processes that underlie the batteries powering smartphones, laptops, and electric cars. A redox process involves transfer of electrons between two species. For example, in a lithium-ion battery, current is generated when conduction electrons from the lithium anode are transferred to the redox orbitals of the cathode material. The ability to visualize or image the redox orbitals and how these orbitals evolve under lithiation and delithiation processes is thus of great fundamental and practical interest for understanding the workings of battery materials. In this study, we show that inelastic scattering spectroscopy using high-energy x-ray photonsmore » (Compton scattering) can yield faithful momentum space images of the redox orbitals by considering lithium iron phosphate (LiFePO 4 or LFP) as an exemplar cathode battery material. Our analysis reveals a new link between voltage and the localization of transition metal 3d orbitals and provides insight into the puzzling mechanism of potential shift and how it is connected to the modification of the bond between the transition metal and oxygen atoms. Our study thus opens a novel spectroscopic pathway for improving the performance of battery materials.« less

Visualizing redox orbitals and their potentials in advanced lithium-ion battery materials using high-resolution x-ray Compton scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hafiz, Hasnain; Suzuki, Kosuke; Barbiellini, Bernardo

Reduction-oxidation (redox) reactions are the key processes that underlie the batteries powering smartphones, laptops, and electric cars. A redox process involves transfer of electrons between two species. For example, in a lithium-ion battery, current is generated when conduction electrons from the lithium anode are transferred to the redox orbitals of the cathode material. The ability to visualize or image the redox orbitals and how these orbitals evolve under lithiation and delithiation processes is thus of great fundamental and practical interest for understanding the workings of battery materials. In this study, we show that inelastic scattering spectroscopy using high-energy x-ray photonsmore » (Compton scattering) can yield faithful momentum space images of the redox orbitals by considering lithium iron phosphate (LiFePO 4 or LFP) as an exemplar cathode battery material. Our analysis reveals a new link between voltage and the localization of transition metal 3d orbitals and provides insight into the puzzling mechanism of potential shift and how it is connected to the modification of the bond between the transition metal and oxygen atoms. Our study thus opens a novel spectroscopic pathway for improving the performance of battery materials.« less

Membrane development for vanadium redox flow batteries.

PubMed

Schwenzer, Birgit; Zhang, Jianlu; Kim, Soowhan; Li, Liyu; Liu, Jun; Yang, Zhenguo

2011-10-17

Large-scale energy storage has become the main bottleneck for increasing the percentage of renewable energy in our electricity grids. Redox flow batteries are considered to be among the best options for electricity storage in the megawatt range and large demonstration systems have already been installed. Although the full technological potential of these systems has not been reached yet, currently the main problem hindering more widespread commercialization is the high cost of redox flow batteries. Nafion, as the preferred membrane material, is responsible for about 11% of the overall cost of a 1 MW/8 MWh system. Therefore, in recent years two main membrane related research threads have emerged: 1) chemical and physical modification of Nafion membranes to optimize their properties with regard to vanadium redox flow battery (VRFB) application; and 2) replacement of the Nafion membranes with different, less expensive materials. This review summarizes the underlying basic scientific issues associated with membrane use in VRFBs and presents an overview of membrane-related research approaches aimed at improving the efficiency of VRFBs and making the technology cost-competitive. Promising research strategies and materials are identified and suggestions are provided on how materials issues could be overcome.

Circadian Rhythm Connections to Oxidative Stress: Implications for Human Health

PubMed Central

Wilking, Melissa; Ndiaye, Mary; Mukhtar, Hasan

2013-01-01

Abstract Significance: Oxygen and circadian rhythmicity are essential in a myriad of physiological processes to maintain homeostasis, from blood pressure and sleep/wake cycles, down to cellular signaling pathways that play critical roles in health and disease. If the human body or cells experience significant stress, their ability to regulate internal systems, including redox levels and circadian rhythms, may become impaired. At cellular as well as organismal levels, impairment in redox regulation and circadian rhythms may lead to a number of adverse effects, including the manifestation of a variety of diseases such as heart diseases, neurodegenerative conditions, and cancer. Recent Advances: Researchers have come to an understanding as to the basics of the circadian rhythm mechanism, as well as the importance of the numerous species of oxidative stress components. The effects of oxidative stress and dysregulated circadian rhythms have been a subject of intense investigations since they were first discovered, and recent investigations into the molecular mechanisms linking the two have started to elucidate the bases of their connection. Critical Issues: While much is known about the mechanics and importance of oxidative stress systems and circadian rhythms, the front where they interact has had very little research focused on it. This review discusses the idea that these two systems are together intricately involved in the healthy body, as well as in disease. Future Directions: We believe that for a more efficacious management of diseases that have both circadian rhythm and oxidative stress components in their pathogenesis, targeting both systems in tandem would be far more successful. Antioxid. Redox Signal. 19, 192–208 PMID:23198849

Ultradian metronome: timekeeper for orchestration of cellular coherence.

PubMed

Lloyd, David; Murray, Douglas B

2005-07-01

Dynamic intracellular spatial and temporal organization emerges from spontaneous synchronization of a massive array of weakly coupled oscillators; the majority of subcellular processes are implicated in this integrated expression of cellular physiology. Evidence for this view comes mainly from studies of Saccharomyces cerevisiae growing in self-synchronized continuous cultures, in which a temperature-compensated ultradian clock (period of approximately 40 min) couples fermentation with redox state in addition to the transcriptome and cell-division-cycle progression. Functions for ultradian clocks have also been determined in other yeasts (e.g. Schizosaccharomyces pombe and Candida utilis), seven protists (e.g. Acanthamoeba castellanii and Paramecium tetraurelia), as well as cultured mammalian cells. We suggest that ultradian timekeeping is a basic universal necessity for coordinated intracellular coherence.

Regulation of autophagy by amino acid availability in S. cerevisiae and mammalian cells.

PubMed

Abeliovich, Hagai

2015-10-01

Autophagy is a catabolic membrane-trafficking process that occurs in all eukaryotic organisms analyzed to date. The study of autophagy has exploded over the last decade or so, branching into numerous aspects of cellular and organismal physiology. From basic functions in starvation and quality control, autophagy has expanded into innate immunity, aging, neurological diseases, redox regulation, and ciliogenesis, to name a few roles. In the present review, I would like to narrow the discussion to the more classical roles of autophagy in supporting viability under nutrient limitation. My aim is to provide a semblance of a historical overview, together with a concise, and perhaps subjective, mechanistic and functional analysis of the central questions in the autophagy field.

Reducing capacities and redox potentials of humic substances extracted from sewage sludge.

PubMed

Yang, Zhen; Du, Mengchan; Jiang, Jie

2016-02-01

Humic substances (HS) are redox active organic materials that can be extracted from sewage sludge generated in wastewater treatment processes. Due to the poor understanding of reducing capacity, redox potentials and redox active functional groups of HS in sewage sludge, the potential contribution of sludge HS in transformation of wastewater contaminants is unclear. In the present study, the number of electrons donated or accepted by sewage sludge HS were quantified before and after reduction by iron compounds that possess different redox potentials and defined as the reducing capacity of the sewage sludge. In contrast to previous studies of soil and commercial humic acids (HA), reduced sludge HA showed a lower reducing capacity than that of native HA, which implies formation of semiquinone radicals since the semiquinone radical/hydroquinone pair has a much higher redox potential than the quinone/hydroquinone pair. It is novel that reducing capacities of sludge HA were determined in the redox potential range from -314 to 430 mV. The formation of semiquinone radicals formed during the reduction of quinone moieties in sludge HA is shown by three-dimensional excitation/emission matrix fluorescence spectroscopies information, increasing fluorescence intensities and blue-shifting of the excitation/emission peak of reduced sludge HA. Knowledge of sludge HS redox potentials and corresponding reducing capacities makes it possible to predict the transformation of redox active pollutants and facilitate manipulation and optimization of sludge loading wastewater treatment processes. Copyright © 2015 Elsevier Ltd. All rights reserved.

Characterization of redox conditions in groundwater contaminant plumes

NASA Astrophysics Data System (ADS)

Christensen, Thomas H.; Bjerg, Poul L.; Banwart, Steven A.; Jakobsen, Rasmus; Heron, Gorm; Albrechtsen, Hans-Jørgen

2000-10-01

Evaluation of redox conditions in groundwater pollution plumes is often a prerequisite for understanding the behaviour of the pollutants in the plume and for selecting remediation approaches. Measuring of redox conditions in pollution plumes is, however, a fairly recent issue and yet relative few cases have been reported. No standardised or generally accepted approach exists. Slow electrode kinetics and the common lack of internal equilibrium of redox processes in pollution plumes make, with a few exceptions, direct electrochemical measurement and rigorous interpretation of redox potentials dubious, if not erroneous. Several other approaches have been used in addressing redox conditions in pollution plumes: redox-sensitive compounds in groundwater samples, hydrogen concentrations in groundwater, concentrations of volatile fatty acids in groundwater, sediment characteristics and microbial tools, such as MPN counts, PLFA biomarkers and redox bioassays. This paper reviews the principles behind the different approaches, summarizes methods used and evaluates the approaches based on the experience from the reported applications.

Unleashing the Power and Energy of LiFePO4-Based Redox Flow Lithium Battery with a Bifunctional Redox Mediator.

PubMed

Zhu, Yun Guang; Du, Yonghua; Jia, Chuankun; Zhou, Mingyue; Fan, Li; Wang, Xingzhu; Wang, Qing

2017-05-10

Redox flow batteries, despite great operation flexibility and scalability for large-scale energy storage, suffer from low energy density and relatively high cost as compared to the state-of-the-art Li-ion batteries. Here we report a redox flow lithium battery, which operates via the redox targeting reactions of LiFePO 4 with a bifunctional redox mediator, 2,3,5,6-tetramethyl-p-phenylenediamine, and presents superb energy density as the Li-ion battery and system flexibility as the redox flow battery. The battery has achieved a tank energy density as high as 1023 Wh/L, power density of 61 mW/cm 2 , and voltage efficiency of 91%. Operando X-ray absorption near-edge structure measurements were conducted to monitor the evolution of LiFePO 4 , which provides insightful information on the redox targeting process, critical to the device operation and optimization.

Online monitoring of Mezcal fermentation based on redox potential measurements.

PubMed

Escalante-Minakata, P; Ibarra-Junquera, V; Rosu, H C; De León-Rodríguez, A; González-García, R

2009-01-01

We describe an algorithm for the continuous monitoring of the biomass and ethanol concentrations as well as the growth rate in the Mezcal fermentation process. The algorithm performs its task having available only the online measurements of the redox potential. The procedure combines an artificial neural network (ANN) that relates the redox potential to the ethanol and biomass concentrations with a nonlinear observer-based algorithm that uses the ANN biomass estimations to infer the growth rate of this fermentation process. The results show that the redox potential is a valuable indicator of the metabolic activity of the microorganisms during Mezcal fermentation. In addition, the estimated growth rate can be considered as a direct evidence of the presence of mixed culture growth in the process. Usually, mixtures of microorganisms could be intuitively clear in this kind of processes; however, the total biomass data do not provide definite evidence by themselves. In this paper, the detailed design of the software sensor as well as its experimental application is presented at the laboratory level.

The rat closely mimics oxidative stress and inflammation in humans after exercise but not after exercise combined with vitamin C administration.

PubMed

Veskoukis, Aristidis S; Goutianos, Georgios; Paschalis, Vassilis; Margaritelis, Nikos V; Tzioura, Aikaterini; Dipla, Konstantina; Zafeiridis, Andreas; Vrabas, Ioannis S; Kyparos, Antonios; Nikolaidis, Michalis G

2016-04-01

The purpose of the present study was to directly compare oxidative stress and inflammation responses between rats and humans. We contrasted rat and human oxidative stress and inflammatory responses to exercise (pro-oxidant stimulus) and/or vitamin C (anti-oxidant stimulus) administration. Vitamin C was administered orally in both species (16 mg kg(-1) of body weight). Twelve redox biomarkers and seven inflammatory biomarkers were determined in plasma and erythrocytes pre- and post-exercise or pre- and post-exercise combined with vitamin C administration. Exercise increased oxidative stress and induced an inflammatory state in rats and humans. There were only 1/19 significant species × exercise interactions (catalase), indicating similar responses to exercise between rats and humans in redox and inflammatory biomarkers. Vitamin C decreased oxidative stress and increased antioxidant capacity only in humans and did not affect the redox state of rats. In contrast, vitamin C induced an anti-inflammatory state only in rats and did not affect the inflammatory state of humans. There were 10/19 significant species × vitamin C interactions, indicating that rats poorly mimic human oxidative stress and inflammatory responses to vitamin C administration. Exercise after acute vitamin C administration altered redox state only in humans and did not affect the redox state of rats. On the contrary, inflammation biomarkers changed similarly after exercise combined with vitamin C in both rats and humans. The rat adequately mimics human responses to exercise in basic blood redox/inflammatory profile, yet this is not the case after exercise combined with vitamin C administration.

Redox Conditions in Selected Principal Aquifers of the United States

USGS Publications Warehouse

McMahon, P.B.; Cowdery, T.K.; Chapelle, F.H.; Jurgens, B.C.

2009-01-01

Reduction/oxidation (redox) processes affect the quality of groundwater in all aquifer systems. Redox processes can alternately mobilize or immobilize potentially toxic metals associated with naturally occurring aquifer materials, contribute to the degradation or preservation of anthropogenic contami-nants, and generate undesirable byproducts, such as dissolved manganese (Mn2+), ferrous iron (Fe2+), hydrogen sulfide (H2S), and methane (CH4). Determining the kinds of redox processes that occur in an aquifer system, documenting their spatial distribution, and understanding how they affect concentrations of natural or anthropogenic contaminants are central to assessing and predicting the chemical quality of groundwater. This Fact Sheet extends the analysis of U.S. Geological Survey authors to additional principal aquifer systems by applying a framework developed by the USGS to a larger set of water-quality data from the USGS national water databases. For a detailed explanation, see the 'Introduction' in the Fact Sheet.

Thioredoxin-linked redox control of metabolism in Methanocaldococcus jannaschii, an evolutionarily deeply-rooted hyperthermophilic methanogenic archaeon

USDA-ARS?s Scientific Manuscript database

Thioredoxin (Trx), a small redox protein, controls multiple processes in eukaryotes and bacteria by changing the thiol redox status of selected proteins. We have investigated this aspect in methanarchaea. These ancient methanogens produce methane almost exclusively from H2 plus CO2 carried approxima...

Couplings

NASA Astrophysics Data System (ADS)

Stošić, Dušan; Auroux, Aline

Basic principles of calorimetry coupled with other techniques are introduced. These methods are used in heterogeneous catalysis for characterization of acidic, basic and red-ox properties of solid catalysts. Estimation of these features is achieved by monitoring the interaction of various probe molecules with the surface of such materials. Overview of gas phase, as well as liquid phase techniques is given. Special attention is devoted to coupled calorimetry-volumetry method. Furthermore, the influence of different experimental parameters on the results of these techniques is discussed, since it is known that they can significantly influence the evaluation of catalytic properties of investigated materials.

Quantitative measures for redox signaling.

PubMed

Pillay, Ché S; Eagling, Beatrice D; Driscoll, Scott R E; Rohwer, Johann M

2016-07-01

Redox signaling is now recognized as an important regulatory mechanism for a number of cellular processes including the antioxidant response, phosphokinase signal transduction and redox metabolism. While there has been considerable progress in identifying the cellular machinery involved in redox signaling, quantitative measures of redox signals have been lacking, limiting efforts aimed at understanding and comparing redox signaling under normoxic and pathogenic conditions. Here we have outlined some of the accepted principles for redox signaling, including the description of hydrogen peroxide as a signaling molecule and the role of kinetics in conferring specificity to these signaling events. Based on these principles, we then develop a working definition for redox signaling and review a number of quantitative methods that have been employed to describe signaling in other systems. Using computational modeling and published data, we show how time- and concentration- dependent analyses, in particular, could be used to quantitatively describe redox signaling and therefore provide important insights into the functional organization of redox networks. Finally, we consider some of the key challenges with implementing these methods. Copyright © 2016 Elsevier Inc. All rights reserved.

Basic Research in Plasma Medicine - A Throughput Approach from Liquids to Cells

PubMed Central

Bekeschus, Sander; Schmidt, Anke; Niessner, Felix; Gerling, Torsten; Weltmann, Klaus-Dieter; Wende, Kristian

2017-01-01

In plasma medicine, ionized gases with temperatures close to that of vertebrate systems are applied to cells and tissues. Cold plasmas generate reactive species known to redox regulate biological processes in health and disease. Pre-clinical and clinical evidence points to beneficial effects of plasma treatment in the healing of chronic ulcer of the skin. Other emerging topics, such as plasma cancer treatment, are receiving increasing attention. Plasma medical research requires interdisciplinary expertise in physics, chemistry, and biomedicine. One goal of plasma research is to characterize plasma-treated cells in a variety of specific applications. This includes, for example, cell count and viability, cellular oxidation, mitochondrial activity, cytotoxicity and mode of cell death, cell cycle analysis, cell surface marker expression, and cytokine release. This study describes the essential equipment and workflows required for such research in plasma biomedicine. It describes the proper operation of an atmospheric pressure argon plasma jet, specifically monitoring its basic emission spectra and feed gas settings to modulate reactive species output. Using a high-precision xyz-table and computer software, the jet is hovered in millisecond-precision over the cavities of 96-well plates in micrometer-precision for maximal reproducibility. Downstream assays for liquid analysis of redox-active molecules are shown, and target cells are plasma-treated. Specifically, melanoma cells are analyzed in an efficient sequence of different consecutive assays but using the same cells: measurement of metabolic activity, total cell area, and surface marker expression of calreticulin, a molecule important for the immunogenic cell death of cancer cells. These assays retrieve content-rich biological information about plasma effects from a single plate. Altogether, this study describes the essential steps and protocols for plasma medical research. PMID:29286412

Basic Research in Plasma Medicine - A Throughput Approach from Liquids to Cells.

PubMed

Bekeschus, Sander; Schmidt, Anke; Niessner, Felix; Gerling, Torsten; Weltmann, Klaus-Dieter; Wende, Kristian

2017-11-17

In plasma medicine, ionized gases with temperatures close to that of vertebrate systems are applied to cells and tissues. Cold plasmas generate reactive species known to redox regulate biological processes in health and disease. Pre-clinical and clinical evidence points to beneficial effects of plasma treatment in the healing of chronic ulcer of the skin. Other emerging topics, such as plasma cancer treatment, are receiving increasing attention. Plasma medical research requires interdisciplinary expertise in physics, chemistry, and biomedicine. One goal of plasma research is to characterize plasma-treated cells in a variety of specific applications. This includes, for example, cell count and viability, cellular oxidation, mitochondrial activity, cytotoxicity and mode of cell death, cell cycle analysis, cell surface marker expression, and cytokine release. This study describes the essential equipment and workflows required for such research in plasma biomedicine. It describes the proper operation of an atmospheric pressure argon plasma jet, specifically monitoring its basic emission spectra and feed gas settings to modulate reactive species output. Using a high-precision xyz-table and computer software, the jet is hovered in millisecond-precision over the cavities of 96-well plates in micrometer-precision for maximal reproducibility. Downstream assays for liquid analysis of redox-active molecules are shown, and target cells are plasma-treated. Specifically, melanoma cells are analyzed in an efficient sequence of different consecutive assays but using the same cells: measurement of metabolic activity, total cell area, and surface marker expression of calreticulin, a molecule important for the immunogenic cell death of cancer cells. These assays retrieve content-rich biological information about plasma effects from a single plate. Altogether, this study describes the essential steps and protocols for plasma medical research.

Synthetic Organic Electrochemistry: Calling All Engineers.

PubMed

Yan, Ming; Kawamata, Yu; Baran, Phil S

2018-04-09

Unmet potential: Electrochemistry is the most simple and basic way of altering the redox-states of organic molecules. Despite extensive studies and its demonstrated promise, it has yet to take off in mainstream synthesis. The reason is due to engineering challenges in instrument design. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Direct structural evidence of protein redox regulation obtained by in-cell NMR.

PubMed

Mercatelli, Eleonora; Barbieri, Letizia; Luchinat, Enrico; Banci, Lucia

2016-02-01

The redox properties of cellular environments are critical to many functional processes, and are strictly controlled in all living organisms. The glutathione-glutathione disulfide (GSH-GSSG) couple is the most abundant intracellular redox couple. A GSH redox potential can be calculated for each cellular compartment, which reflects the redox properties of that environment. This redox potential is often used to predict the redox state of a disulfide-containing protein, based on thermodynamic considerations. However, thiol-disulfide exchange reactions are often catalyzed by specific partners, and the distribution of the redox states of a protein may not correspond to the thermodynamic equilibrium with the GSH pool. Ideally, the protein redox state should be measured directly, bypassing the need to extrapolate from the GSH. Here, by in-cell NMR, we directly observe the redox state of three human proteins, Cox17, Mia40 and SOD1, in the cytoplasm of human and bacterial cells. We compare the observed distributions of redox states with those predicted by the GSH redox potential, and our results partially agree with the predictions. Discrepancies likely arise from the fact that the redox state of SOD1 is controlled by a specific partner, its copper chaperone (CCS), in a pathway which is not linked to the GSH redox potential. In principle, in-cell NMR allows determining whether redox proteins are at the equilibrium with GSH, or they are kinetically regulated. Such approach does not need assumptions on the redox potential of the environment, and provides a way to characterize each redox-regulating pathway separately. Copyright © 2015 Elsevier B.V. All rights reserved.

Intracellular antioxidants dissolve man-made antioxidant nanoparticles: using redox vulnerability of nanoceria to develop a responsive drug delivery system.

PubMed

Muhammad, Faheem; Wang, Aifei; Qi, Wenxiu; Zhang, Shixing; Zhu, Guangshan

2014-01-01

Regeneratable antioxidant property of nanoceria has widely been explored to minimize the deleterious influences of reactive oxygen species. Limited information is, however, available regarding the biological interactions and subsequent fate of nanoceria in body fluids. This study demonstrates a surprising dissolution of stable and ultrasmall (4 nm) cerium oxide nanoparticles (CeO2 NPs) in response to biologically prevalent antioxidant molecules (glutathione, vitamin C). Such a redox sensitive behavior of CeO2 NPs is subsequently exploited to design a redox responsive drug delivery system for transporting anticancer drug (camptothecin). Upon exposing the CeO2 capped and drug loaded nanoconstruct to vitamin c or glutathione, dissolution-accompanied aggregation of CeO2 nanolids unleashes the drug molecules from porous silica to achieve a significant anticancer activity. Besides stimuli responsive drug delivery, immobilization of nanoceria onto the surface of mesoporous silica also facilitates us to gain a basic insight into the biotransformation of CeO2 in physiological mediums.

Protein S-glutathionylation: from current basics to targeted modifications.

PubMed

Popov, Doina

2014-10-01

The interaction between antioxidant glutathione and the free thiol in susceptible cysteine residues of proteins leads to reversible protein S-glutathionylation. This reaction ensures cellular homeostasis control (as a common redox-dependent post-translational modification associated with signal transduction) and intervenes in oxidative stress-related cardiovascular pathology (as initiated by redox imbalance). The purpose of this review is to evaluate the recent knowledge on protein S-glutathionylation in terms of chemistry, broad cellular intervention, specific quantification, and potential for therapeutic exploitation. The data bases searched were Medline and PubMed, from 2009 to 2014 (term: glutathionylation). Protein S-glutathionylation ensures protection of protein thiols against irreversible over-oxidation, operates as a biological redox switch in both cell survival (influencing kinases and protein phosphatases pathways) and cell death (by potentiation of apoptosis), and cross-talks with phosphorylation and with S-nitrosylation. Collectively, protein S-glutathionylation appears as a valuable biomarker for oxidative stress, with potential for translation into novel therapeutic strategies.

The Deep Thioredoxome in Chlamydomonas reinhardtii: New Insights into Redox Regulation.

PubMed

Pérez-Pérez, María Esther; Mauriès, Adeline; Maes, Alexandre; Tourasse, Nicolas J; Hamon, Marion; Lemaire, Stéphane D; Marchand, Christophe H

2017-08-07

Thiol-based redox post-translational modifications have emerged as important mechanisms of signaling and regulation in all organisms, and thioredoxin plays a key role by controlling the thiol-disulfide status of target proteins. Recent redox proteomic studies revealed hundreds of proteins regulated by glutathionylation and nitrosylation in the unicellular green alga Chlamydomonas reinhardtii, while much less is known about the thioredoxin interactome in this organism. By combining qualitative and quantitative proteomic analyses, we have comprehensively investigated the Chlamydomonas thioredoxome and 1188 targets have been identified. They participate in a wide range of metabolic pathways and cellular processes. This study broadens not only the redox regulation to new enzymes involved in well-known thioredoxin-regulated metabolic pathways but also sheds light on cellular processes for which data supporting redox regulation are scarce (aromatic amino acid biosynthesis, nuclear transport, etc). Moreover, we characterized 1052 thioredoxin-dependent regulatory sites and showed that these data constitute a valuable resource for future functional studies in Chlamydomonas. By comparing this thioredoxome with proteomic data for glutathionylation and nitrosylation at the protein and cysteine levels, this work confirms the existence of a complex redox regulation network in Chlamydomonas and provides evidence of a tremendous selectivity of redox post-translational modifications for specific cysteine residues. Copyright © 2017 The Author. Published by Elsevier Inc. All rights reserved.

Intramolecular Redox-Mannich Reactions: Facile Access to the Tetrahydroprotoberberine Core.

PubMed

Ma, Longle; Seidel, Daniel

2015-09-07

Cyclic amines such as pyrrolidine undergo redox-annulations with 2-formylaryl malonates. Concurrent oxidative amine α-CH bond functionalization and reductive N-alkylation render this transformation redox-neutral. This redox-Mannich process provides regioisomers of classic Reinhoudt reaction products as an entry to the tetrahydroprotoberberine core, enabling the synthesis of (±)-thalictricavine and its epimer. An unusually mild amine-promoted dealkoxycarbonylation was discovered in the course of these studies. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Redox Biology in Neurological Function, Dysfunction, and Aging.

PubMed

Franco, Rodrigo; Vargas, Marcelo R

2018-04-23

Reduction oxidation (redox) reactions are central to life and when altered, they can promote disease progression. In the brain, redox homeostasis is recognized to be involved in all aspects of central nervous system (CNS) development, function, aging, and disease. Recent studies have uncovered the diverse nature by which redox reactions and homeostasis contribute to brain physiology, and when dysregulated to pathological consequences. Redox reactions go beyond what is commonly described as oxidative stress and involve redox mechanisms linked to signaling and metabolism. In contrast to the nonspecific nature of oxidative damage, redox signaling involves specific oxidation/reduction reactions that regulate a myriad of neurological processes such as neurotransmission, homeostasis, and degeneration. This Forum is focused on the role of redox metabolism and signaling in the brain. Six review articles from leading scientists in the field that appraise the role of redox metabolism and signaling in different aspects of brain biology including neurodevelopment, neurotransmission, aging, neuroinflammation, neurodegeneration, and neurotoxicity are included. An original research article exemplifying these concepts uncovers a novel link between oxidative modifications, redox signaling, and neurodegeneration. This Forum highlights the recent advances in the field and we hope it encourages future research aimed to understand the mechanisms by which redox metabolism and signaling regulate CNS physiology and pathophysiology. Antioxid. Redox Signal. 00, 000-000.

Neurotoxicity Linked to Dysfunctional Metal Ion Homeostasis and Xenobiotic Metal Exposure: Redox Signaling and Oxidative Stress.

PubMed

Garza-Lombó, Carla; Posadas, Yanahi; Quintanar, Liliana; Gonsebatt, María E; Franco, Rodrigo

2018-06-20

Essential metals such as copper, iron, manganese, and zinc play a role as cofactors in the activity of a wide range of processes involved in cellular homeostasis and survival, as well as during organ and tissue development. Throughout our life span, humans are also exposed to xenobiotic metals from natural and anthropogenic sources, including aluminum, arsenic, cadmium, lead, and mercury. It is well recognized that alterations in the homeostasis of essential metals and an increased environmental/occupational exposure to xenobiotic metals are linked to several neurological disorders, including neurodegeneration and neurodevelopmental alterations. Recent Advances: The redox activity of essential metals is key for neuronal homeostasis and brain function. Alterations in redox homeostasis and signaling are central to the pathological consequences of dysfunctional metal ion homeostasis and increased exposure to xenobiotic metals. Both redox-active and redox-inactive metals trigger oxidative stress and damage in the central nervous system, and the exact mechanisms involved are starting to become delineated. In this review, we aim to appraise the role of essential metals in determining the redox balance in the brain and the mechanisms by which alterations in the homeostasis of essential metals and exposure to xenobiotic metals disturb the cellular redox balance and signaling. We focus on recent literature regarding their transport, metabolism, and mechanisms of toxicity in neural systems. Delineating the specific mechanisms by which metals alter redox homeostasis is key to understand the pathological processes that convey chronic neuronal dysfunction in neurodegenerative and neurodevelopmental disorders. Antioxid. Redox Signal. 28, 1669-1703.

Redox processes and water quality of selected principal aquifer systems

USGS Publications Warehouse

McMahon, P.B.; Chapelle, F.H.

2008-01-01

Reduction/oxidation (redox) conditions in 15 principal aquifer (PA) systems of the United States, and their impact on several water quality issues, were assessed from a large data base collected by the National Water-Quality Assessment Program of the USGS. The logic of these assessments was based on the observed ecological succession of electron acceptors such as dissolved oxygen, nitrate, and sulfate and threshold concentrations of these substrates needed to support active microbial metabolism. Similarly, the utilization of solid-phase electron acceptors such as Mn(IV) and Fe(III) is indicated by the production of dissolved manganese and iron. An internally consistent set of threshold concentration criteria was developed and applied to a large data set of 1692 water samples from the PAs to assess ambient redox conditions. The indicated redox conditions then were related to the occurrence of selected natural (arsenic) and anthropogenic (nitrate and volatile organic compounds) contaminants in ground water. For the natural and anthropogenic contaminants assessed in this study, considering redox conditions as defined by this framework of redox indicator species and threshold concentrations explained many water quality trends observed at a regional scale. An important finding of this study was that samples indicating mixed redox processes provide information on redox heterogeneity that is useful for assessing common water quality issues. Given the interpretive power of the redox framework and given that it is relatively inexpensive and easy to measure the chemical parameters included in the framework, those parameters should be included in routine water quality monitoring programs whenever possible.

The concept of electron activity and its relation to redox potentials in aqueous geochemical systems

USGS Publications Warehouse

Thorstenson, D.C.

1984-01-01

The definition of a formal thermodynamic activity of electrons in redox reactions appears in the literature of the 1920's. The concept of pe as -log (electron activity) was introduced by Jorgensen in 1945 and popularized in the geochemical literature by Sillen, who considered pe and pH as master variables in geochemical reactions. The physical significance of the concept of electron activity was challenged as early as 1928. However, only in the last two decades have sufficient thermodynamic data become available to examine this question quantitatively. The chemical nature of hydrated electrons differs greatly from that of hydrated protons, and thermodynamic data show that hydrated electrons cannot exist at physically meaningful equilibrium concentrations under natural conditions. This has important consequences for the understanding of redox processes in natural waters. These are: (1) the analogy between pe and pH as master variables is generally carried much further than is justified; (2) a thermodynamically meaningful value of redox potential cannot be assigned to disequilibrium systems; (3) the most useful approach to the study of redox characteristics is the analysis and study of multiple redox couples in the system; and (4) for all practical purposes, thermodynamically defined redox potentials do not exist (and thus cannot be measured) in natural waters. The overall implication for natural systems is that, in terms of redox reactions, each case must be considered on an individual and detailed basis. Field studies would appear to be a mandatory part of any site-specific study; conclusions regarding redox processes cannot be based solely on electrode measurements or thermodynamic stability calculations. (USGS)

Microbial Functional Gene Diversity with a Shift of Subsurface Redox Conditions during In Situ Uranium Reduction

PubMed Central

Liang, Yuting; Van Nostrand, Joy D.; N′Guessan, Lucie A.; Peacock, Aaron D.; Deng, Ye; Long, Philip E.; Resch, C. Tom; Wu, Liyou; He, Zhili; Li, Guanghe; Hazen, Terry C.; Lovley, Derek R.

2012-01-01

To better understand the microbial functional diversity changes with subsurface redox conditions during in situ uranium bioremediation, key functional genes were studied with GeoChip, a comprehensive functional gene microarray, in field experiments at a uranium mill tailings remedial action (UMTRA) site (Rifle, CO). The results indicated that functional microbial communities altered with a shift in the dominant metabolic process, as documented by hierarchical cluster and ordination analyses of all detected functional genes. The abundance of dsrAB genes (dissimilatory sulfite reductase genes) and methane generation-related mcr genes (methyl coenzyme M reductase coding genes) increased when redox conditions shifted from Fe-reducing to sulfate-reducing conditions. The cytochrome genes detected were primarily from Geobacter sp. and decreased with lower subsurface redox conditions. Statistical analysis of environmental parameters and functional genes indicated that acetate, U(VI), and redox potential (Eh) were the most significant geochemical variables linked to microbial functional gene structures, and changes in microbial functional diversity were strongly related to the dominant terminal electron-accepting process following acetate addition. The study indicates that the microbial functional genes clearly reflect the in situ redox conditions and the dominant microbial processes, which in turn influence uranium bioreduction. Microbial functional genes thus could be very useful for tracking microbial community structure and dynamics during bioremediation. PMID:22327592

Redox Regulation of the Superoxide Dismutases SOD3 and SOD2 in the Pulmonary Circulation.

PubMed

Hernandez-Saavedra, Daniel; Swain, Kalin; Tuder, Rubin; Petersen, Steen V; Nozik-Grayck, Eva

2017-01-01

When evaluating the role of redox-regulating signaling in pulmonary vascular diseases, it is intriguing to consider the modulation of key antioxidant enzymes like superoxide dismutase (SOD) because SOD isoforms are regulated by redox reactions, and, in turn, modulate downstream redox sensitive processes. The emerging field of redox biology is built upon understanding the regulation and consequences of tightly controlled and specific reduction-oxidation reactions that are critical for diverse cellular processes including cell signaling. Of relevance, both the site of production of specific reactive oxygen and nitrogen species and the site of the antioxidant defenses are highly compartmentalized within the cell. For example, superoxide is generated during oxidative phosphorylation in the mitochondria as well as by a number of enzymatic sources within the cytosol and at the cell membrane. In the pulmonary circulation, these sources include the mitochondrial electron transport chain, NADPH oxidases (NOX1-4, Duox1,2), nitric oxide synthases, and xanthine oxidase; this important topic has been thoroughly reviewed recently [1]. In parallel with these different cellular sites of superoxide production, the three SOD isoforms are also specifically localized to the cytosol (SOD1), mitochondria (SOD2) or extracellular compartment (SOD3). This chapter focuses on the role of redox mechanisms regulating SOD2 and SOD3, with an emphasis on these processes in the setting of pulmonary hypertension.

Estimating the system price of redox flow batteries for grid storage

NASA Astrophysics Data System (ADS)

Ha, Seungbum; Gallagher, Kevin G.

2015-11-01

Low-cost energy storage systems are required to support extensive deployment of intermittent renewable energy on the electricity grid. Redox flow batteries have potential advantages to meet the stringent cost target for grid applications as compared to more traditional batteries based on an enclosed architecture. However, the manufacturing process and therefore potential high-volume production price of redox flow batteries is largely unquantified. We present a comprehensive assessment of a prospective production process for aqueous all vanadium flow battery and nonaqueous lithium polysulfide flow battery. The estimated investment and variable costs are translated to fixed expenses, profit, and warranty as a function of production volume. When compared to lithium-ion batteries, redox flow batteries are estimated to exhibit lower costs of manufacture, here calculated as the unit price less materials costs, owing to their simpler reactor (cell) design, lower required area, and thus simpler manufacturing process. Redox flow batteries are also projected to achieve the majority of manufacturing scale benefits at lower production volumes as compared to lithium-ion. However, this advantage is offset due to the dramatically lower present production volume of flow batteries compared to competitive technologies such as lithium-ion.

Iron-sulfur cluster biogenesis in mammalian cells: new insights into the molecular mechanisms of cluster delivery

PubMed Central

Maio, Nunziata; Rouault, Tracey. A.

2014-01-01

Iron-sulfur (Fe-S) clusters are ancient, ubiquitous cofactors composed of iron and inorganic sulfur. The combination of the chemical reactivity of iron and sulfur, together with many variations of cluster composition, oxidation states and protein environments, enables Fe-S clusters to participate in numerous biological processes. Fe-S clusters are essential to redox catalysis in nitrogen fixation, mitochondrial respiration and photosynthesis, to regulatory sensing in key metabolic pathways (i. e. cellular iron homeostasis and oxidative stress response), and to the replication and maintenance of the nuclear genome. Fe-S cluster biogenesis is a multistep process that involves a complex sequence of catalyzed protein- protein interactions and coupled conformational changes between the components of several dedicated multimeric complexes. Intensive studies of the assembly process have clarified key points in the biogenesis of Fe-S proteins. However several critical questions still remain, such as: what is the role of frataxin? Why do some defects of Fe-S cluster biogenesis cause mitochondrial iron overload? How are specific Fe-S recipient proteins recognized in the process of Fe-S transfer? This review focuses on the basic steps of Fe-S cluster biogenesis, drawing attention to recent advances achieved on the identification of molecular features that guide selection of specific subsets of nascent Fe-S recipients by the cochaperone HSC20. Additionally, it outlines the distinctive phenotypes of human diseases due to mutations in the components of the basic pathway. PMID:25245479

Bicarbonate Induced Redox Proteome Changes in Arabidopsis Suspension Cells.

PubMed

Yin, Zepeng; Balmant, Kelly; Geng, Sisi; Zhu, Ning; Zhang, Tong; Dufresne, Craig; Dai, Shaojun; Chen, Sixue

2017-01-01

Climate change as a result of increasing atmospheric CO 2 affects plant growth and productivity. CO 2 is not only a carbon donor for photosynthesis but also an environmental signal that can perturb cellular redox homeostasis and lead to modifications of redox-sensitive proteins. Although redox regulation of protein functions has emerged as an important mechanism in several biological processes, protein redox modifications and how they function in plant CO 2 response remain unclear. Here a new iodoTMTRAQ proteomics technology was employed to analyze changes in protein redox modifications in Arabidopsis thaliana suspension cells in response to bicarbonate (mimic of elevated CO 2 ) in a time-course study. A total of 47 potential redox-regulated proteins were identified with functions in carbohydrate and energy metabolism, transport, ROS scavenging, cell structure modulation and protein turnover. This inventory of previously unknown redox responsive proteins in Arabidopsis bicarbonate responses lays a foundation for future research toward understanding the molecular mechanisms underlying plant CO 2 responses.

Bicarbonate Induced Redox Proteome Changes in Arabidopsis Suspension Cells

PubMed Central

Yin, Zepeng; Balmant, Kelly; Geng, Sisi; Zhu, Ning; Zhang, Tong; Dufresne, Craig; Dai, Shaojun; Chen, Sixue

2017-01-01

Climate change as a result of increasing atmospheric CO2 affects plant growth and productivity. CO2 is not only a carbon donor for photosynthesis but also an environmental signal that can perturb cellular redox homeostasis and lead to modifications of redox-sensitive proteins. Although redox regulation of protein functions has emerged as an important mechanism in several biological processes, protein redox modifications and how they function in plant CO2 response remain unclear. Here a new iodoTMTRAQ proteomics technology was employed to analyze changes in protein redox modifications in Arabidopsis thaliana suspension cells in response to bicarbonate (mimic of elevated CO2) in a time-course study. A total of 47 potential redox-regulated proteins were identified with functions in carbohydrate and energy metabolism, transport, ROS scavenging, cell structure modulation and protein turnover. This inventory of previously unknown redox responsive proteins in Arabidopsis bicarbonate responses lays a foundation for future research toward understanding the molecular mechanisms underlying plant CO2 responses. PMID:28184230

Perovskite nanocomposites as effective CO2-splitting agents in a cyclic redox scheme

PubMed Central

Zhang, Junshe; Haribal, Vasudev; Li, Fanxing

2017-01-01

We report iron-containing mixed-oxide nanocomposites as highly effective redox materials for thermochemical CO2 splitting and methane partial oxidation in a cyclic redox scheme, where methane was introduced as an oxygen “sink” to promote the reduction of the redox materials followed by reoxidation through CO2 splitting. Up to 96% syngas selectivity in the methane partial oxidation step and close to complete conversion of CO2 to CO in the CO2-splitting step were achieved at 900° to 980°C with good redox stability. The productivity and production rate of CO in the CO2-splitting step were about seven times higher than those in state-of-the-art solar-thermal CO2-splitting processes, which are carried out at significantly higher temperatures. The proposed approach can potentially be applied for acetic acid synthesis with up to 84% reduction in CO2 emission when compared to state-of-the-art processes. PMID:28875171

Basic Principles and Emerging Concepts in the Redox Control of Transcription Factors

PubMed Central

Flohé, Leopold

2011-01-01

Abstract Convincing concepts of redox control of gene transcription have been worked out for prokaryotes and lower eukaryotes, whereas the knowledge on complex mammalian systems still resembles a patchwork of poorly connected findings. The article, therefore, reviews principles of redox regulation with special emphasis on chemical feasibility, kinetic requirements, specificity, and physiological context, taking well investigated mammalian transcription factor systems, nuclear transcription factor of bone marrow-derived lymphocytes (NF-κB), and kelch-like ECH-associated protein-1 (Keap1)/Nrf2, as paradigms. Major conclusions are that (i) direct signaling by free radicals is restricted to O2•− and •NO and can be excluded for fast reacting radicals such as •OH, •OR, or Cl•; (ii) oxidant signals are H2O2, enzymatically generated lipid hydroperoxides, and peroxynitrite; (iii) free radical damage is sensed via generation of Michael acceptors; (iv) protein thiol oxidation/alkylation is the prominent mechanism to modulate function; (v) redox sensors must be thiol peroxidases by themselves or proteins with similarly reactive cysteine or selenocysteine (Sec) residues to kinetically compete with glutathione peroxidase (GPx)- and peroxiredoxin (Prx)-type peroxidases or glutathione-S-transferases, respectively, a postulate that still has to be verified for putative mammalian sensors. S-transferases and Prxs are considered for system complementation. The impact of NF-κB and Nrf2 on hormesis, management of inflammatory diseases, and cancer prevention is critically discussed. Antioxid. Redox Signal. 15, 2335–2381. PMID:21194351

Grid Scale Energy Storage (Symposium EE8)

DTIC Science & Technology

2016-06-01

27709-2211 Grid-Scale Energy Storage, electrolytes, systems ntegration, Lithium - ion chemistry, Redox flow batteries REPORT DOCUMENTATION PAGE 11... Lithium - Ion Chemistry (4) Redox Flow Batteries Christopher J. Orendorff from Sandia National Laboratories kicked off the symposium on Tuesday...for redox flow batteries . SEI formation is a well-known process in standard lithium - ion battery operation; however, using aqueous electrolytes does

Redox conditions and the efficiency of chlorinated ethene biodegradation: Field studies

USGS Publications Warehouse

Chapelle, F.H.; Bradley, P.M.

2000-01-01

The effect of redox conditions on the efficiency of chlorinated ethene biodegradation was investigated at two field sites. One site (NAS Cecil Field, FL) is characterized by predominantly Fe(III)-reducing conditions in the contaminant source area, grading to predominantly sulfate- reducing conditions downgradient. This sequence of redox conditions led to relatively inefficient biodegradation of chlorinated ethenes, with high concentrations of trichloroethene extending more than 400 meters downgradient of the source area. In contrast, a second site (NBS Kings Bay, GA) characterized by predominantly sulfate-reducing conditions in the source area followed by Fe(III)-reducing conditions downgradient. In this system perchloroethene (PCE) and TCE were rapidly biodegraded and extended less than 100 meters downgradient. Rates of ground- water transport are similar at the two sites (???0.2 m/d) indicating that the succession of redox processes, rather than other hydrologic factors, is the principal control on biodegradation. In particular, redox conditions that favor the initial reduction of highly chlorinated ethenes (methanogenic or sulfate-reducing conditions) followed by more oxidizing conditions (Fe(III)- reducing or oxic conditions) favors efficient biodegradation. Thus, documenting the succession of redox processes is an important step in understanding the efficiency of chlorinated ethene biodegradation in ground-water systems.

MICROSCALE METABOLIC, REDOX AND ABIOTIC REACTIONS IN HANFORD 300 AREA SUBSURFACE SEDIMENTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beyenal, Haluk; McLEan, Jeff; Majors, Paul

2013-11-14

The Hanford 300 Area is a unique site due to periodic hydrologic influence of river water resulting in changes in groundwater elevation and flow direction. This area is also highly subject to uranium remobilization, the source of which is currently believed to be the region at the base of the vadose zone that is subject to period saturation due to the changes in the water levels in the Columbia River. We found that microbial processes and redox and abiotic reactions which operate at the microscale were critical to understanding factors controlling the macroscopic fate and transport of contaminants in themore » subsurface. The combined laboratory and field research showed how microscale conditions control uranium mobility and how biotic, abiotic and redox reactions relate to each other. Our findings extended the current knowledge to examine U(VI) reduction and immobilization using natural 300 Area communities as well as selected model organisms on redox-sensitive and redox-insensitive minerals. Using innovative techniques developed specifically to probe biogeochemical processes at the microscale, our research expanded our current understanding of the roles played by mineral surfaces, bacterial competition, and local biotic, abiotic and redox reaction rates on the reduction and immobilization of uranium.« less

Metabolic and redox barriers in the skin exposed to drugs and xenobiotics.

PubMed

Korkina, Liudmila

2016-01-01

Growing exposure of human skin to environmental and occupational hazards, to numerous skin care/beauty products, and to topical drugs led to a biomedical concern regarding sustainability of cutaneous chemical defence that is essential for protection against intoxication. Since skin is the largest extra-hepatic drug/xenobiotic metabolising organ where redox-dependent metabolic pathways prevail, in this review, publications on metabolic processes leading to redox imbalance (oxidative stress) and its autocrine/endocrine impact to cutaneous drug/xenobiotic metabolism were scrutinised. Chemical and photo-chemical skin barriers contain metabolic and redox compartments: their protective and homeostatic functions. The review will examine the striking similarity of adaptive responses to exogenous chemical/photo-chemical stressors and endogenous toxins in cutaneous metabolic and redox system; the role(s) of xenobiotics/drugs and phase II enzymes in the endogenous antioxidant defence and maintenance of redox balance; redox regulation of interactions between metabolic and inflammatory responses in skin cells; skin diseases sharing metabolic and redox problems (contact dermatitis, lupus erythematosus, and vitiligo) Due to exceptional the redox dependence of cutaneous metabolic pathways and interaction of redox active metabolites/exogenous antioxidants with drug/xenobiotic metabolism, metabolic tests of topical xenobiotics/drugs should be combined with appropriate redox analyses and performed on 3D human skin models.

Effect of protonation, composition and isomerism on the redox properties and electron (de)localization of classical polyoxometalates

NASA Astrophysics Data System (ADS)

López, Xavier

2017-10-01

This publication reviews some relevant features related with the redox activity of two inorganic compounds: [XM12O40]q- (Keggin structure) and [X2M18O62]q- (Wells-Dawson structure). These are two well-known specimens of the vast Polyoxometalate (POM) family, which has been the subject of extensive experimental and theoretical research owing to their unmatched properties. In particular, their redox activity focus a great deal of attention from scientists due to their prospective related applications. POMs are habitually seen as `electron sponges' since many of them accept several electrons without losing their chemical identity. This makes them excellent models to study mechanisms of electrochemical nature. Their redox properties depend on: (i) the type and number of transition metal atoms in the structure, (ii) the basicity of the first reduced species and, occasionally, of the fully oxidized species; (iii) the size of the molecule, (iv) the overall negative charge of the POM, and (v) the size of the central heteroatom. In the last years, important collaboration between the experimental and theoretical areas has been usual on the development of POM science. In the present chapter three of these synergies are highlighted: the influence of the internal heteroatom upon the redox potentials of Keggin anions; the dependence of the redox waves of Fe-substituted Wells-Dawson compounds with pH; and the role of electron delocalization and pairing in mixed-metal Mo/W Wells-Dawson compounds in their ability to accept electrons. In these three cases, a complete understanding of the problem would not have been possible without the mutual benefit of experimental and computational data.

Electron transfer properties of peat organic matter: from electrochemical analysis to redox processes in peatlands

NASA Astrophysics Data System (ADS)

Sander, Michael; Getzinger, Gordon; Walpen, Nicolas

2017-04-01

Peat organic matter contains redox-active functional groups that can accept and/or donate electrons from and to biotic and abiotic reaction partners present in peatlands. Several studies have provided evidence that electron accepting quinone moieties in the peat organic matter may act as terminal electron acceptors for anaerobic microbial respiration. This respiration pathway may competitively suppress methanogenesis and thereby lead to excess carbon dioxide to methane formation in peatlands. Electron donating phenolic moieties in peat organic matter have long been considered to inhibit microbial and enzymatic activities in peatlands, thereby contributing to carbon stabilization and accumulation in these systems. Phenols are expected to be comparatively stable in anoxic parts of the peats as phenoloxidases, a class of enzymes capable of oxidatively degrading phenols, require molecular oxygen as co-substrate. Despite the general recognition of the importance of redox-active moieties in peat organic matter, the abundance, redox properties and reactivities of these moieties remain poorly studied and understood, in large part due to analytical challenges. This contribution will, in a first part, summarize recent advances in our research group on the analytical chemistry of redox-active moieties in peat organic matter. We will show how mediated electrochemical analysis can be used to quantify the capacities of electron accepting and donating moieties in both dissolved and particulate peat organic matter. We will link these capacities to the physicochemical properties of peat organic matter and provide evidence for quinones and phenols as major electron accepting and donating moieties, respectively. The second part of this contribution will highlight how these electroanalytical techniques can be utilized to advance a more fundamental understanding of electron transfer processes involving peat organic matter. These processes include the redox cycling (i.e., repeated reduction and re-oxidation) of peat organic matter under alternating anoxic-oxic conditions as well as the oxidation of phenolic moieties in peat organic matter by phenol oxidases in the presence of molecular oxygen. Overall, this contribution will attempt to link molecular-level insights into the redox properties of peat organic matter to larger scale redox processes that are important to carbon cycling in peatlands.

Method for characterization of the rate of movement of an oxidation front in cementitious materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Almond, Philip M.; Langton, Christine A.; Stefanko, David B.

2016-03-01

Disclosed are methods for determining the redox condition of cementitious materials. The methods are leaching methods that utilize a redox active transition metal indicator that is present in the cementitious material and exhibits variable solubility depending upon the oxidation state of the indicator. When the leaching process is carried out under anaerobic conditions, the presence or absence of the indicator in the leachate can be utilized to determine the redox condition of and location of the oxidation front in the material that has been subjected to the leaching process.

Redox Regulation in Amyotrophic Lateral Sclerosis

PubMed Central

Parakh, Sonam; Spencer, Damian M.; Halloran, Mark A.; Soo, Kai Y.; Atkin, Julie D.

2013-01-01

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease that results from the death of upper and lower motor neurons. Due to a lack of effective treatment, it is imperative to understand the underlying mechanisms and processes involved in disease progression. Regulations in cellular reduction/oxidation (redox) processes are being increasingly implicated in disease. Here we discuss the possible involvement of redox dysregulation in the pathophysiology of ALS, either as a cause of cellular abnormalities or a consequence. We focus on its possible role in oxidative stress, protein misfolding, glutamate excitotoxicity, lipid peroxidation and cholesterol esterification, mitochondrial dysfunction, impaired axonal transport and neurofilament aggregation, autophagic stress, and endoplasmic reticulum (ER) stress. We also speculate that an ER chaperone protein disulphide isomerase (PDI) could play a key role in this dysregulation. PDI is essential for normal protein folding by oxidation and reduction of disulphide bonds, and hence any disruption to this process may have consequences for motor neurons. Addressing the mechanism underlying redox regulation and dysregulation may therefore help to unravel the molecular mechanism involved in ALS. PMID:23533690

Redox doping behaviour of poly(3,4-ethylenedithiothiophene) - The counterion effect

NASA Astrophysics Data System (ADS)

Domagala, Wojciech; Palutkiewicz, Dawid; Cortizo-Lacalle, Diego; Kanibolotsky, Alexander L.; Skabara, Peter J.

2011-07-01

Poly(3,4-ethylenedithiothiophene) - PEDTT, an alkylene sulphur derivative of PEDOT, presents itself as an interesting polymer with a number of disparate redox and chromic properties compared to its close analogue - PEDOT. In this study we present the results of an investigation into the electrochemical doping process of PEDTT, using four different electrolyte solutions, differing in anion content of the chosen salt. The results show that the anion identity plays a key role in the redox reactions accompanying these processes in what could be interpreted as anion ionochromism. In situ UV-Vis spectroelectrochemical experiments reveal an intriguing double electrochromic transition of PEDTT films during their oxidative doping, going from golden-yellow through green to pomegranate - a quality not so common within the family of electroactive conjugated polymers. The evolution of each UV-Vis spectrum over a potential range indicates that different redox states of the polymer are responsible for the chromatic changes. In the reduction half-cycle, the dedoping process of PEDTT appears to follow a path dissimilar to the p-doping one, featuring only one, direct electrochromic transition of the film's colour, bypassing the green state, and a distinct two-step bleaching process of doping-induced charge carrier bands. The observed electrochemical and spectral phenomena have been accredited to the specific redox behaviour of doping-induced radical cation and cationic defect states interacting with the dithioalkylene sulphur atom.

Interactions between magnetite and humic substances: redox reactions and dissolution processes.

PubMed

Sundman, Anneli; Byrne, James M; Bauer, Iris; Menguy, Nicolas; Kappler, Andreas

2017-10-19

Humic substances (HS) are redox-active compounds that are ubiquitous in the environment and can serve as electron shuttles during microbial Fe(III) reduction thus reducing a variety of Fe(III) minerals. However, not much is known about redox reactions between HS and the mixed-valent mineral magnetite (Fe 3 O 4 ) that can potentially lead to changes in Fe(II)/Fe(III) stoichiometry and even dissolve the magnetite. To address this knowledge gap, we incubated non-reduced (native) and reduced HS with four types of magnetite that varied in particle size and solid-phase Fe(II)/Fe(III) stoichiometry. We followed dissolved and solid-phase Fe(II) and Fe(III) concentrations over time to quantify redox reactions between HS and magnetite. Magnetite redox reactions and dissolution processes with HS varied depending on the initial magnetite and HS properties. The interaction between biogenic magnetite and reduced HS resulted in dissolution of the solid magnetite mineral, as well as an overall reduction of the magnetite. In contrast, a slight oxidation and no dissolution was observed when native and reduced HS interacted with 500 nm magnetite. This variability in the solubility and electron accepting and donating capacity of the different types of magnetite is likely an effect of differences in their reduction potential that is correlated to the magnetite Fe(II)/Fe(III) stoichiometry, particle size, and crystallinity. Our study suggests that redox-active HS play an important role for Fe redox speciation within minerals such as magnetite and thereby influence the reactivity of these Fe minerals and their role in biogeochemical Fe cycling. Furthermore, such processes are also likely to have an effect on the fate of other elements bound to the surface of Fe minerals.

Paradoxical Roles of Antioxidant Enzymes: Basic Mechanisms and Health Implications

PubMed Central

Lei, Xin Gen; Zhu, Jian-Hong; Cheng, Wen-Hsing; Bao, Yongping; Ho, Ye-Shih; Reddi, Amit R.; Holmgren, Arne; Arnér, Elias S. J.

2015-01-01

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are generated from aerobic metabolism, as a result of accidental electron leakage as well as regulated enzymatic processes. Because ROS/RNS can induce oxidative injury and act in redox signaling, enzymes metabolizing them will inherently promote either health or disease, depending on the physiological context. It is thus misleading to consider conventionally called antioxidant enzymes to be largely, if not exclusively, health protective. Because such a notion is nonetheless common, we herein attempt to rationalize why this simplistic view should be avoided. First we give an updated summary of physiological phenotypes triggered in mouse models of overexpression or knockout of major antioxidant enzymes. Subsequently, we focus on a series of striking cases that demonstrate “paradoxical” outcomes, i.e., increased fitness upon deletion of antioxidant enzymes or disease triggered by their overexpression. We elaborate mechanisms by which these phenotypes are mediated via chemical, biological, and metabolic interactions of the antioxidant enzymes with their substrates, downstream events, and cellular context. Furthermore, we propose that novel treatments of antioxidant enzyme-related human diseases may be enabled by deliberate targeting of dual roles of the pertaining enzymes. We also discuss the potential of “antioxidant” nutrients and phytochemicals, via regulating the expression or function of antioxidant enzymes, in preventing, treating, or aggravating chronic diseases. We conclude that “paradoxical” roles of antioxidant enzymes in physiology, health, and disease derive from sophisticated molecular mechanisms of redox biology and metabolic homeostasis. Simply viewing antioxidant enzymes as always being beneficial is not only conceptually misleading but also clinically hazardous if such notions underpin medical treatment protocols based on modulation of redox pathways. PMID:26681794

High-capacity electrode materials for rechargeable lithium batteries: Li3NbO4-based system with cation-disordered rocksalt structure.

PubMed

Yabuuchi, Naoaki; Takeuchi, Mitsue; Nakayama, Masanobu; Shiiba, Hiromasa; Ogawa, Masahiro; Nakayama, Keisuke; Ohta, Toshiaki; Endo, Daisuke; Ozaki, Tetsuya; Inamasu, Tokuo; Sato, Kei; Komaba, Shinichi

2015-06-23

Rechargeable lithium batteries have rapidly risen to prominence as fundamental devices for green and sustainable energy development. Lithium batteries are now used as power sources for electric vehicles. However, materials innovations are still needed to satisfy the growing demand for increasing energy density of lithium batteries. In the past decade, lithium-excess compounds, Li2MeO3 (Me = Mn(4+), Ru(4+), etc.), have been extensively studied as high-capacity positive electrode materials. Although the origin as the high reversible capacity has been a debatable subject for a long time, recently it has been confirmed that charge compensation is partly achieved by solid-state redox of nonmetal anions (i.e., oxide ions), coupled with solid-state redox of transition metals, which is the basic theory used for classic lithium insertion materials, such as LiMeO2 (Me = Co(3+), Ni(3+), etc.). Herein, as a compound with further excess lithium contents, a cation-ordered rocksalt phase with lithium and pentavalent niobium ions, Li3NbO4, is first examined as the host structure of a new series of high-capacity positive electrode materials for rechargeable lithium batteries. Approximately 300 mAh ⋅ g(-1) of high-reversible capacity at 50 °C is experimentally observed, which partly originates from charge compensation by solid-state redox of oxide ions. It is proposed that such a charge compensation process by oxide ions is effectively stabilized by the presence of electrochemically inactive niobium ions. These results will contribute to the development of a new class of high-capacity electrode materials, potentially with further lithium enrichment (and fewer transition metals) in the close-packed framework structure with oxide ions.

Paradoxical Roles of Antioxidant Enzymes: Basic Mechanisms and Health Implications.

PubMed

Lei, Xin Gen; Zhu, Jian-Hong; Cheng, Wen-Hsing; Bao, Yongping; Ho, Ye-Shih; Reddi, Amit R; Holmgren, Arne; Arnér, Elias S J

2016-01-01

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are generated from aerobic metabolism, as a result of accidental electron leakage as well as regulated enzymatic processes. Because ROS/RNS can induce oxidative injury and act in redox signaling, enzymes metabolizing them will inherently promote either health or disease, depending on the physiological context. It is thus misleading to consider conventionally called antioxidant enzymes to be largely, if not exclusively, health protective. Because such a notion is nonetheless common, we herein attempt to rationalize why this simplistic view should be avoided. First we give an updated summary of physiological phenotypes triggered in mouse models of overexpression or knockout of major antioxidant enzymes. Subsequently, we focus on a series of striking cases that demonstrate "paradoxical" outcomes, i.e., increased fitness upon deletion of antioxidant enzymes or disease triggered by their overexpression. We elaborate mechanisms by which these phenotypes are mediated via chemical, biological, and metabolic interactions of the antioxidant enzymes with their substrates, downstream events, and cellular context. Furthermore, we propose that novel treatments of antioxidant enzyme-related human diseases may be enabled by deliberate targeting of dual roles of the pertaining enzymes. We also discuss the potential of "antioxidant" nutrients and phytochemicals, via regulating the expression or function of antioxidant enzymes, in preventing, treating, or aggravating chronic diseases. We conclude that "paradoxical" roles of antioxidant enzymes in physiology, health, and disease derive from sophisticated molecular mechanisms of redox biology and metabolic homeostasis. Simply viewing antioxidant enzymes as always being beneficial is not only conceptually misleading but also clinically hazardous if such notions underpin medical treatment protocols based on modulation of redox pathways. Copyright © 2016 the American Physiological Society.

A Multistep Equilibria-Redox-Complexation Demonstration to Illustrate Le Chatelier's Principle.

ERIC Educational Resources Information Center

Berger, Tomas G.; Mellon, Edward K.

1996-01-01

Describes a process that can be used to illustrate a number of chemical principles including Le Chatelier's principle, redox chemistry, equilibria versus steady state situations, and solubility of species. (JRH)

Circulating membrane-derived microvesicles in redox biology.

PubMed

Larson, Michael Craig; Hillery, Cheryl A; Hogg, Neil

2014-08-01

Microparticles or microvesicles (MVs) are subcellular membrane blebs shed from all cells in response to various stimuli. MVs carry a battery of signaling molecules, many of them related to redox-regulated processes. The role of MVs, either as a cause or as a result of cellular redox signaling, has been increasingly recognized over the past decade. This is in part due to advances in flow cytometry and its detection of MVs. Notably, recent studies have shown that circulating MVs from platelets and endothelial cells drive reactive species-dependent angiogenesis; circulating MVs in cancer alter the microenvironment and enhance invasion through horizontal transfer of mutated proteins and nucleic acids and harbor redox-regulated matrix metalloproteinases and procoagulative surface molecules; and circulating MVs from red blood cells and other cells modulate cell-cell interactions through scavenging or production of nitric oxide and other free radicals. Although our recognition of MVs in redox-related processes is growing, especially in the vascular biology field, much remains unknown regarding the various biologic and pathologic functions of MVs. Like reactive oxygen and nitrogen species, MVs were originally believed to have a solely pathological role in biology. And like our understanding of reactive species, it is now clear that MVs also play an important role in normal growth, development, and homeostasis. We are just beginning to understand how MVs are involved in various biological processes-developmental, homeostatic, and pathological-and the role of MVs in redox signaling is a rich and exciting area of investigation. Copyright © 2014 Elsevier Inc. All rights reserved.

Redox Control of Inflammation in Macrophages

PubMed Central

Dehne, Nathalie; Grossmann, Nina; Jung, Michaela; Namgaladze, Dmitry; Schmid, Tobias; von Knethen, Andreas; Weigert, Andreas

2013-01-01

Abstract Macrophages are present throughout the human body, constitute important immune effector cells, and have variable roles in a great number of pathological, but also physiological, settings. It is apparent that macrophages need to adjust their activation profile toward a steadily changing environment that requires altering their phenotype, a process known as macrophage polarization. Formation of reactive oxygen species (ROS), derived from NADPH-oxidases, mitochondria, or NO-producing enzymes, are not necessarily toxic, but rather compose a network signaling system, known as redox regulation. Formation of redox signals in classically versus alternatively activated macrophages, their action and interaction at the level of key targets, and the resulting physiology still are insufficiently understood. We review the identity, source, and biological activities of ROS produced during macrophage activation, and discuss how they shape the key transcriptional responses evoked by hypoxia-inducible transcription factors, nuclear-erythroid 2-p45-related factor 2 (Nrf2), and peroxisome proliferator-activated receptor-γ. We summarize the mechanisms how redox signals add to the process of macrophage polarization and reprogramming, how this is controlled by the interaction of macrophages with their environment, and addresses the outcome of the polarization process in health and disease. Future studies need to tackle the option whether we can use the knowledge of redox biology in macrophages to shape their mediator profile in pathophysiology, to accelerate healing in injured tissue, to fight the invading pathogens, or to eliminate settings of altered self in tumors. Antioxid. Redox Signal. 19, 595–637. PMID:23311665

Breast Cancer Redox Heterogeneity Detectable with Chemical Exchange Satruation Transfer (CEST) MRI

PubMed Central

Cai, Kejia; Xu, He N.; Singh, Anup; Moon, Lily; Haris, Mohammad; Reddy, Ravinder; Li, Lin

2014-01-01

Purpose Tissue redox state is an important mediator of various biological processes in health and diseases such as cancer. Previously, we discovered that the mitochondrial redox state of ex vivo tissues detected by redox scanning (an optical imaging method) revealed interesting tumor redox state heterogeneity that could differentiate tumor aggressiveness. Because the noninvasive chemical exchange saturation transfer (CEST) MRI can probe the proton transfer and generate contrasts from endogenous metabolites, we aim to investigate if the in vivo CEST contrast is sensitive to proton transfer of the redox reactions so as to reveal the tissue redox states in breast cancer animal models. Procedures CEST MRI has been employed to characterize tumor metabolic heterogeneity and correlated with the redox states measured by the redox scanning in two human breast cancer mouse xenograft models, MDA-MB-231 and MCF-7. The possible biological mechanism on the correlation between the two imaging modalities was further investigated by phantom studies where the reductants and the oxidants of the representative redox reactions were measured. Results The CEST contrast is found linearly correlated with NADH concentration and the NADH redox ratio with high statistical significance, where NADH is the reduced form of nicotinamide adenine dinucleotide. The phantom studies showed that the reductants of the redox reactions have more CEST contrast than the corresponding oxidants, indicating that higher CEST effect corresponds to the more reduced redox state. Conclusions This preliminary study suggests that CEST MRI, once calibrated, might provide a novel noninvasive imaging surrogate for the tissue redox state and a possible diagnostic biomarker for breast cancer in the clinic. PMID:24811957

Breast cancer redox heterogeneity detectable with chemical exchange saturation transfer (CEST) MRI.

PubMed

Cai, Kejia; Xu, He N; Singh, Anup; Moon, Lily; Haris, Mohammad; Reddy, Ravinder; Li, Lin Z

2014-10-01

Tissue redox state is an important mediator of various biological processes in health and diseases such as cancer. Previously, we discovered that the mitochondrial redox state of ex vivo tissues detected by redox scanning (an optical imaging method) revealed interesting tumor redox state heterogeneity that could differentiate tumor aggressiveness. Because the noninvasive chemical exchange saturation transfer (CEST) MRI can probe the proton transfer and generate contrasts from endogenous metabolites, we aim to investigate if the in vivo CEST contrast is sensitive to proton transfer of the redox reactions so as to reveal the tissue redox states in breast cancer animal models. CEST MRI has been employed to characterize tumor metabolic heterogeneity and correlated with the redox states measured by the redox scanning in two human breast cancer mouse xenograft models, MDA-MB-231 and MCF-7. The possible biological mechanism on the correlation between the two imaging modalities was further investigated by phantom studies where the reductants and the oxidants of the representative redox reactions were measured. The CEST contrast is found linearly correlated with NADH concentration and the NADH redox ratio with high statistical significance, where NADH is the reduced form of nicotinamide adenine dinucleotide. The phantom studies showed that the reductants of the redox reactions have more CEST contrast than the corresponding oxidants, indicating that higher CEST effect corresponds to the more reduced redox state. This preliminary study suggests that CEST MRI, once calibrated, might provide a novel noninvasive imaging surrogate for the tissue redox state and a possible diagnostic biomarker for breast cancer in the clinic.

Redox biology response in germinating Phaseolus vulgaris seeds exposed to copper: Evidence for differential redox buffering in seedlings and cotyledon.

PubMed

Karmous, Inès; Trevisan, Rafael; El Ferjani, Ezzeddine; Chaoui, Abdelilah; Sheehan, David

2017-01-01

In agriculture, heavy metal contamination of soil interferes with processes associated with plant growth, development and productivity. Here, we describe oxidative and redox changes, and deleterious injury within cotyledons and seedlings caused by exposure of germinating (Phaseolus vulgaris L. var. soisson nain hâtif) seeds to copper (Cu). Cu induced a marked delay in seedling growth, and was associated with biochemical disturbances in terms of intracellular oxidative status, redox regulation and energy metabolism. In response to these alterations, modulation of activities of antioxidant proteins (thioredoxin and glutathione reductase, peroxiredoxin) occurred, thus preventing oxidative damage. In addition, oxidative modification of proteins was detected in both cotyledons and seedlings by one- and two-dimensional electrophoresis. These modified proteins may play roles in redox buffering. The changes in activities of redox proteins underline their fundamental roles in controlling redox homeostasis. However, observed differential redox responses in cotyledon and seedling tissues showed a major capacity of the seedlings' redox systems to protect the reduced status of protein thiols, thus suggesting quantitatively greater antioxidant protection of proteins in seedlings compared to cotyledon. To our knowledge, this is the first comprehensive redox biology investigation of the effect of Cu on seed germination.

Redox proteomics of tomato in response to Pseudomonas syringae infection

PubMed Central

Balmant, Kelly Mayrink; Parker, Jennifer; Yoo, Mi-Jeong; Zhu, Ning; Dufresne, Craig; Chen, Sixue

2015-01-01

Unlike mammals with adaptive immunity, plants rely on their innate immunity based on pattern-triggered immunity (PTI) and effector-triggered immunity (ETI) for pathogen defense. Reactive oxygen species, known to play crucial roles in PTI and ETI, can perturb cellular redox homeostasis and lead to changes of redox-sensitive proteins through modification of cysteine sulfhydryl groups. Although redox regulation of protein functions has emerged as an important mechanism in several biological processes, little is known about redox proteins and how they function in PTI and ETI. In this study, cysTMT proteomics technology was used to identify similarities and differences of protein redox modifications in tomato resistant (PtoR) and susceptible (prf3) genotypes in response to Pseudomonas syringae pv tomato (Pst) infection. In addition, the results of the redox changes were compared and corrected with the protein level changes. A total of 90 potential redox-regulated proteins were identified with functions in carbohydrate and energy metabolism, biosynthesis of cysteine, sucrose and brassinosteroid, cell wall biogenesis, polysaccharide/starch biosynthesis, cuticle development, lipid metabolism, proteolysis, tricarboxylic acid cycle, protein targeting to vacuole, and oxidation–reduction. This inventory of previously unknown protein redox switches in tomato pathogen defense lays a foundation for future research toward understanding the biological significance of protein redox modifications in plant defense responses. PMID:26504582

Renal redox stress and remodeling in metabolic syndrome, type 2 diabetes mellitus, and diabetic nephropathy: paying homage to the podocyte.

PubMed

Hayden, Melvin R; Whaley-Connell, Adam; Sowers, James R

2005-01-01

Type 2 diabetes mellitus has reached epidemic proportions and diabetic nephropathy is the leading cause of end-stage renal disease. The metabolic syndrome constitutes a milieu conducive to tissue redox stress. This loss of redox homeostasis contributes to renal remodeling and parallels the concurrent increased vascular redox stress associated with the cardiometabolic syndrome. The multiple metabolic toxicities, redox stress and endothelial dysfunction combine to weave the complicated mosaic fabric of diabetic glomerulosclerosis and diabetic nephropathy. A better understanding may provide both the clinician and researcher tools to unravel this complicated disease process. Cellular remodeling of podocyte foot processes in the Ren-2 transgenic rat model of tissue angiotensin II overexpression (TG(mREN-2)27) and the Zucker diabetic fatty model of type 2 diabetes mellitus have been observed in preliminary studies. Importantly, angiotensin II receptor blockers have been shown to abrogate these ultrastructural changes in the foot processes of the podocyte in preliminary studies. An integrated, global risk reduction, approach in therapy addressing the multiple metabolic abnormalities combined with attempts to reach therapeutic goals at an earlier stage could have a profound effect on the development and progressive nature to end-stage renal disease and ultimately renal replacement therapy.

Redox electrodeposition polymers: adaptation of the redox potential of polymer-bound Os complexes for bioanalytical applications.

PubMed

Guschin, Dmitrii A; Castillo, John; Dimcheva, Nina; Schuhmann, Wolfgang

2010-10-01

The design of polymers carrying suitable ligands for coordinating Os complexes in ligand exchange reactions against labile chloro ligands is a strategy for the synthesis of redox polymers with bound Os centers which exhibit a wide variation in their redox potential. This strategy is applied to polymers with an additional variation of the properties of the polymer backbone with respect to pH-dependent solubility, monomer composition, hydrophilicity etc. A library of Os-complex-modified electrodeposition polymers was synthesized and initially tested with respect to their electron-transfer ability in combination with enzymes such as glucose oxidase, cellobiose dehydrogenase, and PQQ-dependent glucose dehydrogenase entrapped during the pH-induced deposition process. The different polymer-bound Os complexes in a library containing 50 different redox polymers allowed the statistical evaluation of the impact of an individual ligand to the overall redox potential of an Os complex. Using a simple linear regression algorithm prediction of the redox potential of Os complexes becomes feasible. Thus, a redox polymer can now be designed to optimally interact in electron-transfer reactions with a selected enzyme.

Redox proteomics for the assessment of redox-related posttranslational regulation in plants.

PubMed

Mock, Hans-Peter; Dietz, Karl-Josef

2016-08-01

The methodological developments of in vivo and in vitro protein labeling and subsequent detection enable sensitive and specific detection of redox modifications. Such methods are presently applied to diverse cells and tissues, subproteomes and developmental as well as environmental conditions. The chloroplast proteome is particularly suitable for such kind of studies, because redox regulation of chloroplast proteins is well established, many plastid proteins are abundant, redox network components have been inventoried in great depth, and functional consequences explored. Thus the repertoire of redox-related posttranslational modifications on the one hand side and their abundance on the other pose a challenge for the near future to understand their contribution to physiological regulation. The various posttranslational redox modifications are introduced, followed by a description of the available proteomics methods. The significance of the redox-related posttranslational modification is exemplarily worked out using established examples from photosynthesis. This article is part of a Special Issue entitled: Plant Proteomics--a bridge between fundamental processes and crop production, edited by Dr. Hans-Peter Mock. Copyright © 2016. Published by Elsevier B.V.

Antioxidant enzymes as redox-based biomarkers: a brief review.

PubMed

Yang, Hee-Young; Lee, Tae-Hoon

2015-04-01

The field of redox proteomics focuses to a large extent on analyzing cysteine oxidation in proteins under different experimental conditions and states of diseases. The identification and localization of oxidized cysteines within the cellular milieu is critical for understanding the redox regulation of proteins under physiological and pathophysiological conditions, and it will in turn provide important information that are potentially useful for the development of novel strategies in the treatment and prevention of diseases associated with oxidative stress. Antioxidant enzymes that catalyze oxidation/reduction processes are able to serve as redox biomarkers in various human diseases, and they are key regulators controlling the redox state of functional proteins. Redox regulators with antioxidant properties related to active mediators, cellular organelles, and the surrounding environments are all connected within a network and are involved in diseases related to redox imbalance including cancer, ischemia/reperfusion injury, neurodegenerative diseases, as well as normal aging. In this review, we will briefly look at the selected aspects of oxidative thiol modification in antioxidant enzymes and thiol oxidation in proteins affected by redox control of antioxidant enzymes and their relation to disease.

Redox-activated MRI contrast agents based on lanthanide and transition metal ions.

PubMed

Tsitovich, Pavel B; Burns, Patrick J; McKay, Adam M; Morrow, Janet R

2014-04-01

The reduction/oxidation (redox) potential of tissue is tightly regulated in order to maintain normal physiological processes, but is disrupted in disease states. Thus, the development of new tools to map tissue redox potential may be clinically important for the diagnosis of diseases that lead to redox imbalances. One promising area of chemical research is the development of redox-activated probes for mapping tissue through magnetic resonance imaging (MRI). In this review, we summarize several strategies for the design of redox-responsive MRI contrast agents. Our emphasis is on both lanthanide(III) and transition metal(II/III) ion complexes that provide contrast either as T1 relaxivity MRI contrast agents or as paramagnetic chemical exchange saturation transfer (PARACEST) contrast agents. These agents are redox-triggered by a variety of chemical reactions or switches including redox-activated thiol groups, and heterocyclic groups that interact with the metal ion or influence properties of other ancillary ligands. Metal ion centered redox is an approach which is ripe for development by coordination chemists. Redox-triggered metal ion approaches have great potential for creating large differences in magnetic properties that lead to changes in contrast. An attractive feature of these agents is the ease of fine-tuning the metal ion redox potential over a biologically relevant range. Copyright © 2014 Elsevier Inc. All rights reserved.

Reciprocal Control of the Circadian Clock and Cellular Redox State - a Critical Appraisal.

PubMed

Putker, Marrit; O'Neill, John Stuart

2016-01-01

Redox signalling comprises the biology of molecular signal transduction mediated by reactive oxygen (or nitrogen) species. By specific and reversible oxidation of redox-sensitive cysteines, many biological processes sense and respond to signals from the intracellular redox environment. Redox signals are therefore important regulators of cellular homeostasis. Recently, it has become apparent that the cellular redox state oscillates in vivo and in vitro, with a period of about one day (circadian). Circadian time-keeping allows cells and organisms to adapt their biology to resonate with the 24-hour cycle of day/night. The importance of this innate biological time-keeping is illustrated by the association of clock disruption with the early onset of several diseases (e.g. type II diabetes, stroke and several forms of cancer). Circadian regulation of cellular redox balance suggests potentially two distinct roles for redox signalling in relation to the cellular clock: one where it is regulated by the clock, and one where it regulates the clock. Here, we introduce the concepts of redox signalling and cellular timekeeping, and then critically appraise the evidence for the reciprocal regulation between cellular redox state and the circadian clock. We conclude there is a substantial body of evidence supporting circadian regulation of cellular redox state, but that it would be premature to conclude that the converse is also true. We therefore propose some approaches that might yield more insight into redox control of cellular timekeeping.

Reciprocal Control of the Circadian Clock and Cellular Redox State - a Critical Appraisal

PubMed Central

Putker, Marrit; O’Neill, John Stuart

2016-01-01

Redox signalling comprises the biology of molecular signal transduction mediated by reactive oxygen (or nitrogen) species. By specific and reversible oxidation of redox-sensitive cysteines, many biological processes sense and respond to signals from the intracellular redox environment. Redox signals are therefore important regulators of cellular homeostasis. Recently, it has become apparent that the cellular redox state oscillates in vivo and in vitro, with a period of about one day (circadian). Circadian time-keeping allows cells and organisms to adapt their biology to resonate with the 24-hour cycle of day/night. The importance of this innate biological time-keeping is illustrated by the association of clock disruption with the early onset of several diseases (e.g. type II diabetes, stroke and several forms of cancer). Circadian regulation of cellular redox balance suggests potentially two distinct roles for redox signalling in relation to the cellular clock: one where it is regulated by the clock, and one where it regulates the clock. Here, we introduce the concepts of redox signalling and cellular timekeeping, and then critically appraise the evidence for the reciprocal regulation between cellular redox state and the circadian clock. We conclude there is a substantial body of evidence supporting circadian regulation of cellular redox state, but that it would be premature to conclude that the converse is also true. We therefore propose some approaches that might yield more insight into redox control of cellular timekeeping. PMID:26810072

Fasting, but Not Aging, Dramatically Alters the Redox Status of Cysteine Residues on Proteins in Drosophila melanogaster

PubMed Central

Menger, Katja E.; James, Andrew M.; Cochemé, Helena M.; Harbour, Michael E.; Chouchani, Edward T.; Ding, Shujing; Fearnley, Ian M.; Partridge, Linda; Murphy, Michael P.

2015-01-01

Summary Altering the redox state of cysteine residues on protein surfaces is an important response to environmental challenges. Although aging and fasting alter many redox processes, the role of cysteine residues is uncertain. To address this, we used a redox proteomic technique, oxidative isotope-coded affinity tags (OxICAT), to assess cysteine-residue redox changes in Drosophila melanogaster during aging and fasting. This approach enabled us to simultaneously identify and quantify the redox state of several hundred cysteine residues in vivo. Cysteine residues within young flies had a bimodal distribution with peaks at ∼10% and ∼85% reversibly oxidized. Surprisingly, these cysteine residues did not become more oxidized with age. In contrast, 24 hr of fasting dramatically oxidized cysteine residues that were reduced under fed conditions while also reducing cysteine residues that were initially oxidized. We conclude that fasting, but not aging, dramatically alters cysteine-residue redox status in D. melanogaster. PMID:26095360

A novel mitochondria-targeted two-photon fluorescent probe for dynamic and reversible detection of the redox cycles between peroxynitrite and glutathione.

PubMed

Sun, Chunlong; Du, Wen; Wang, Peng; Wu, Yang; Wang, Baoqin; Wang, Jun; Xie, Wenjun

2017-12-16

Redox homeostasis is important for maintenance of normal physiological functions within cells. Redox state of cells is primarily a consequence of precise balance between levels of reducing equivalents and reactive oxygen species. Redox homeostasis between peroxynitrite (ONOO - ) and glutathione (GSH) is closely associated with physiological and pathological processes, such as prolonged relaxation in vascular tissues and smooth muscle preparations, attenuation of hepatic necrosis, and activation of matrix metalloproteinase-2. We report a two-photon fluorescent probe (TP-Se) based on water-soluble carbazole-based compound, which integrates with organic selenium, to monitor changes in ONOO - /GSH levels in cells. This probe can reversibly respond to ONOO - and GSH and exhibits high selectivity, sensitivity, and mitochondrial targeting. The probe was successfully applied to visualize changes in redox cycles during ONOO - outbreak and antioxidant GSH repair in cells. The probe will lead to significant development on redox events involved in cellular redox regulation. Copyright © 2017 Elsevier Inc. All rights reserved.

Redox implications of AMPK-mediated signal transduction beyond energetic clues.

PubMed

Cardaci, Simone; Filomeni, Giuseppe; Ciriolo, Maria Rosa

2012-05-01

Since the discovery of AMP-dependent protein kinase (AMPK), its fundamental role in regulating metabolic pathways and the molecular mechanism underlying the regulation of its activity by adenine nucleotides has been widely studied. AMPK is not only an energy-responsive enzyme, but it also senses redox signals. This review aims at recapitulating the recent lines of evidence that demonstrate the responsiveness of this kinase to metabolic and nitroxidative imbalance, thus providing new insights into the intimate networks of redox-based signals upstream of AMPK. In particular, we discuss its well-recognized activation downstream of mitochondrial dysfunction, debate the recent findings that AMPK is directly targeted by pro-oxidant species, and question alternative redox pathways that allow AMPK to be included into the large class of redox-sensing proteins. The possible therapeutic implications of the role of AMPK in redox-associated pathologies, such as cancer and neurodegeneration, are also discussed in light of recent advances that suggest a role for AMPK in the tuning of redox-dependent processes, such as apoptosis and autophagy.

Multiple Sclerosis: Molecular Mechanisms and Therapeutic Opportunities

PubMed Central

Miljković, Djordje; Spasojević, Ivan

2013-01-01

Abstract The pathophysiology of multiple sclerosis (MS) involves several components: redox, inflammatory/autoimmune, vascular, and neurodegenerative. All of them are supported by the intertwined lines of evidence, and none of them should be written off. However, the exact mechanisms of MS initiation, its development, and progression are still elusive, despite the impressive pace by which the data on MS are accumulating. In this review, we will try to integrate the current facts and concepts, focusing on the role of redox changes and various reactive species in MS. Knowing the schedule of initial changes in pathogenic factors and the key turning points, as well as understanding the redox processes involved in MS pathogenesis is the way to enable MS prevention, early treatment, and the development of therapies that target specific pathophysiological components of the heterogeneous mechanisms of MS, which could alleviate the symptoms and hopefully stop MS. Pertinent to this, we will outline (i) redox processes involved in MS initiation; (ii) the role of reactive species in inflammation; (iii) prooxidative changes responsible for neurodegeneration; and (iv) the potential of antioxidative therapy. Antioxid. Redox Signal. 19, 2286–2334. PMID:23473637

Redox signaling, Nox5 and vascular remodeling in hypertension.

PubMed

Montezano, Augusto C; Tsiropoulou, Sofia; Dulak-Lis, Maria; Harvey, Adam; Camargo, Livia De Lucca; Touyz, Rhian M

2015-09-01

Extensive data indicate a role for reactive oxygen species (ROS) and redox signaling in vascular damage in hypertension. However, molecular mechanisms underlying these processes remain unclear, but oxidative post-translational modification of vascular proteins is critical. This review discusses how proteins are oxidatively modified and how redox signaling influences vascular smooth muscle cell growth and vascular remodeling in hypertension. We also highlight Nox5 as a novel vascular ROS-generating oxidase. Oxidative stress in hypertension leads to oxidative imbalance that affects vascular cell function through redox signaling. Many Nox isoforms produce ROS in the vascular wall, and recent findings show that Nox5 may be important in humans. ROS regulate signaling by numerous processes including cysteine oxidative post-translational modification such as S-nitrosylation, S-glutathionylation and sulfydration. In vascular smooth muscle cells, this influences cellular responses to oxidative stimuli promoting changes from a contractile to a proliferative phenotype. In hypertension, Nox-induced ROS production is increased, leading to perturbed redox signaling through oxidative modifications of vascular proteins. This influences mitogenic signaling and cell cycle regulation, leading to altered cell growth and vascular remodeling in hypertension.

Extracellular bioreduction

DOEpatents

Chidambaram, Devicharan [Middle Island, NY; Francis, Arokiasamy J [Middle Island, NY

2012-04-17

A method for processing environmental or industrial samples to remove, reclaim or otherwise reduce the level of chemical species present in the sample that act as redox active species. The redox active species is kept in a waste chamber and is separated from an aqueous bacterial culture that is held in a culture chamber. The waste chamber and the culture chamber are separated by a porous membrane through which electron transfer can occur but through which the aqueous bacterial culture cannot pass. The redox active species substantially remains in the waste chamber and is in non-contact with the aqueous bacterial culture during the process of removal, reduction or reclamation.

Introduction to the thematic minireview series on redox-active protein modifications and signaling.

PubMed

Banerjee, Ruma

2013-09-13

The dynamics of redox metabolism necessitate cellular strategies for sensing redox changes and for responding to them. A common mechanism for receiving and transmitting redox changes is via reversible modifications of protein cysteine residues. A plethora of cysteine modifications have been described, including sulfenylation, glutathionylation, and disulfide formation. These post-translational modifications have the potential to alter protein structure and/or function and to modulate cellular processes ranging from division to death and from circadian rhythms to secretion. The focus of this thematic minireview series is cysteine modifications in response to reactive oxygen and nitrogen species.

Library of electrocatalytic sites in nano-structured domains: electrocatalysis of hydrogen peroxide.

PubMed

Pandey, Prem C; Singh, Bhupendra

2008-12-01

Electrochemical detection of hydrogen peroxide at eight types of ormosil-modified electrodes, referred as hexacyanoferrate-system; Prussian blue systems (PB-1, PB-2, and PB-3), palladium (Pd-) system, graphite (Gr-) system, gold nanoparticle (AuNPs) system and palladium-gold nanoparticle (Pd-AuNPs) system were studied. The results on electrochemical detection suggested that hydrogen peroxide does not undergo homogeneous electrochemical mediation; however, the presence of redox mediator within nano-structured domains facilitates the electro-analysis of the same via redox electrocatalysis. Four approaches causing manipulation in nano-structured domains are described: (a) increase in the molecular size of the components generating nano-structured domains; (b) modulation via chemical reactivity; (c) modulation by non-reactive moieties and known nanoparticles; and (d) modulation by mixed approaches (a-c), all leading to decrease in a nano-structured domains. The results demonstrated that an increase in the size of nano-structured domains or decrease in micro-porous geometry increases the efficiency of electrocatalysis. The basic reaction protocol adopted in generating nano-structured domains, followed by manipulation protocols, supported the introduction of a library for creating electrocatalytic sites with varying electrocatalytic efficiency within the same basic nano-structured platform.

ARSENIC LEACHING FROM IRON RICH MINERAL PROCESSING WASTE: INFLUENCE OF PH AND REDOX POTENTIAL

EPA Science Inventory

This paper presents the effect of pH and redox potential on the potential mobility of arsenic (As) from a contaminated mineral processing waste. The selected waste contained about 0.47 g kg^-1 of As and 66.2 g kg^-1 of iron (Fe). The characteristic of the wast...

Molecular inflammation as an underlying mechanism of the aging process and age-related diseases.

PubMed

Chung, H Y; Lee, E K; Choi, Y J; Kim, J M; Kim, D H; Zou, Y; Kim, C H; Lee, J; Kim, H S; Kim, N D; Jung, J H; Yu, B P

2011-07-01

Aging is a biological process characterized by time-dependent functional declines that are influenced by changes in redox status and by oxidative stress-induced inflammatory reactions. An organism's pro-inflammatory status may underlie the aging process and age-related diseases. In this review, we explore the molecular basis of low-grade, unresolved, subclinical inflammation as a major risk factor for exacerbating the aging process and age-related diseases. We focus on the redox-sensitive transcription factors, NF-κB and FOXO, which play essential roles in the expression of pro-inflammatory mediators and anti-oxidant enzymes, respectively. Major players in molecular inflammation are discussed with respect to the age-related up-regulation of pro-inflammatory cytokines and adhesion molecules, cyclo-oxygenase-2, lipoxygenase, and inducible nitric oxide synthase. The molecular inflammation hypothesis proposed by our laboratory is briefly described to give further molecular insights into the intricate interplay among redox balance, pro-inflammatory gene activation, and chronic age-related inflammatory diseases. The final section discusses calorie restriction as an aging-retarding intervention that also exhibits extraordinarily effective anti-inflammatory activity by modulating GSH redox, NF-κB, SIRT1, PPARs, and FOXOs.

Comparison of Eh and H2 measurements for delineating redox processes in a contaminated aquifer

USGS Publications Warehouse

Chapelle, Francis H.; Haack, Sheridan K.; Adriaens, Peter; Henry, Mark A.; Bradley, Paul M.

1996-01-01

Measurements of oxidation-reduction potential (Eh) and concentrations of dissolved hydrogen (H2) were made in a shallow groundwater system contaminated with solvents and jet fuel to delineate the zonation of redox processes. Eh measurements ranged from +69 to -158 mV in a cross section of the contaminated plume and accurately delineated oxic from anoxic groundwater. Plotting measured Eh and pH values on an equilibrium stability diagram indicated that Fe(III) reduction was the predominant redox process in the anoxic zone and did not indicate the presence of methanogenesis and sulfate reduction. In contrast, measurements of H2concentrations indicated that methanogenesis predominated in heavily contaminated sediments near the water table surface (H2 ∼ 7.0 nM) and that the methanogenic zone was surrounded by distinct sulfate-reducing (H2 ∼ 1-4 nM) and Fe(III)-reducing (H2 ∼ 0.1-0.8 nM) zones. The presence of methanogenesis, sulfate reduction, and Fe(III) reduction was confirmed by the distribution of dissolved oxygen, sulfate, Fe(II), and methane in groundwater. These results show that H2 concentrations were more useful for identifying anoxic redox processes than Ehmeasurements in this groundwater system. However, H2-based redox zone delineations are more reliable when H2 concentrations are interpreted in the context of electron-acceptor (oxygen, nitrate, sulfate) availability and the presence of final products [Fe(II), sulfide, methane] of microbial metabolism.

Cancer drug resistance: redox resetting renders a way

PubMed Central

Xie, Na; Nice, Edouard C.; Zhang, Haiyuan; Huang, Canhua; Lei, Yunlong

2016-01-01

Disruption of redox homeostasis is a crucial factor in the development of drug resistance, which is a major problem facing current cancer treatment. Compared with normal cells, tumor cells generally exhibit higher levels of reactive oxygen species (ROS), which can promote tumor progression and development. Upon drug treatment, some tumor cells can undergo a process of ‘Redox Resetting’ to acquire a new redox balance with higher levels of ROS accumulation and stronger antioxidant systems. Evidence has accumulated showing that the ‘Redox Resetting’ enables cancer cells to become resistant to anticancer drugs by multiple mechanisms, including increased rates of drug efflux, altered drug metabolism and drug targets, activated prosurvival pathways and inefficient induction of cell death. In this article, we provide insight into the role of ‘Redox Resetting’ on the emergence of drug resistance that may contribute to pharmacological modulation of resistance. PMID:27057637

Redox-related metabolites and gene expression modulated by sugar in sunflower leaves: similarities with Sunflower chlorotic mottle virus-induced symptom.

PubMed

Rodríguez, Marianela; Muñoz, Nacira; Lenardon, Sergio; Lascano, Ramiro

2013-01-01

Sugars are part of an integrated redox system, since they are key regulators of respiration and photosynthesis, and therefore of the levels of reducing power, ATP and ROS. These elements are major determinants of the cellular redox state, which is involved in the perception and regulation of many endogenous and environmental stimuli. Our previous findings suggested that early sugar increase produced during compatible Sunflower chlorotic mottle virus (SuCMoV) infection might modulate chlorotic symptom development through redox state alteration in sunflower. The purpose of this work was to characterize redox-related metabolites and gene expression changes associated with high sugar availability and symptom development induced by SuCMoV. The results show that sugar caused an increase in glutathione, ascorbate, pyridine nucleotides, and ATP. In addition, higher sugar availability reduced hydrogen peroxide and ΦPSII. This finding suggests that high sugar availability would be associated with cellular redox alteration and photoinhibitory process. The expression of the genes analyzed was also strongly affected by sugar, such as the down-regulation of psbA and up-regulation of psbO and cp29. The expression level of cytoplasmic (apx-1 and gr)- and chloroplastic (Fe-sod)-targeted genes was also significantly enhanced in sugar-treated leaves. Therefore, all these responses suggest that sugars induce chloroplastic redox state alteration with photoinhibition process that could be contributing to chlorotic symptom development during SuCMoV infection.

Thioredoxin 1-Mediated Post-Translational Modifications: Reduction, Transnitrosylation, Denitrosylation, and Related Proteomics Methodologies

PubMed Central

Wu, Changgong; Parrott, Andrew M.; Fu, Cexiong; Liu, Tong; Marino, Stefano M.; Gladyshev, Vadim N.; Jain, Mohit R.; Baykal, Ahmet T.; Li, Qing; Oka, Shinichi; Sadoshima, Junichi; Beuve, Annie; Simmons, William J.

2011-01-01

Abstract Despite the significance of redox post-translational modifications (PTMs) in regulating diverse signal transduction pathways, the enzymatic systems that catalyze reversible and specific oxidative or reductive modifications have yet to be firmly established. Thioredoxin 1 (Trx1) is a conserved antioxidant protein that is well known for its disulfide reductase activity. Interestingly, Trx1 is also able to transnitrosylate or denitrosylate (defined as processes to transfer or remove a nitric oxide entity to/from substrates) specific proteins. An intricate redox regulatory mechanism has recently been uncovered that accounts for the ability of Trx1 to catalyze these different redox PTMs. In this review, we will summarize the available evidence in support of Trx1 as a specific disulfide reductase, and denitrosylation and transnitrosylation agent, as well as the biological significance of the diverse array of Trx1-regulated pathways and processes under different physiological contexts. The dramatic progress in redox proteomics techniques has enabled the identification of an increasing number of proteins, including peroxiredoxin 1, whose disulfide bond formation and nitrosylation status are regulated by Trx1. This review will also summarize the advancements of redox proteomics techniques for the identification of the protein targets of Trx1-mediated PTMs. Collectively, these studies have shed light on the mechanisms that regulate Trx1-mediated reduction, transnitrosylation, and denitrosylation of specific target proteins, solidifying the role of Trx1 as a master regulator of redox signal transduction. Antioxid. Redox Signal. 15, 2565–2604. PMID:21453190

In vivo NAD assay reveals the intracellular NAD contents and redox state in healthy human brain and their age dependences

PubMed Central

Zhu, Xiao-Hong; Lu, Ming; Lee, Byeong-Yeul; Ugurbil, Kamil; Chen, Wei

2015-01-01

NAD is an essential metabolite that exists in NAD+ or NADH form in all living cells. Despite its critical roles in regulating mitochondrial energy production through the NAD+/NADH redox state and modulating cellular signaling processes through the activity of the NAD+-dependent enzymes, the method for quantifying intracellular NAD contents and redox state is limited to a few in vitro or ex vivo assays, which are not suitable for studying a living brain or organ. Here, we present a magnetic resonance (MR) -based in vivo NAD assay that uses the high-field MR scanner and is capable of noninvasively assessing NAD+ and NADH contents and the NAD+/NADH redox state in intact human brain. The results of this study provide the first insight, to our knowledge, into the cellular NAD concentrations and redox state in the brains of healthy volunteers. Furthermore, an age-dependent increase of intracellular NADH and age-dependent reductions in NAD+, total NAD contents, and NAD+/NADH redox potential of the healthy human brain were revealed in this study. The overall findings not only provide direct evidence of declined mitochondrial functions and altered NAD homeostasis that accompany the normal aging process but also, elucidate the merits and potentials of this new NAD assay for noninvasively studying the intracellular NAD metabolism and redox state in normal and diseased human brain or other organs in situ. PMID:25730862

Microbial Response to Experimentally Controlled Redox Transitions at the Sediment Water Interface.

PubMed

Frindte, Katharina; Allgaier, Martin; Grossart, Hans-Peter; Eckert, Werner

2015-01-01

The sediment-water interface of freshwater lakes is characterized by sharp chemical gradients, shaped by the interplay between physical, chemical and microbial processes. As dissolved oxygen is depleted in the uppermost sediment, the availability of alternative electron acceptors, e.g. nitrate and sulfate, becomes the limiting factor. We performed a time series experiment in a mesocosm to simulate the transition from aerobic to anaerobic conditions at the sediment-water interface. Our goal was to identify changes in the microbial activity due to redox transitions induced by successive depletion of available electron acceptors. Monitoring critical hydrochemical parameters in the overlying water in conjunction with a new sampling strategy for sediment bacteria enabled us to correlate redox changes in the water to shifts in the active microbial community and the expression of functional genes representing specific redox-dependent microbial processes. Our results show that during several transitions from oxic-heterotrophic condition to sulfate-reducing condition, nitrate-availability and the on-set of sulfate reduction strongly affected the corresponding functional gene expression. There was evidence of anaerobic methane oxidation with NOx. DGGE analysis revealed redox-related changes in microbial activity and expression of functional genes involved in sulfate and nitrite reduction, whereas methanogenesis and methanotrophy showed only minor changes during redox transitions. The combination of high-frequency chemical measurements and molecular methods provide new insights into the temporal dynamics of the interplay between microbial activity and specific redox transitions at the sediment-water interface.

Redox Disproportionation of Glucose as a Major Biosynthetic Energy Source

NASA Technical Reports Server (NTRS)

Weber, Arthur L.

1996-01-01

Previous studies have concluded that very little if any energy is required for the microbial biosynthesis of amino acids and lipids from glucose -- processes that yield almost as much ATP (adenosine triphosphate) as they consume. However, these studies did not establish the strength nor the nature of the energy source driving these biological transformations. To identify and estimate the strength of the energy source behind these processes, we calculated the free energy change due to the redox disproportionation of substrate carbon of (a) 26 redox-balanced fermentation reactions, and (b) the biosynthesis of amino acids, lipids, and nucleotides of E. coli from glucose. A plot of the negative free energy of these reactions per mmole of carbon as a function of the number of disproportionative electron transfers per mmol of carbon showed that the energy yields of these fermentations and biosyntheses were directly proportional to the degree of redox disproportionation of carbon. Since this linear relationship showed that redox disproportionation was the dominant energy source of these reactions, we were able to establish that amino acid and lipid biosynthesis obtained most of their energy from redox disproportionation (greater than 94%). In contrast nucleotide biosynthesis was not driven by redox disproportionation of carbon, and consequently depended completely on ATP for energy. This crucial and previously unrecognized role of sugars as an energy source of biosynthesis suggests that sugars were involved at the earliest stage in the origin of anabolic metabolism.

Plasmonic tunnel junctions for single-molecule redox chemistry.

PubMed

de Nijs, Bart; Benz, Felix; Barrow, Steven J; Sigle, Daniel O; Chikkaraddy, Rohit; Palma, Aniello; Carnegie, Cloudy; Kamp, Marlous; Sundararaman, Ravishankar; Narang, Prineha; Scherman, Oren A; Baumberg, Jeremy J

2017-10-20

Nanoparticles attached just above a flat metallic surface can trap optical fields in the nanoscale gap. This enables local spectroscopy of a few molecules within each coupled plasmonic hotspot, with near thousand-fold enhancement of the incident fields. As a result of non-radiative relaxation pathways, the plasmons in such sub-nanometre cavities generate hot charge carriers, which can catalyse chemical reactions or induce redox processes in molecules located within the plasmonic hotspots. Here, surface-enhanced Raman spectroscopy allows us to track these hot-electron-induced chemical reduction processes in a series of different aromatic molecules. We demonstrate that by increasing the tunnelling barrier height and the dephasing strength, a transition from coherent to hopping electron transport occurs, enabling observation of redox processes in real time at the single-molecule level.

Operando X-ray absorption and EPR evidence for a single electron redox process in copper catalysis

DOE PAGES

Lu, Qingquan; Zhang, Jian; Peng, Pan; ...

2015-05-26

An unprecedented single electron redox process in copper catalysis is confirmed using operando X-ray absorption and EPR spectroscopies. The oxidation state of the copper species in the interaction between Cu(II) and a sulfinic acid at room temperature, and the accurate characterization of the formed Cu(I) are clearly shown using operando X-ray absorption and EPR evidence. Further investigation of anion effects on Cu(II) discloses that bromine ions can dramatically increase the rate of the redox process. Moreover, it is proven that the sulfinic acids are converted into sulfonyl radicals, which can be trapped by 2-arylacrylic acids and various valuable β-keto sulfonesmore » are synthesized with good to excellent yields under mild conditions.« less

Concerted One-Electron Two-Proton Transfer Processes in Models Inspired by the Tyr-His Couple of Photosystem II

DOE PAGES

Huynh, Mioy T.; Mora, S. Jimena; Villalba, Matias; ...

2017-05-09

Nature employs a TyrZ-His pair as a redox relay that couples proton transfer to the redox process between P680 and the water oxidizing catalyst in photosystem II. Artificial redox relays composed of different benzimidazole–phenol dyads (benzimidazole models His and phenol models Tyr) with substituents designed to simulate the hydrogen bond network surrounding the TyrZ-His pair have been prepared. Furthermore, when the benzimidazole substituents are strong proton acceptors such as primary or tertiary amines, theory predicts that a concerted two proton transfer process associated with the electrochemical oxidation of the phenol will take place. Furthermore, theory predicts a decrease in themore » redox potential of the phenol by ~300 mV and a small kinetic isotope effect (KIE). Indeed, electrochemical, spectroelectrochemical, and KIE experimental data are consistent with these predictions. Our results were obtained by using theory to guide the rational design of artificial systems and have implications for managing proton activity to optimize efficiency at energy conversion sites involving water oxidation and reduction.« less

Nrf2 and Nrf2-Related Proteins in Development and Developmental Toxicity: Insights from studies in Zebrafish (Danio rerio)

PubMed Central

Hahn, Mark E.; Timme-Laragy, Alicia R.; Karchner, Sibel I.; Stegeman, John J.

2015-01-01

Oxidative stress is an important mechanism of chemical toxicity, contributing to developmental toxicity and teratogenesis as well as to cardiovascular and neurodegenerative diseases and diabetic embryopathy. Developing animals are especially sensitive to effects of chemicals that disrupt the balance of processes generating reactive species and oxidative stress, and those anti-oxidant defenses that protect against oxidative stress. The expression and inducibility of anti-oxidant defenses through activation of NFE2-related factor 2 (Nrf2) and related proteins is an essential process affecting the susceptibility to oxidants, but the complex interactions of Nrf2 in determining embryonic response to oxidants and oxidative stress are only beginning to be understood. The zebrafish (Danio rerio) is an established model in developmental biology and now also in developmental toxicology and redox signaling. Here we review the regulation of genes involved in protection against oxidative stress in developing vertebrates, with a focus on Nrf2 and related cap’n’collar (CNC)-basic-leucine zipper (bZIP) transcription factors. Vertebrate animals including zebrafish share Nfe2, Nrf1, Nrf2, and Nrf3 as well as a core set of genes that respond to oxidative stress, contributing to the value of zebrafish as a model system with which to investigate the mechanisms involved in regulation of redox signaling and the response to oxidative stress during embryolarval development. Moreover, studies in zebrafish have revealed nrf and keap1 gene duplications that provide an opportunity to dissect multiple functions of vertebrate NRF genes, including multiple sensing mechanisms involved in chemical-specific effects. PMID:26130508

Mitochondria targeting by environmental stressors: Implications for redox cellular signaling.

PubMed

Blajszczak, Chuck; Bonini, Marcelo G

2017-11-01

Mitochondria are cellular powerhouses as well as metabolic and signaling hubs regulating diverse cellular functions, from basic physiology to phenotypic fate determination. It is widely accepted that reactive oxygen species (ROS) generated in mitochondria participate in the regulation of cellular signaling, and that some mitochondria chronically operate at a high ROS baseline. However, it is not completely understood how mitochondria adapt to persistently high ROS states and to environmental stressors that disturb the redox balance. Here we will review some of the current concepts regarding how mitochondria resist oxidative damage, how they are replaced when excessive oxidative damage compromises function, and the effect of environmental toxicants (i.e. heavy metals) on the regulation of mitochondrial ROS (mtROS) production and subsequent impact. Copyright © 2017 Elsevier B.V. All rights reserved.

WORKSHOP ON MONITORING OXIDATION-REDUCTION PROCESSES FOR GROUND-WATER RESTORATION

EPA Science Inventory

Redox conditions are among the most important parameters for controlling contaminant transport and fate in ground-water systems. Oxidation-reduction (redox) reactions mediate the chemical behavior of both inorganic and organic chemical constituents by affecting solubility, rea...

Redox regulation in cancer stem cells

USDA-ARS?s Scientific Manuscript database

Reactive oxygen species (ROS) and ROS-dependent (redox regulation) signaling pathways and transcriptional activities are thought to be critical in stem cell self-renewal and differentiation during growth and organogenesis. Aberrant ROS burst and dysregulation of those ROS-dependent cellular processe...

Altered redox state of monocytes from cryopyrin-associated periodic syndromes causes accelerated IL-1β secretion

PubMed Central

Tassi, Sara; Carta, Sonia; Delfino, Laura; Caorsi, Roberta; Martini, Alberto; Gattorno, Marco; Rubartelli, Anna

2010-01-01

In healthy monocytes, Toll-like receptor (TLR) engagement induces production of reactive oxygen species (ROS), followed by an antioxidant response involved in IL-1β processing and secretion. Markers of the antioxidant response include intracellular thioredoxin and extracellular release of reduced cysteine. Cryopyrin-associated periodic syndromes (CAPS) are autoinflammatory diseases in which Nod-like receptor family pyrin domain–containing 3 (NLRP3) gene mutations lead to increased IL-1β secretion. We show in a large cohort of patients that IL-1β secretion by CAPS monocytes is much faster than that by healthy monocytes. This accelerated kinetics is caused by alterations in the basal redox state, as well as in the redox response to TLR triggering displayed by CAPS monocytes. Indeed, unstimulated CAPS monocytes are under a mild oxidative stress, with elevated levels of both ROS and antioxidants. The redox response to LPS is quickened, with early generation of the reducing conditions favoring IL-1β processing and secretion, and then rapidly exhausted. Therefore, secretion of IL-1β is accelerated, but reaches a plateau much earlier than in healthy controls. Pharmacologic inhibition of the redox response hinders IL-1β release, confirming the functional link between redox impairment and altered kinetics of secretion. Monocytes from patients with juvenile idiopathic arthritis display normal kinetics of redox response and IL-1β secretion, excluding a role of chronic inflammation in the alterations observed in CAPS. We conclude that preexisting redox alterations distinct from CAPS monocytes anticipate the pathogen-associated molecular pattern molecule–induced generation of the reducing environment favorable to inflammasome activation and IL-1β secretion. PMID:20445104

Altered redox state of monocytes from cryopyrin-associated periodic syndromes causes accelerated IL-1beta secretion.

PubMed

Tassi, Sara; Carta, Sonia; Delfino, Laura; Caorsi, Roberta; Martini, Alberto; Gattorno, Marco; Rubartelli, Anna

2010-05-25

In healthy monocytes, Toll-like receptor (TLR) engagement induces production of reactive oxygen species (ROS), followed by an antioxidant response involved in IL-1beta processing and secretion. Markers of the antioxidant response include intracellular thioredoxin and extracellular release of reduced cysteine. Cryopyrin-associated periodic syndromes (CAPS) are autoinflammatory diseases in which Nod-like receptor family pyrin domain-containing 3 (NLRP3) gene mutations lead to increased IL-1beta secretion. We show in a large cohort of patients that IL-1beta secretion by CAPS monocytes is much faster than that by healthy monocytes. This accelerated kinetics is caused by alterations in the basal redox state, as well as in the redox response to TLR triggering displayed by CAPS monocytes. Indeed, unstimulated CAPS monocytes are under a mild oxidative stress, with elevated levels of both ROS and antioxidants. The redox response to LPS is quickened, with early generation of the reducing conditions favoring IL-1beta processing and secretion, and then rapidly exhausted. Therefore, secretion of IL-1beta is accelerated, but reaches a plateau much earlier than in healthy controls. Pharmacologic inhibition of the redox response hinders IL-1beta release, confirming the functional link between redox impairment and altered kinetics of secretion. Monocytes from patients with juvenile idiopathic arthritis display normal kinetics of redox response and IL-1beta secretion, excluding a role of chronic inflammation in the alterations observed in CAPS. We conclude that preexisting redox alterations distinct from CAPS monocytes anticipate the pathogen-associated molecular pattern molecule-induced generation of the reducing environment favorable to inflammasome activation and IL-1beta secretion.

Reply to 'Comment on kinetic modeling of microbially-driven redox chemistry of subsurface environments: coupling transport, microbial metabolism and geochemistry' by J. Griffioen

NASA Astrophysics Data System (ADS)

Hunter, K. S.; Van Cappellen, P.

2000-01-01

Our paper, 'Kinetic modeling of microbially-driven redox chemistry of subsurface environments: coupling transport, microbial metabolism and geochemistry' (Hunter et al., 1998), presents a theoretical exploration of biogeochemical reaction networks and their importance to the biogeochemistry of groundwater systems. As with any other model, the kinetic reaction-transport model developed in our paper includes only a subset of all physically, biologically and chemically relevant processes in subsurface environments. It considers aquifer systems where the primary energy source driving microbial activity is the degradation of organic matter. In addition to the primary biodegradation pathways of organic matter (i.e. respiration and fermentation), the redox chemistry of groundwaters is also affected by reactions not directly involving organic matter oxidation. We refer to the latter as secondary reactions. By including secondary redox reactions which consume reduced reaction products (e.g., Mn2+, FeS, H2S), and in the process compete with microbial heterotrophic populations for available oxidants (i.e. O2, NO3-, Mn(IV), Fe(III), SO42-), we predict spatio-temporal distributions of microbial activity which differ significantly from those of models which consider only the biodegradation reactions. That is, the secondary reactions have a significant impact on the distributions of the rates of heterotrophic and chemolithotrophic metabolic pathways. We further show that secondary redox reactions, as well as non-redox reactions, significantly influence the acid-base chemistry of groundwaters. The distributions of dissolved inorganic redox species along flowpaths, however, are similar in simulations with and without secondary reactions (see Figs. 3(b) and 7(b) in Hunter et al., 1998), indicating that very different biogeochemical reaction dynamics may lead to essentially the same chemical redox zonation of a groundwater system.

Thiol-based Redox Proteins in Brassica napus Guard Cell Abscisic Acid and Methyl Jasmonate Signaling

PubMed Central

Zhu, Mengmeng; Zhu, Ning; Song, Wen-yuan; Harmon, Alice C.; Assmann, Sarah M.; Chen, Sixue

2014-01-01

SUMMARY Reversibly oxidized cysteine sulfhydryl groups serve as redox sensors or targets of redox sensing that are important in different physiological processes. Little is known, however, about redox sensitive proteins in guard cells and how they function in stomatal signaling. In this study, Brassica napus guard cell proteins altered by redox in response to abscisic acid (ABA) or methyl jasmonate (MeJA) were identified by complementary proteomics approaches, saturation differential in-gel electrophoresis (DIGE) and isotope-coded affinity tag (ICAT). In total, 65 and 118 potential redox responsive proteins were identified in ABA and MeJA treated guard cells, respectively. All the proteins contain at least one cysteine, and over half of them are predicted to form intra-molecular disulfide bonds. Most of the proteins fall into the functional groups of energy, stress and defense, and metabolism. Based on the peptide sequences identified by mass spectrometry, 30 proteins were common to ABA and MeJA treated samples. A total of 44 cysteines was mapped in all the identified proteins, and their levels of redox sensitivity were quantified. Two of the proteins, a SNRK2 kinase and an isopropylmalate dehydrogenase were confirmed to be redox regulated and involved in stomatal movement. This study creates an inventory of potential redox switches, and highlights a protein redox regulatory mechanism in guard cell ABA and MeJA signal transduction. PMID:24580573

Monitoring intra- and extracellular redox capacity of intact barley aleurone layers responding to phytohormones.

PubMed

Mark, Christina; Zór, Kinga; Heiskanen, Arto; Dufva, Martin; Emnéus, Jenny; Finnie, Christine

2016-12-15

Redox regulation is important for numerous processes in plant cells including abiotic stress, pathogen defence, tissue development, seed germination and programmed cell death. However, there are few methods allowing redox homeostasis to be addressed in whole plant cells, providing insight into the intact in vivo environment. An electrochemical redox assay that applies the menadione-ferricyanide double mediator is used to assess changes in the intracellular and extracellular redox environment in living aleurone layers of barley (Hordeum vulgare cv. Himalaya) grains, which respond to the phytohormones gibberellic acid and abscisic acid. Gibberellic acid is shown to elicit a mobilisation of electrons as detected by an increase in the reducing capacity of the aleurone layers. By taking advantage of the membrane-permeable menadione/menadiol redox pair to probe the membrane-impermeable ferricyanide/ferrocyanide redox pair, the mobilisation of electrons was dissected into an intracellular and an extracellular, plasma membrane-associated component. The intracellular and extracellular increases in reducing capacity were both suppressed when the aleurone layers were incubated with abscisic acid. By probing redox levels in intact plant tissue, the method provides a complementary approach to assays of reactive oxygen species and redox-related enzyme activities in tissue extracts. Copyright © 2016 Elsevier Inc. All rights reserved.

Thioredoxins, Glutaredoxins, and Peroxiredoxins—Molecular Mechanisms and Health Significance: from Cofactors to Antioxidants to Redox Signaling

PubMed Central

Hanschmann, Eva-Maria; Godoy, José Rodrigo; Berndt, Carsten; Hudemann, Christoph

2013-01-01

Abstract Thioredoxins (Trxs), glutaredoxins (Grxs), and peroxiredoxins (Prxs) have been characterized as electron donors, guards of the intracellular redox state, and “antioxidants”. Today, these redox catalysts are increasingly recognized for their specific role in redox signaling. The number of publications published on the functions of these proteins continues to increase exponentially. The field is experiencing an exciting transformation, from looking at a general redox homeostasis and the pathological oxidative stress model to realizing redox changes as a part of localized, rapid, specific, and reversible redox-regulated signaling events. This review summarizes the almost 50 years of research on these proteins, focusing primarily on data from vertebrates and mammals. The role of Trx fold proteins in redox signaling is discussed by looking at reaction mechanisms, reversible oxidative post-translational modifications of proteins, and characterized interaction partners. On the basis of this analysis, the specific regulatory functions are exemplified for the cellular processes of apoptosis, proliferation, and iron metabolism. The importance of Trxs, Grxs, and Prxs for human health is addressed in the second part of this review, that is, their potential impact and functions in different cell types, tissues, and various pathological conditions. Antioxid. Redox Signal. 19, 1539–1605. PMID:23397885

Redox homeostasis: The Golden Mean of healthy living

PubMed Central

Ursini, Fulvio; Maiorino, Matilde; Forman, Henry Jay

2016-01-01

The notion that electrophiles serve as messengers in cell signaling is now widely accepted. Nonetheless, major issues restrain acceptance of redox homeostasis and redox signaling as components of maintenance of a normal physiological steady state. The first is that redox signaling requires sudden switching on of oxidant production and bypassing of antioxidant mechanisms rather than a continuous process that, like other signaling mechanisms, can be smoothly turned up or down. The second is the misperception that reactions in redox signaling involve “reactive oxygen species” rather than reaction of specific electrophiles with specific protein thiolates. The third is that hormesis provides protection against oxidants by increasing cellular defense or repair mechanisms rather than by specifically addressing the offset of redox homeostasis. Instead, we propose that both oxidant and antioxidant signaling are main features of redox homeostasis. As the redox shift is rapidly reversed by feedback reactions, homeostasis is maintained by continuous signaling for production and elimination of electrophiles and nucleophiles. Redox homeostasis, which is the maintenance of nucleophilic tone, accounts for a healthy physiological steady state. Electrophiles and nucleophiles are not intrinsically harmful or protective, and redox homeostasis is an essential feature of both the response to challenges and subsequent feedback. While the balance between oxidants and nucleophiles is preserved in redox homeostasis, oxidative stress provokes the establishment of a new radically altered redox steady state. The popular belief that scavenging free radicals by antioxidants has a beneficial effect is wishful thinking. We propose, instead, that continuous feedback preserves nucleophilic tone and that this is supported by redox active nutritional phytochemicals. These nonessential compounds, by activating Nrf2, mimic the effect of endogenously produced electrophiles (parahormesis). In summary, while hormesis, although globally protective, results in setting up of a new phenotype, parahormesis contributes to health by favoring maintenance of homeostasis. PMID:26820564

Natural photosystems from an engineer's perspective: length, time, and energy scales of charge and energy transfer.

PubMed

Noy, Dror

2008-01-01

The vast structural and functional information database of photosynthetic enzymes includes, in addition to detailed kinetic records from decades of research on physical processes and chemical reaction-pathways, a variety of high and medium resolution crystal structures of key photosynthetic enzymes. Here, it is examined from an engineer's point of view with the long-term goal of reproducing the key features of natural photosystems in novel biological and non-biological solar-energy conversion systems. This survey reveals that the basic physics of the transfer processes, namely, the time constraints imposed by the rates of incoming photon flux and the various decay processes allow for a large degree of tolerance in the engineering parameters. Furthermore, the requirements to guarantee energy and electron transfer rates that yield high efficiency in natural photosystems are largely met by control of distance between chromophores and redox cofactors. This underlines a critical challenge for projected de novo designed constructions, that is, the control of spatial organization of cofactor molecules within dense array of different cofactors, some well within 1 nm from each other.

Antioxidant enzymes as redox-based biomarkers: a brief review

PubMed Central

Yang, Hee-Young; Lee, Tae-Hoon

2015-01-01

The field of redox proteomics focuses to a large extent on analyzing cysteine oxidation in proteins under different experimental conditions and states of diseases. The identification and localization of oxidized cysteines within the cellular milieu is critical for understanding the redox regulation of proteins under physiological and pathophysiological conditions, and it will in turn provide important information that are potentially useful for the development of novel strategies in the treatment and prevention of diseases associated with oxidative stress. Antioxidant enzymes that catalyze oxidation/reduction processes are able to serve as redox biomarkers in various human diseases, and they are key regulators controlling the redox state of functional proteins. Redox regulators with antioxidant properties related to active mediators, cellular organelles, and the surrounding environments are all connected within a network and are involved in diseases related to redox imbalance including cancer, ischemia/reperfusion injury, neurodegenerative diseases, as well as normal aging. In this review, we will briefly look at the selected aspects of oxidative thiol modification in antioxidant enzymes and thiol oxidation in proteins affected by redox control of antioxidant enzymes and their relation to disease. [BMB Reports 2015; 48(4): 200-208] PMID:25560698

Redox proteomics screening cellular factors associated with oxidative stress in hepatocarcinogenesis.

PubMed

Zhou, Li; Wen, Ji; Huang, Zhao; Nice, Edouard C; Huang, Canhua; Zhang, Haiyuan; Li, Qifu

2017-03-01

Liver cancer is a major global health problem being the sixth most common cancer and the third cause of cancer-related death, with hepatocellular carcinoma (HCC) representing more than 90% of primary liver cancers. Mounting evidence suggests that, compared with their normal counterparts, many types of cancer cell have increased levels of ROS. Therefore, cancer cells need to combat high levels of ROS, especially at early stages of tumor development. Recent studies have revealed that ROS-mediated regulation of redox-sensitive proteins (redox sensors) is involved in the pathogenesis and/or progression of many human diseases, including cancer. Unraveling the altered functions of redox sensors and the underlying mechanisms in hepatocarcinogenesis is critical for the development of novel cancer therapeutics. For this reason, redox proteomics has been developed for the high-throughput screening of redox sensors, which will benefit the development of novel therapeutic strategies for the treatment of HCC. In this review, we will briefly introduce several novel redox proteomics techniques that are currently available to study various oxidative modifications in hepatocarcinogenesis and summarize the most important discoveries in the study of redox processes related to the development and progression of HCC. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Imaging Redox State in Mouse Muscles of Different Ages.

PubMed

Moon, Lily; Frederick, David W; Baur, Joseph A; Li, Lin Z

2017-01-01

Aging is the greatest risk factor for many diseases. Intracellular concentrations of nicotinamide adenine dinucleotide (NAD + ) and the NAD + -coupled redox state have been proposed to moderate many aging-related processes, yet the specific mechanisms remain unclear. The concentration of NAD + falls with age in skeletal muscle, yet there is no consensus on whether aging will increase or decrease the redox potential of NAD + /NADH. Oxidized flavin groups (Fp) (e.g. FAD, i.e., flavin adenine dinucleotide, contained in flavoproteins) and NADH are intrinsic fluorescent indicators of oxidation and reduction status of tissue, respectively. The redox ratio, i.e., the ratio of Fp to NADH, may be a surrogate indicator of the NAD + /NADH redox potential. In this study we used the Chance redox scanner (NADH/Fp fluorescence imaging at low temperature) to investigate the effect of aging on the redox state of mitochondria in skeletal muscles. The results showed that there are borderline significant differences in nominal concentrations of Fp and NADH, but not in the redox ratio s when comparing 3.5-month and 13-month old muscles of mice (n = 6). It may be necessary to increase the number of muscle samples and study mice of more advanced age.

Thioredoxins, glutaredoxins, and peroxiredoxins--molecular mechanisms and health significance: from cofactors to antioxidants to redox signaling.

PubMed

Hanschmann, Eva-Maria; Godoy, José Rodrigo; Berndt, Carsten; Hudemann, Christoph; Lillig, Christopher Horst

2013-11-01

Thioredoxins (Trxs), glutaredoxins (Grxs), and peroxiredoxins (Prxs) have been characterized as electron donors, guards of the intracellular redox state, and "antioxidants". Today, these redox catalysts are increasingly recognized for their specific role in redox signaling. The number of publications published on the functions of these proteins continues to increase exponentially. The field is experiencing an exciting transformation, from looking at a general redox homeostasis and the pathological oxidative stress model to realizing redox changes as a part of localized, rapid, specific, and reversible redox-regulated signaling events. This review summarizes the almost 50 years of research on these proteins, focusing primarily on data from vertebrates and mammals. The role of Trx fold proteins in redox signaling is discussed by looking at reaction mechanisms, reversible oxidative post-translational modifications of proteins, and characterized interaction partners. On the basis of this analysis, the specific regulatory functions are exemplified for the cellular processes of apoptosis, proliferation, and iron metabolism. The importance of Trxs, Grxs, and Prxs for human health is addressed in the second part of this review, that is, their potential impact and functions in different cell types, tissues, and various pathological conditions.

Electrochemistry of LB films of mixed MGDG:UQ on ITO.

PubMed

Hoyo, Javier; Guaus, Ester; Torrent-Burgués, Juan; Sanz, Fausto

2015-08-01

The electrochemical behaviour of biomimetic monolayers of monogalactosyldiacylglycerol (MGDG) incorporating ubiquinone-10 (UQ) has been investigated. MGDG is the principal component in the thylakoid membrane and UQ seems a good substitute for plastoquinone-9, involved in photosynthesis chain. The monolayers have been performed using the Langmuir and Langmuir-Blodgett (LB) techniques and the redox behaviour of the LB films, transferred at several surface pressures on a glass covered with indium-tin oxide (ITO), has been characterized by cyclic voltammetry. The cyclic voltammograms show that UQ molecules present two redox processes (I and II) at high UQ content and high surface pressures, and only one redox process (I) at low UQ content and low surface pressures. The apparent rate constants calculated for processes I and II indicate a different kinetic control for the reduction and the oxidation of UQ/UQH2 redox couple, being k(Rapp)(I) = 2.2 · 10(-5) s(-1), k(Rapp)(II) = 5.1 · 10(-14) k(Oapp)(I) = 3.3 · 10(-3) s(-1) and k(Oapp)(II) = 6.1 · 10(-6) s(-1), respectively. The correlation of the redox response with the physical states of the LB films allows determining the positions of the UQ molecules in the biomimetic monolayer, which change with the surface pressure and the UQ content. These positions are known as diving and swimming. Copyright © 2015 Elsevier B.V. All rights reserved.

Extracting the redox orbitals in Li battery materials with high-resolution x-ray compton scattering spectroscopy.

PubMed

Suzuki, K; Barbiellini, B; Orikasa, Y; Go, N; Sakurai, H; Kaprzyk, S; Itou, M; Yamamoto, K; Uchimoto, Y; Wang, Yung Jui; Hafiz, H; Bansil, A; Sakurai, Y

2015-02-27

We present an incisive spectroscopic technique for directly probing redox orbitals based on bulk electron momentum density measurements via high-resolution x-ray Compton scattering. Application of our method to spinel Li_{x}Mn_{2}O_{4}, a lithium ion battery cathode material, is discussed. The orbital involved in the lithium insertion and extraction process is shown to mainly be the oxygen 2p orbital. Moreover, the manganese 3d states are shown to experience spatial delocalization involving 0.16±0.05 electrons per Mn site during the battery operation. Our analysis provides a clear understanding of the fundamental redox process involved in the working of a lithium ion battery.

Soil Metabolome and Metabolic Fate: Microbial Insights into Freshwater Tidal Wetland Redox Biogeochemistry

NASA Astrophysics Data System (ADS)

Roy Chowdhury, T.; Bramer, L.; Hoyt, D. W.; Kim, Y. M.; Metz, T. O.; McCue, L. A.; Jansson, J.; Bailey, V. L.

2017-12-01

Earth System Models predict climate extremes that will impact regional and global hydrology. Aquatic-terrestrial transition zones like wetlands will experience the immediate consequence of climate change as shifts in the magnitude and dynamics of hydrologic flow. Such fluctuating hydrology can alter the structure and function of the soil microbial populations that in turn will alter the nature and rate of biogeochemical transformations and significantly impact the carbon balance of the ecosystem. We tested the impacts of shifting hydrology on the soil microbiome and the role of antecedent moisture condition on redox active microbial processes in soils sampled from a tidal freshwater wetland system in the lower Columbia River, WA, USA. Our objectives were to characterize changes in the soil microbial community composition in response to soil moisture legacy effects, and to elucidate relationships between community response, geochemical signatures and metabolite profiles in this soil. The 16S rRNA gene sequencing showed significant decreases in bacterial abundance capable of anaerobic metabolism in response to drying, but quickly recovered to the antecedent moisture condition, as observed by redox processes. Metabolomics and biogeochemical process rates generated evidence for moisture-driven redox conditions as principal controls on the community and metabolic function. Fluctuating redox conditions altered terminal electron acceptor and donor availability and recovery strengths of these pools in soil such that a disproportionate release of carbon dioxide stemmed from alternative anaerobic degradation processes like sulfate and iron reduction in compared to methanogenesis. Our results show that anoxic conditions impact microbial communities in both permanently and temporarily saturated conditions and that rapid change in hydrology can increase substrate availability for both aerobic and anaerobic decomposition processes, including methanogenesis.

Coupling desalination and energy storage with redox flow electrodes.

PubMed

Hou, Xianhua; Liang, Qian; Hu, Xiaoqiao; Zhou, Yu; Ru, Qiang; Chen, Fuming; Hu, Shejun

2018-06-26

Both freshwater shortage and energy crisis are global issues. Herein, we present a double-function system of faradaic desalination and a redox flow battery consisting of VCl3|NaI redox flow electrodes and a feed stream. The system has a nominal cell potential (E0 = +0.79 V). During the discharge process, the salt ions in the feed are extracted by the redox reaction of the flow electrodes, which is indicated by salt removal. Stable and reversible salt removal capacity and electricity can be achieved up to 30 cycles. The energy consumption is as low as 10.27 kJ mol-1 salt. The energy efficiency is as high as 50% in the current aqueous redox flow battery. With energy recovery, the desalination energy consumption decreases greatly to 5.38 kJ mol-1; this is the lowest reported value to date. This "redox flow battery desalination generator" can be operated in a voltage range of 0.3-1.1 V. Our research provides a novel method for obtaining energy-saving desalination and redox flow batteries.

Redox-Assisted Protein Folding Systems in Eukaryotic Parasites

PubMed Central

Haque, Saikh Jaharul; Majumdar, Tanmay

2012-01-01

Abstract Significance: The cysteine (Cys) residues of proteins play two fundamentally important roles. They serve as sites of post-translational redox modifications as well as influence the conformation of the protein through the formation of disulfide bonds. Recent Advances: Redox-related and redox-associated protein folding in protozoan parasites has been found to be a major mode of regulation, affecting myriad aspects of the parasitic life cycle, host-parasite interactions, and the disease pathology. Available genome sequences of various parasites have begun to complement the classical biochemical and enzymological studies of these processes. In this article, we summarize the reversible Cys disulfide (S-S) bond formation in various classes of strategically important parasitic proteins, and its structural consequence and functional relevance. Critical Issues: Molecular mechanisms of folding remain under-studied and often disconnected from functional relevance. Future Directions: The clinical benefit of redox research will require a comprehensive characterization of the various isoforms and paralogs of the redox enzymes and their concerted effect on the structure and function of the specific parasitic client proteins. Antioxid. Redox Signal. 17, 674–683. PMID:22122448

Model creation of moving redox reaction boundary in agarose gel electrophoresis by traditional potassium permanganate method.

PubMed

Xie, Hai-Yang; Liu, Qian; Li, Jia-Hao; Fan, Liu-Yin; Cao, Cheng-Xi

2013-02-21

A novel moving redox reaction boundary (MRRB) model was developed for studying electrophoretic behaviors of analytes involving redox reaction on the principle of moving reaction boundary (MRB). Traditional potassium permanganate method was used to create the boundary model in agarose gel electrophoresis because of the rapid reaction rate associated with MnO(4)(-) ions and Fe(2+) ions. MRB velocity equation was proposed to describe the general functional relationship between velocity of moving redox reaction boundary (V(MRRB)) and concentration of reactant, and can be extrapolated to similar MRB techniques. Parameters affecting the redox reaction boundary were investigated in detail. Under the selected conditions, good linear relationship between boundary movement distance and time were obtained. The potential application of MRRB in electromigration redox reaction titration was performed in two different concentration levels. The precision of the V(MRRB) was studied and the relative standard deviations were below 8.1%, illustrating the good repeatability achieved in this experiment. The proposed MRRB model enriches the MRB theory and also provides a feasible realization of manual control of redox reaction process in electrophoretic analysis.

Understanding controls on redox processes in floodplain sediments of the Upper Colorado River Basin

DOE PAGES

Noël, Vincent; Boye, Kristin; Kukkadapu, Ravi K.; ...

2017-12-15

Floodplains, heavily used for water supplies, housing, agriculture, mining, and industry, are important repositories of organic carbon, nutrients, and metal contaminants. The accumulation and release of these species is often mediated by redox processes. By understanding the physicochemical, hydrological, and biogeochemical controls on the distribution and variability of sediment redox conditions we can develop conceptual and numerical models of contaminant transport within floodplains. The Upper Colorado River Basin (UCRB) is impacted by former uranium and vanadium ore processing, resulting in contamination by V, Cr, Mn, As, Se, Mo and U. Previous authors have suggested that sediment redox activity occurring withinmore » organic carbon-enriched bodies located below the groundwater level may be regionally important to the maintenance and release of contaminant inventories, particularly uranium. To help assess this hypothesis, vertical distributions of Fe and S redox states and sulfide mineralogy were assessed in sediment cores from three floodplain sites spanning a 250 km transect of the central UCRB. Our results support the hypothesis that organic-enriched reduced sediments are important zones of biogeochemical activity within UCRB floodplains. Furthermore, we found that the presence of organic carbon, together with pore saturation, are the key requirements for maintaining reducing conditions, which were dominated by sulfate-reduction products. Sediment texture was found to be of secondary importance and to moderate the response of the system to external forcing, such as oxidant diffusion. Consequently, fine-grain sediments are relatively resistant to oxidation in comparison to coarser-grained sediments. Exposure to oxidants consumes precipitated sulfides, with a disproportionate loss of mackinawite (FeS) as compared to the more stable pyrite. The accompanying loss of redox buffering capacity creates the potential for release of sequestered radionuclides and metals. Because of their redox reactivity and stores of metals, C, and N, organic-enriched sediments are likely to be important to nutrient and contaminant mobility within UCRB floodplain aquifers.« less

Understanding controls on redox processes in floodplain sediments of the Upper Colorado River Basin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Noël, Vincent; Boye, Kristin; Kukkadapu, Ravi K.

Floodplains, heavily used for water supplies, housing, agriculture, mining, and industry, are important repositories of organic carbon, nutrients, and metal contaminants. The accumulation and release of these species is often mediated by redox processes. By understanding the physicochemical, hydrological, and biogeochemical controls on the distribution and variability of sediment redox conditions we can develop conceptual and numerical models of contaminant transport within floodplains. The Upper Colorado River Basin (UCRB) is impacted by former uranium and vanadium ore processing, resulting in contamination by V, Cr, Mn, As, Se, Mo and U. Previous authors have suggested that sediment redox activity occurring withinmore » organic carbon-enriched bodies located below the groundwater level may be regionally important to the maintenance and release of contaminant inventories, particularly uranium. To help assess this hypothesis, vertical distributions of Fe and S redox states and sulfide mineralogy were assessed in sediment cores from three floodplain sites spanning a 250 km transect of the central UCRB. Our results support the hypothesis that organic-enriched reduced sediments are important zones of biogeochemical activity within UCRB floodplains. Furthermore, we found that the presence of organic carbon, together with pore saturation, are the key requirements for maintaining reducing conditions, which were dominated by sulfate-reduction products. Sediment texture was found to be of secondary importance and to moderate the response of the system to external forcing, such as oxidant diffusion. Consequently, fine-grain sediments are relatively resistant to oxidation in comparison to coarser-grained sediments. Exposure to oxidants consumes precipitated sulfides, with a disproportionate loss of mackinawite (FeS) as compared to the more stable pyrite. The accompanying loss of redox buffering capacity creates the potential for release of sequestered radionuclides and metals. Because of their redox reactivity and stores of metals, C, and N, organic-enriched sediments are likely to be important to nutrient and contaminant mobility within UCRB floodplain aquifers.« less

Improvement of Human Keratinocyte Migration by a Redox Active Bioelectric Dressing

PubMed Central

Banerjee, Jaideep; Das Ghatak, Piya; Roy, Sashwati; Khanna, Savita; Sequin, Emily K.; Bellman, Karen; Dickinson, Bryan C.; Suri, Prerna; Subramaniam, Vish V.; Chang, Christopher J.; Sen, Chandan K.

2014-01-01

Exogenous application of an electric field can direct cell migration and improve wound healing; however clinical application of the therapy remains elusive due to lack of a suitable device and hence, limitations in understanding the molecular mechanisms. Here we report on a novel FDA approved redox-active Ag/Zn bioelectric dressing (BED) which generates electric fields. To develop a mechanistic understanding of how the BED may potentially influence wound re-epithelialization, we direct emphasis on understanding the influence of BED on human keratinocyte cell migration. Mapping of the electrical field generated by BED led to the observation that BED increases keratinocyte migration by three mechanisms: (i) generating hydrogen peroxide, known to be a potent driver of redox signaling, (ii) phosphorylation of redox-sensitive IGF1R directly implicated in cell migration, and (iii) reduction of protein thiols and increase in integrinαv expression, both of which are known to be drivers of cell migration. BED also increased keratinocyte mitochondrial membrane potential consistent with its ability to fuel an energy demanding migration process. Electric fields generated by a Ag/Zn BED can cross-talk with keratinocytes via redox-dependent processes improving keratinocyte migration, a critical event in wound re-epithelialization. PMID:24595050

MINERALOGICAL PRESERVATION OF SOLID SAMPLES COLLECTED FROM ANOXIC SUBSURFACE ENVIRONMENTS

EPA Science Inventory

Remedial technologies utilized at hazardous waste sites for the treatment of metal and metalloid contaminants often take advantage of reduction-oxidation (redox) processes to reach ground water clean up goals. This is because redox reactions, in many cases, govern the biogeochem...

Understanding controls on redox processes in floodplain sediments of the Upper Colorado River Basin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Noël, Vincent; Boye, Kristin; Kukkadapu, Ravi K.

River floodplains, heavily used for water supplies, housing, agriculture, mining, and industry, may have water quality jeopardized by native or exogenous metals. Redox processes mediate the accumulation and release of these species in groundwater. Understanding the physicochemical, hydrological, and biogeochemical controls on the distribution and variability and variability of redox conditions is therefore critical to developing conceptual and numerical models of contaminants transport within floodplains. The distribution and intensity of redox activity at the Rifle, CO, site within the Upper Colorado River Basin (UCRB), are believed to be controlled by textural and compositional heterogeneities. Regionally, the UCRB is impacted bymore » former uranium and vanadium ore processing, resulting in contaminations by U, Mo, V, As, Se, and Mn. Floodplains throughout the UCRB share sediment and groundwater characteristics, making redox activity regionally important to metal and radionuclide mobility. In this study, Fe and S speciation were used to track the distribution and stability of redox processes in sediment cores from three floodplain sites covering a 250 km range in the central portion of the UCRB. The results of the present study support the hypothesis that Fe(III) and sulfate reducing sediments are regionally important in the UCRB. The presence of organic carbon together with pore saturation were the key requirements for reducing conditions, dominated by sulfate-reduction. Sediment texture moderated the response of the system to external forcing, such as oxidant infusion, making fine-grain sediments resistant to change in comparison to coarser-grained sediments. Exposure to O2 and NO3- mediates the reactivity and longevity of freshly precipitated sulfides creating the potential for release of sequestered radionuclides and metals. The physical and chemical parameters of reducing zones evidenced in this study are thus thought to be key parameters on the dynamic exchange of contaminants with surrounding aquifers.« less

Preservation of organic matter in nontronite against iron redox cycling.

NASA Astrophysics Data System (ADS)

Zeng, Q.

2015-12-01

It is generally believed that clay minerals can protect organic matter from degradation in redox active environments, but both biotic and abiotic factors can influence the redox process and thus potentially change the clay-organic associations. However, the specific mechanisms involved in this process remain poorly understood. In this study, a model organic compound, 12-Aminolauric acid (ALA) was selected to intercalate into the structural interlayer of nontronite (an iron-rich smectite, NAu-2) to form an ALA-intercalated NAu-2 composite (ALA-NAu-2). Shawanella putrefaciens CN32 and sodium dithionite were used to reduce structural Fe(III) to Fe(II) in NAu-2 and ALA-NAu-2. The bioreduced ALA-NAu-2 was subsequently re-oxidized by air. The rates and extents of bioreduction and air re-oxidation were determined with wet chemistry methods. ALA release from ALA-NAu-2 via redox process was monitored. Mineralogical changes after iron redox cycle were investigated with X-ray diffraction, infrared spectroscopy, and scanning and transmission electron microscopy. At the beginning stage of bioreduction, S. putrefaciens CN32 reduced Fe(III) from the edges of nontronite and preferentially reduced and dissolved small and poorly crystalline particles, and released ALA, resulting a positive correlation between ALA release and iron reduction extent (<12%). The subsequent bioreduction (reduction extent ranged from 12~30%) and complete air re-oxidation showed no effect on ALA release. These results suggest that released ALA was largely from small and poorly crystalline NAu-2 particles. In contrast to bioreduction, chemical reduction did not exhibit any selectivity in reducing ALA-NAu-2 particles, and a considerable amount of reductive dissolution was responsible for a large amount of ALA release (>80%). Because bacteria are the principal agent for mediating redox process in natural environments, our results demonstrated that the structural interlayer of smectite can serve as a potential shelter to protect organic matter from oxidation.

The pH dependence of the cathodic peak potential of the active sites in bilirubin oxidase.

PubMed

Filip, Jaroslav; Tkac, Jan

2014-04-01

This is the first study showing pH dependence of three distinct redox sites within bilirubin oxidase (BOD) adsorbed on a nanocomposite modified electrode. The 1st redox centre with the highest redox potential Ec(1st)=404 mV vs. Ag/AgCl (614 mV vs. NHE at pH7.0) exhibited pH dependence with a slope -dEc(1st)/dpH=66(±3) mV under a non-turnover process. The 2nd redox centre with a potential Ec(2nd)=228 mV vs. Ag/AgCl (438 mV vs. NHE at pH7.0) was not dependent on pH in the absence and presence of O2. Finally, the 3rd redox site with a redox potential Ec(3rd)=92 mV vs. Ag/AgCl (302 mV vs. NHE at pH7.0) exhibited pH dependence for a cathodic process with -dEc(3rd)/dpH=70(±6) mV and for anodic process with -dEa(3rd)/dpH=73(±2) mV, respectively. Moreover, two break points for dependence of Ec(1st) or Ec(3rd) on pH were observed for the 1st (T1) site and the 3rd site assigned to involvement of two acidic amino acids (Asp105 and Glu463). A diagram of a potential difference between cathodic peaks of BOD as a dependence on pH is shown. The results obtained can be of interest for construction of biofuel cells based on BOD such as for generation of a low level of electricity from body fluids. Copyright © 2013 Elsevier B.V. All rights reserved.

Engineered Proteins: Redox Properties and Their Applications

PubMed Central

Prabhulkar, Shradha; Tian, Hui; Wang, Xiaotang; Zhu, Jun-Jie

2012-01-01

Abstract Oxidoreductases and metalloproteins, representing more than one third of all known proteins, serve as significant catalysts for numerous biological processes that involve electron transfers such as photosynthesis, respiration, metabolism, and molecular signaling. The functional properties of the oxidoreductases/metalloproteins are determined by the nature of their redox centers. Protein engineering is a powerful approach that is used to incorporate biological and abiological redox cofactors as well as novel enzymes and redox proteins with predictable structures and desirable functions for important biological and chemical applications. The methods of protein engineering, mainly rational design, directed evolution, protein surface modifications, and domain shuffling, have allowed the creation and study of a number of redox proteins. This review presents a selection of engineered redox proteins achieved through these methods, resulting in a manipulation in redox potentials, an increase in electron-transfer efficiency, and an expansion of native proteins by de novo design. Such engineered/modified redox proteins with desired properties have led to a broad spectrum of practical applications, ranging from biosensors, biofuel cells, to pharmaceuticals and hybrid catalysis. Glucose biosensors are one of the most successful products in enzyme electrochemistry, with reconstituted glucose oxidase achieving effective electrical communication with the sensor electrode; direct electron-transfer-type biofuel cells are developed to avoid thermodynamic loss and mediator leakage; and fusion proteins of P450s and redox partners make the biocatalytic generation of drug metabolites possible. In summary, this review includes the properties and applications of the engineered redox proteins as well as their significance and great potential in the exploration of bioelectrochemical sensing devices. Antioxid. Redox Signal. 17, 1796–1822. PMID:22435347

Adaptive changes in renal mitochondrial redox status in diabetic nephropathy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Putt, David A.; Zhong, Qing; Lash, Lawrence H., E-mail: l.h.lash@wayne.edu

2012-01-15

Nephropathy is a serious and common complication of diabetes. In the streptozotocin (STZ)-treated rat model of diabetes, nephropathy does not typically develop until 30 to 45 days post-injection, although hyperglycemia occurs within 24 h. We tested the hypothesis that chronic hyperglycemia results in a modest degree of oxidative stress that is accompanied by compensatory changes in certain antioxidants and mitochondrial redox status. We propose that as kidneys progress to a state of diabetic nephropathy, further adaptations occur in mitochondrial redox status. Basic parameters of renal function in vivo and several parameters of mitochondrial function and glutathione (GSH) and redox statusmore » in isolated renal cortical mitochondria from STZ-treated and age-matched control rats were examined at 30 days and 90 days post-injection. While there was no effect of diabetes on blood urea nitrogen, measurement of other, more sensitive parameters, such as urinary albumin and protein, and histopathology showed significant and progressive worsening in diabetic rats. Thus, renal function is compromised even prior to the onset of frank nephropathy. Changes in mitochondrial respiration and enzyme activities indicated existence of a hypermetabolic state. Higher mitochondrial GSH content and rates of GSH transport into mitochondria in kidneys from diabetic rats were only partially due to changes in expression of mitochondrial GSH carriers and were mostly due to higher substrate supply. Although there are few clear indicators of oxidative stress, there are several redox changes that occur early and change further as nephropathy progresses, highlighting the complexity of the disease. Highlights: ►Adaptive changes in renal mitochondrial and redox status in diabetic rats. ►Modest renal dysfunction even prior to onset of nephropathy. ►Elevated concentrations of mitochondrial GSH in diabetic kidneys. ►Change in GSH due partly to increased protein expression of transporter. ►Oxidatively modified proteins in renal mitochondria from diabetic rats.« less

The decay of Redox-stress Response Capacity is a substantive characteristic of aging: Revising the redox theory of aging.

PubMed

Meng, Jiao; Lv, Zhenyu; Qiao, Xinhua; Li, Xiaopeng; Li, Yazi; Zhang, Yuying; Chen, Chang

2017-04-01

Aging is tightly associated with redox events. The free radical theory of aging indicates that redox imbalance may be an important factor in the aging process. Most studies about redox and aging focused on the static status of oxidative stress levels, there has been little research investigating differential responses to redox challenge during aging. In this study, we used Caenorhabditis elegans and human fibroblasts as models to compare differential responses to oxidative stress challenge in young and old individuals. In response to paraquat stress, young individuals generated more ROS and activated signaling pathways including p-ERK, p-AKT and p-AMPKα/β. After the initial response, young individuals then promoted NRF2 translocation and induced additional antioxidant enzymes and higher expression of phase II enzymes, including SOD, CAT, GPX, HO-1, GSTP-1and others, to maintain redox homeostasis. Moreover, young individuals also demonstrated a better ability to degrade damaged proteins by up-regulating the expression of chaperones and improving proteasome activity. Based on these data, we propose a new concept "Redox-stress Response Capacity (RRC)", which suggests cells or organisms are capable of generating dynamic redox responses to activate cellular signaling and maintain cellular homeostasis. The decay of RRC is the substantive characteristic of aging, which gives a new understand of the redox theory of aging. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

Redox zonation for different groundwater flow paths during bank filtration: a case study at Liao River, Shenyang, northeastern China

NASA Astrophysics Data System (ADS)

Su, Xiaosi; Lu, Shuai; Yuan, Wenzhen; Woo, Nam Chil; Dai, Zhenxue; Dong, Weihong; Du, Shanghai; Zhang, Xinyue

2018-03-01

The spatial and temporal distribution of redox zones in an aquifer is important when designing groundwater supply systems. Redox zonation can have direct or indirect control of the biological and chemical reactions and mobility of pollutants. In this study, redox conditions are characterized by interpreting the hydrogeological conditions and water chemistry in groundwater during bank infiltration at a site in Shenyang, northeast China. The relevant redox processes and zonal differences in a shallow flow path and deeper flow path at the field scale were revealed by monitoring the redox parameters and chemistry of groundwater near the Liao River. The results show obvious horizontal and vertical components of redox zones during bank filtration. Variations in the horizontal extent of the redox zone were controlled by the different permeabilities of the riverbed sediments and aquifer with depth. Horizontally, the redox zone was situated within 17 m of the riverbank for the shallow flow path and within 200 m for the deep flow path. The vertical extent of the redox zone was affected by precipitation and seasonal river floods and extended to 10 m below the surface. During bank filtration, iron and manganese oxides or hydroxides were reductively dissolved, and arsenic that was adsorbed onto the medium surface or coprecipitated is released into the groundwater. This leads to increased arsenic content in groundwater, which poses a serious threat to water supply security.

Thiol-based redox proteins in abscisic acid and methyl jasmonate signaling in Brassica napus guard cells.

PubMed

Zhu, Mengmeng; Zhu, Ning; Song, Wen-yuan; Harmon, Alice C; Assmann, Sarah M; Chen, Sixue

2014-05-01

Reversibly oxidized cysteine sulfhydryl groups serve as redox sensors or targets of redox sensing that are important in various physiological processes. However, little is known about redox-sensitive proteins in guard cells and how they function in stomatal signaling. In this study, Brassica napus guard-cell proteins altered by redox in response to abscisic acid (ABA) or methyl jasmonate (MeJA) were identified by complementary proteomics approaches, saturation differential in-gel electrophoresis and isotope-coded affinity tagging. In total, 65 and 118 potential redox-responsive proteins were identified in ABA- and MeJA-treated guard cells, respectively. All the proteins contain at least one cysteine, and over half of them are predicted to form intra-molecular disulfide bonds. Most of the proteins fall into the functional groups of 'energy', 'stress and defense' and 'metabolism'. Based on the peptide sequences identified by mass spectrometry, 30 proteins were common to ABA- and MeJA-treated samples. A total of 44 cysteines were mapped in the identified proteins, and their levels of redox sensitivity were quantified. Two of the proteins, a sucrose non-fermenting 1-related protein kinase and an isopropylmalate dehydrogenase, were confirmed to be redox-regulated and involved in stomatal movement. This study creates an inventory of potential redox switches, and highlights a protein redox regulatory mechanism in ABA and MeJA signal transduction in guard cells. © 2014 The Authors The Plant Journal © 2014 John Wiley & Sons Ltd.

U redox fronts and kaolinisation in basement-hosted unconformity-related U ores of the Athabasca Basin (Canada): late U remobilisation by meteoric fluids

NASA Astrophysics Data System (ADS)

Mercadier, Julien; Cuney, Michel; Cathelineau, Michel; Lacorde, Mathieu

2011-02-01

Proterozoic basement-hosted unconformity-related uranium deposits of the Athabasca Basin (Saskatchewan, Canada) were affected by significant uranium redistribution along oxidation-reduction redox fronts related to cold and late meteoric fluid infiltration. These redox fronts exhibit the same mineralogical and geochemical features as the well-studied uranium roll-front deposits in siliclastic rocks. The primary hydrothermal uranium mineralisation (1.6-1.3 Ga) of basement-hosted deposits is strongly reworked to new disseminated ores comprising three distinctly coloured zones: a white-green zone corresponding to the previous clay-rich alteration halo contemporaneous with hydrothermal ores, a uranium front corresponding to the uranium deposition zone of the redox front (brownish zone, rich in goethite) and a hematite-rich red zone marking the front progression. The three zones directly reflect the mineralogical zonation related to uranium oxides (pitchblende), sulphides, iron minerals (hematite and goethite) and alumino-phosphate-sulphate (APS) minerals. The zoning can be explained by processes of dissolution-precipitation along a redox interface and was produced by the infiltration of cold (<50°C) meteoric fluids to the hydrothermally altered areas. U, Fe, Ca, Pb, S, REE, V, Y, W, Mo and Se were the main mobile elements in this process, and their distribution within the three zones was, for most of them, directly dependent on their redox potential. The elements concentrated in the redox fronts were sourced by the alteration of previously crystallised hydrothermal minerals, such as uranium oxides and light rare earth element (LREE)-rich APS. The uranium oxides from the redox front are characterised by LREE-enriched patterns, which differ from those of unconformity-related ores and clearly demonstrate their distinct conditions of formation. Uranium redox front formation is thought to be linked to fluid circulation episodes initiated during the 400-300 Ma period during uplift and erosion of the Athabasca Basin when it was near the Equator and to have been still active during the last million years. A major kaolinisation event was caused by changes in the fluid circulation regime, reworking the primary uranium redox fronts and causing the redistribution of elements originally concentrated in the uranium-enriched meteoric-related redox fronts.

TEMPOL increases NAD(+) and improves redox imbalance in obese mice.

PubMed

Yamato, Mayumi; Kawano, Kimika; Yamanaka, Yuki; Saiga, Misako; Yamada, Ken-Ichi

2016-08-01

Continuous energy conversion is controlled by reduction-oxidation (redox) processes. NAD(+) and NADH represent an important redox couple in energy metabolism. 4-Hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPOL) is a redox-cycling nitroxide that promotes the scavenging of several reactive oxygen species (ROS) and is reduced to hydroxylamine by NADH. TEMPOL is also involved in NAD(+) production in the ascorbic acid-glutathione redox cycle. We utilized the chemical properties of TEMPOL to investigate the effects of antioxidants and NAD(+)/NADH modulators on the metabolic imbalance in obese mice. Increases in the NAD(+)/NADH ratio by TEMPOL ameliorated the metabolic imbalance when combined with a dietary intervention, changing from a high-fat diet to a normal diet. Plasma levels of the superoxide marker dihydroethidium were higher in mice receiving the dietary intervention compared with a control diet, but were normalized with TEMPOL consumption. These findings provide novel insights into redox regulation in obesity. Copyright © 2016. Published by Elsevier B.V.

Disulfide proteome yields a detailed understanding of redox regulations: a model study of thioredoxin-linked reactions in seed germination.

PubMed

Yano, Hiroyuki; Kuroda, Masaharu

2006-01-01

Accumulating evidence suggests that redox regulations play important roles in a broad spectrum of biological processes. Recently, Yano et al. developed a disulfide proteome technique that comprehensively visualizes redox change in proteins. In this paper, using the disulfide proteome, we examined rice bran and identified fragments of embryo-specific protein and dienelactone hydrolase as putative targets of thioredoxin. Also, monitoring of the endogenous and recombinant effects of thioredoxin on rice bran proteins and supporting in vivo observations propose a mechanism of redox regulation in seed germination, in which thioredoxin activates cysteine protease with a concurrent unfolding of its substrate, the embryo-specific protein. Our findings suggest that thioredoxin controls the lifetime of specific proteins effectively by regulating the redox reactions coordinately. The model study demonstrates that the disulfide proteome technique is useful not only for identifying targets of thioredoxin, but also for clarify the detailed mechanism of redox regulation.

Proteomic identification of early salicylate- and flg22-responsive redox-sensitive proteins in Arabidopsis

PubMed Central

Liu, Pei; Zhang, Huoming; Yu, Boying; Xiong, Liming; Xia, Yiji

2015-01-01

Accumulation of reactive oxygen species (ROS) is one of the early defense responses against pathogen infection in plants. The mechanism about the initial and direct regulation of the defense signaling pathway by ROS remains elusive. Perturbation of cellular redox homeostasis by ROS is believed to alter functions of redox-sensitive proteins through their oxidative modifications. Here we report an OxiTRAQ-based proteomic study in identifying proteins whose cysteines underwent oxidative modifications in Arabidopsis cells during the early response to salicylate or flg22, two defense pathway elicitors that are known to disturb cellular redox homeostasis. Among the salicylate- and/or flg22-responsive redox-sensitive proteins are those involved in transcriptional regulation, chromatin remodeling, RNA processing, post-translational modifications, and nucleocytoplasmic shuttling. The identification of the salicylate-/flg22-responsive redox-sensitive proteins provides a foundation from which further study can be conducted toward understanding biological significance of their oxidative modifications during the plant defense response. PMID:25720653

Reversible near-infrared fluorescent probe introducing tellurium to mimetic glutathione peroxidase for monitoring the redox cycles between peroxynitrite and glutathione in vivo.

PubMed

Yu, Fabiao; Li, Peng; Wang, Bingshuai; Han, Keli

2013-05-22

The redox homeostasis between peroxynitrite and glutathione is closely associated with the physiological and pathological processes, e.g. vascular tissue prolonged relaxation and smooth muscle preparations, attenuation hepatic necrosis, and activation matrix metalloproteinase-2. We report a near-infrared fluorescent probe based on heptamethine cyanine, which integrates with telluroenzyme mimics for monitoring the changes of ONOO(-)/GSH levels in cells and in vivo. The probe can reversibly respond to ONOO(-) and GSH and exhibits high selectivity, sensitivity, and mitochondrial target. It is successfully applied to visualize the changes of redox cycles during the outbreak of ONOO(-) and the antioxidant GSH repair in cells and animal. The probe would provide a significant advance on the redox events involved in the cellular redox regulation.

Detection of Cysteine Redox States in Mitochondrial Proteins in Intact Mammalian Cells.

PubMed

Habich, Markus; Riemer, Jan

2017-01-01

Import, folding, and activity regulation of mitochondrial proteins are important for mitochondrial function. Cysteine residues play crucial roles in these processes as their thiol groups can undergo (reversible) oxidation reactions. For example, during import of many intermembrane space (IMS) proteins, cysteine oxidation drives protein folding and translocation over the outer membrane. Mature mitochondrial proteins can undergo changes in the redox state of specific cysteine residues, for example, as part of their enzymatic reaction cycle or as adaptations to changes of the local redox environment which might influence their activity. Here we describe methods to study changes in cysteine residue redox states in intact cells. These approaches allow to monitor oxidation-driven protein import as well as changes of cysteine redox states in mature proteins during oxidative stress or during the reaction cycle of thiol-dependent enzymes like oxidoreductases.

Redox signaling in the cardiomyocyte: From physiology to failure.

PubMed

Santos, Celio X C; Raza, Sadaf; Shah, Ajay M

2016-05-01

The specific effect of oxygen and reactive oxygen species (ROS) in mediating post-translational modification of protein targets has emerged as a key mechanism regulating signaling components, a process termed redox signaling. ROS act in the post-translational modification of multiple target proteins including receptors, kinases, phosphatases, ion channels and transcription factors. Both O2 and ROS are major source of electrons in redox reactions in aerobic organisms. Because the heart has the highest O2 consumption among body organs, it is not surprising that redox signaling is central to heart function and pathophysiology. In this article, we review some of the main cardiac redox signaling pathways and their roles in the cardiomyocyte and in heart failure, with particular focus on the specific molecular targets of ROS in the heart. Copyright © 2016 Elsevier Ltd. All rights reserved.

On the potential of redox potential measurements for the characterization of greenhouse gas emissions - preliminary results

NASA Astrophysics Data System (ADS)

Wang, Jihuan; Bogena, Heye; Brüggemann, Nicolas

2017-04-01

Soil greenhouse gas (GHG) emissions contribute to global warming. In order to support mitigation measures against global warming it is important to understand the controlling processes of GHG emissions. Previous studies focused mainly on the paddy rice fields or wetlands showed a strong relationship between soil redox potential and GHG emission (e.g. N2O). Recent sensor developments open the possibility for the long-term monitoring of field scale soil redox potential changes. Here, we performed laboratory lysimeter experiments to investigate how changes in the redox potential, induced by changes in the water level, affect GHG emissions from agricultural soil. Under our experimental conditions, we found that N2O emissions followed closely the changes in redox potential. The dynamics of redox potential were induced by changing the water-table depth in a laboratory lysimeter. During saturated conditions we found a clear negative correlation between redox potentials and N2O emission rates N2O. After switching from saturated to unsaturated conditions, N2O emission quickly decreased. In contrast, the emissions of CO2 increased with increasing soil redox potentials. The level of N2O emission also depended on the fertilization level of the soil. We propose that redox potential measurements are a viable method for better understanding of the controlling factors of GHG emission and the development agricultural management practices to reduce such emissions.

Pyruvate dehydrogenase complex and nicotinamide nucleotide transhydrogenase constitute an energy consuming redox circuit

PubMed Central

Fisher-Wellman, Kelsey H.; Lin, Chien-Te; Ryan, Terence E.; Reese, Lauren R.; Gilliam, Laura A. A.; Cathey, Brook L.; Lark, Daniel S.; Smith, Cody D.; Muoio, Deborah M.; Neufer, P. Darrell

2015-01-01

SUMMARY Cellular proteins rely on reversible redox reactions to establish and maintain biological structure and function. How redox catabolic (NAD+:NADH) and anabolic (NADP+:NADPH) processes integrate during metabolism to maintain cellular redox homeostasis however is unknown. The present work identifies a continuously cycling, mitochondrial membrane potential-dependent redox circuit between the pyruvate dehydrogenase complex (PDHC) and nicotinamide nucleotide transhydrogenase (NNT). PDHC is shown to produce H2O2 in relation to reducing pressure within the complex. The H2O2 produced however is effectively masked by a continuously cycling redox circuit that links, via glutathione/thioredoxin, to NNT, which catalyzes the regeneration of NADPH from NADH at the expense of the mitochondrial membrane potential. The net effect is an automatic fine tuning of NNT-mediated energy expenditure to metabolic balance at the level of PDHC. In mitochondria, genetic or pharmacological disruptions in the PDHC-NNT redox circuit negate counterbalance changes in energy expenditure. At the whole animal level, mice lacking functional NNT (C57BL/6J) are characterized by lower energy expenditure rates, consistent with their well known susceptibility to diet-induced obesity. These findings suggest the integration of redox sensing of metabolic balance with compensatory changes in energy expenditure provides a potential mechanism by which cellular redox homeostasis is maintained and body weight is defended during periods of positive and negative energy balance. PMID:25643703

Pyruvate dehydrogenase complex and nicotinamide nucleotide transhydrogenase constitute an energy-consuming redox circuit.

PubMed

Fisher-Wellman, Kelsey H; Lin, Chien-Te; Ryan, Terence E; Reese, Lauren R; Gilliam, Laura A A; Cathey, Brook L; Lark, Daniel S; Smith, Cody D; Muoio, Deborah M; Neufer, P Darrell

2015-04-15

Cellular proteins rely on reversible redox reactions to establish and maintain biological structure and function. How redox catabolic (NAD+/NADH) and anabolic (NADP+/NADPH) processes integrate during metabolism to maintain cellular redox homoeostasis, however, is unknown. The present work identifies a continuously cycling mitochondrial membrane potential (ΔΨm)-dependent redox circuit between the pyruvate dehydrogenase complex (PDHC) and nicotinamide nucleotide transhydrogenase (NNT). PDHC is shown to produce H2O2 in relation to reducing pressure within the complex. The H2O2 produced, however, is effectively masked by a continuously cycling redox circuit that links, via glutathione/thioredoxin, to NNT, which catalyses the regeneration of NADPH from NADH at the expense of ΔΨm. The net effect is an automatic fine-tuning of NNT-mediated energy expenditure to metabolic balance at the level of PDHC. In mitochondria, genetic or pharmacological disruptions in the PDHC-NNT redox circuit negate counterbalance changes in energy expenditure. At the whole animal level, mice lacking functional NNT (C57BL/6J) are characterized by lower energy-expenditure rates, consistent with their well-known susceptibility to diet-induced obesity. These findings suggest the integration of redox sensing of metabolic balance with compensatory changes in energy expenditure provides a potential mechanism by which cellular redox homoeostasis is maintained and body weight is defended during periods of positive and negative energy balance.

Reactive oxygen species and redox regulation in mesophyll and bundle sheath cells of C4 plants.

PubMed

Turkan, Ismail; Uzilday, Baris; Dietz, Karl-Josef; Bräutigam, Andrea; Ozgur, Rengin

2018-02-26

Redox regulation, antioxidant defence and ROS signalling are critical in realizing and tuning metabolic activities. However, our concepts were mostly developed for C3 plants since Arabidopsis thaliana is major model. Efforts to convert C3 plants to C4 plants to increase yield (see C4 rice; c4rice.irri.org/) entails better understanding of these processes in C4 plants. Various photosynthetic enzymes that take part in light reactions and carbon reactions are regulated via redox components such as thioredoxins as redox transmitters and peroxiredoxins. Due to this, understanding redox regulation in mesophyll and bundle sheath chloroplasts of C4 plants is of paramount importance. It appears impossible to utilize efficient C4 photosynthesis without understanding its exact redox needs and regulation mechanisms used during light reactions. In this review we will discuss available knowledge on redox regulation in C3 and C4 plants with special emphasis on mesophyll and bundle sheath differences in C4. In these two cell types of C4 plants, linear and cyclic electron transport in chloroplasts operate differentially when compared to C3 chloroplasts, changing the redox needs of the cell. Therefore, the focus is given to photosynthetic light reactions, ROS production dynamics, antioxidant defence and thiol based redox regulation with the aim to draw a picture of current knowledge.

Redox Redone.

ERIC Educational Resources Information Center

Petty, John T.

1996-01-01

Presents an extension of the change in oxidation number method that is used for balancing skeletal redox reactions in aqueous solutions. Retains most of the simplicity of the change in oxidation number method but provides the additional step-by-step process necessary for the beginner to balance an equation. (JRH)

Redox control of plant growth and development.

PubMed

Kocsy, Gábor; Tari, Irma; Vanková, Radomíra; Zechmann, Bernd; Gulyás, Zsolt; Poór, Péter; Galiba, Gábor

2013-10-01

Redox changes determined by genetic and environmental factors display well-organized interactions in the control of plant growth and development. Diurnal and seasonal changes in the environmental conditions are important for the normal course of these physiological processes and, similarly to their mild irregular alterations, for stress adaptation. However, fast or large-scale environmental changes may lead to damage or death of sensitive plants. The spatial and temporal redox changes influence growth and development due to the reprogramming of metabolism. In this process reactive oxygen and nitrogen species and antioxidants are involved as components of signalling networks. The control of growth, development and flowering by reactive oxygen and nitrogen species and antioxidants in interaction with hormones at organ, tissue, cellular and subcellular level will be discussed in the present review. Unsolved problems of the field, among others the need for identification of new components and interactions in the redox regulatory network at various organization levels using systems biology approaches will be also indicated. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

The role of oxidative stress in the metabolic syndrome.

PubMed

Whaley-Connell, Adam; McCullough, Peter A; Sowers, James R

2011-01-01

Loss of reduction-oxidation (redox) homeostasis and generation of excess free oxygen radicals play an important role in the pathogenesis of diabetes, hypertension, and consequent cardiovascular disease. Reactive oxygen species are integral in routine in physiologic mechanisms. However, loss of redox homeostasis contributes to proinflammatory and profibrotic pathways that promote impairments in insulin metabolic signaling, reduced endothelial-mediated vasorelaxation, and associated cardiovascular and renal structural and functional abnormalities. Redox control of metabolic function is a dynamic process with reversible pro- and anti-free radical processes. Labile iron is necessary for the catalysis of superoxide anion, hydrogen peroxide, and the generation of the damaging hydroxyl radical. Acute hypoxia and cellular damage in cardiovascular tissue liberate larger amounts of cytosolic and extracellular iron that is poorly liganded; thus, large increases in the generation of oxygen free radicals are possible, causing tissue damage. The understanding of iron and the imbalance of redox homeostasis within the vasculature is integral in hypertension and progression of metabolic dysregulation that contributes to insulin resistance, endothelial dysfunction, and cardiovascular and kidney disease.

Quantifying redox-induced Schottky barrier variations in memristive devices via in operando spectromicroscopy with graphene electrodes

PubMed Central

Baeumer, Christoph; Schmitz, Christoph; Marchewka, Astrid; Mueller, David N.; Valenta, Richard; Hackl, Johanna; Raab, Nicolas; Rogers, Steven P.; Khan, M. Imtiaz; Nemsak, Slavomir; Shim, Moonsub; Menzel, Stephan; Schneider, Claus Michael; Waser, Rainer; Dittmann, Regina

2016-01-01

The continuing revolutionary success of mobile computing and smart devices calls for the development of novel, cost- and energy-efficient memories. Resistive switching is attractive because of, inter alia, increased switching speed and device density. On electrical stimulus, complex nanoscale redox processes are suspected to induce a resistance change in memristive devices. Quantitative information about these processes, which has been experimentally inaccessible so far, is essential for further advances. Here we use in operando spectromicroscopy to verify that redox reactions drive the resistance change. A remarkable agreement between experimental quantification of the redox state and device simulation reveals that changes in donor concentration by a factor of 2–3 at electrode-oxide interfaces cause a modulation of the effective Schottky barrier and lead to >2 orders of magnitude change in device resistance. These findings allow realistic device simulations, opening a route to less empirical and more predictive design of future memory cells. PMID:27539213

Quantifying redox-induced Schottky barrier variations in memristive devices via in operando spectromicroscopy with graphene electrodes.

PubMed

Baeumer, Christoph; Schmitz, Christoph; Marchewka, Astrid; Mueller, David N; Valenta, Richard; Hackl, Johanna; Raab, Nicolas; Rogers, Steven P; Khan, M Imtiaz; Nemsak, Slavomir; Shim, Moonsub; Menzel, Stephan; Schneider, Claus Michael; Waser, Rainer; Dittmann, Regina

2016-08-19

The continuing revolutionary success of mobile computing and smart devices calls for the development of novel, cost- and energy-efficient memories. Resistive switching is attractive because of, inter alia, increased switching speed and device density. On electrical stimulus, complex nanoscale redox processes are suspected to induce a resistance change in memristive devices. Quantitative information about these processes, which has been experimentally inaccessible so far, is essential for further advances. Here we use in operando spectromicroscopy to verify that redox reactions drive the resistance change. A remarkable agreement between experimental quantification of the redox state and device simulation reveals that changes in donor concentration by a factor of 2-3 at electrode-oxide interfaces cause a modulation of the effective Schottky barrier and lead to >2 orders of magnitude change in device resistance. These findings allow realistic device simulations, opening a route to less empirical and more predictive design of future memory cells.

Quantifying redox-induced Schottky barrier variations in memristive devices via in operando spectromicroscopy with graphene electrodes

NASA Astrophysics Data System (ADS)

Baeumer, Christoph; Schmitz, Christoph; Marchewka, Astrid; Mueller, David N.; Valenta, Richard; Hackl, Johanna; Raab, Nicolas; Rogers, Steven P.; Khan, M. Imtiaz; Nemsak, Slavomir; Shim, Moonsub; Menzel, Stephan; Schneider, Claus Michael; Waser, Rainer; Dittmann, Regina

2016-08-01

The continuing revolutionary success of mobile computing and smart devices calls for the development of novel, cost- and energy-efficient memories. Resistive switching is attractive because of, inter alia, increased switching speed and device density. On electrical stimulus, complex nanoscale redox processes are suspected to induce a resistance change in memristive devices. Quantitative information about these processes, which has been experimentally inaccessible so far, is essential for further advances. Here we use in operando spectromicroscopy to verify that redox reactions drive the resistance change. A remarkable agreement between experimental quantification of the redox state and device simulation reveals that changes in donor concentration by a factor of 2-3 at electrode-oxide interfaces cause a modulation of the effective Schottky barrier and lead to >2 orders of magnitude change in device resistance. These findings allow realistic device simulations, opening a route to less empirical and more predictive design of future memory cells.

Optical impedance spectroscopy with single-mode electro-active-integrated optical waveguides.

PubMed

Han, Xue; Mendes, Sergio B

2014-02-04

An optical impedance spectroscopy (OIS) technique based on a single-mode electro-active-integrated optical waveguide (EA-IOW) was developed to investigate electron-transfer processes of redox adsorbates. A highly sensitive single-mode EA-IOW device was used to optically follow the time-dependent faradaic current originated from a submonolayer of cytochrome c undergoing redox exchanges driven by a harmonic modulation of the electric potential at several dc bias potentials and at several frequencies. To properly retrieve the faradaic current density from the ac-modulated optical signal, we introduce here a mathematical formalism that (i) accounts for intrinsic changes that invariably occur in the optical baseline of the EA-IOW device during potential modulation and (ii) provides accurate results for the electro-chemical parameters. We are able to optically reconstruct the faradaic current density profile against the dc bias potential in the working electrode, identify the formal potential, and determine the energy-width of the electron-transfer process. In addition, by combining the optically reconstructed faradaic signal with simple electrical measurements of impedance across the whole electrochemical cell and the capacitance of the electric double-layer, we are able to determine the time-constant connected to the redox reaction of the adsorbed protein assembly. For cytochrome c directly immobilized onto the indium tin oxide (ITO) surface, we measured a reaction rate constant of 26.5 s(-1). Finally, we calculate the charge-transfer resistance and pseudocapacitance associated with the electron-transfer process and show that the frequency dependence of the redox reaction of the protein submonolayer follows as expected the electrical equivalent of an RC-series admittance diagram. Above all, we show here that OIS with single-mode EA-IOW's provide strong analytical signals that can be readily monitored even for small surface-densities of species involved in the redox process (e.g., fmol/cm(2), 0.1% of a full protein monolayer). This experimental approach, when combined with the analytical formalism described here, brings additional sensitivity, accuracy, and simplicity to electro-chemical analysis and is expected to become a useful tool in investigations of redox processes.

Redox regulation of the Calvin–Benson cycle: something old, something new

PubMed Central

Michelet, Laure; Zaffagnini, Mirko; Morisse, Samuel; Sparla, Francesca; Pérez-Pérez, María Esther; Francia, Francesco; Danon, Antoine; Marchand, Christophe H.; Fermani, Simona; Trost, Paolo; Lemaire, Stéphane D.

2013-01-01

Reversible redox post-translational modifications such as oxido-reduction of disulfide bonds, S-nitrosylation, and S-glutathionylation, play a prominent role in the regulation of cell metabolism and signaling in all organisms. These modifications are mainly controlled by members of the thioredoxin and glutaredoxin families. Early studies in photosynthetic organisms have identified the Calvin–Benson cycle, the photosynthetic pathway responsible for carbon assimilation, as a redox regulated process. Indeed, 4 out of 11 enzymes of the cycle were shown to have a low activity in the dark and to be activated in the light through thioredoxin-dependent reduction of regulatory disulfide bonds. The underlying molecular mechanisms were extensively studied at the biochemical and structural level. Unexpectedly, recent biochemical and proteomic studies have suggested that all enzymes of the cycle and several associated regulatory proteins may undergo redox regulation through multiple redox post-translational modifications including glutathionylation and nitrosylation. The aim of this review is to detail the well-established mechanisms of redox regulation of Calvin–Benson cycle enzymes as well as the most recent reports indicating that this pathway is tightly controlled by multiple interconnected redox post-translational modifications. This redox control is likely allowing fine tuning of the Calvin–Benson cycle required for adaptation to varying environmental conditions, especially during responses to biotic and abiotic stresses. PMID:24324475

The redox processes in Hg-contaminated soils from Descoberto (Minas Gerais, Brazil): implications for the mercury cycle.

PubMed

Windmöller, Cláudia C; Durão Júnior, Walter A; de Oliveira, Aline; do Valle, Cláudia M

2015-02-01

Investigations of the redox process and chemical speciation of Hg(II) lead to a better understanding of biogeochemical processes controlling the transformation of Hg(II) into toxic and bioaccumulative monomethyl mercury, mainly in areas contaminated with Hg(0). This study investigates the speciation and redox processes of Hg in soil samples from a small area contaminated with Hg(0) as a result of gold mining activities in the rural municipality of Descoberto (Minas Gerais, Brazil). Soil samples were prepared by adding Hg(0) and HgCl2 separately to dry soil, and the Hg redox process was monitored using thermodesorption coupled to atomic absorption spectrometry. A portion of the Hg(0) added was volatilized (up to 37.4±2.0%) or oxidized (from 36±7% to 88±16%). A correlation with Mn suggests that this oxidation is favored, but many other factors must be evaluated, such as the presence of microorganisms and the types of organic matter present. The interaction of Hg with the matrix is suggested to involve Hg(II)-complexes formed with inorganic and organic sulfur ligands and/or nonspecific adsorption onto oxides of Fe, Al and/or Mn. The kinetics of the oxidation reaction was approximated for two first-order reactions; the faster reaction was attributed to the oxidation of Hg(0)/Hg(I), and the slower reaction corresponded to Hg(I)/Hg(II). The second stage was 43-139 times slower than the first. The samples spiked with Hg(II) showed low volatilization and a shifting of the signal of Hg(II) to lower temperatures. These results show that the extent, rate and type of redox process can be adverse in soils. Descoberto can serve as an example for areas contaminated with Hg(0). Copyright © 2014 Elsevier Inc. All rights reserved.

Use of dissolved H2 concentrations to determine distribution of microbially catalyzed redox reactions in anoxic groundwater

USGS Publications Warehouse

Lovley, D.R.; Chapelle, F.H.; Woodward, J.C.

1994-01-01

The potential for using concentrations of dissolved H2 to determine the distribution of redox processes in anoxic groundwaters was evaluated. In pristine aquifers in which standard geochemical measurements indicated that Fe-(III) reduction, sulfate reduction, or methanogenesis was the terminal electron accepting process (TEAP), the H2 concentrations were similar to the H2 concentrations that have previously been reported for aquatic sediments with the same TEAPs. In two aquifers contaminated with petroleum products, it was impossible with standard geochemical analyses to determine which TEAPs predominated in specific locations. However, the TEAPs predicted from measurements of dissolved H2 were the same as those determined directly through measurements of microbial processes in incubated aquifer material. These results suggest that H2 concentrations may be a useful tool for analyzing the redox chemistry of nonequilibrium groundwaters.

Electrochemical and spectroelectrochemical study on novel non-peripherally tetra 1,2,4-triazole substituted phthalocyanines

NASA Astrophysics Data System (ADS)

Demirbaş, Ümit; Akyüz, Duygu; Akçay, Hakkı Türker; Koca, Atıf; Bekircan, Olcay; Kantekin, Halit

2018-03-01

In the present study novel tetra 4-(4-fluorophenyl)-5-(4-methoxyphenyl)-4H-1,2,4-triazole-3-thio substituted non-peripherally metal free (4), zinc(II) (5), lead (II) (6) and copper(II) (7) phthalocyanines were synthesized. The obtained novel compounds were characterized by a combination of FT-IR, 1H NMR, UV-Vis and MALDI-TOF techniques. The redox properties of the complexes have been investigated via cyclic voltammetry, square wave voltammetry and in situ spectroelectrochemistry. The compounds displayed ring-based, reversible and/or quasi-reversible reduction and oxidation processes and aggregation of the complexes influenced the redox character of the processes. The color changes during the redox processes of metallo phthalocyanine were recorded by in-situ spectroelectrochemical measurements. In situ UV-vis spectroelectrochemical measurements, which was associated with color change of the complexes, showed their applicability in the fields of the electrochemical technologies.

SERS as a tool for in vitro toxicology.

PubMed

Fisher, Kate M; McLeish, Jennifer A; Jamieson, Lauren E; Jiang, Jing; Hopgood, James R; McLaughlin, Stephen; Donaldson, Ken; Campbell, Colin J

2016-06-23

Measuring markers of stress such as pH and redox potential are important when studying toxicology in in vitro models because they are markers of oxidative stress, apoptosis and viability. While surface enhanced Raman spectroscopy is ideally suited to the measurement of redox potential and pH in live cells, the time-intensive nature and perceived difficulty in signal analysis and interpretation can be a barrier to its broad uptake by the biological community. In this paper we detail the development of signal processing and analysis algorithms that allow SERS spectra to be automatically processed so that the output of the processing is a pH or redox potential value. By automating signal processing we were able to carry out a comparative evaluation of the toxicology of silver and zinc oxide nanoparticles and correlate our findings with qPCR analysis. The combination of these two analytical techniques sheds light on the differences in toxicology between these two materials from the perspective of oxidative stress.

Uranium redox transition pathways in acetate-amended sediments

USGS Publications Warehouse

Bargar, John R.; Williams, Kenneth H.; Campbell, Kate M.; Long, Philip E.; Stubbs, Joanne E.; Suvorova, Elenal I.; Lezama-Pacheco, Juan S.; Alessi, Daniel S.; Stylo, Malgorzata; Webb, Samuel M.; Davis, James A.; Giammar, Daniel E.; Blue, Lisa Y.; Bernier-Latmani, Rizlan

2013-01-01

Redox transitions of uranium [from U(VI) to U(IV)] in low-temperature sediments govern the mobility of uranium in the environment and the accumulation of uranium in ore bodies, and inform our understanding of Earth’s geochemical history. The molecular-scale mechanistic pathways of these transitions determine the U(IV) products formed, thus influencing uranium isotope fractionation, reoxidation, and transport in sediments. Studies that improve our understanding of these pathways have the potential to substantially advance process understanding across a number of earth sciences disciplines. Detailed mechanistic information regarding uranium redox transitions in field sediments is largely nonexistent, owing to the difficulty of directly observing molecular-scale processes in the subsurface and the compositional/physical complexity of subsurface systems. Here, we present results from an in situ study of uranium redox transitions occurring in aquifer sediments under sulfate-reducing conditions. Based on molecular-scale spectroscopic, pore-scale geochemical, and macroscale aqueous evidence, we propose a biotic–abiotic transition pathway in which biomass-hosted mackinawite (FeS) is an electron source to reduce U(VI) to U(IV), which subsequently reacts with biomass to produce monomeric U(IV) species. A species resembling nanoscale uraninite is also present, implying the operation of at least two redox transition pathways. The presence of multiple pathways in low-temperature sediments unifies apparently contrasting prior observations and helps to explain sustained uranium reduction under disparate biogeochemical conditions. These findings have direct implications for our understanding of uranium bioremediation, ore formation, and global geochemical processes.

Mitochondrial Energy and Redox Signaling in Plants

PubMed Central

Schwarzländer, Markus

2013-01-01

Abstract Significance: For a plant to grow and develop, energy and appropriate building blocks are a fundamental requirement. Mitochondrial respiration is a vital source for both. The delicate redox processes that make up respiration are affected by the plant's changing environment. Therefore, mitochondrial regulation is critically important to maintain cellular homeostasis. This involves sensing signals from changes in mitochondrial physiology, transducing this information, and mounting tailored responses, by either adjusting mitochondrial and cellular functions directly or reprogramming gene expression. Recent Advances: Retrograde (RTG) signaling, by which mitochondrial signals control nuclear gene expression, has been a field of very active research in recent years. Nevertheless, no mitochondrial RTG-signaling pathway is yet understood in plants. This review summarizes recent advances toward elucidating redox processes and other bioenergetic factors as a part of RTG signaling of plant mitochondria. Critical Issues: Novel insights into mitochondrial physiology and redox-regulation provide a framework of upstream signaling. On the other end, downstream responses to modified mitochondrial function have become available, including transcriptomic data and mitochondrial phenotypes, revealing processes in the plant that are under mitochondrial control. Future Directions: Drawing parallels to chloroplast signaling and mitochondrial signaling in animal systems allows to bridge gaps in the current understanding and to deduce promising directions for future research. It is proposed that targeted usage of new technical approaches, such as quantitative in vivo imaging, will provide novel leverage to the dissection of plant mitochondrial signaling. Antioxid. Redox Signal. 18, 2122–2144. PMID:23234467

Prediction of redox-sensitive cysteines using sequential distance and other sequence-based features.

PubMed

Sun, Ming-An; Zhang, Qing; Wang, Yejun; Ge, Wei; Guo, Dianjing

2016-08-24

Reactive oxygen species can modify the structure and function of proteins and may also act as important signaling molecules in various cellular processes. Cysteine thiol groups of proteins are particularly susceptible to oxidation. Meanwhile, their reversible oxidation is of critical roles for redox regulation and signaling. Recently, several computational tools have been developed for predicting redox-sensitive cysteines; however, those methods either only focus on catalytic redox-sensitive cysteines in thiol oxidoreductases, or heavily depend on protein structural data, thus cannot be widely used. In this study, we analyzed various sequence-based features potentially related to cysteine redox-sensitivity, and identified three types of features for efficient computational prediction of redox-sensitive cysteines. These features are: sequential distance to the nearby cysteines, PSSM profile and predicted secondary structure of flanking residues. After further feature selection using SVM-RFE, we developed Redox-Sensitive Cysteine Predictor (RSCP), a SVM based classifier for redox-sensitive cysteine prediction using primary sequence only. Using 10-fold cross-validation on RSC758 dataset, the accuracy, sensitivity, specificity, MCC and AUC were estimated as 0.679, 0.602, 0.756, 0.362 and 0.727, respectively. When evaluated using 10-fold cross-validation with BALOSCTdb dataset which has structure information, the model achieved performance comparable to current structure-based method. Further validation using an independent dataset indicates it is robust and of relatively better accuracy for predicting redox-sensitive cysteines from non-enzyme proteins. In this study, we developed a sequence-based classifier for predicting redox-sensitive cysteines. The major advantage of this method is that it does not rely on protein structure data, which ensures more extensive application compared to other current implementations. Accurate prediction of redox-sensitive cysteines not only enhances our understanding about the redox sensitivity of cysteine, it may also complement the proteomics approach and facilitate further experimental investigation of important redox-sensitive cysteines.

Redox homeostasis: The Golden Mean of healthy living.

PubMed

Ursini, Fulvio; Maiorino, Matilde; Forman, Henry Jay

2016-08-01

The notion that electrophiles serve as messengers in cell signaling is now widely accepted. Nonetheless, major issues restrain acceptance of redox homeostasis and redox signaling as components of maintenance of a normal physiological steady state. The first is that redox signaling requires sudden switching on of oxidant production and bypassing of antioxidant mechanisms rather than a continuous process that, like other signaling mechanisms, can be smoothly turned up or down. The second is the misperception that reactions in redox signaling involve "reactive oxygen species" rather than reaction of specific electrophiles with specific protein thiolates. The third is that hormesis provides protection against oxidants by increasing cellular defense or repair mechanisms rather than by specifically addressing the offset of redox homeostasis. Instead, we propose that both oxidant and antioxidant signaling are main features of redox homeostasis. As the redox shift is rapidly reversed by feedback reactions, homeostasis is maintained by continuous signaling for production and elimination of electrophiles and nucleophiles. Redox homeostasis, which is the maintenance of nucleophilic tone, accounts for a healthy physiological steady state. Electrophiles and nucleophiles are not intrinsically harmful or protective, and redox homeostasis is an essential feature of both the response to challenges and subsequent feedback. While the balance between oxidants and nucleophiles is preserved in redox homeostasis, oxidative stress provokes the establishment of a new radically altered redox steady state. The popular belief that scavenging free radicals by antioxidants has a beneficial effect is wishful thinking. We propose, instead, that continuous feedback preserves nucleophilic tone and that this is supported by redox active nutritional phytochemicals. These nonessential compounds, by activating Nrf2, mimic the effect of endogenously produced electrophiles (parahormesis). In summary, while hormesis, although globally protective, results in setting up of a new phenotype, parahormesis contributes to health by favoring maintenance of homeostasis. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

Thermodynamic properties of an emerging chemical disinfectant, peracetic acid.

PubMed

Zhang, Chiqian; Brown, Pamela J B; Hu, Zhiqiang

2018-04-15

Peracetic acid (PAA or CH 3 COOOH) is an emerging disinfectant with a low potential to form carcinogenic disinfection by-products (DBPs). Basic thermodynamic properties of PAA are, however, absent or inconsistently reported in the literature. This review aimed to summarize important thermodynamic properties of PAA, including standard Gibbs energy of formation and oxidation-reduction (redox) potential. The standard Gibbs energies of formation of CH 3 COOOH (aq) , CH 3 COOOH (g) , CH 3 COOOH (l) , and CH 3 COOO (aq) - are -299.41kJ·mol -1 , -283.02kJ·mol -1 , -276.10kJ·mol -1 , and -252.60kJ·mol -1 , respectively. The standard redox potentials of PAA are 1.748V and 1.005V vs. standard hydrogen electrode (SHE) at pH 0 and pH 14, respectively. Under biochemical standard state conditions (pH 7, 25°C, 101,325Pa), PAA has a redox potential of 1.385V vs. SHE, higher than many disinfectants. Finally, the environmental implications of the thermodynamic properties of PAA were systematically discussed. Those properties can be used to predict the physicochemical and biological behavior of aquatic systems exposed to PAA. Copyright © 2017 Elsevier B.V. All rights reserved.

Redox-Relevant Aspects of the Extracellular Matrix and Its Cellular Contacts via Integrins

PubMed Central

de Rezende, Flávia Figueiredo

2014-01-01

Abstract Significance: The extracellular matrix (ECM) fulfills essential functions in multicellular organisms. It provides the mechanical scaffold and environmental cues to cells. Upon cell attachment, the ECM signals into the cells. In this process, reactive oxygen species (ROS) are physiologically used as signalizing molecules. Recent Advances: ECM attachment influences the ROS-production of cells. In turn, ROS affect the production, assembly and turnover of the ECM during wound healing and matrix remodeling. Pathological changes of ROS levels lead to excess ECM production and increased tissue contraction in fibrotic disorders and desmoplastic tumors. Integrins are cell adhesion molecules which mediate cell adhesion and force transmission between cells and the ECM. They have been identified as a target of redox-regulation by ROS. Cysteine-based redox-modifications, together with structural data, highlighted particular regions within integrin heterodimers that may be subject to redox-dependent conformational changes along with an alteration of integrin binding activity. Critical Issues: In a molecular model, a long-range disulfide-bridge within the integrin β-subunit and disulfide bridges within the genu and calf-2 domains of the integrin α-subunit may control the transition between the bent/inactive and upright/active conformation of the integrin ectodomain. These thiol-based intramolecular cross-linkages occur in the stalk domain of both integrin subunits, whereas the ligand-binding integrin headpiece is apparently unaffected by redox-regulation. Future Directions: Redox-regulation of the integrin activation state may explain the effect of ROS in physiological processes. A deeper understanding of the underlying mechanism may open new prospects for the treatment of fibrotic disorders. Antioxid. Redox Signal. 20, 1977–1993. PMID:24040997

Electrochemical Detection of Circadian Redox Rhythm in Cyanobacterial Cells via Extracellular Electron Transfer.

PubMed

Nishio, Koichi; Pornpitra, Tunanunkul; Izawa, Seiichiro; Nishiwaki-Ohkawa, Taeko; Kato, Souichiro; Hashimoto, Kazuhito; Nakanishi, Shuji

2015-06-01

Recent research on cellular circadian rhythms suggests that the coupling of transcription-translation feedback loops and intracellular redox oscillations is essential for robust circadian timekeeping. For clarification of the molecular mechanism underlying the circadian rhythm, methods that allow for the dynamic and simultaneous detection of transcription/translation and redox oscillations in living cells are needed. Herein, we report that the cyanobacterial circadian redox rhythm can be electrochemically detected based on extracellular electron transfer (EET), a process in which intracellular electrons are exchanged with an extracellular electrode. As the EET-based method is non-destructive, concurrent detection with transcription/translation rhythm using bioluminescent reporter strains becomes possible. An EET pathway that electrochemically connected the intracellular region of cyanobacterial cells with an extracellular electrode was constructed via a newly synthesized electron mediator with cell membrane permeability. In the presence of the mediator, the open circuit potential of the culture medium exhibited temperature-compensated rhythm with approximately 24 h periodicity. Importantly, such circadian rhythm of the open circuit potential was not observed in the absence of the electron mediator, indicating that the EET process conveys the dynamic information regarding the intracellular redox state to the extracellular electrode. These findings represent the first direct demonstration of the intracellular circadian redox rhythm of cyanobacterial cells. © The Author 2015. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Circulating Membrane-Derived Microvesicles in Redox Biology

PubMed Central

Larson, Michael Craig; Hillery, Cheryl A.; Hogg, Neil

2015-01-01

Microparticles or microvesicles (MV) are sub-cellular membrane blebs shed from all cells in response to various stimuli. MVs carry a battery of signaling molecules, many of them related to redox-regulated processes. The role of MVs, either as a cause or result of cellular redox signaling has been increasingly recognized over the past decade. This is in part due to advances in flow cytometry and its detection of MVs. Notably, recent studies have shown circulating MVs from platelets and endothelial cells drive reactive species-dependent angiogenesis; circulating MVs in cancer alter the microenvironment and enhance invasion through horizontal transfer of mutated proteins and nucleic acids, and harbor redox-regulated matrix metalloproteinases and pro-coagulative surface molecules; and circulating MVs from RBCs and other cells modulate cell-cell interactions through scavenging or production of nitric oxide and other free radicals. While our recognition of MVs in redox-related processes is growing, especially in the vascular biology field, much remains unknown regarding the various biologic and pathologic functions of MVs. Like reactive oxygen and nitrogen species, MVs were originally believed to have a solely a pathological role in biology. And like our understanding of reactive species, it is now clear that MVs also play an important role in normal growth, development, and homeostasis. We are just beginning to understand how MVs are involved in various biological processes—developmental, homeostatic and pathological—and the role of MVs in redox signaling is an rich and exciting area of investigation. PMID:24751526

Redox Aspects of Chaperones in Cardiac Function

PubMed Central

Penna, Claudia; Sorge, Matteo; Femminò, Saveria; Pagliaro, Pasquale; Brancaccio, Mara

2018-01-01

Molecular chaperones are stress proteins that allow the correct folding or unfolding as well as the assembly or disassembly of macromolecular cellular components. Changes in expression and post-translational modifications of chaperones have been linked to a number of age- and stress-related diseases including cancer, neurodegeneration, and cardiovascular diseases. Redox sensible post-translational modifications, such as S-nitrosylation, glutathionylation and phosphorylation of chaperone proteins have been reported. Redox-dependent regulation of chaperones is likely to be a phenomenon involved in metabolic processes and may represent an adaptive response to several stress conditions, especially within mitochondria, where it impacts cellular bioenergetics. These post-translational modifications might underlie the mechanisms leading to cardioprotection by conditioning maneuvers as well as to ischemia/reperfusion injury. In this review, we discuss this topic and focus on two important aspects of redox-regulated chaperones, namely redox regulation of mitochondrial chaperone function and cardiac protection against ischemia/reperfusion injury. PMID:29615920

Bacterial Community Morphogenesis Is Intimately Linked to the Intracellular Redox State

PubMed Central

Okegbe, Chinweike; Price-Whelan, Alexa; Sakhtah, Hassan; Hunter, Ryan C.; Newman, Dianne K.

2013-01-01

Many microbial species form multicellular structures comprising elaborate wrinkles and concentric rings, yet the rules governing their architecture are poorly understood. The opportunistic pathogen Pseudomonas aeruginosa produces phenazines, small molecules that act as alternate electron acceptors to oxygen and nitrate to oxidize the intracellular redox state and that influence biofilm morphogenesis. Here, we show that the depth occupied by cells within colony biofilms correlates well with electron acceptor availability. Perturbations in the environmental provision, endogenous production, and utilization of electron acceptors affect colony development in a manner consistent with redox control. Intracellular NADH levels peak before the induction of colony wrinkling. These results suggest that redox imbalance is a major factor driving the morphogenesis of P. aeruginosa biofilms and that wrinkling itself is an adaptation that maximizes oxygen accessibility and thereby supports metabolic homeostasis. This type of redox-driven morphological change is reminiscent of developmental processes that occur in metazoans. PMID:23292774

Incorporating redox processes improves prediction of carbon and nutrient cycling and greenhouse gas emission

NASA Astrophysics Data System (ADS)

Tang, Guoping; Zheng, Jianqiu; Yang, Ziming; Graham, David; Gu, Baohua; Mayes, Melanie; Painter, Scott; Thornton, Peter

2016-04-01

Among the coupled thermal, hydrological, geochemical, and biological processes, redox processes play major roles in carbon and nutrient cycling and greenhouse gas (GHG) emission. Increasingly, mechanistic representation of redox processes is acknowledged as necessary for accurate prediction of GHG emission in the assessment of land-atmosphere interactions. Simple organic substrates, Fe reduction, microbial reactions, and the Windermere Humic Aqueous Model (WHAM) were added to a reaction network used in the land component of an Earth system model. In conjunction with this amended reaction network, various temperature response functions used in ecosystem models were assessed for their ability to describe experimental observations from incubation tests with arctic soils. Incorporation of Fe reduction reactions improves the prediction of the lag time between CO2 and CH4 accumulation. The inclusion of the WHAM model enables us to approximately simulate the initial pH drop due to organic acid accumulation and then a pH increase due to Fe reduction without parameter adjustment. The CLM4.0, CENTURY, and Ratkowsky temperature response functions better described the observations than the Q10 method, Arrhenius equation, and ROTH-C. As electron acceptors between O2 and CO2 (e.g., Fe(III), SO42-) are often involved, our results support inclusion of these redox reactions for accurate prediction of CH4 production and consumption. Ongoing work includes improving the parameterization of organic matter decomposition to produce simple organic substrates, examining the influence of redox potential on methanogenesis under thermodynamically favorable conditions, and refining temperature response representation near the freezing point by additional model-experiment iterations. We will use the model to describe observed GHG emission at arctic and tropical sites.

Mechanism-based Proteomic Screening Identifies Targets of Thioredoxin-like Proteins*

PubMed Central

Nakao, Lia S.; Everley, Robert A.; Marino, Stefano M.; Lo, Sze M.; de Souza, Luiz E.; Gygi, Steven P.; Gladyshev, Vadim N.

2015-01-01

Thioredoxin (Trx)-fold proteins are protagonists of numerous cellular pathways that are subject to thiol-based redox control. The best characterized regulator of thiols in proteins is Trx1 itself, which together with thioredoxin reductase 1 (TR1) and peroxiredoxins (Prxs) comprises a key redox regulatory system in mammalian cells. However, there are numerous other Trx-like proteins, whose functions and redox interactors are unknown. It is also unclear if the principles of Trx1-based redox control apply to these proteins. Here, we employed a proteomic strategy to four Trx-like proteins containing CXXC motifs, namely Trx1, Rdx12, Trx-like protein 1 (Txnl1) and nucleoredoxin 1 (Nrx1), whose cellular targets were trapped in vivo using mutant Trx-like proteins, under conditions of low endogenous expression of these proteins. Prxs were detected as key redox targets of Trx1, but this approach also supported the detection of TR1, which is the Trx1 reductant, as well as mitochondrial intermembrane proteins AIF and Mia40. In addition, glutathione peroxidase 4 was found to be a Rdx12 redox target. In contrast, no redox targets of Txnl1 and Nrx1 could be detected, suggesting that their CXXC motifs do not engage in mixed disulfides with cellular proteins. For some Trx-like proteins, the method allowed distinguishing redox and non-redox interactions. Parallel, comparative analyses of multiple thiol oxidoreductases revealed differences in the functions of their CXXC motifs, providing important insights into thiol-based redox control of cellular processes. PMID:25561728

Rational design of metal nitride redox materials for solar-driven ammonia synthesis.

PubMed

Michalsky, Ronald; Pfromm, Peter H; Steinfeld, Aldo

2015-06-06

Fixed nitrogen is an essential chemical building block for plant and animal protein, which makes ammonia (NH3) a central component of synthetic fertilizer for the global production of food and biofuels. A global project on artificial photosynthesis may foster the development of production technologies for renewable NH3 fertilizer, hydrogen carrier and combustion fuel. This article presents an alternative path for the production of NH3 from nitrogen, water and solar energy. The process is based on a thermochemical redox cycle driven by concentrated solar process heat at 700-1200°C that yields NH3 via the oxidation of a metal nitride with water. The metal nitride is recycled via solar-driven reduction of the oxidized redox material with nitrogen at atmospheric pressure. We employ electronic structure theory for the rational high-throughput design of novel metal nitride redox materials and to show how transition-metal doping controls the formation and consumption of nitrogen vacancies in metal nitrides. We confirm experimentally that iron doping of manganese nitride increases the concentration of nitrogen vacancies compared with no doping. The experiments are rationalized through the average energy of the dopant d-states, a descriptor for the theory-based design of advanced metal nitride redox materials to produce sustainable solar thermochemical ammonia.

Rational design of metal nitride redox materials for solar-driven ammonia synthesis

PubMed Central

Michalsky, Ronald; Pfromm, Peter H.; Steinfeld, Aldo

2015-01-01

Fixed nitrogen is an essential chemical building block for plant and animal protein, which makes ammonia (NH3) a central component of synthetic fertilizer for the global production of food and biofuels. A global project on artificial photosynthesis may foster the development of production technologies for renewable NH3 fertilizer, hydrogen carrier and combustion fuel. This article presents an alternative path for the production of NH3 from nitrogen, water and solar energy. The process is based on a thermochemical redox cycle driven by concentrated solar process heat at 700–1200°C that yields NH3 via the oxidation of a metal nitride with water. The metal nitride is recycled via solar-driven reduction of the oxidized redox material with nitrogen at atmospheric pressure. We employ electronic structure theory for the rational high-throughput design of novel metal nitride redox materials and to show how transition-metal doping controls the formation and consumption of nitrogen vacancies in metal nitrides. We confirm experimentally that iron doping of manganese nitride increases the concentration of nitrogen vacancies compared with no doping. The experiments are rationalized through the average energy of the dopant d-states, a descriptor for the theory-based design of advanced metal nitride redox materials to produce sustainable solar thermochemical ammonia. PMID:26052421

Connecting Biology to Electronics: Molecular Communication via Redox Modality.

PubMed

Liu, Yi; Li, Jinyang; Tschirhart, Tanya; Terrell, Jessica L; Kim, Eunkyoung; Tsao, Chen-Yu; Kelly, Deanna L; Bentley, William E; Payne, Gregory F

2017-12-01

Biology and electronics are both expert at for accessing, analyzing, and responding to information. Biology uses ions, small molecules, and macromolecules to receive, analyze, store, and transmit information, whereas electronic devices receive input in the form of electromagnetic radiation, process the information using electrons, and then transmit output as electromagnetic waves. Generating the capabilities to connect biology-electronic modalities offers exciting opportunities to shape the future of biosensors, point-of-care medicine, and wearable/implantable devices. Redox reactions offer unique opportunities for bio-device communication that spans the molecular modalities of biology and electrical modality of devices. Here, an approach to search for redox information through an interactive electrochemical probing that is analogous to sonar is adopted. The capabilities of this approach to access global chemical information as well as information of specific redox-active chemical entities are illustrated using recent examples. An example of the use of synthetic biology to recognize external molecular information, process this information through intracellular signal transduction pathways, and generate output responses that can be detected by electrical modalities is also provided. Finally, exciting results in the use of redox reactions to actuate biology are provided to illustrate that synthetic biology offers the potential to guide biological response through electrical cues. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of gold nanoparticles on the structure and electron-transfer characteristics of glucose oxidase redox polyelectrolyte-surfactant complexes.

PubMed

Cortez, M Lorena; Marmisollé, Waldemar; Pallarola, Diego; Pietrasanta, Lía I; Murgida, Daniel H; Ceolín, Marcelo; Azzaroni, Omar; Battaglini, Fernando

2014-10-06

Efficient electrical communication between redox proteins and electrodes is a critical issue in the operation and development of amperometric biosensors. The present study explores the advantages of a nanostructured redox-active polyelectrolyte-surfactant complex containing [Os(bpy)2Clpy](2+) (bpy=2,2'-bipyridine, py= pyridine) as the redox centers and gold nanoparticles (AuNPs) as nanodomains for boosting the electron-transfer propagation throughout the assembled film in the presence of glucose oxidase (GOx). Film structure was characterized by grazing-incidence small-angle X-ray scattering (GISAXS) and atomic force microscopy (AFM), GOx incorporation was followed by surface plasmon resonance (SPR) and quartz-crystal microbalance with dissipation (QCM-D), whereas Raman spectroelectrochemistry and electrochemical studies confirmed the ability of the entrapped gold nanoparticles to enhance the electron-transfer processes between the enzyme and the electrode surface. Our results show that nanocomposite films exhibit five-fold increase in current response to glucose compared with analogous supramolecular AuNP-free films. The introduction of colloidal gold promotes drastic mesostructural changes in the film, which in turn leads to a rigid, amorphous interfacial architecture where nanoparticles, redox centers, and GOx remain in close proximity, thus improving the electron-transfer process. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hypoxia and Redox Signaling on Extracellular Matrix Remodeling: From Mechanisms to Pathological Implications.

PubMed

Labrousse-Arias, David; Martínez-Ruiz, Antonio; Calzada, María J

2017-10-20

The extracellular matrix (ECM) is an essential modulator of cell behavior that influences tissue organization. It has a strong relevance in homeostasis and translational implications for human disease. In addition to ECM structural proteins, matricellular proteins are important regulators of the ECM that are involved in a myriad of different pathologies. Recent Advances: Biochemical studies, animal models, and study of human diseases have contributed to the knowledge of molecular mechanisms involved in remodeling of the ECM, both in homeostasis and disease. Some of them might help in the development of new therapeutic strategies. This review aims to review what is known about some of the most studied matricellular proteins and their regulation by hypoxia and redox signaling, as well as the pathological implications of such regulation. Matricellular proteins have complex regulatory functions and are modulated by hypoxia and redox signaling through diverse mechanisms, in some cases with controversial effects that can be cell or tissue specific and context dependent. Therefore, a better understanding of these regulatory processes would be of great benefit and will open new avenues of considerable therapeutic potential. Characterizing the specific molecular mechanisms that modulate matricellular proteins in pathological processes that involve hypoxia and redox signaling warrants additional consideration to harness the potential therapeutic value of these regulatory proteins. Antioxid. Redox Signal. 27, 802-822.

Modeling Equilibrium Fe Isotope Fractionation in Fe-Organic Complexes: Implications for the use of Fe Isotopes as a Biomarker and Trends Based on the Properties of Bound Ligands

NASA Astrophysics Data System (ADS)

Domagal-Goldman, S.; Kubicki, J. D.

2006-05-01

Fe Isotopes have been proposed as a useful tracer of biological and geochemical processes. Key to understanding the effects these various processes have on Fe isotopes is accurate modeling of the reactions responsible for the isotope fractionations. In this study, we examined the theoretical basis for the claims that Fe isotopes can be used as a biomarker. This was done by using molecular orbital/density functional theory (MO/DFT) calculations to predict the equilibrium fractionation of Fe isotopes due to changes in the redox state and the bonding environment of Fe. Specifically, we predicted vibrational frequencies for iron desferrioxamine (Fe-DFOB), iron triscatechol (Fe(cat)3), iron trisoxalate (Fe(ox)3), and hexaaquo iron (Fe(H2O)6) for complexes containing both ferrous (Fe2+) and ferric (Fe3+) iron. Using these vibrational frequencies, we then predicted fractionation factors between these six complexes. The predicted fractionation factors resulting from changes in the redox state of Fe fell in the range 2.5- 3.5‰. The fractionation factors resulting from changes in the bonding environment of Fe ranged from 0.2 to 1.4‰. These results indicate that changes in the bonding strength of Fe ligands are less important to Fe isotope fractionation processes than are changes to the redox state of Fe. The implications for use of Fe as a tracer of biological processes is clear: abiological redox changes must be ruled out in a sample before Fe isotopes are considered as a potential biomarker. Furthermore, the use of Fe isotopes to measure the redox state of the Earths surface environment through time is supported by this work, since changes in the redox state of Fe appear to be the more important driver of isotopic fractionations. In addition to the large differences between redox-driven fractionations and ligand-driven fractionations, we will also show general trends in the demand for heavy Fe isotopes as a function of properties of the bound ligand. This will help the future analysis of Fe isotope fractionation. Future directions in the theoretical study of metal isotope fractionations will also be discussed, including the modeling of reactions on mineral surfaces.

Nrf2 and Nrf2-related proteins in development and developmental toxicity: Insights from studies in zebrafish (Danio rerio).

PubMed

Hahn, Mark E; Timme-Laragy, Alicia R; Karchner, Sibel I; Stegeman, John J

2015-11-01

Oxidative stress is an important mechanism of chemical toxicity, contributing to developmental toxicity and teratogenesis as well as to cardiovascular and neurodegenerative diseases and diabetic embryopathy. Developing animals are especially sensitive to effects of chemicals that disrupt the balance of processes generating reactive species and oxidative stress, and those anti-oxidant defenses that protect against oxidative stress. The expression and inducibility of anti-oxidant defenses through activation of NFE2-related factor 2 (Nrf2) and related proteins is an essential process affecting the susceptibility to oxidants, but the complex interactions of Nrf2 in determining embryonic response to oxidants and oxidative stress are only beginning to be understood. The zebrafish (Danio rerio) is an established model in developmental biology and now also in developmental toxicology and redox signaling. Here we review the regulation of genes involved in protection against oxidative stress in developing vertebrates, with a focus on Nrf2 and related cap'n'collar (CNC)-basic-leucine zipper (bZIP) transcription factors. Vertebrate animals including zebrafish share Nfe2, Nrf1, Nrf2, and Nrf3 as well as a core set of genes that respond to oxidative stress, contributing to the value of zebrafish as a model system with which to investigate the mechanisms involved in regulation of redox signaling and the response to oxidative stress during embryolarval development. Moreover, studies in zebrafish have revealed nrf and keap1 gene duplications that provide an opportunity to dissect multiple functions of vertebrate NRF genes, including multiple sensing mechanisms involved in chemical-specific effects. Copyright © 2015. Published by Elsevier Inc.

TEMPO/viologen electrochemical heterojunction for diffusion-controlled redox mediation: a highly rectifying bilayer-sandwiched device based on cross-reaction at the interface between dissimilar redox polymers.

PubMed

Tokue, Hiroshi; Oyaizu, Kenichi; Sukegawa, Takashi; Nishide, Hiroyuki

2014-03-26

A couple of totally reversible redox-active molecules, which are different in redox potentials, 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) and viologen (V(2+)), were employed to give rise to a rectified redox conduction effect. Single-layer and bilayer devices were fabricated using polymers containing these sites as pendant groups per repeating unit. The devices were obtained by sandwiching the redox polymer layer(s) with indium tin oxide (ITO)/glass and Pt foil electrodes. Electrochemical measurements of the single-layer device composed of polynorbornene-bearing TEMPO (PTNB) exhibited a diffusion-limited current-voltage response based on the TEMPO(+)/TEMPO exchange reaction, which was almost equivalent to a redox gradient through the PTNB layer depending upon the thickness. The bilayer device gave rise to the current rectification because of the thermodynamically favored cross-reaction between TEMPO(+) and V(+) at the polymer/polymer interface. A current-voltage response obtained for the bilayer device demonstrated a two-step diffusion-limited current behavior as a result of the concurrent V(2+)/V(+) and V(+)/V(0) exchange reactions according to the voltage and suggested that the charge transport process through the device was most likely to be rate-determined by a redox gradient in the polymer layer. Current collection experiments revealed a charge transport balance throughout the device, as a result of the electrochemical stability and robustness of the polymers in both redox states.

Compromised redox homeostasis, altered nitroso–redox balance, and therapeutic possibilities in atrial fibrillation

PubMed Central

Simon, Jillian N.; Ziberna, Klemen; Casadei, Barbara

2016-01-01

Although the initiation, development, and maintenance of atrial fibrillation (AF) have been linked to alterations in myocyte redox state, the field lacks a complete understanding of the impact these changes may have on cellular signalling, atrial electrophysiology, and disease progression. Recent studies demonstrate spatiotemporal changes in reactive oxygen species production shortly after the induction of AF in animal models with an uncoupling of nitric oxide synthase activity ensuing in the presence of long-standing persistent AF, ultimately leading to a major shift in nitroso–redox balance. However, it remains unclear which radical or non-radical species are primarily involved in the underlying mechanisms of AF or which proteins are targeted for redox modification. In most instances, only free radical oxygen species have been assessed; yet evidence from the redox signalling field suggests that non-radical species are more likely to regulate cellular processes. A wider appreciation for the distinction of these species and how both species may be involved in the development and maintenance of AF could impact treatment strategies. In this review, we summarize how redox second-messenger systems are regulated and discuss the recent evidence for alterations in redox regulation in the atrial myocardium in the presence of AF, while identifying some critical missing links. We also examine studies looking at antioxidants for the prevention and treatment of AF and propose alternative redox targets that may serve as superior therapeutic options for the treatment of AF. PMID:26786158

Hourly and daily variation of sediment redox potential in tidal wetland sediments

USGS Publications Warehouse

Catallo, W. James

1999-01-01

Variation of electrochemical oxidation-reduction (redox) potential was examined in surface salt march sediments under conditions of flooding and tidal simulation in mesocosms and field sites. Time series were generated of redox potential measured in sediment profiles at 2-10 cm depth using combination Pt-Ag/AgCl (ORP) electrodes. Redox potential data were acquired at rapid rates (1-55 samples/h) over extended periods (3-104 days) along with similar times series of temperature (water, air, soil) and pH. It was found that redox potential vaired as a result of water level changes and was unrelated to diurnal changes in temperature or pH, the latter of which changed by 370 mV redox potential decrease in under 48 hours). Attenuatoin of microbial activity by [gamma] y-radiation and toxic chemicals elimintated this response. In tidal salt marsh mesocosms where the sediment-plant assemblages were exposed to a simulated diurnal tide, redox potenial oscillations of 40-300 mV amplitude were recoded that has the same periodicity as the flood-drain cycle. Periodic redoc potential time series were observed repeatedly in sediments receiving tidal pulsing but not in those sediments exposed to static hydrological conditions. Data collected over 12 days from a coastal marsh site experiencing diurnal tides showed similar fluctuations in redox potential. Data from the experimentents indicated that (a) redox potential can be a dynamic, nonlinear variable in coastal and estuarine wetland sediments over hourly and daily scales, and the designs of biogeochemical experiments should reflect this, (b) redox potential can change rapidly and signigicantly in coastal wetland sediments in response of flooding and draining, (c) microbial community processes are primarily determinants of the time course of redox potential in wetland sediments, and elimination of inhibition of microbial activity (e.g. by pollutants) can significantly alter that behavior, and (d) fast redox potential dynamics appear to be characteristic of sediments that experience changes in hydrology. The rapid redox potential changes observed in these systems indicated dynamic metabolic and biogeochemical conditions in the field, and confirmed that hourly and daily redox potential variations should be resolved in studies of sediment functioning.

Biological Relevance of Free Radicals and Nitroxides.

PubMed

Prescott, Christopher; Bottle, Steven E

2017-06-01

Nitroxides are stable, kinetically-persistent free radicals which have been successfully used in the study and intervention of oxidative stress, a critical issue pertaining to cellular health which results from an imbalance in the levels of damaging free radicals and redox-active species in the cellular environment. This review gives an overview of some of the biological processes that produce radicals and other reactive oxygen species with relevance to oxidative stress, and then discusses interactions of nitroxides with these species in terms of the use of nitroxides as redox-sensitive probes and redox-active therapeutic agents.

Anticancer activity of metal complexes: involvement of redox processes.

PubMed

Jungwirth, Ute; Kowol, Christian R; Keppler, Bernhard K; Hartinger, Christian G; Berger, Walter; Heffeter, Petra

2011-08-15

Cells require tight regulation of the intracellular redox balance and consequently of reactive oxygen species for proper redox signaling and maintenance of metal (e.g., of iron and copper) homeostasis. In several diseases, including cancer, this balance is disturbed. Therefore, anticancer drugs targeting the redox systems, for example, glutathione and thioredoxin, have entered focus of interest. Anticancer metal complexes (platinum, gold, arsenic, ruthenium, rhodium, copper, vanadium, cobalt, manganese, gadolinium, and molybdenum) have been shown to strongly interact with or even disturb cellular redox homeostasis. In this context, especially the hypothesis of "activation by reduction" as well as the "hard and soft acids and bases" theory with respect to coordination of metal ions to cellular ligands represent important concepts to understand the molecular modes of action of anticancer metal drugs. The aim of this review is to highlight specific interactions of metal-based anticancer drugs with the cellular redox homeostasis and to explain this behavior by considering chemical properties of the respective anticancer metal complexes currently either in (pre)clinical development or in daily clinical routine in oncology.

Anticancer Activity of Metal Complexes: Involvement of Redox Processes

PubMed Central

Jungwirth, Ute; Kowol, Christian R.; Keppler, Bernhard K.; Hartinger, Christian G.; Berger, Walter; Heffeter, Petra

2012-01-01

Cells require tight regulation of the intracellular redox balance and consequently of reactive oxygen species for proper redox signaling and maintenance of metal (e.g., of iron and copper) homeostasis. In several diseases, including cancer, this balance is disturbed. Therefore, anticancer drugs targeting the redox systems, for example, glutathione and thioredoxin, have entered focus of interest. Anticancer metal complexes (platinum, gold, arsenic, ruthenium, rhodium, copper, vanadium, cobalt, manganese, gadolinium, and molybdenum) have been shown to strongly interact with or even disturb cellular redox homeostasis. In this context, especially the hypothesis of “activation by reduction” as well as the “hard and soft acids and bases” theory with respect to coordination of metal ions to cellular ligands represent important concepts to understand the molecular modes of action of anticancer metal drugs. The aim of this review is to highlight specific interactions of metal-based anticancer drugs with the cellular redox homeostasis and to explain this behavior by considering chemical properties of the respective anticancer metal complexes currently either in (pre)clinical development or in daily clinical routine in oncology. PMID:21275772

Anionic Redox Chemistry in Polysulfide Electrode Materials for Rechargeable Batteries.

PubMed

Grayfer, Ekaterina D; Pazhetnov, Egor M; Kozlova, Mariia N; Artemkina, Sofya B; Fedorov, Vladimir E

2017-12-22

Classical Li-ion battery technology is based on the insertion of lithium ions into cathode materials involving metal (cationic) redox reactions. However, this vision is now being reconsidered, as many new-generation electrode materials with enhanced reversible capacities operate through combined cationic and anionic (non-metal) reversible redox processes or even exclusively through anionic redox transformations. Anionic participation in the redox reactions is observed in materials with more pronounced covalency, which is less typical for oxides, but quite common for phosphides or chalcogenides. In this Concept, we would like to draw the reader's attention to this new idea, especially, as it applies to transition-metal polychalcogenides, such as FeS 2 , VS 4 , TiS 3 , NbS 3 , TiS 4 , MoS 3 , etc., in which the key role is played by the (S-S) 2- /2 S 2- redox reaction. The exploration and better understanding of the anion-driven chemistry is important for designing advanced materials for battery and other energy-related applications. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Organic matter and modeling redox reactions during river bank filtration in an alluvial aquifer of the Lot River, France.

PubMed

Kedziorek, Monika A M; Geoffriau, Stephane; Bourg, Alain C M

2008-04-15

A 3 year study of the infiltration of Lot River water into a well field located in an adjacent gravel and clay alluvial aquifer was conducted to assess the importance of organic matter regarding the redox processes which influence groundwater quality in a positive (denitrification) or negative (Mn dissolution) manner. Chloride was used to quantify the mixing of river water with groundwater. According to modeling with PHREEQC, the biodegradation of the infiltrated dissolved organic carbon (DOCi) is not sufficient to explain the observed consequences of the redox reactions (dissolved O2 depletion, denitrification, Mn dissolution). Another electron donor source must therefore be involved: we propose solid organic carbon (SOC) as a likely candidate, if made available for degradation by prior hydrolysis. Its contribution to redox reactions could be significant (30-80% of the total organic carbon consumed by redox reactions during river bank filtration). We show here also that even though the first few meters of infiltration are highly reactive, significant redox reactions can take place further in the aquifer, possibly affecting groundwater quality away from the river bank.

Redox and Reactive Oxygen Species Regulation of Mitochondrial Cytochrome c Oxidase Biogenesis

PubMed Central

Bourens, Myriam; Fontanesi, Flavia; Soto, Iliana C.; Liu, Jingjing

2013-01-01

Abstract Significance: Cytochrome c oxidase (COX), the last enzyme of the mitochondrial respiratory chain, is the major oxygen consumer enzyme in the cell. COX biogenesis involves several redox-regulated steps. The process is highly regulated to prevent the formation of pro-oxidant intermediates. Recent Advances: Regulation of COX assembly involves several reactive oxygen species and redox-regulated steps. These include: (i) Intricate redox-controlled machineries coordinate the expression of COX isoenzymes depending on the environmental oxygen concentration. (ii) COX is a heme A-copper metalloenzyme. COX copper metallation involves the copper chaperone Cox17 and several other recently described cysteine-rich proteins, which are oxidatively folded in the mitochondrial intermembrane space. Copper transfer to COX subunits 1 and 2 requires concomitant transfer of redox power. (iii) To avoid the accumulation of reactive assembly intermediates, COX is regulated at the translational level to minimize synthesis of the heme A-containing Cox1 subunit when assembly is impaired. Critical Issues: An increasing number of regulatory pathways converge to facilitate efficient COX assembly, thus preventing oxidative stress. Future Directions: Here we will review on the redox-regulated COX biogenesis steps and will discuss their physiological relevance. Forthcoming insights into the precise regulation of mitochondrial COX biogenesis in normal and stress conditions will likely open future perspectives for understanding mitochondrial redox regulation and prevention of oxidative stress. Antioxid. Redox Signal. 19, 1940–1952. PMID:22937827

Eu3+ as a dual probe for the determination of IL anion donor power: A combined luminescence spectroscopic and electrochemical approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Babai, Arash; Kopiec, Gabriel; Lackmann, Anastasia

2014-04-01

This work is aimed at giving proof that Eu(Tf2N)(3) (Tf2N = bis(trifluoromethanesulfonyl)amide) can act as both an optical and electrochemical probe for the determination of the Lewis acidity of an ionic liquid anion. For that reason the luminescence spectra and cyclic voltammograms of dilute solutions of Eu(Tf2N)(3) in various ionic liquids were investigated. The Eu2+/3+ redox potential in the investigated ILs can be related to the Lewis basicity of the IL anion. The IL cation had little influence. The lower the determined halfwave potential, the higher the IL anion basicity. The obtained ranking can be confirmed by luminescence spectroscopy wheremore » a bathochromic shift of the D-5(0) -> F-7(4) transition indicates a stronger Lewis basicity of the IL anion. (C) 2014 Published by Elsevier B.V.« less

Visual perception and imagery: a new molecular hypothesis.

PubMed

Bókkon, I

2009-05-01

Here, we put forward a redox molecular hypothesis about the natural biophysical substrate of visual perception and visual imagery. This hypothesis is based on the redox and bioluminescent processes of neuronal cells in retinotopically organized cytochrome oxidase-rich visual areas. Our hypothesis is in line with the functional roles of reactive oxygen and nitrogen species in living cells that are not part of haphazard process, but rather a very strict mechanism used in signaling pathways. We point out that there is a direct relationship between neuronal activity and the biophoton emission process in the brain. Electrical and biochemical processes in the brain represent sensory information from the external world. During encoding or retrieval of information, electrical signals of neurons can be converted into synchronized biophoton signals by bioluminescent radical and non-radical processes. Therefore, information in the brain appears not only as an electrical (chemical) signal but also as a regulated biophoton (weak optical) signal inside neurons. During visual perception, the topological distribution of photon stimuli on the retina is represented by electrical neuronal activity in retinotopically organized visual areas. These retinotopic electrical signals in visual neurons can be converted into synchronized biophoton signals by radical and non-radical processes in retinotopically organized mitochondria-rich areas. As a result, regulated bioluminescent biophotons can create intrinsic pictures (depictive representation) in retinotopically organized cytochrome oxidase-rich visual areas during visual imagery and visual perception. The long-term visual memory is interpreted as epigenetic information regulated by free radicals and redox processes. This hypothesis does not claim to solve the secret of consciousness, but proposes that the evolution of higher levels of complexity made the intrinsic picture representation of the external visual world possible by regulated redox and bioluminescent reactions in the visual system during visual perception and visual imagery.

The limits of life on Earth and searching for life on Mars

NASA Technical Reports Server (NTRS)

Nealson, K. H.

1997-01-01

Considerations of basic properties of bacteria such as size, structure, and metabolic versatility allow one to understand how these remarkable life-forms are so adaptable to environments previously thought to be uninhabitable. It is now appreciated that bacteria on Earth can utilize almost any redox couple that yields energy, taking advantage of this energy, while transforming the elements during metabolism. The ability to grow at the expense of inorganic redox couples allows the microbes to occupy niches not available to the more metabolically constrained eukaryotes. Furthermore, the simplicity of the bacterial structure allows them considerably more resistance to environmental variables (pH, salinity, temperature) that are toxic or lethal to more complex organisms. This information can be used to explain the predominance of prokaryotes in extreme environments on Earth, and to speculate as to simple types of metabolism and biogeochemical cycles that may exist on this planet, Mars, and perhaps other non-Earth environments.

The limits of life on Earth and searching for life on Mars.

PubMed

Nealson, K H

1997-10-25

Considerations of basic properties of bacteria such as size, structure, and metabolic versatility allow one to understand how these remarkable life-forms are so adaptable to environments previously thought to be uninhabitable. It is now appreciated that bacteria on Earth can utilize almost any redox couple that yields energy, taking advantage of this energy, while transforming the elements during metabolism. The ability to grow at the expense of inorganic redox couples allows the microbes to occupy niches not available to the more metabolically constrained eukaryotes. Furthermore, the simplicity of the bacterial structure allows them considerably more resistance to environmental variables (pH, salinity, temperature) that are toxic or lethal to more complex organisms. This information can be used to explain the predominance of prokaryotes in extreme environments on Earth, and to speculate as to simple types of metabolism and biogeochemical cycles that may exist on this planet, Mars, and perhaps other non-Earth environments.

Influence of Iron Speciation on Redox Cycling and Reactivity with Persistent Organic Contaminants

ERIC Educational Resources Information Center

Kim, Dongwook

2009-01-01

Although a number of past studies have been aimed at characterizing iron's redox properties in aqueous systems and its contribution to natural attenuation processes of groundwater contaminants, many questions remain. It is especially important to understand the molecular properties that control the reactivity of both Fe[superscript II] and…

INFLUENCE OF PH AND REDOX CONDITIONS ON COPPER LEACHING

EPA Science Inventory

Leaching behavior of metals from a mineral processing waste at varying pH and redox conditions was studies. Effect of combinations of pH and Eh on leaching of copper is described. Leaching of copper was found to be dependent on both pH and Eh. Higher concentrations of Cu were ...

Kinetic Classroom: Acid-Base and Redox Demonstrations with Student Movement.

ERIC Educational Resources Information Center

Lomax, Joseph F.

1994-01-01

Describes classroom activities that involve student movement to demonstrate principles of kinetics. This classroom method can be used for any topic related to dynamic processes. The method used in this activity illustrates Brxnsted-Lowry acid-base theory and redox reactions. Takes advantage of analogies between proton and electron transfers. Use…

Regulation of cell growth by redox-mediated extracellular proteolysis of platelet-derived growth factor receptor beta.

PubMed

Okuyama, H; Shimahara, Y; Kawada, N; Seki, S; Kristensen, D B; Yoshizato, K; Uyama, N; Yamaoka, Y

2001-07-27

Redox-regulated processes are important elements in various cellular functions. Reducing agents, such as N-acetyl-l-cysteine (NAC), are known to regulate signal transduction and cell growth through their radical scavenging action. However, recent studies have shown that reactive oxygen species are not always involved in ligand-stimulated intracellular signaling. Here, we report a novel mechanism by which NAC blocks platelet-derived growth factor (PDGF)-induced signaling pathways in hepatic stellate cells, a fibrogenic player in the liver. Unlike in vascular smooth muscle cells, we found that reducing agents, including NAC, triggered extracellular proteolysis of PDGF receptor-beta, leading to desensitization of hepatic stellate cells toward PDGF-BB. This effect was mediated by secreted mature cathepsin B. In addition, type II transforming growth factor-beta receptor was also down-regulated. Furthermore, these events seemed to cause a dramatic improvement of rat liver fibrosis. These results indicated that redox processes impact the cell's response to growth factors by regulating the turnover of growth factor receptors and that "redox therapy" is promising for fibrosis-related disease.

Principles for integrating reactive species into in vivo biological processes: Examples from exercise physiology.

PubMed

Margaritelis, Nikos V; Cobley, James N; Paschalis, Vassilis; Veskoukis, Aristidis S; Theodorou, Anastasios A; Kyparos, Antonios; Nikolaidis, Michalis G

2016-04-01

The equivocal role of reactive species and redox signaling in exercise responses and adaptations is an example clearly showing the inadequacy of current redox biology research to shed light on fundamental biological processes in vivo. Part of the answer probably relies on the extreme complexity of the in vivo redox biology and the limitations of the currently applied methodological and experimental tools. We propose six fundamental principles that should be considered in future studies to mechanistically link reactive species production to exercise responses or adaptations: 1) identify and quantify the reactive species, 2) determine the potential signaling properties of the reactive species, 3) detect the sources of reactive species, 4) locate the domain modified and verify the (ir)reversibility of post-translational modifications, 5) establish causality between redox and physiological measurements, 6) use selective and targeted antioxidants. Fulfilling these principles requires an idealized human experimental setting, which is certainly a utopia. Thus, researchers should choose to satisfy those principles, which, based on scientific evidence, are most critical for their specific research question. Copyright © 2015 Elsevier Inc. All rights reserved.

Microbial mediated iron redox cycling in Fe (hydr)oxides for nitrite removal.

PubMed

Lu, Yongsheng; Xu, Lu; Shu, Weikang; Zhou, Jizhi; Chen, Xueping; Xu, Yunfeng; Qian, Guangren

2017-01-01

Nitrite, at an environmentally relevant concentration, was significantly reduced with iron (hydr)oxides mediated by Shewanella oneidensis MR-1. The average nitrite removal rates of 1.28±0.08 and 0.65±0.02(mgL -1 )h -1 were achieved with ferrihydrite and magnetite, respectively. The results showed that nitrite removal was able to undergo multiple redox cycles with iron (hydr)oxides mediated by Shewanella oneidensis MR-1. During the bioreduction of the following cycles, biogenic Fe(II) was subsequently chemically oxidized to Fe(III), which is associated with nitrite reduction. There was 11.18±1.26mgL -1 of NH 4 + -N generated in the process of redox cycling of ferrihydrite. Additionally, results obtained by using X-ray diffraction showed that ferrihydrite and magnetite remained mainly stable in the system. This study indicated that redox cycling of Fe in iron (hydr)oxides was a potential process associated with NO 2 - -N removal from solution, and reduced most nitrite abiotically to gaseous nitrogen species. Copyright © 2016 Elsevier Ltd. All rights reserved.

In situ electrochemical-electron spin resonance investigations of multi-electron redox reaction for organic radical cathodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Qian; Walter, Eric D.; Cosimbescu, Lelia

2016-02-29

Organic radical batteries (ORBs) bearing robust radical polymers as energy storage species, are emerging promisingly with durable high energy and power characteristics by unique tunable redox properties. Here we report the development and application of in situ electrochemical-electron spin resonance (ESR) methodologies to identify the charge transfer mechanism of Poly(2,2,6,6- tetramethylpiperidinyloxy-4-yl methacrylate) (PTMA) based organic radical composite cathodes in the charge-discharge process of lithium half cells. The in situ experiments allow each electrochemical state to be associated with the chemical state (or environment) of the radical species upon the cell cycling. In situ ESR spectra of the composite cathode demonstratemore » a two-electron redox reaction of PTMA. Moreover, two different local environments of radical species are found in the composite electrode that includes both concentrated and isolated radicals. These two types of radicals show similarities during the redox reaction process while behave quite differently in the non-faradic reaction of ion sorption/desorption on the electrode surface.« less

Investigation of Iron Oxide Morphology in a Cyclic Redox Water Splitting Process for Hydrogen Generation

PubMed Central

Bobek, Michael M.; Stehle, Richard C.; Hahn, David W.

2012-01-01

A solar fuels generation research program is focused on hydrogen production by means of reactive metal water splitting in a cyclic iron-based redox process. Iron-based oxides are explored as an intermediary reactive material to dissociate water molecules at significantly reduced thermal energies. With a goal of studying the resulting oxide chemistry and morphology, chemical assistance via CO is used to complete the redox cycle. In order to exploit the unique characteristics of highly reactive materials at the solar reactor scale, a monolithic laboratory scale reactor has been designed to explore the redox cycle at temperatures ranging from 675 to 875 K. Using high resolution scanning electron microscope (SEM) and electron dispersive X-ray spectroscopy (EDS), the oxide morphology and the oxide state are quantified, including spatial distributions. These images show the change of the oxide layers directly after oxidation and after reduction. The findings show a significant non-stoichiometric O/Fe gradient in the atomic ratio following oxidation, which is consistent with a previous kinetics model, and a relatively constant, non-stoichiometric O/Fe atomic ratio following reduction.

Redox potential: An indicator of site productivity in forest management

NASA Astrophysics Data System (ADS)

Sajedi, Toktam; Prescott, Cindy; Lavkulich, Les

2010-05-01

Redox potential (Eh) is an integrated soil measurement that reflects several environmental conditions in the soil associated with aeration, moisture and carbon (organic matter) dynamics. Its measurement can be related to water table fluctuations, precipitation and landscape gradients, organic matter decomposition rates, nutrient dynamics, biological diversity and plant species distribution. Redox is an excellent indicator of soil biological processes, as it is largely a reflection of microbial activities which to a large extent govern carbon dynamics and nutrient cycling. Redox thus serves as an ecological indicator of site productivity at the ecosystem scale and may be used for management purposes as its magnitude can be altered by activities such as harvesting and drainage. A threshold value of 300 mv has been documented as the critical value below which anaerobic conditions in the soil develop. However, redox measurements and its impacts on ecosystem processes such as nutrient cycling and productivity, especially in forest ecosystems, have not received the attention that this "master" variable deserves, On northern Vancouver Island, Canada, regenerating stands of western redcedar-western hemlock (CH) sites exhibit symptoms of nutrient deficiencies and slow growth, but this phenomenon does not occur on adjacent western hemlock- amabalis fir (HA) sites. We tested the hypothesis that differences in nutrient supply and distribution of plant species was caused by differences in moisture regime and redox potential. Redox potential, pH, soil aeration depth (steel rods), organic matter thickness, bulk density, soil carbon store, plant species distribution and richness were measured at five old-growth and five 10-year-old cutover blocks. Results of investigations confirmed that CH forests were wetter, had redox values lower than the critical 300mv and a shallower aerated zone, compared with adjacent regenerating HA sites. Fifty percent of the CH plots had redox values less than +300 mv in the forest floor; whereas only 15 percent of the HA plots had such low values. Composition of the forest understory species was related to soil moisture/aeration. Soil aeration was the most important soil variable influencing plant species composition, explaining 25% of the plant community variability. Eh was always greater than +300 mv in the mineral soil of old growth HA forests but below +300 mv in HA clearcuts, suggesting paludification; however it was below or at this threshold in both CH forests and clearcuts. The reduction in measured redox without a noticeable change in the watertable in HA sites suggests that harvesting HA forests shifts the ecosystem towards more anaerobic conditions more similar to CH sites. In a complimentary study, the significance of redox was assessed in a cedar swamp cutover by exploring the relationships between soil redox potential and tree growth, and mineralization of C and soil C store along a gradient of moisture caused by drainage. Drainage improved aeration in the rooting zone, expressed as redox, and above- and below ground C storage; however C mineralization measured as CO2 evolution was not affected. Tree growth was positively correlated with redox potential. Our results indicate that drainage could be a useful silvicultural practice for improving the productivity of these ecosystems and that it may be possible to improve tree growth without stimulating loss of soil C. This requires that drainage improve aeration in the rooting zone while maintaining redox levels of less than +300 mV in the bulk soil, indicating that redox measurements should be incorporated into silviculture interventions to improve productivity of these forests.

A redox-based mechanism for nitric oxide-induced inhibition of DNA synthesis in human vascular smooth muscle cells

PubMed Central

Bundy, Ruth E; Marczin, Nándor; Chester, Adrian H; Yacoub, Magdi

2000-01-01

The current study explored potential redox mechanisms of nitric oxide (NO)-induced inhibition of DNA synthesis in cultured human and rat aortic smooth muscle cells.Exposure to S-nitrosothiols, DETA-NONOate and NO itself inhibited ongoing DNA synthesis and S phase progression in a concentration-dependent manner, as measured by thymidine incorporation and flow cytometry. Inhibition by NO donors occurred by release of NO, as detected by chemiluminescence and judged by the effects of NO scavengers, haemoglobin and cPTIO.Co-incubation with redox compounds, N-acetyl-L-cysteine, glutathione and L-ascorbic acid prevented NO inhibition of DNA synthesis. These observations suggest that redox agents may alternatively attenuate NO bioactivity extracellularly, interfere with intracellular actions of NO on the DNA synthesis machinery or restore DNA synthesis after established inhibition by NO.Recovery of DNA synthesis after inhibition by NO was similar with and without redox agents suggesting that augmented restoration of DNA synthesis is an unlikely mechanism to explain redox regulation.Study of extracellular interactions revealed that all redox agents potentiated S-nitrosothiol decomposition and NO release.Examination of intracellular NO bioactivity showed that as opposed to attenuation of NO inhibition of DNA synthesis by redox agents, there was no inhibition (potentiation in the presence of ascorbic acid) of soluble guanylate cyclase (sGC) activation judged by cyclic GMP accumulation in rat cells.These data provide evidence that NO-induced inhibition of ongoing DNA synthesis is sensitive to redox environment. Redox processes might protect the DNA synthesis machinery from inhibition by NO, in the setting of augmented liberation of biologically active NO from NO donors. PMID:10742309

An anaerobic field injection experiment in a landfill leachate plume, Grindsted, Denmark: 2. Deduction of anaerobic (methanogenic, sulfate-, and Fe (III)-reducing) redox conditions

NASA Astrophysics Data System (ADS)

Albrechtsen, Hans-JøRgen; Bjerg, Poul L.; Ludvigsen, Liselotte; Rügge, Kirsten; Christensen, Thomas H.

1999-04-01

Redox conditions may be environmental factors which affect the fate of the xenobiotic organic compounds. Therefore the redox conditions were characterized in an anaerobic, leachate-contaminated aquifer 15-60 m downgradient from the Grindsted Landfill, Denmark, where an field injection experiment was carried out. Furthermore, the stability of the redox conditions spatially and over time were investigated, and different approaches to deduce the redox conditions were evaluated. The redox conditions were evaluated in a set of 20 sediment and groundwater samples taken from locations adjacent to the sediment samples. Samples were investigated with respect to groundwater chemistry, including hydrogen and volatile fatty acids (VFAs) and sediment geochemistry, and bioassays were performed. The groundwater chemistry, including redox sensitive species for a large number of samples, varied over time during the experimental period of 924 days owing to variations in the leachate from the landfill. However, no indication of change in the redox environment resulting from the field injection experiment or natural variation was observed in the individual sampling points. The methane, Fe(II), hydrogen, and VFA groundwater chemistry parameters strongly indicated a Fe(III)-reducing environment. This was further supported by the bioassays, although methane production and sulfate-reduction were also observed in a few samples close to the landfill. On the basis of the calculated carbon conversion, Fe(III) was the dominant electron acceptor in the region of the aquifer, which was investigated. Because of the complexity of a landfill leachate plume, several redox processes may occur simultaneously, and an array of methods must be applied for redox characterization in such multicomponent systems.

Identification of Early Nuclear Target Genes of Plastidial Redox Signals that Trigger the Long-Term Response of Arabidopsis to Light Quality Shifts.

PubMed

Dietzel, Lars; Gläßer, Christine; Liebers, Monique; Hiekel, Stefan; Courtois, Florence; Czarnecki, Olaf; Schlicke, Hagen; Zubo, Yan; Börner, Thomas; Mayer, Klaus; Grimm, Bernhard; Pfannschmidt, Thomas

2015-08-01

Natural illumination conditions are highly variable and because of their sessile life style, plants are forced to acclimate to them at the cellular and molecular level. Changes in light intensity or quality induce changes in the reduction/oxidation (redox) state of the photosynthetic electron chain that acts as a trigger for compensatory acclimation responses comprising functional and structural adjustments of photosynthesis and metabolism. Such responses include redox-controlled changes in plant gene expression in the nucleus and organelles. Here we describe a strategy for the identification of early redox-regulated genes (ERGs) in the nucleus of the model organism Arabidopsis thaliana that respond significantly 30 or 60 min after the generation of a reduction signal in the photosynthetic electron transport chain. By comparing the response of wild-type plants with that of the acclimation mutant stn7, we could specifically identify ERGs. The results reveal a significant impact of chloroplast redox signals on distinct nuclear gene groups including genes for the mitochondrial electron transport chain, tetrapyrrole biosynthesis, carbohydrate metabolism, and signaling lipid synthesis. These expression profiles are clearly different from those observed in response to the reduction of photosynthetic electron transport by high light treatments. Thus, the ERGs identified are unique to redox imbalances in photosynthetic electron transport and were then used for analyzing potential redox-responsive cis-elements, trans-factors, and chromosomal regulatory hot spots. The data identify a novel redox-responsive element and indicate extensive redox control at transcriptional and chromosomal levels that point to an unprecedented impact of redox signals on epigenetic processes. Copyright © 2015 The Author. Published by Elsevier Inc. All rights reserved.

Particle size effect of redox reactions for Co species supported on silica

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chotiwan, Siwaruk; Tomiga, Hiroki; Katagiri, Masaki

Conversions of chemical states during redox reactions of two silica-supported Co catalysts, which were prepared by the impregnation method, were evaluated by using an in situ XAFS technique. The addition of citric acid into the precursor solution led to the formation on silica of more homogeneous and smaller Co particles, with an average diameter of 4 nm. The supported Co{sub 3}O{sub 4} species were reduced to metallic Co via the divalent CoO species during a temperature-programmed reduction process. The reduced Co species were quantitatively oxidized with a temperature-programmed oxidation process. The higher observed reduction temperature of the smaller CoO particlesmore » and the lower observed oxidation temperature of the smaller metallic Co particles were induced by the higher dispersion of the Co oxide species, which apparently led to a stronger interaction with supporting silica. The redox temperature between CoO and Co{sub 3}O{sub 4} was found to be independent of the particle size. - Graphical abstract: Chemical state conversions of SiO{sub 2}-supported Co species and the particle size effect have been analyzed by means of in situ XAFS technique. The small CoO particles have endurance against the reduction and exist in a wide temperature range. Display Omitted - Highlights: • The conversions of the chemical state of supported Co species during redox reaction are evaluated. • In operando XAFS technique were applied to measure redox properties of small Co particles. • A small particle size affects to the redox temperatures of cobalt catalysts.« less

Age-related alterations of plasma glutathione and oxidation of redox potentials in chimpanzee (Pan troglodytes) and rhesus monkey (Macaca mulatta).

PubMed

Paredes, Jamespaul; Jones, Dean P; Wilson, Mark E; Herndon, James G

2014-04-01

Chimpanzee (Pan troglodytes) and rhesus macaque (Macaca mulatta) and humans (Homo sapiens) share physiological and genetic characteristics, but have remarkably different life spans, with chimpanzees living 50-60 % and the rhesus living 35-40 % of maximum human survival. Since oxidative processes are associated with aging and longevity, we might expect to see species differences in age-related oxidative processes. Blood and extracellular fluid contain two major thiol redox nodes, glutathione (GSH)/glutathione-disulfide (GSSG) and cysteine (Cys)/cystine (CySS), which are subject to reversible oxidation-reduction reactions and are maintained in a dynamic non-equilibrium state. Disruption of these thiol redox nodes leads to oxidation of their redox potentials (EhGSSG and EhCySS) which affects cellular physiology and is associated with aging and the development of chronic diseases in humans. The purpose of this study was to measure age-related changes in these redox thiols and their corresponding redox potentials (Eh) in chimpanzees and rhesus monkeys. Our results show similar age-related decreases in the concentration of plasma GSH and Total GSH as well as oxidation of the EhGSSG in male and female chimpanzees. Female chimpanzees and female rhesus monkeys also were similar in several outcome measures. For example, similar age-related decreases in the concentration of plasma GSH and Total GSH, as well as age-related oxidation of the EhGSSG were observed. The data collected from chimpanzees and rhesus monkeys corroborates previous reports on oxidative changes in humans and confirms their value as a comparative reference for primate aging.

Pyridine nucleotides in regulation of cell death and survival by redox and non-redox reactions.

PubMed

Novak Kujundžić, Renata; Žarković, Neven; Gall Trošelj, Koraljka

2014-01-01

Changes of the level and ratios of pyridine nucleotides determine metabolism- dependent cellular redox status and the activity of poly(ADP-ribose) polymerases (PARPs) and sirtuins, thereby influencing several processes closely related to cell survival and death. Pyridine nucleotides participate in numerous metabolic reactions whereby their net cellular level remains constant, but the ratios of NAD+/NADP+ and NADH/NADPH oscillate according to metabolic changes in response to diverse stress signals. In non-redox reactions, NAD+ is degraded and quickly, afterward, resynthesized in the NAD+ salvage pathway, unless overwhelming activation of PARP-1 consumes NAD+ to the point of no return, when the cell can no longer generate enough ATP to accommodate NAD+ resynthesis. The activity of PARP-1 is mandatory for the onset of cytoprotective autophagy on sublethal stress signals. It has become increasingly clear that redox status, largely influenced by the metabolism-dependent composition of the pyridine nucleotides pool, plays an important role in the synthesis of pro-apoptotic and anti-apoptotic sphingolipids. Awareness of the involvement of the prosurvival sphingolipid, sphingosine-1-phosphate, in transition from inflammation to malignant transformation has recently emerged. Here, the participation of pyridine nucleotides in redox and non-redox reactions, sphingolipid metabolism, and their role in cell fate decisions is reviewed.

Changes in redox properties of humic acids upon sorption to alumina

NASA Astrophysics Data System (ADS)

Subdiaga, Edisson; Orsetti, Silvia; Jindal, Sharmishta; Haderlein, Stefan B.

2016-04-01

1. Introduction A prominent role of Natural Organic Matter (NOM) in biogeochemical processes is its ability to act as an electron shuttle, accelerating rates between a bulk electron donor and an acceptor. The underlying processes are reversible redox reactions of quinone moieties.1 This shuttling effect has been studied in two major areas: transformation of redox active pollutants and microbial respiration.2-3 Previous studies primarily compared effects in the presence or absence of NOM without addressing the redox properties of NOM nor its speciation. The interaction between humic acids (HA) and minerals might change properties and reactivity of organic matter. Specifically, we investigate whether changes in the redox properties of a HA occur upon sorption to redox inactive minerals. Since fractionation and conformational rearrangements of NOM moieties upon sorption are likely to happen, the redox properties of the NOM fractions upon sorption might differ as well. 2. Materials and methods Elliot Soil Humic Acid (ESHA), Pahokee Peat Humic Acid (PPHA) and Suwannee River Humic Acid (SRHA) were used as received from IHSS. Aluminum oxide (Al2O3) was suspended in 0.1M KCl. Sorption was studied at pH 7.0 in duplicate batch experiments for several HA/Al2O3 ratios. For the suspension (mineral + sorbed HA, plus dissolved HA), the filtrate (0.45μm) and the HA stock solution, the electron donating and accepting capacities (EDC and EAC) were determined following established procedures.4 3. Results All studied HA-Al2O3 systems showed similar behavior with regard to changes in redox properties. There was a significant increase in the EDC of the whole suspension compared to the stock solutions and the non-sorbed HA in the filtrate (up to 300% for PPHA). This effect was more pronounced with increasing amounts of sorbed HA in the suspension. Although ESHA had the highest sorption capacity on Al2O3 (~ 6 times higher than PPHA & SRHA), it showed the smallest changes in redox properties upon sorption. Considering the total electron exchange capacities, significant changes were found mainly at higher amounts of sorbed PPHA and SRHA. 4. Conclusions Overall, our results suggest a change in the redox properties of sorbed HA but not for the dissolved fraction. The sorbed fraction showed a higher redox capacity than the stock samples. Given the absence of redox transfer between the HA and the redox inert aluminum oxide, such changes might be due to conformational changes in the humic substances. 5. References [1] Scott D., Mcknight, D., Blunt-Harris, E., Kolesar, S., Lovley, A. Environ. Sci. Technol. 1998, 32, 2984-2989. [2] Dunnivant, F. Schwarzenbach, R., Macalady, D. Environ. Sci. Technol. 1992, 26(11), 2133-2141. [3] Jiang, J. & Kappler, A. Environ. Sci. Technol. 2008, 42(10), 3562-3569. [4] Aeschbacher, M., Sander M., Schwarzenbach, R. Environ. Sci. Technol. 2010, 44(1), 87-93.

Compromised redox homeostasis, altered nitroso-redox balance, and therapeutic possibilities in atrial fibrillation.

PubMed

Simon, Jillian N; Ziberna, Klemen; Casadei, Barbara

2016-04-01

Although the initiation, development, and maintenance of atrial fibrillation (AF) have been linked to alterations in myocyte redox state, the field lacks a complete understanding of the impact these changes may have on cellular signalling, atrial electrophysiology, and disease progression. Recent studies demonstrate spatiotemporal changes in reactive oxygen species production shortly after the induction of AF in animal models with an uncoupling of nitric oxide synthase activity ensuing in the presence of long-standing persistent AF, ultimately leading to a major shift in nitroso-redox balance. However, it remains unclear which radical or non-radical species are primarily involved in the underlying mechanisms of AF or which proteins are targeted for redox modification. In most instances, only free radical oxygen species have been assessed; yet evidence from the redox signalling field suggests that non-radical species are more likely to regulate cellular processes. A wider appreciation for the distinction of these species and how both species may be involved in the development and maintenance of AF could impact treatment strategies. In this review, we summarize how redox second-messenger systems are regulated and discuss the recent evidence for alterations in redox regulation in the atrial myocardium in the presence of AF, while identifying some critical missing links. We also examine studies looking at antioxidants for the prevention and treatment of AF and propose alternative redox targets that may serve as superior therapeutic options for the treatment of AF. © The Author 2016. Published by Oxford University Press on behalf of the European Society of Cardiology.

A study on the selection of indigenous leaching-bacteria for effective bioleaching

NASA Astrophysics Data System (ADS)

Oh, S. J.; Cho, K. H.; Kim, B. J.; Choi, N. C.; Park, C. Y.

2012-04-01

Bioleaching technology, which is based on the ability of microorganisms to transform solid compounds into soluble and extractable valuable elements that can be recovered, has been rapidly developed in recent decades for its advantages, which include mild reaction condition, low energy consumption, simple process, low environmental impact and being suitable for low grade mine tailings and residues. The bacteria activities (survival, adaptation of toxically environments etc.) in the bioleaching technology play a key role in the solubilization of metals. The purpose of this study was to selection of optimal leaching-bacteria through changed pH and redox potential on bio-oxidation in batch experiments for successful bioleaching technology. Twenty three indigenous bacteria used throughout this study, leaching-bacteria were obtained from various geochemical conditions; bacteria inhabitation type (acid mine drainage, mine wastes leachate and sulfur hot springs) and base-metal type (sulfur, sulfide, iron and coal). Bio-oxidation experiment result was showed that 9 cycles (1 cycle - 28days) after the leaching-bacteria were inoculated to a leaching medium, pH was observed decreasing and redox potential increased. In the bacteria inhabitation type, bio-oxidation of sulfur hot springs bacteria was greater than other types (acid mine drainage and mine wastes leachate). In addition, bio-oxidation on base-metal type was appeared sulfur was greater than other types (sulfide, iron and coal). This study informs basic knowledge when bacteria apply to eco-/economic resources utilization studies including the biomining and the recycling of mine waste system.

Fatiguing contractions increase protein S-glutathionylation occupancy in mouse skeletal muscle

DOE PAGES

Kramer, Philip A.; Duan, Jicheng; Gaffrey, Matthew J.; ...

2018-05-23

Protein S-glutathionylation is an important reversible post-translational modification implicated in redox signaling. Oxidative modifications to protein thiols can alter the activity of metabolic enzymes, transcription factors, kinases, phosphatases, and the function of contractile proteins. However, the extent to which muscle contraction induces oxidative modifications in redox sensitive thiols is not known. The purpose of this study was to determine the targets of S-glutathionylation redox signaling following fatiguing contractions. Anesthetized adult male CB6F1 (BALB/cBy × C57BL/6) mice were subjected to acute fatiguing contractions for 15 min using in vivo stimulations. The right (stimulated) and left (unstimulated) gastrocnemius muscleswere collected 60 minmore » after the last stimulation and processed for redox proteomics assay of S-glutathionylation.« less

Fatiguing contractions increase protein S-glutathionylation occupancy in mouse skeletal muscle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kramer, Philip A.; Duan, Jicheng; Gaffrey, Matthew J.

Protein S-glutathionylation is an important reversible post-translational modification implicated in redox signaling. Oxidative modifications to protein thiols can alter the activity of metabolic enzymes, transcription factors, kinases, phosphatases, and the function of contractile proteins. However, the extent to which muscle contraction induces oxidative modifications in redox sensitive thiols is not known. The purpose of this study was to determine the targets of S-glutathionylation redox signaling following fatiguing contractions. Anesthetized adult male CB6F1 (BALB/cBy × C57BL/6) mice were subjected to acute fatiguing contractions for 15 min using in vivo stimulations. The right (stimulated) and left (unstimulated) gastrocnemius muscleswere collected 60 minmore » after the last stimulation and processed for redox proteomics assay of S-glutathionylation.« less

Trapped in the coordination sphere: Nitrate ion transfer driven by the cerium(III/IV) redox couple

DOE PAGES

Ellis, Ross J.; Bera, Mrinal K.; Reinhart, Benjamin; ...

2016-11-07

Redox-driven ion transfer between phases underpins many biological and technological processes, including industrial separation of ions. Here we investigate the electrochemical transfer of nitrate anions between oil and water phases, driven by the reduction and oxidation of cerium coordination complexes in oil phases. We find that the coordination environment around the cerium cation has a pronounced impact on the overall redox potential, particularly with regard to the number of coordinated nitrate anions. Our results suggest a new fundamental mechanism for tuning ion transfer between phases; by 'trapping' the migrating ion inside the coordination sphere of a redox-active complex. Here, thismore » presents a new route for controlling anion transfer in electrochemically-driven separation applications.« less

Subcellular Redox Signaling.

PubMed

Zhu, Liping; Lu, Yankai; Zhang, Jiwei; Hu, Qinghua

2017-01-01

Oxidative and antioxidative system of cells and tissues maintains a balanced state under physiological conditions. A disruption in this balance of redox status has been associated with numerous pathological processes. Reactive oxygen species (ROS) as a major redox signaling generates in a spatiotemporally dependent manner. Subcellular organelles such as mitochondria, endoplasmic reticulum, plasma membrane and nuclei contribute to the production of ROS. In addition to downstream effects of ROS signaling regulated by average ROS changes in cytoplasm, whether subcelluar ROS mediate biological effect(s) has drawn greater attentions. With the advance in redox-sensitive probes targeted to different subcellular compartments, the investigation of subcellular ROS signaling and its associated cellular function has become feasible. In this review, we discuss the subcellular ROS signaling, with particular focus on mechanisms of subcellular ROS production and its downstream effects.

Electrochemical Probing through a Redox Capacitor To Acquire Chemical Information on Biothiols

PubMed Central

2016-01-01

The acquisition of chemical information is a critical need for medical diagnostics, food/environmental monitoring, and national security. Here, we report an electrochemical information processing approach that integrates (i) complex electrical inputs/outputs, (ii) mediators to transduce the electrical I/O into redox signals that can actively probe the chemical environment, and (iii) a redox capacitor that manipulates signals for information extraction. We demonstrate the capabilities of this chemical information processing strategy using biothiols because of the emerging importance of these molecules in medicine and because their distinct chemical properties allow evaluation of hypothesis-driven information probing. We show that input sequences can be tailored to probe for chemical information both qualitatively (step inputs probe for thiol-specific signatures) and quantitatively. Specifically, we observed picomolar limits of detection and linear responses to concentrations over 5 orders of magnitude (1 pM–0.1 μM). This approach allows the capabilities of signal processing to be extended for rapid, robust, and on-site analysis of chemical information. PMID:27385047

Electrochemical Probing through a Redox Capacitor To Acquire Chemical Information on Biothiols.

PubMed

Liu, Zhengchun; Liu, Yi; Kim, Eunkyoung; Bentley, William E; Payne, Gregory F

2016-07-19

The acquisition of chemical information is a critical need for medical diagnostics, food/environmental monitoring, and national security. Here, we report an electrochemical information processing approach that integrates (i) complex electrical inputs/outputs, (ii) mediators to transduce the electrical I/O into redox signals that can actively probe the chemical environment, and (iii) a redox capacitor that manipulates signals for information extraction. We demonstrate the capabilities of this chemical information processing strategy using biothiols because of the emerging importance of these molecules in medicine and because their distinct chemical properties allow evaluation of hypothesis-driven information probing. We show that input sequences can be tailored to probe for chemical information both qualitatively (step inputs probe for thiol-specific signatures) and quantitatively. Specifically, we observed picomolar limits of detection and linear responses to concentrations over 5 orders of magnitude (1 pM-0.1 μM). This approach allows the capabilities of signal processing to be extended for rapid, robust, and on-site analysis of chemical information.

A small electron donor in cobalt complex electrolyte significantly improves efficiency in dye-sensitized solar cells

PubMed Central

Hao, Yan; Yang, Wenxing; Zhang, Lei; Jiang, Roger; Mijangos, Edgar; Saygili, Yasemin; Hammarström, Leif; Hagfeldt, Anders; Boschloo, Gerrit

2016-01-01

Photoelectrochemical approach to solar energy conversion demands a kinetic optimization of various light-induced electron transfer processes. Of great importance are the redox mediator systems accomplishing the electron transfer processes at the semiconductor/electrolyte interface, therefore affecting profoundly the performance of various photoelectrochemical cells. Here, we develop a strategy—by addition of a small organic electron donor, tris(4-methoxyphenyl)amine, into state-of-art cobalt tris(bipyridine) redox electrolyte—to significantly improve the efficiency of dye-sensitized solar cells. The developed solar cells exhibit efficiency of 11.7 and 10.5%, at 0.46 and one-sun illumination, respectively, corresponding to a 26% efficiency improvement compared with the standard electrolyte. Preliminary stability tests showed the solar cell retained 90% of its initial efficiency after 250 h continuous one-sun light soaking. Detailed mechanistic studies reveal the crucial role of the electron transfer cascade processes within the new redox system. PMID:28000672

Oxic to anoxic transition in bottom waters during formation of the Citronen Fjord sediment-hosted Zn-Pb deposit, North Greenland

USGS Publications Warehouse

Slack, John F.; Rosa, Diogo; Falck, Hendrik

2015-01-01

Bulk geochemical data acquired for host sedimentary rocks to the Late Ordovician Citronen Fjord sediment-hosted Zn-Pb deposit in North Greenland constrain the redox state of bottom waters prior to and during sulphide mineralization. Downhole profiles for one drill core show trends for redox proxies (MnO, Mo, Ce anomalies) that suggest the local basin bottom waters were initially oxic, changing to anoxic and locally sulphidic concurrent with sulphide mineralization. We propose that this major redox change was caused by two broadly coeval processes (1) emplacement of debris-flow conglomerates that sealed off the basin from oxic seawater, and (2) venting of reduced hydrothermal fluids into the basin. Both processes may have increased H2S in bottom waters and thus prevented the oxidation of sulphides on the sea floor.

Arsenic behavior in river sediments under redox gradient: a review.

PubMed

Gorny, Josselin; Billon, Gabriel; Lesven, Ludovic; Dumoulin, David; Madé, Benoît; Noiriel, Catherine

2015-02-01

The fate of arsenic - a redox sensitive metalloid - in surface sediments is closely linked to early diagenetic processes. The review presents the main redox mechanisms and final products of As that have been evidenced over the last years. Oxidation of organic matter and concomitant reduction of oxidants by bacterial activity result in redox transformations of As species. The evolution of the sediment reactivity will also induce secondary abiotic reactions like complexation/de-complexation, sorption, precipitation/dissolution and biotic reactions that could, for instance, lead to the detoxification of some As species. Overall, abiotic redox reactions that govern the speciation of As mostly involve manganese (hydr)-oxides and reduced sulfur species produced by the sulfate-reducing bacteria. Bacterial activity is also responsible for the inter-conversion between As(V) and As(III), as well as for the production of methylated arsenic species. In surficial sediments, sorption processes also control the fate of inorganic As(V), through the formation of inner sphere complexes with iron (hydr)-oxides, that are biologically reduced in buried sediment. Arsenic species can also be bound to organic matter, either directly to functional groups or indirectly through metal complexes. Finally, even if the role of reduced sulfur species in the cycling of arsenic in sediments has been evidenced, some of the transformations remain hypothetical and deserve further investigation. Copyright © 2014 Elsevier B.V. All rights reserved.

An allosterically regulated reversible mechanical molecular switch: A de novo protein maquette functions as a redox/ionic strength sensor coupling chemical binding energy or charge interactions to conformational change

NASA Astrophysics Data System (ADS)

Grosset, Anne Marie

2000-10-01

Switch-like structural rearrangements of subunits due to charge-interactions are common in the basic biological action of proteins that couple and transfer chemical and ionic signals, sensing and regulation, mechanical force and electrochemical free energy. A simple synthetic protein model (maquette) has been designed to better understand the engineering of natural switches. Basic thermodynamic principles define the two key elements required for biological or chemical function of a switch. First, there must be two well-defined states. In this case, the two conformational states must have an energetic difference (DeltaDeltaG°) that is spanned by the applied driving force. Second, there must be an external stimulus, which preferentially interacts with one of the two states. The external stimulus provides the driving force that shifts the equilibrium from the first state to the second state (≥10:1 shifting towards ≤1:10). The energetic difference between the states must be the same order of magnitude as the driving force. In this synthetic protein, the two conformational states correspond to parallel (syn) and antiparallel (anti) assembly of the two identical helix-ss-helix subunits that bind heme close to the di-sulfide loop region. Charge interactions between two ferric hemes bound to histidines provide a driving force on the order of 2 kcal/mol (corresponding in the syn-topology to the 75--100 mV split in the heme redox potentials, or the 25--80 times weaker binding for the second ferric heme). The tetra-alpha-helix bundle has been modified to have a DeltaG around 1.8--2.5 kcal/mol (a 50--80 fold difference in the anti/syn ratio). Therefore, oxidation and reduction of the heme, or the binding of a second charged ferric heme can reversibly switch between syn- and anti-topologies, providing a sensitive detector of redox state or heme concentration. External solution conditions (e.g. ionic composition) can act on the protein remotely from the primary internal switch action and confer a secondary level of allosteric regulation. Bifunctional ligands can link subunits to shift topology. Scanning redox potentiometry can monitor the kinetics of topological change. Point amino acid substitutions and computer repacking of the hydrophobic core can modulate both the kinetics and the energetics.

Antisite occupation induced single anionic redox chemistry and structural stabilization of layered sodium chromium sulfide

DOE PAGES

Shadike, Zulipiya; Zhou, Yong -Ning; Chen, Lan -Li; ...

2017-08-30

The intercalation compounds with various electrochemically active or inactive elements in the layered structure have been the subject of increasing interest due to their high capacities, good reversibility, simple structures and ease of synthesis. However, their reversible intercalation/deintercalation redox chemistries in all previous compounds involve a single cationic redox reaction or a cumulative cationic and anionic redox reaction. Here we report an anionic redox only chemistry and structural stabilization of layered sodium chromium sulfide. It is discovered that sulfur in sodium chromium sulfide is electrochemical active undergoing oxidation/reduction of sulfur rather than chromium. Significantly, sodium ions can successfully move outmore » and into without changing its lattice parameter c, which is explained in terms of the occurrence of chromium/sodium vacancy antisite during desodiation and sodiation processes. Here, our present work not only enriches the electrochemistry of layered intercalation compounds, but also extends the scope of investigation on high-capacity electrodes.« less

Redox Conditions Affect Ultrafast Exciton Transport in Photosynthetic Pigment-Protein Complexes.

PubMed

Allodi, Marco A; Otto, John P; Sohail, Sara H; Saer, Rafael G; Wood, Ryan E; Rolczynski, Brian S; Massey, Sara C; Ting, Po-Chieh; Blankenship, Robert E; Engel, Gregory S

2018-01-04

Pigment-protein complexes in photosynthetic antennae can suffer oxidative damage from reactive oxygen species generated during solar light harvesting. How the redox environment of a pigment-protein complex affects energy transport on the ultrafast light-harvesting time scale remains poorly understood. Using two-dimensional electronic spectroscopy, we observe differences in femtosecond energy-transfer processes in the Fenna-Matthews-Olson (FMO) antenna complex under different redox conditions. We attribute these differences in the ultrafast dynamics to changes to the system-bath coupling around specific chromophores, and we identify a highly conserved tyrosine/tryptophan chain near the chromophores showing the largest changes. We discuss how the mechanism of tyrosine/tryptophan chain oxidation may contribute to these differences in ultrafast dynamics that can moderate energy transfer to downstream complexes where reactive oxygen species are formed. These results highlight the importance of redox conditions on the ultrafast transport of energy in photosynthesis. Tailoring the redox environment may enable energy transport engineering in synthetic light-harvesting systems.

Antisite occupation induced single anionic redox chemistry and structural stabilization of layered sodium chromium sulfide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shadike, Zulipiya; Zhou, Yong -Ning; Chen, Lan -Li

The intercalation compounds with various electrochemically active or inactive elements in the layered structure have been the subject of increasing interest due to their high capacities, good reversibility, simple structures and ease of synthesis. However, their reversible intercalation/deintercalation redox chemistries in all previous compounds involve a single cationic redox reaction or a cumulative cationic and anionic redox reaction. Here we report an anionic redox only chemistry and structural stabilization of layered sodium chromium sulfide. It is discovered that sulfur in sodium chromium sulfide is electrochemical active undergoing oxidation/reduction of sulfur rather than chromium. Significantly, sodium ions can successfully move outmore » and into without changing its lattice parameter c, which is explained in terms of the occurrence of chromium/sodium vacancy antisite during desodiation and sodiation processes. Here, our present work not only enriches the electrochemistry of layered intercalation compounds, but also extends the scope of investigation on high-capacity electrodes.« less

DNA-programmable multiplexing for scalable, renewable redox protein bio-nanoelectronics.

PubMed

Withey, Gary D; Kim, Jin Ho; Xu, Jimmy

2008-11-01

A universal, site-addressable DNA linking strategy is deployed for the programmable assembly of multifunctional, long-lasting redox protein nanoelectronic devices. This addressable linker, the first incorporated into a redox enzyme-nanoelectronic system, promotes versatility and renewability by allowing the reconfiguration and replacement of enzymes at will. The linker is transferable to all redox proteins due to the simple conjugation chemistry involved. The efficacy of this linking strategy is assessed using two model enzymes, glucose oxidase (GOx) and alcohol dehydrogenase (ADH), self-assembled onto separate nanoelectrode regions comprised of a highly ordered carbon nanotube (CNT) array. The sequence-specificity of DNA hybridization provides the means of encoding spatial address to the self-assembling process that conjugates enzymes tagged with single-stranded DNA (ssDNA) to the tips of designated CNTs functionalized with the complementary strands. In this study, we demonstrate the feasibility of multiplexed, scalable, reconfigurable and renewable transduction of redox protein signals by virtue of DNA addressing.

Production of cellobionate from cellulose using an engineered Neurospora crassa strain with laccase and redox mediator addition

USDA-ARS?s Scientific Manuscript database

We report a novel production process for cellobionic acid from cellulose using an engineered fungal strain with the exogenous addition of laccase and a redox mediator. A previously engineered strain of Neurospora crassa (F5'ace-1'cre-1'ndvB) was shown to produce cellobionate directly from cellulose ...

Microbial Preference for Soil Organic Carbon Changes Along Redox Gradients as a Function of the Energetic Cost of Respiration

NASA Astrophysics Data System (ADS)

Naughton, H.; Keiluweit, M.; Fendorf, S. E.; Farrant, D. N.

2016-12-01

Soil organic carbon (SOC) chemistry is known to impact carbon preservation via mineral associations and physical protection, which chemically or physically block SOC from microbial enzymatic access for decomposition. However, SOC decay models that include these processes do not reliably predict SOC dynamics. We propose that the energetics of respiration additionally regulate SOC cycling. Specifically, organic carbon will only be respired if the available electron acceptors yield enough energy for microbial growth when metabolically coupled to the SOC. To test this hypothesis, we constructed dual pore domain reactors in which water flows normal to a column of packed soil, allowing oxygen to diffuse from the upper channel through the soil and establish a redox gradient. With increasing depth into the soil column, the soil experiences a typical redox profile indicative of anaerobic respiration processes: after oxygen is consumed, nitrate, Mn, Fe, and sulfate serve as electron acceptors. We measure porewater and effluent for nitrate, sulfate, Fe(II) and Mn(II) and take microsensor profiles of dissolved oxygen and H2S to characterize the redox gradient and respiration pathways. To this we couple incubations of solid material at each depth post-experiment and quantify CO2 and CH4 production to assess respiration potential along the redox gradient. Porewater SOC chemistry is analyzed via spectroscopy and mass spectrometry to interpret SOC oxidation state and composition and thus test thermodynamic predictions on SOC stability given the available redox acceptors at a given depth in the reactor. Within 0.5 cm of the soil surface, oxygen concentrations drop below detection and signs of anaerobic respiration (Fe(II) production, loss of nitrate) initiate while respiration rates drops precipitously. More oxidized SOC is preferentially utilized with progression along the redox gradient, supporting thermodynamic predictions. This work highlights the potential of SOC chemistry within specific redox metabolic zones of soils and sediments to drive carbon utilization. An improved understanding on organic carbon utliization is critical to predict SOC dynamics under changing hydrology (e.g. saltwater intrusion, permafrost melting), temperature, and other factors impacting microbial respiration energetics.

Visualization of Nicotine Adenine Dinucleotide Redox Homeostasis with Genetically Encoded Fluorescent Sensors.

PubMed

Zhao, Yuzheng; Zhang, Zhuo; Zou, Yejun; Yang, Yi

2018-01-20

Beyond their roles as redox currency in living organisms, pyridine dinucleotides (NAD + /NADH and NADP + /NADPH) are also precursors or cosubstrates of great significance in various physiologic and pathologic processes. Recent Advances: For many years, it was challenging to develop methodologies for monitoring pyridine dinucleotides in situ or in vivo. Recent advances in fluorescent protein-based sensors provide a rapid, sensitive, specific, and real-time readout of pyridine dinucleotide dynamics in single cells or in vivo, thereby opening a new era of pyridine dinucleotide bioimaging. In this article, we summarize the developments in genetically encoded fluorescent sensors for NAD + /NADH and NADP + /NADPH redox states, as well as their applications in life sciences and drug discovery. The strengths and weaknesses of individual sensors are also discussed. These sensors have the advantages of being specific and organelle targetable, enabling real-time monitoring and subcellular-level quantification of targeted molecules in living cells and in vivo. NAD + /NADH and NADP + /NADPH have distinct functions in metabolic and redox regulation, and thus, a comprehensive evaluation of metabolic and redox states must be multiplexed with a combination of various metabolite sensors in a single cell. Antioxid. Redox Signal. 28, 213-229.

Redox active molecules cytochrome c and vitamin C enhance heme-enzyme peroxidations by serving as non-specific agents for redox relay

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gade, Sudeep Kumar; Bhattacharya, Subarna; Manoj, Kelath Murali, E-mail: satyamjayatu@yahoo.com

2012-03-09

Highlights: Black-Right-Pointing-Pointer At low concentrations, cytochrome c/vitamin C do not catalyze peroxidations. Black-Right-Pointing-Pointer But low levels of cytochrome c/vitamin C enhance diverse heme peroxidase activities. Black-Right-Pointing-Pointer Enhancement positively correlates to the concentration of peroxide in reaction. Black-Right-Pointing-Pointer Reducible additives serve as non-specific agents for redox relay in the system. Black-Right-Pointing-Pointer Insight into electron transfer processes in routine and oxidative-stress states. -- Abstract: We report that incorporation of very low concentrations of redox protein cytochrome c and redox active small molecule vitamin C impacted the outcome of one-electron oxidations mediated by structurally distinct plant/fungal heme peroxidases. Evidence suggests that cytochrome cmore » and vitamin C function as a redox relay for diffusible reduced oxygen species in the reaction system, without invoking specific or affinity-based molecular interactions for electron transfers. The findings provide novel perspectives to understanding - (1) the promiscuous role of cytochrome b{sub 5} in the metabolism mediated by liver microsomal xenobiotic metabolizing systems and (2) the roles of antioxidant molecules in affording relief from oxidative stress.« less

Iterative absolute electroanalytical approach to characterization of bulk redox conducting systems.

PubMed

Lewera, Adam; Miecznikowski, Krzysztof; Chojak, Malgorzata; Makowski, Oktawian; Golimowski, Jerzy; Kulesza, Pawel J

2004-05-15

A novel electroanalytical approach is proposed here, and it is demonstrated with the direct and simultaneous determination of two unknowns: the concentration of redox sites and the apparent diffusion coefficient for charge propagation in a single crystal of dodecatungstophosphoric acid. This Keggin-type polyoxometalate serves as a model bulk redox conducting inorganic material for solid-state voltammetry. The system has been investigated using an ultramicrodisk working electrode in the absence of external liquid supporting electrolyte. The analytical method requires numerical solution of the combination of two equations in which the first one describes current (or charge) in a well-defined (either spherical or linear) diffusional regime and the second general equation describes chronoamperometric (or normal pulse voltammetric current) under mixed (linear-spherical) conditions. The iterative approach is based on successive approximations through calculation and minimizing the least-squares error function. The method is fairly universal, and in principle, it can be extended to the investigation of other bulk systems including sol-gel processed materials, redox melts, and solutions on condition that they are electroactive and well behaved, they contain redox centers at sufficiently high level, and a number of electrons for the redox reaction considered is known.

Redox Reactivity of Cerium Oxide Nanoparticles Induces the Formation of Disulfide Bridges in Thiol-Containing Biomolecules.

PubMed

Rollin-Genetet, Françoise; Seidel, Caroline; Artells, Ester; Auffan, Mélanie; Thiéry, Alain; Vidaud, Claude

2015-12-21

The redox state of disulfide bonds is implicated in many redox control systems, such as the cysteine-cystine couple. Among proteins, ubiquitous cysteine-rich metallothioneins possess thiolate metal binding groups susceptible to metal exchange in detoxification processes. CeO2 NPs are commonly used in various industrial applications due to their redox properties. These redox properties that enable dual oxidation states (Ce(IV)/Ce(III)) to exist at their surface may act as oxidants for biomolecules. The interaction among metallothioneins, cysteine, and CeO2 NPs was investigated through various biophysical approaches to shed light on the potential effects of the Ce(4+)/Ce(3+) redox system on the thiol groups of these biomolecules. The possible reaction mechanisms include the formation of a disulfide bridge/Ce(III) complex resulting from the interaction between Ce(IV) and the thiol groups, leading to metal unloading from the MTs, depending on their metal content and cluster type. The formation of stable Ce(3+) disulfide complexes has been demonstrated via their fluorescence properties. This work provides the first evidence of thiol concentration-dependent catalytic oxidation mechanisms between pristine CeO2 NPs and thiol-containing biomolecules.

Molecular Orbital Principles of Oxygen-Redox Battery Electrodes.

PubMed

Okubo, Masashi; Yamada, Atsuo

2017-10-25

Lithium-ion batteries are key energy-storage devices for a sustainable society. The most widely used positive electrode materials are LiMO 2 (M: transition metal), in which a redox reaction of M occurs in association with Li + (de)intercalation. Recent developments of Li-excess transition-metal oxides, which deliver a large capacity of more than 200 mAh/g using an extra redox reaction of oxygen, introduce new possibilities for designing higher energy density lithium-ion batteries. For better engineering using this fascinating new chemistry, it is necessary to achieve a full understanding of the reaction mechanism by gaining knowledge on the chemical state of oxygen. In this review, a summary of the recent advances in oxygen-redox battery electrodes is provided, followed by a systematic demonstration of the overall electronic structures based on molecular orbitals with a focus on the local coordination environment around oxygen. We show that a π-type molecular orbital plays an important role in stabilizing the oxidized oxygen that emerges upon the charging process. Molecular orbital principles are convenient for an atomic-level understanding of how reversible oxygen-redox reactions occur in bulk, providing a solid foundation toward improved oxygen-redox positive electrode materials for high energy-density batteries.

Energy Metabolism and Inflammation in Brain Aging and Alzheimer’s Disease

PubMed Central

Yin, Fei; Sancheti, Harsh; Patil, Ishan; Cadenas, Enrique

2016-01-01

The high energy demand of the brain renders it sensitive to changes in energy fuel supply and mitochondrial function. Deficits in glucose availability and mitochondrial function are well-known hallmarks of brain aging and are particularly accentuated in neurodegenerative disorders such as Alzheimer’s disease. As important cellular sources of H2O2, mitochondrial dysfunction is usually associated with altered redox status. Bioenergetic deficits and chronic oxidative stress are both major contributors to cognitive decline associated with brain aging and Alzheimer’s disease. Neuroinflammatory changes, including microglial activation and production of inflammatory cytokines, are observed in neurodegenerative diseases and normal aging. The bioenergetic hypothesis advocates for sequential events from metabolic deficits to propagation of neuronal dysfunction, to aging, and to neurodegeneration, while the inflammatory hypothesis supports microglia activation as the driving force for neuroinflammation. Nevertheless, growing evidence suggests that these diverse mechanisms have redox dysregulation as a common denominator and connector. An independent view of the mechanisms underlying brain aging and neurodegeneration is being replaced by one that entails multiple mechanisms coordinating and interacting with each other. This review focuses on the alterations in energy metabolism and inflammatory responses and their connection via redox regulation in normal brain aging and Alzheimer’s disease. Interactions of these systems is reviewed based on basic research and clinical studies. PMID:27154981

Red Blood Cell Function and Dysfunction: Redox Regulation, Nitric Oxide Metabolism, Anemia

PubMed Central

Kuhn, Viktoria; Diederich, Lukas; Keller, T.C. Stevenson; Kramer, Christian M.; Lückstädt, Wiebke; Panknin, Christina; Suvorava, Tatsiana; Isakson, Brant E.; Kelm, Malte

2017-01-01

Abstract Significance: Recent clinical evidence identified anemia to be correlated with severe complications of cardiovascular disease (CVD) such as bleeding, thromboembolic events, stroke, hypertension, arrhythmias, and inflammation, particularly in elderly patients. The underlying mechanisms of these complications are largely unidentified. Recent Advances: Previously, red blood cells (RBCs) were considered exclusively as transporters of oxygen and nutrients to the tissues. More recent experimental evidence indicates that RBCs are important interorgan communication systems with additional functions, including participation in control of systemic nitric oxide metabolism, redox regulation, blood rheology, and viscosity. In this article, we aim to revise and discuss the potential impact of these noncanonical functions of RBCs and their dysfunction in the cardiovascular system and in anemia. Critical Issues: The mechanistic links between changes of RBC functional properties and cardiovascular complications related to anemia have not been untangled so far. Future Directions: To allow a better understanding of the complications associated with anemia in CVD, basic and translational science studies should be focused on identifying the role of noncanonical functions of RBCs in the cardiovascular system and on defining intrinsic and/or systemic dysfunction of RBCs in anemia and its relationship to CVD both in animal models and clinical settings. Antioxid. Redox Signal. 26, 718–742. PMID:27889956

The Azomethine Ylide Route to Amine C–H Functionalization: Redox-Versions of Classic Reactions and a Pathway to New Transformations

PubMed Central

2016-01-01

Conspectus Redox-neutral methods for the functionalization of amine α-C–H bonds are inherently efficient because they avoid external oxidants and reductants and often do not generate unwanted byproducts. However, most of the current methods for amine α-C–H bond functionalization are oxidative in nature. While the most efficient variants utilize atmospheric oxygen as the terminal oxidant, many such transformations require the use of expensive or toxic oxidants, often coupled with the need for transition metal catalysts. Redox-neutral amine α-functionalizations that involve intramolecular hydride transfer steps provide viable alternatives to certain oxidative reactions. These processes have been known for some time and are particularly well suited for tertiary amine substrates. A mechanistically distinct strategy for secondary amines has emerged only recently, despite sharing common features with a range of classic organic transformations. Among those are such widely used reactions as the Strecker, Mannich, Pictet–Spengler, and Kabachnik–Fields reactions, Friedel–Crafts alkylations, and iminium alkynylations. In these classic processes, condensation of a secondary amine with an aldehyde (or a ketone) typically leads to the formation of an intermediate iminium ion, which is subsequently attacked by a nucleophile. The corresponding redox-versions of these transformations utilize identical starting materials but incorporate an isomerization step that enables α-C–H bond functionalization. Intramolecular versions of these reactions include redox-neutral amine α-amination, α-oxygenation, and α-sulfenylation. In all cases, a reductive N-alkylation is effectively combined with an oxidative α-functionalization, generating water as the only byproduct. Reactions are promoted by simple carboxylic acids and in some cases require no additives. Azomethine ylides, dipolar species whose usage is predominantly in [3 + 2] cycloadditions and other pericyclic processes, have been identified as common intermediates. Extension of this chemistry to amine α,β-difunctionalization has been shown to be possible by way of converting the intermediate azomethine ylides into transient enamines. This Account details the evolution of this general strategy and the progress made to date. Further included is a discussion of related decarboxylative reactions and transformations that result in the redox-neutral aromatization of (partially) saturated cyclic amines. These processes also involve azomethine ylides, reactive intermediates that appear to be far more prevalent in condensation chemistry of amines and carbonyl compounds than previously considered. In contrast, as exemplified by some redox transformations that have been studied in greater detail, iminium ions are not necessarily involved in all amine/aldehyde condensation reactions. PMID:25560649

The azomethine ylide route to amine C-H functionalization: redox-versions of classic reactions and a pathway to new transformations.

PubMed

Seidel, Daniel

2015-02-17

Conspectus Redox-neutral methods for the functionalization of amine α-C-H bonds are inherently efficient because they avoid external oxidants and reductants and often do not generate unwanted byproducts. However, most of the current methods for amine α-C-H bond functionalization are oxidative in nature. While the most efficient variants utilize atmospheric oxygen as the terminal oxidant, many such transformations require the use of expensive or toxic oxidants, often coupled with the need for transition metal catalysts. Redox-neutral amine α-functionalizations that involve intramolecular hydride transfer steps provide viable alternatives to certain oxidative reactions. These processes have been known for some time and are particularly well suited for tertiary amine substrates. A mechanistically distinct strategy for secondary amines has emerged only recently, despite sharing common features with a range of classic organic transformations. Among those are such widely used reactions as the Strecker, Mannich, Pictet-Spengler, and Kabachnik-Fields reactions, Friedel-Crafts alkylations, and iminium alkynylations. In these classic processes, condensation of a secondary amine with an aldehyde (or a ketone) typically leads to the formation of an intermediate iminium ion, which is subsequently attacked by a nucleophile. The corresponding redox-versions of these transformations utilize identical starting materials but incorporate an isomerization step that enables α-C-H bond functionalization. Intramolecular versions of these reactions include redox-neutral amine α-amination, α-oxygenation, and α-sulfenylation. In all cases, a reductive N-alkylation is effectively combined with an oxidative α-functionalization, generating water as the only byproduct. Reactions are promoted by simple carboxylic acids and in some cases require no additives. Azomethine ylides, dipolar species whose usage is predominantly in [3 + 2] cycloadditions and other pericyclic processes, have been identified as common intermediates. Extension of this chemistry to amine α,β-difunctionalization has been shown to be possible by way of converting the intermediate azomethine ylides into transient enamines. This Account details the evolution of this general strategy and the progress made to date. Further included is a discussion of related decarboxylative reactions and transformations that result in the redox-neutral aromatization of (partially) saturated cyclic amines. These processes also involve azomethine ylides, reactive intermediates that appear to be far more prevalent in condensation chemistry of amines and carbonyl compounds than previously considered. In contrast, as exemplified by some redox transformations that have been studied in greater detail, iminium ions are not necessarily involved in all amine/aldehyde condensation reactions.

Interactions between microbial iron reduction and metal geochemistry: effect of redox cycling on transition metal speciation in iron bearing sediments.

PubMed

Cooper, D Craig; Picardal, Flynn F; Coby, Aaron J

2006-03-15

Microbial iron reduction is an important biogeochemical process that can affect metal geochemistry in sediments through direct and indirect mechanisms. With respectto Fe(III) (hydr)oxides bearing sorbed divalent metals, recent reports have indicated that (1) microbial reduction of goethite/ferrihydrite mixtures preferentially removes ferrihydrite, (2) this process can incorporate previously sorbed Zn(II) into an authigenic crystalline phase that is insoluble in 0.5 M HCl, (3) this new phase is probably goethite, and (4) the presence of nonreducible minerals can inhibit this transformation. This study demonstrates that a range of sorbed transition metals can be selectively sequestered into a 0.5 M HCl insoluble phase and that the process can be stimulated through sequential steps of microbial iron reduction and air oxidation. Microbial reduction experiments with divalent Cd, Co, Mn, Ni, Pb, and Zn indicate that all metals save Mn experienced some sequestration, with the degree of metal incorporation into the 0.5 M HCl insoluble phase correlating positively with crystalline ionic radius at coordination number = 6. Redox cycling experiments with Zn adsorbed to synthetic goethite/ferrihydrite or iron-bearing natural sediments indicate that redox cycling from iron reducing to iron oxidizing conditions sequesters more Zn within authigenic minerals than microbial iron reduction alone. In addition, the process is more effective in goethite/ferrihydrite mixtures than in iron-bearing natural sediments. Microbial reduction alone resulted in a -3x increase in 0.5 M HCl insoluble Zn and increased aqueous Zn (Zn-aq) in goethite/ferrihydrite, but did not significantly affect Zn speciation in natural sediments. Redox cycling enhanced the Zn sequestration by approximately 12% in both goethite/ferrihydrite and natural sediments and reduced Zn-aq to levels equal to the uninoculated control in goethite/ferrihydrite and less than the uninoculated control in natural sediments. These data suggest that in situ redox cycling may serve as an effective method for

Surface engineering on CeO2 nanorods by chemical redox etching and their enhanced catalytic activity for CO oxidation

NASA Astrophysics Data System (ADS)

Gao, Wei; Zhang, Zhiyun; Li, Jing; Ma, Yuanyuan; Qu, Yongquan

2015-07-01

Controllable surface properties of nanocerias are desired for various catalytic processes. There is a lack of efficient approaches to adjust the surface properties of ceria to date. Herein, a redox chemical etching method was developed to controllably engineer the surface properties of ceria nanorods. Ascorbic acid and hydrogen peroxide were used to perform the redox chemical etching process, resulting in a rough surface and/or pores on the surface of ceria nanorods. Increasing the etching cycles induced a steady increase of the specific surface area, oxygen vacancies and surface Ce3+ fractions. As a result, the etched nanorods delivered enhanced catalytic activity for CO oxidation, compared to the non-etched ceria nanorods. Our method provides a novel and facile approach to continuously adjust the surface properties of ceria for practical applications.Controllable surface properties of nanocerias are desired for various catalytic processes. There is a lack of efficient approaches to adjust the surface properties of ceria to date. Herein, a redox chemical etching method was developed to controllably engineer the surface properties of ceria nanorods. Ascorbic acid and hydrogen peroxide were used to perform the redox chemical etching process, resulting in a rough surface and/or pores on the surface of ceria nanorods. Increasing the etching cycles induced a steady increase of the specific surface area, oxygen vacancies and surface Ce3+ fractions. As a result, the etched nanorods delivered enhanced catalytic activity for CO oxidation, compared to the non-etched ceria nanorods. Our method provides a novel and facile approach to continuously adjust the surface properties of ceria for practical applications. Electronic supplementary information (ESI) available: Diameter distributions of as-prepared and etched samples, optical images, specific catalytic data of CO oxidation and comparison of CO oxidation. See DOI: 10.1039/c5nr01846c

Differentiating cancerous from normal breast tissue by redox imaging

NASA Astrophysics Data System (ADS)

Xu, He N.; Tchou, Julia; Feng, Min; Zhao, Huaqing; Li, Lin Z.

2015-02-01

Abnormal metabolism can be a hallmark of cancer occurring early before detectable histological changes and may serve as an early detection biomarker. The current gold standard to establish breast cancer (BC) diagnosis is histological examination of biopsy. Previously we have found that pre-cancer and cancer tissues in animal models displayed abnormal mitochondrial redox state. Our technique of quantitatively measuring the mitochondrial redox state has the potential to be implemented as an early detection tool for cancer and may provide prognostic value. We therefore in this present study, investigated the feasibility of quantifying the redox state of tumor samples from 16 BC patients. Tumor tissue aliquots were collected from both normal and cancerous tissue from the affected cancer-bearing breasts of 16 female patients (5 TNBC, 9 ER+, 2 ER+/Her2+) shortly after surgical resection. All specimens were snap-frozen with liquid nitrogen on site and scanned later with the Chance redox scanner, i.e., the 3D cryogenic NADH/oxidized flavoprotein (Fp) fluorescence imager. Our preliminary results showed that both NADH and Fp (including FAD, i.e., flavin adenine dinucleotide) signals in the cancerous tissues roughly tripled to quadrupled those in the normal tissues (p<0.05) and the redox ratio Fp/(NADH+Fp) was about 27% higher in the cancerous tissues than in the normal ones (p<0.05). Our findings suggest that the redox state could differentiate between cancer and non-cancer breast tissues in human patients and this novel redox scanning procedure may assist in tissue diagnosis in freshly procured biopsy samples prior to tissue fixation. We are in the process of evaluating the prognostic value of the redox imaging indices for BC.

Imposed glutathione-mediated redox switch modulates the tobacco wound-induced protein kinase and salicylic acid-induced protein kinase activation state and impacts on defence against Pseudomonas syringae

PubMed Central

Matern, Sanja; Peskan-Berghoefer, Tatjana; Gromes, Roland; Kiesel, Rebecca Vazquez; Rausch, Thomas

2015-01-01

The role of the redox-active tripeptide glutathione in plant defence against pathogens has been studied extensively; however, the impact of changes in cellular glutathione redox potential on signalling processes during defence reactions has remained elusive. This study explored the impact of elevated glutathione content on the cytosolic redox potential and on early defence signalling at the level of mitogen-activated protein kinases (MAPKs), as well as on subsequent defence reactions, including changes in salicylic acid (SA) content, pathogenesis-related gene expression, callose depositions, and the hypersensitive response. Wild-type (WT) Nicotiana tabacum L. and transgenic high-glutathione lines (HGL) were transformed with the cytosol-targeted sensor GRX1-roGFP2 to monitor the cytosolic redox state. Surprisingly, HGLs displayed an oxidative shift in their cytosolic redox potential and an activation of the tobacco MAPKs wound-induced protein kinase (WIPK) and SA-induced protein kinase (SIPK). This activation occurred in the absence of any change in free SA content, but was accompanied by constitutively increased expression of several defence genes. Similarly, rapid activation of MAPKs could be induced in WT tobacco by exposure to either reduced or oxidized glutathione. When HGL plants were challenged with adapted or non-adapted Pseudomonas syringae pathovars, the cytosolic redox shift was further amplified and the defence response was markedly increased, showing a priming effect for SA and callose; however, the initial and transient hyperactivation of MAPK signalling was attenuated in HGLs. The results suggest that, in tobacco, MAPK and SA signalling may operate independently, both possibly being modulated by the glutathione redox potential. Possible mechanisms for redox-mediated MAPK activation are discussed. PMID:25628332

Improving metabolic efficiency of the reverse beta-oxidation cycle by balancing redox cofactor requirement.

PubMed

Wu, Junjun; Zhang, Xia; Zhou, Peng; Huang, Jiaying; Xia, Xiudong; Li, Wei; Zhou, Ziyu; Chen, Yue; Liu, Yinghao; Dong, Mingsheng

2017-11-01

Previous studies have made many exciting achievements on pushing the functional reversal of beta-oxidation cycle (r-BOX) to more widespread adoption for synthesis of a wide variety of fuels and chemicals. However, the redox cofactor requirement for the efficient operation of r-BOX remains unclear. In this work, the metabolic efficiency of r-BOX for medium-chain fatty acid (C 6 -C 10 , MCFA) production was optimized by redox cofactor engineering. Stoichiometric analysis of the r-BOX pathway and further experimental examination identified NADH as a crucial determinant of r-BOX process yield. Furthermore, the introduction of formate dehydrogenase from Candida boidinii using fermentative inhibitor byproduct formate as a redox NADH sink improved MCFA titer from initial 1.2g/L to 3.1g/L. Moreover, coupling of increasing the supply of acetyl-CoA with NADH to achieve fermentative redox balance enabled product synthesis at maximum titers. To this end, the acetate re-assimilation pathway was further optimized to increase acetyl-CoA availability associated with the new supply of NADH. It was found that the acetyl-CoA synthetase activity and intracellular ATP levels constrained the activity of acetate re-assimilation pathway, and 4.7g/L of MCFA titer was finally achieved after alleviating these two limiting factors. To the best of our knowledge, this represented the highest titer reported to date. These results demonstrated that the key constraint of r-BOX was redox imbalance and redox engineering could further unleash the lipogenic potential of this cycle. The redox engineering strategies could be applied to acetyl-CoA-derived products or other bio-products requiring multiple redox cofactors for biosynthesis. Copyright © 2017 International Metabolic Engineering Society. Published by Elsevier Inc. All rights reserved.

DNA Charge Transport within the Cell

PubMed Central

Grodick, Michael A.; Muren, Natalie B.; Barton, Jacqueline K.

2015-01-01

The unique characteristics of DNA charge transport (CT) have prompted an examination of roles for this chemistry within a biological context. Not only can DNA CT facilitate long range oxidative damage of DNA, but redox-active proteins can couple to the DNA base stack and participate in long range redox reactions using DNA CT. DNA transcription factors with redox-active moieties such as SoxR and p53 can use DNA CT as a form of redox sensing. DNA CT chemistry also provides a means to monitor the integrity of the DNA, given the sensitivity of DNA CT to perturbations in base stacking as arise with mismatches and lesions. Enzymes that utilize this chemistry include an interesting and ever-growing class of DNA-processing enzymes involved in DNA repair, replication, and transcription that have been found to contain 4Fe-4S clusters. DNA repair enzymes containing 4Fe-4S clusters, that include Endonuclease III (EndoIII), MutY, and DinG from bacteria, as well as XPD from archaea, have been shown to be redox-active when bound to DNA, share a DNA-bound redox potential, and can be reduced and oxidized at long range via DNA CT. Interactions between DNA and these proteins in solution, in addition to genetics experiments within E. coli, suggest that DNA-mediated CT can be used as a means of cooperative signaling among DNA repair proteins that contain 4Fe-4S clusters as a first step in finding DNA damage, even within cells. Based on these data, we can consider also how DNA-mediated CT may be used as a means of signaling to coordinate DNA processing across the genome. PMID:25606780

Evidence for anionic redox activity in a tridimensional-ordered Li-rich positive electrode β-Li2IrO3.

PubMed

Pearce, Paul E; Perez, Arnaud J; Rousse, Gwenaelle; Saubanère, Mathieu; Batuk, Dmitry; Foix, Dominique; McCalla, Eric; Abakumov, Artem M; Van Tendeloo, Gustaaf; Doublet, Marie-Liesse; Tarascon, Jean-Marie

2017-05-01

Lithium-ion battery cathode materials have relied on cationic redox reactions until the recent discovery of anionic redox activity in Li-rich layered compounds which enables capacities as high as 300 mAh g -1 . In the quest for new high-capacity electrodes with anionic redox, a still unanswered question was remaining regarding the importance of the structural dimensionality. The present manuscript provides an answer. We herein report on a β-Li 2 IrO 3 phase which, in spite of having the Ir arranged in a tridimensional (3D) framework instead of the typical two-dimensional (2D) layers seen in other Li-rich oxides, can reversibly exchange 2.5 e - per Ir, the highest value ever reported for any insertion reaction involving d-metals. We show that such a large activity results from joint reversible cationic (M n+ ) and anionic (O 2 ) n- redox processes, the latter being visualized via complementary transmission electron microscopy and neutron diffraction experiments, and confirmed by density functional theory calculations. Moreover, β-Li 2 IrO 3 presents a good cycling behaviour while showing neither cationic migration nor shearing of atomic layers as seen in 2D-layered Li-rich materials. Remarkably, the anionic redox process occurs jointly with the oxidation of Ir 4+ at potentials as low as 3.4 V versus Li + /Li 0 , as equivalently observed in the layered α-Li 2 IrO 3 polymorph. Theoretical calculations elucidate the electrochemical similarities and differences of the 3D versus 2D polymorphs in terms of structural, electronic and mechanical descriptors. Our findings free the structural dimensionality constraint and broaden the possibilities in designing high-energy-density electrodes for the next generation of Li-ion batteries.

Evidence for anionic redox activity in a tridimensional-ordered Li-rich positive electrode β-Li2IrO3

NASA Astrophysics Data System (ADS)

Pearce, Paul E.; Perez, Arnaud J.; Rousse, Gwenaelle; Saubanère, Mathieu; Batuk, Dmitry; Foix, Dominique; McCalla, Eric; Abakumov, Artem M.; van Tendeloo, Gustaaf; Doublet, Marie-Liesse; Tarascon, Jean-Marie

2017-05-01

Lithium-ion battery cathode materials have relied on cationic redox reactions until the recent discovery of anionic redox activity in Li-rich layered compounds which enables capacities as high as 300 mAh g-1. In the quest for new high-capacity electrodes with anionic redox, a still unanswered question was remaining regarding the importance of the structural dimensionality. The present manuscript provides an answer. We herein report on a β-Li2IrO3 phase which, in spite of having the Ir arranged in a tridimensional (3D) framework instead of the typical two-dimensional (2D) layers seen in other Li-rich oxides, can reversibly exchange 2.5 e- per Ir, the highest value ever reported for any insertion reaction involving d-metals. We show that such a large activity results from joint reversible cationic (Mn+) and anionic (O2)n- redox processes, the latter being visualized via complementary transmission electron microscopy and neutron diffraction experiments, and confirmed by density functional theory calculations. Moreover, β-Li2IrO3 presents a good cycling behaviour while showing neither cationic migration nor shearing of atomic layers as seen in 2D-layered Li-rich materials. Remarkably, the anionic redox process occurs jointly with the oxidation of Ir4+ at potentials as low as 3.4 V versus Li+/Li0, as equivalently observed in the layered α-Li2IrO3 polymorph. Theoretical calculations elucidate the electrochemical similarities and differences of the 3D versus 2D polymorphs in terms of structural, electronic and mechanical descriptors. Our findings free the structural dimensionality constraint and broaden the possibilities in designing high-energy-density electrodes for the next generation of Li-ion batteries.

Microbiology, Redox and Contaminat Fate in the Grindsted Landfill Leachate Plume - A Summary of 25 Years of work

NASA Astrophysics Data System (ADS)

Christensen, T. H.

2001-05-01

The contamination by leachate of the upper aquifer at the Grindsted Landfill (Denmark) stretches about 300 m downgradient from the landfill. The plume has been described with respect to water chemistry, sediment chemistry, pollutant distribution, microbial counts, PLFA and redox rates determined by unamended bioassays. This presentation summaries the findings and discusses unanswered questions. The landfill was active from 1930 to the mid 1970 and has no engineered leachate collection system. Leachate from municipal as well as from industrial waste has entered the aquifer for more than thirty years. The redox conditions change from strongly anaerobic (methanogenic, sulfate reducing, iron reducing) close to the landfill over manganese reduction and denitrification to aerobic conditions in the outskirts of the plume The redox conditions were determined from groundwater sample composition, hydrogen concentrations and sediment chemistry. The plume showed strong attenuation of aromatic compounds within the first 100 m downgradient of the landfill. Degradation experiments (batch, in-situ testers, long term field injection experiments) could not fully document degradation of all the compounds. MPN-measurements of methanogens, sulfate-reducers, iron-reducers, manganese-reducers and denitrifiers showed abundance of all groups with a slight trend with the redox conditions. PLFA measurements did not provide much insight into the microbial populations of the plume, but confirmed some previous observations. Bioassays gave estimates of the rates of the various redox processes, but showed for some samples more simultaneous redox processes. More than 25 years of work has been put into the Grindsted Landfill leachate plume. References Bjerg, P.L., Rugge, K., Cortsen, J., Nielsen, P.H. & Christensen, T.H. (1999): Degradation of aromatic and chlorinated aliphatic hydrocarbons in the anaerobic part of the Grindsted Landfill leachate plume: In situ microcosm and laboratory batch experiments. Ground Water, 37, 113-121. Bjerg, P.L., Rugge, K., Pedersen, J.K. & Christensen, T.H. (1995): Distribution of redox sensitive groundwater quality parameters downgradient of a landfill (Grindsted, Denmark). Environmental Science and Technology, 29, 1387-1394. Heron, G., Bjerg, P.L., Gravesen, P., Ludvigsen, L. & Christensen, T.H. (1998): Geology and sediment geochemistry of a landfill leachate contaminated aquifer (Grindsted, Denmark). Journal of Contaminant Hydrology, 29, 301-317. Jakobsen, R., Albrechtsen, H.-J., Rasmussen, M., Bay, H., Bjerg, P.L. & Christensen, T.H. (1998): H2 concentrations in a landfill leachate plume (Grindsted, Denmark): In situ energetics of terminal electron acceptor processes. Environmental Science and Technology, 32, 2142-2148. Ludvigsen, L., Albrechtsen, H.-J., Heron, G., Bjerg, P.L. & Christensen, T.H. (1998): Anaerobic microbial redox processes in a landfill leachate contaminated aquifer (Grindsted, Denmark). Journal of Contaminant Hydrology, 33, 273-291. Ludvigsen, L., Albrechtsen, H.-J., Ringelberg, D., Ekelund, F. & Christensen, T.H. (1999): Distribution and composition of microbial populations in a landfill leachate contaminated aquifer (Grindsted, Denmark). Microbial Ecology, 37, (3), 197-207. Rugge, K., Bjerg, P.L. & Christensen, T.H. (1995): Distribution of organic compounds from municipal solid waste in the groundwater downgradient of a landfill (Grindsted, Denmark). Environmental Science and Technology, 29, 1395-1400.

Inhibition of Ape1 Redox Activity Promotes Odonto/osteogenic Differentiation of Dental Papilla Cells.

PubMed

Chen, Tian; Liu, Zhi; Sun, Wenhua; Li, Jingyu; Liang, Yan; Yang, Xianrui; Xu, Yang; Yu, Mei; Tian, Weidong; Chen, Guoqing; Bai, Ding

2015-12-07

Dentinogenesis is the formation of dentin, a substance that forms the majority of teeth, and this process is performed by odontoblasts. Dental papilla cells (DPCs), as the progenitor cells of odontoblasts, undergo the odontogenic differentiation regulated by multiple cytokines and paracrine signal molecules. Ape1 is a perfect paradigm of the function complexity of a biological macromolecule with two major functional regions for DNA repair and redox regulation, respectively. To date, it remains unclear whether Ape1 can regulate the dentinogenesis in DPCs. In the present study, we firstly examed the spatio-temporal expression of Ape1 during tooth germ developmental process, and found the Ape1 expression was initially high and then gradually reduced along with the tooth development. Secondly, the osteo/odontogenic differentiation capacity of DPCs was up-regulated when treated with either Ape1-shRNA or E3330 (a specific inhibitor of the Ape1 redox function), respectively. Moreover, we found that the canonical Wnt signaling pathway was activated in this process, and E3330 reinforced-osteo/odontogenic differentiation capacity was suppressed by Dickkopf1 (DKK1), a potent antagonist of canonical Wnt signaling pathway. Taken together, we for the first time showed that inhibition of Ape1 redox regulation could promote the osteo/odontogenic differentiation capacity of DPCs via canonical Wnt signaling pathway.

Biomarker-specific conjugated nanopolyplexes for the active coloring of stem-like cancer cells

NASA Astrophysics Data System (ADS)

Hong, Yoochan; Lee, Eugene; Choi, Jihye; Haam, Seungjoo; Suh, Jin-Suck; Yang, Jaemoon

2016-06-01

Stem-like cancer cells possess intrinsic features and their CD44 regulate redox balance in cancer cells to survive under stress conditions. Thus, we have fabricated biomarker-specific conjugated polyplexes using CD44-targetable hyaluronic acid and redox-sensible polyaniline based on a nanoemulsion method. For the most sensitive recognition of the cellular redox at a single nanoparticle scale, a nano-scattering spectrum imaging analyzer system was introduced. The conjugated polyplexes showed a specific targeting ability toward CD44-expressing cancer cells as well as a dramatic change in its color, which depended on the redox potential in the light-scattered images. Therefore, these polyaniline-based conjugated polyplexes as well as analytical processes that include light-scattering imaging and measurements of scattering spectra, clearly establish a systematic method for the detection and monitoring of cancer microenvironments.

Impact of Redox Reactions on Colloid Transport in Saturated Porous Media: An Example of Ferrihydrite Colloids Transport in the Presence of Sulfide.

PubMed

Liao, Peng; Yuan, Songhu; Wang, Dengjun

2016-10-18

Transport of colloids in the subsurface is an important environmental process with most research interests centered on the transport in chemically stable conditions. While colloids can be formed under dynamic redox conditions, the impact of redox reactions on their transport is largely overlooked. Taking the redox reactions between ferrihydrite colloids and sulfide as an example, we investigated how and to what extent the redox reactions modulated the transport of ferrihydrite colloids in anoxic sand columns over a range of environmentally relevant conditions. Our results reveal that the presence of sulfide (7.8-46.9 μM) significantly decreased the breakthrough of ferrihydrite colloids in the sand column. The estimated travel distance of ferrihydrite colloids in the absence of sulfide was nearly 7-fold larger than that in the presence of 46.9 μM sulfide. The reduced breakthrough was primarily attributed to the reductive dissolution of ferrihydrite colloids by sulfide in parallel with formation of elemental sulfur (S(0)) particles from sulfide oxidation. Reductive dissolution decreased the total mass of ferrihydrite colloids, while the negatively charged S(0) decreased the overall zeta potential of ferrihydrite colloids by attaching onto their surfaces and thus enhanced their retention in the sand. Our findings provide novel insights into the critical role of redox reactions on the transport of redox-sensitive colloids in saturated porous media.

MetILs 3: A Strategy for High Density Energy Storage Using Redox-Active Ionic Liquids

DOE PAGES

Small, Leo J.; Pratt, Harry D.; Staiger, Chad L.; ...

2017-07-26

We present a systematic approach for increasing the concentration of redox-active species in electrolytes for nonaqueous redox flow batteries (RFBs). Starting with an ionic liquid consisting of a metal coordination cation (MetIL), ferrocene-containing ligands and iodide anions are substituted incrementally into the structure. While chemical structures can be drawn for molecules with 10 m redox-active electrons (RAE), practical limitations such as melting point and phase stability constrain the structures to 4.2 m RAE, a 2.3× improvement over the original MetIL. Dubbed “MetILs 3,” these ionic liquids possess redox activity in the cation core, ligands, and anions. Throughout all compositions, infraredmore » spectroscopy shows the ethanolamine-based ligands primarily coordinate to the Fe 2+ core via hydroxyl groups. Calorimetry conveys a profound change in thermophysical properties, not only in melting temperature but also in suppression of a cold crystallization only observed in the original MetIL. Square wave voltammetry reveals redox processes characteristic of each molecular location. Testing a laboratory-scale RFB demonstrates Coulombic efficiencies >95% and increased voltage efficiencies due to more facile redox kinetics, effectively increasing capacity 4×. Application of this strategy to other chemistries, optimizing melting point and conductivity, can yield >10 m RAE, making nonaqueous RFB a viable technology for grid scale storage.« less

Better than Nature: Nicotinamide Biomimetics That Outperform Natural Coenzymes.

PubMed

Knaus, Tanja; Paul, Caroline E; Levy, Colin W; de Vries, Simon; Mutti, Francesco G; Hollmann, Frank; Scrutton, Nigel S

2016-01-27

The search for affordable, green biocatalytic processes is a challenge for chemicals manufacture. Redox biotransformations are potentially attractive, but they rely on unstable and expensive nicotinamide coenzymes that have prevented their widespread exploitation. Stoichiometric use of natural coenzymes is not viable economically, and the instability of these molecules hinders catalytic processes that employ coenzyme recycling. Here, we investigate the efficiency of man-made synthetic biomimetics of the natural coenzymes NAD(P)H in redox biocatalysis. Extensive studies with a range of oxidoreductases belonging to the "ene" reductase family show that these biomimetics are excellent analogues of the natural coenzymes, revealed also in crystal structures of the ene reductase XenA with selected biomimetics. In selected cases, these biomimetics outperform the natural coenzymes. "Better-than-Nature" biomimetics should find widespread application in fine and specialty chemicals production by harnessing the power of high stereo-, regio-, and chemoselective redox biocatalysts and enabling reactions under mild conditions at low cost.

Early cysteine-dependent inactivation of 26S proteasomes does not involve particle disassembly.

PubMed

Hugo, Martín; Korovila, Ioanna; Köhler, Markus; García-García, Carlos; Cabrera-García, J Daniel; Marina, Anabel; Martínez-Ruiz, Antonio; Grune, Tilman

2018-06-01

Under oxidative stress 26S proteasomes suffer reversible disassembly into its 20S and 19S subunits, a process mediated by HSP70. This inhibits the degradation of polyubiquitinated proteins by the 26S proteasome and allows the degradation of oxidized proteins by a free 20S proteasome. Low fluxes of antimycin A-stimulated ROS production caused dimerization of mitochondrial peroxiredoxin 3 and cytosolic peroxiredoxin 2, but not peroxiredoxin overoxidation and overall oxidation of cellular protein thiols. This moderate redox imbalance was sufficient to inhibit the ATP stimulation of 26S proteasome activity. This process was dependent on reversible cysteine oxidation. Moreover, our results show that this early inhibition of ATP stimulation occurs previous to particle disassembly, indicating an intermediate step during the redox regulation of the 26S proteasome with special relevance under redox signaling rather than oxidative stress conditions. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

Vitamin C in Health and Disease: Its Role in the Metabolism of Cells and Redox State in the Brain.

PubMed

Figueroa-Méndez, Rodrigo; Rivas-Arancibia, Selva

2015-01-01

Ever since Linus Pauling published his studies, the effects of vitamin C have been surrounded by contradictory results. This may be because its effects depend on a number of factors such as the redox state of the body, the dose used, and also on the tissue metabolism. This review deals with vitamin C pharmacokinetics and its participation in neurophysiological processes, as well as its role in the maintenance of redox balance. The distribution and the concentration of vitamin C in the organs depend on the ascorbate requirements of each and on the tissue distribution of sodium-dependent vitamin C transporter 1 and 2 (SVCT1 and SVCT2). This determines the specific distribution pattern of vitamin C in the body. Vitamin C is involved in the physiology of the nervous system, including the support and the structure of the neurons, the processes of differentiation, maturation, and neuronal survival; the synthesis of catecholamine, and the modulation of neurotransmission. This antioxidant interacts with self-recycling mechanisms, including its participation in the endogenous antioxidant system. We conclude that the pharmacokinetic properties of ascorbate are related to the redox state and its functions and effects in tissues.

Vitamin C in Health and Disease: Its Role in the Metabolism of Cells and Redox State in the Brain

PubMed Central

Figueroa-Méndez, Rodrigo; Rivas-Arancibia, Selva

2015-01-01

Ever since Linus Pauling published his studies, the effects of vitamin C have been surrounded by contradictory results. This may be because its effects depend on a number of factors such as the redox state of the body, the dose used, and also on the tissue metabolism. This review deals with vitamin C pharmacokinetics and its participation in neurophysiological processes, as well as its role in the maintenance of redox balance. The distribution and the concentration of vitamin C in the organs depend on the ascorbate requirements of each and on the tissue distribution of sodium-dependent vitamin C transporter 1 and 2 (SVCT1 and SVCT2). This determines the specific distribution pattern of vitamin C in the body. Vitamin C is involved in the physiology of the nervous system, including the support and the structure of the neurons, the processes of differentiation, maturation, and neuronal survival; the synthesis of catecholamine, and the modulation of neurotransmission. This antioxidant interacts with self-recycling mechanisms, including its participation in the endogenous antioxidant system. We conclude that the pharmacokinetic properties of ascorbate are related to the redox state and its functions and effects in tissues. PMID:26779027

Examination and Mitigation of Electron Interception Processes in Dye-sensitized Solar Cells through Redox Shuttle and Photoelectrode Modification

NASA Astrophysics Data System (ADS)

Hoffeditz, William Lawrence

With the dual challenges of meeting global energy demand and mitigating anthropogenic climate change, significant effort is being applied to generating power from renewable sources. The dye-sensitized solar cell (DSC) is a photovoltaic technology capable of generating electricity from sunlight, but suffers losses in efficiency due to deleterious electron transfer processes. Controlling these processes is essential if DSCs are to continue to advance, and this dissertation focuses on isolation, interrogation, and mitigation of these processes via controllable inorganic redox/coordination chemistry and atomic layer deposition (ALD). The redox shuttle is often the subject of innovation in DSCs, the goal being to increase obtainable photovoltage without sacrificing photocurrent. A copper redox shuttle with a favorable (II/I) redox potential for DSC use and intriguing inner-sphere reorganization energy was investigated. The shuttle completely replaces its tetradentate coordinating ligand upon oxidation with multiple pyridine molecules. This new species displays markedly slower electron interception, necessitating fabrication of a new counter electrode in order for the shuttle to function. Upon reduction, the tetradentate ligand re-coordinates, creating a dual-species shuttle that outperforms either species as a Cu(II/I) shuttle in isolation. Photoelectrode modification is also the subject of innovation in DSCs. ALD is ideally suited for this type of innovation as it can coat high aspect surfaces with metal-oxide films of uniform thickness. The ALD post-treatment technique is described and used to deposit Al2O3 around a TiO2 adsorbed zinc-porphyrin dye. This technique is shown to prevent dye degradation from ambient air and/or light. Additionally, the architecture allows the study of dye-influenced electron interception processes. It was found that the presence of dye increased interception, which was attributed to dye-mediated electron hopping and/or superexchange mechanisms. Finally, ALD was used to fabricate thin-film Nb2O5, which is a promising overcoat material to potentially improved photovoltage without harming charge injection. The conduction band potential of films specifically fabricated via ALD was thus determined and compared to that of TiO2 films fabricated by ALD. Taken together, the research presented herein increases the underlying understanding of the numerous complicated electron transfer processes in DSC-type devices and offers new strategies to combat deleterious processes, specifically electron interception.

Influence of redox fluctuations and rainfall on pedogenic iron alteration and soil magnetic properties (Invited)

NASA Astrophysics Data System (ADS)

Thompson, A.; Rancourt, D.; Chadwick, O.; Chorover, J. D.

2009-12-01

Soil iron mineral composition emerges from a dynamic interplay between processes causing selective mineral addition/removal (both physically and chemically-driven) and processes affecting in situ mineral transformation. Discerning the influence of these pedogenic processes in a temporally integrated manner is fundamentally relevant to many biogeochemical questions. Among them is to what extent the Fe-mineral system can be used to constrain paleo-interpretations of oceanic sediments and geological deposits. Here we describe results from field and laboratory experiments designed to explore the effects of variable redox conditions on soil iron mineral transformation. Our experimental systems include: (1) a climate gradient of basaltic soils from the island of Maui, HI (MCG) with a documented decrease in Eh. and (2) laboratory incubations where we subjected soil slurries to a series of bacterially-driven reduction-oxidation cycles. Our prior work in these systems examining the iron isotopic and mineral composition will be combined with in-progress analysis of magnetic susceptibility. Current results indicate that across the field gradient (MCG) we find average increases of 0.56‰±0.09‰ δ56Fe for the surface and subsurface soils that correlate very well (R2=0.88) with 57Fe Mössbauer-determined Fe-oxyhydroxide fraction. Such a correlation is difficult to explain on the basis of strict parameter co-variation with rainfall, and suggests isotopic and mineral composition may be coupled through in situ mineral transformation processes in these soils. In our soil slurry incubation experiments we reported previously that repeated redox oscillations generate a cumulative increase in Fe mineral crystallinity. Integration of these results with magnetic susceptibility measurements will provide the context for discussing how dynamic redox processes alter soil magnetic properties most often drawn on for paleoclimate interpretations.

Electrochemical reverse engineering: A systems-level tool to probe the redox-based molecular communication of biology.

PubMed

Li, Jinyang; Liu, Yi; Kim, Eunkyoung; March, John C; Bentley, William E; Payne, Gregory F

2017-04-01

The intestine is the site of digestion and forms a critical interface between the host and the outside world. This interface is composed of host epithelium and a complex microbiota which is "connected" through an extensive web of chemical and biological interactions that determine the balance between health and disease for the host. This biology and the associated chemical dialogues occur within a context of a steep oxygen gradient that provides the driving force for a variety of reduction and oxidation (redox) reactions. While some redox couples (e.g., catecholics) can spontaneously exchange electrons, many others are kinetically "insulated" (e.g., biothiols) allowing the biology to set and control their redox states far from equilibrium. It is well known that within cells, such non-equilibrated redox couples are poised to transfer electrons to perform reactions essential to immune defense (e.g., transfer from NADH to O 2 for reactive oxygen species, ROS, generation) and protection from such oxidative stresses (e.g., glutathione-based reduction of ROS). More recently, it has been recognized that some of these redox-active species (e.g., H 2 O 2 ) cross membranes and diffuse into the extracellular environment including lumen to transmit redox information that is received by atomically-specific receptors (e.g., cysteine-based sulfur switches) that regulate biological functions. Thus, redox has emerged as an important modality in the chemical signaling that occurs in the intestine and there have been emerging efforts to develop the experimental tools needed to probe this modality. We suggest that electrochemistry provides a unique tool to experimentally probe redox interactions at a systems level. Importantly, electrochemistry offers the potential to enlist the extensive theories established in signal processing in an effort to "reverse engineer" the molecular communication occurring in this complex biological system. Here, we review our efforts to develop this electrochemical tool for in vitro redox-probing. Copyright © 2017 Elsevier Inc. All rights reserved.

Redox Roll-Front Mobilization of Geogenic Uranium by Nitrate Input into Aquifers: Risks for Groundwater Resources.

PubMed

van Berk, Wolfgang; Fu, Yunjiao

2017-01-03

Redox conditions are seen as the key to controlling aqueous uranium concentrations (cU (aq) ). Groundwater data collected by a state-wide groundwater quality monitoring study in Mecklenburg-Western Pomerania (Germany) reveal peak cU (aq) up to 75 μg L -1 but low background uranium concentrations (median cU (aq) < 0.5 μg L -1 ). To characterize the hydrogeochemical processes causing such groundwater contamination by peak cU (aq) , we reanalyzed measured redox potentials and total concentrations of aqueous uranium, nitrate, and sulfate species in groundwater together with their distribution across the aquifer depth and performed semigeneric 2D reactive mass transport modeling which is based on chemical thermodynamics. The combined interpretation of modeling results and measured data reveals that high cU (aq) and its depth-specific distribution depending on redox conditions is a result of a nitrate-triggered roll-front mobilization of geogenic uranium in the studied aquifers which are unaffected by nuclear activities. The modeling results show that groundwater recharge containing (fertilizer-derived) nitrate drives the redox shift from originally reducing toward oxidizing environments, when nitrate input has consumed the reducing capacity of the aquifers, which is present as pyrite, degradable organic carbon, and geogenic U(IV) minerals. This redox shift controls the uranium roll-front mobilization and results in high cU (aq) within the redoxcline. Moreover, the modeling results indicate that peak cU (aq) occurring at this redox front increase along with the temporal progress of such redox conversion within the aquifer.

Thioredoxin and Thioredoxin Target Proteins: From Molecular Mechanisms to Functional Significance

PubMed Central

Lee, Samuel; Kim, Soo Min

2013-01-01

Abstract The thioredoxin (Trx) system is one of the central antioxidant systems in mammalian cells, maintaining a reducing environment by catalyzing electron flux from nicotinamide adenine dinucleotide phosphate through Trx reductase to Trx, which reduces its target proteins using highly conserved thiol groups. While the importance of protecting cells from the detrimental effects of reactive oxygen species is clear, decades of research in this field revealed that there is a network of redox-sensitive proteins forming redox-dependent signaling pathways that are crucial for fundamental cellular processes, including metabolism, proliferation, differentiation, migration, and apoptosis. Trx participates in signaling pathways interacting with different proteins to control their dynamic regulation of structure and function. In this review, we focus on Trx target proteins that are involved in redox-dependent signaling pathways. Specifically, Trx-dependent reductive enzymes that participate in classical redox reactions and redox-sensitive signaling molecules are discussed in greater detail. The latter are extensively discussed, as ongoing research unveils more and more details about the complex signaling networks of Trx-sensitive signaling molecules such as apoptosis signal-regulating kinase 1, Trx interacting protein, and phosphatase and tensin homolog, thus highlighting the potential direct and indirect impact of their redox-dependent interaction with Trx. Overall, the findings that are described here illustrate the importance and complexity of Trx-dependent, redox-sensitive signaling in the cell. Our increasing understanding of the components and mechanisms of these signaling pathways could lead to the identification of new potential targets for the treatment of diseases, including cancer and diabetes. Antioxid. Redox Signal. 18, 1165–1207. PMID:22607099

Mantle redox evolution and the oxidation state of the Archean atmosphere

NASA Technical Reports Server (NTRS)

Kasting, J. F.; Eggler, D. H.; Raeburn, S. P.

1993-01-01

Current models predict that the early atmosphere consisted mostly of CO2, N2, and H2O, along with traces of H2 and CO. Such models are based on the assumption that the redox state of the upper mantle has not changed, so that volcanic gas composition has remained approximately constant with time. We argue here that this assumption is probably incorrect: the upper mantle was originally more reduced than today, although not as reduced as the metal arrest level, and has become progressively more oxidized as a consequence of the release of reduced volcanic gases and the subduction of hydrated, oxidized seafloor. Data on the redox state of sulfide and chromite inclusions in diamonds imply that the process of mantle oxidation was slow, so that reduced conditions could have prevailed for as much as half of the earth's history. To be sure, other oxybarometers of ancient rocks give different results, so the question of when the mantle redox state has changed remains unresolved. Mantle redox evolution is intimately linked to the oxidation state of the primitive atmosphere: A reduced Archean atmosphere would have had a high hydrogen escape rate and should correspond to a changing mantle redox state; an oxidized Archean atmosphere should be associated with a constant mantle redox state. The converses of these statements are also true. Finally, our theory of mantle redox evolution may explain why the Archean atmosphere remained oxygen-deficient until approximately 2.0 billion years ago (Ga) despite a probable early origin for photosynthesis.

Protein Thiol Redox Signaling in Monocytes and Macrophages.

PubMed

Short, John D; Downs, Kevin; Tavakoli, Sina; Asmis, Reto

2016-11-20

Monocyte and macrophage dysfunction plays a critical role in a wide range of inflammatory disease processes, including obesity, impaired wound healing diabetic complications, and atherosclerosis. Emerging evidence suggests that the earliest events in monocyte or macrophage dysregulation include elevated reactive oxygen species production, thiol modifications, and disruption of redox-sensitive signaling pathways. This review focuses on the current state of research in thiol redox signaling in monocytes and macrophages, including (i) the molecular mechanisms by which reversible protein-S-glutathionylation occurs, (ii) the identification of bona fide S-glutathionylated proteins that occur under physiological conditions, and (iii) how disruptions of thiol redox signaling affect monocyte and macrophage functions and contribute to atherosclerosis. Recent Advances: Recent advances in redox biochemistry and biology as well as redox proteomic techniques have led to the identification of many new thiol redox-regulated proteins and pathways. In addition, major advances have been made in expanding the list of S-glutathionylated proteins and assessing the role that protein-S-glutathionylation and S-glutathionylation-regulating enzymes play in monocyte and macrophage functions, including monocyte transmigration, macrophage polarization, foam cell formation, and macrophage cell death. Protein-S-glutathionylation/deglutathionylation in monocytes and macrophages has emerged as a new and important signaling paradigm, which provides a molecular basis for the well-established relationship between metabolic disorders, oxidative stress, and cardiovascular diseases. The identification of specific S-glutathionylated proteins as well as the mechanisms that control this post-translational protein modification in monocytes and macrophages will facilitate the development of new preventive and therapeutic strategies to combat atherosclerosis and other metabolic diseases. Antioxid. Redox Signal. 25, 816-835.

Relating hyporheic fluxes, residence times, and redox-sensitive biogeochemical processes upstream of beaver dams

USGS Publications Warehouse

Briggs, Martin A.; Lautz, Laura; Hare, Danielle K.

2013-01-01

¨hler number seemed to overestimate the actual transition as indicated by multiple secondary electron acceptors, illustrating the gradient nature of anaerobic transition. Temporal flux variability in low-flux morphologies generated a much greater range in hyporheic redox conditions compared to high-flux zones, and chemical responses to changing flux rates were consistent with those predicted from the empirical relationship between redox condition and residence time. The Raz tracer revealed that hyporheic flow paths have strong net aerobic respiration, particularly at higher residence time, but this reactive exchange did not affect the net stream signal at the reach scale.

Hemoglobin redox reactions and red blood cell aging.

PubMed

Rifkind, Joseph M; Nagababu, Enika

2013-06-10

The physiological mechanism(s) for recognition and removal of red blood cells (RBCs) from circulation after 120 days of its lifespan is not fully understood. Many of the processes thought to be associated with the removal of RBCs involve oxidative stress. We have focused on hemoglobin (Hb) redox reactions, which is the major source of RBC oxidative stress. The importance of Hb redox reactions have been shown to originate in large parts from the continuous slow autoxidation of Hb producing superoxide and its dramatic increase under hypoxic conditions. In addition, oxidative stress has been shown to be associated with redox reactions that originate from Hb reactions with nitrite and nitric oxide (NO) and the resultant formation of highly toxic peroxynitrite when NO reacts with superoxide released during Hb autoxidation. The interaction of Hb, particularly under hypoxic conditions with band 3 of the RBC membrane is critical for the generating the RBC membrane changes that trigger the removal of cells from circulation. These changes include exposure of antigenic sites, increased calcium leakage into the RBC, and the resultant leakage of potassium out of the RBC causing cell shrinkage and impaired deformability. The need to understand the oxidative damage to specific membrane proteins that result from redox reactions occurring when Hb is bound to the membrane. Proteomic studies that can pinpoint the specific proteins damaged under different conditions will help elucidate the cellular aging processes that result in cells being removed from circulation.

Redox processes as revealed by voltammetry in the surface sediments of the Gotland Basin, Baltic Sea

NASA Astrophysics Data System (ADS)

Yücel, Mustafa; Dale, Andy; Sommer, Stefan; Pfannkuche, Olaf

2014-05-01

Sulfur cycling in marine sediments undergoes dramatic changes with changing redox conditions of the overlying waters. The upper sediments of the anoxic Gotland Basin, central Baltic Sea represent a dynamic redox environment with extensive mats of sulfide oxidizing bacteria covering the seafloor beneath the chemocline. In order to investigate sulfur redox cycling at the sediment-water interface, sediment cores were sampled over a transect covering 65 - 174 m water depth in August-September 2013. High resolution (0.25 mm minimum) vertical microprofiles of electroactive redox species including dissolved sulfide and iron were obtained with solid state Au-Hg voltammetric microelectrodes. This approach enabled a fine-scale comparison of porewater profiles across the basin. The steepest sulfide gradients (i.e. the highest sulfide consumption) occurred within the upper 10 mm in sediments covered by surficial mats (2.10 to 3.08 mmol m-2 day-1). In sediments under permanently anoxic waters (>140m), voltammetric signals for Fe(II) and aqueous FeS were detected below a subsurface maximum in dissolved sulfide, indicating a Fe flux originating from older, deeper sedimentary layers. Our results point to a unique sulfur cycling in the Gotland basin seafloor where sulfide accumulation is moderated by sulfide oxidation at the sediment surface and by FeS precipitation in deeper sediment layers. These processes may play an important role in minimizing benthic sulfide fluxes to bottom waters around the major basins of the Baltic Sea.

Hydroxyl radical generation in electro-Fenton process with a gas-diffusion electrode: Linkages with electro-chemical generation of hydrogen peroxide and iron redox cycle.

PubMed

Yatagai, Tomonori; Ohkawa, Yoshiko; Kubo, Daichi; Kawase, Yoshinori

2017-01-02

The hydroxyl radical generation in an electro-Fenton process with a gas-diffusion electrode which is strongly linked with electro-chemical generation of hydrogen peroxide and iron redox cycle was studied. The OH radical generation subsequent to electro-chemical generations of H 2 O 2 was examined under the constant potential in the range of Fe 2+ dosage from 0 to 1.0 mM. The amount of generated OH radical initially increased and gradually decreased after the maximum was reached. The initial rate of OH radical generation increased for the Fe 2+ dosage <0.25 mM and at higher Fe 2+ dosages remained constant. At higher Fe 2+ dosages the precipitation of Fe might inhibit the enhancement of OH radical generation. The experiments for decolorization and total organic carbon (TOC) removal of azo-dye Orange II by the electro-Fenton process were conducted and the quick decolorization and slow TOC removal of Orange II were found. To quantify the linkages of OH radical generation with dynamic behaviors of electro-chemically generated H 2 O 2 and iron redox cycle and to investigate effects of OH radical generation on the decolorization and TOC removal of Orange II, novel reaction kinetic models were developed. The proposed models could satisfactory clarify the linkages of OH radical generation with electro-chemically generated H 2 O 2 and iron redox cycle and simulate the decolorization and TOC removal of Orange II by the electro-Fenton process.

Aquaporin-facilitated transmembrane diffusion of hydrogen peroxide.

PubMed

Bienert, Gerd P; Chaumont, François

2014-05-01

Hydrogen peroxide (H2O2) is an important signaling compound that has recently been identified as a new substrate for several members of the aquaporin superfamily in various organisms. Evidence is emerging about the physiological significance of aquaporin-facilitated H2O2 diffusion. This review summarizes current knowledge about aquaporin-facilitated H2O2 diffusion across cellular membranes. It focuses on physicochemical and experimental evidence demonstrating the involvement of aquaporins in the transport of this redox signaling compound and discusses the regulation and structural prerequisites of these channels to transmit this signal. It also provides perspectives about the potential importance of aquaporin-facilitated H2O2 diffusion processes and places this knowledge in the context of the current understanding of transmembrane redox signaling processes. Specific aquaporin isoforms facilitate the passive diffusion of H2O2 across biological membranes and control H2O2 membrane permeability and signaling in living organisms. Redox signaling is a very important process regulating the physiology of cells and organisms in a similar way to the well-characterized hormonal and calcium signaling pathways. Efficient transmembrane diffusion of H2O2, a key molecule in the redox signaling network, requires aquaporins and makes these channels important players in this signaling process. Channel-mediated membrane transport allows the fine adjustment of H2O2 levels in the cytoplasm, intracellular organelles, the apoplast, and the extracellular space, which are essential for it to function as a signal molecule. This article is part of a Special Issue entitled Aquaporins. © 2013.

IMPACTS OF ANTIFOAM ADDITIONS AND ARGON BUBBLING ON DEFENSE WASTE PROCESSING FACILITY REDUCTION/OXIDATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jantzen, C.; Johnson, F.

2012-06-05

During melting of HLW glass, the REDOX of the melt pool cannot be measured. Therefore, the Fe{sup +2}/{Sigma}Fe ratio in the glass poured from the melter must be related to melter feed organic and oxidant concentrations to ensure production of a high quality glass without impacting production rate (e.g., foaming) or melter life (e.g., metal formation and accumulation). A production facility such as the Defense Waste Processing Facility (DWPF) cannot wait until the melt or waste glass has been made to assess its acceptability, since by then no further changes to the glass composition and acceptability are possible. therefore, themore » acceptability decision is made on the upstream process, rather than on the downstream melt or glass product. That is, it is based on 'feed foward' statistical process control (SPC) rather than statistical quality control (SQC). In SPC, the feed composition to the melter is controlled prior to vitrification. Use of the DWPF REDOX model has controlled the balanjce of feed reductants and oxidants in the Sludge Receipt and Adjustment Tank (SRAT). Once the alkali/alkaline earth salts (both reduced and oxidized) are formed during reflux in the SRAT, the REDOX can only change if (1) additional reductants or oxidants are added to the SRAT, the Slurry Mix Evaporator (SME), or the Melter Feed Tank (MFT) or (2) if the melt pool is bubble dwith an oxidizing gas or sparging gas that imposes a different REDOX target than the chemical balance set during reflux in the SRAT.« less

Impact on the Fe redox cycling of organic ligands released by Synechococcus PCC 7002, under different iron fertilization scenarios. Modeling approach

NASA Astrophysics Data System (ADS)

Samperio-Ramos, Guillermo; González-Dávila, Melchor; Santana-Casiano, J. Magdalena

2018-06-01

The kinetics of Fe redox transformations are of crucial importance in determining the bioavailability of iron, due to inorganic Fe(II) and Fe weakly organic complexes being the most easily assimilated species by phytoplankton. The role played by the natural organic ligands excreted by the cyanobacteria Synecococcus PCC 7002 on the iron redox chemistry was studied at different stages of growth, considering changes in the organic exudation of the cyanobacteria, associated with growth under two different scenarios of iron availability. The oxidation/reduction processes of iron were studied at nanomolar levels and under different physicochemical conditions of pH (7.2- 8.2), temperature (5- 35 °C) and salinity (10- 37). The presence of natural organic exudates of Synechococcus affected the redox behavior of iron. A pH-dependent and photo-induced Fe(III) reduction process was detected in the presence of exudates produced under Fe-Low conditions. Photolytic reactions also modified the reactivity of those exudates with respect to Fe(II), increasing its lifetime in seawater. Without light mediated processes, organic ligands excreted under iron deficient conditions intensified the Fe(II) oxidation at pH < 7.5. The organic exudates released under High-Fe conditions retarded the Fe(II) oxidation rate, as a function of DOC produced. The changes in the apparent oxidation rate were fitted to polynomial functions for both of the Fe-scenarios considered. A kinetic modeling approach to describe the speciation and the contribution of individual Fe(II) species to the overall oxidation rate was applied, considering the experimental data and delimiting the equilibrium and redox constants between iron and the major ligands present in solution. Two organic type ligands for the exudates of Synechococcus PCC 7002, with different iron-chelation properties were included in the model. The Fe(II) speciation was radically affected when organic ligands were considered. The individual contributions to the overall Fe(II) oxidation rate demonstrated that these organic ligands played a key role in the oxidation process, although their contributions were dependent on the prescribed iron conditions. The study, therefore, suggests that the variability in the composition and nature of organic exudates released, due to iron availability conditions, might determine the redox behaviour of iron in seawater.

Base excision repair, the redox environment and therapeutic implications.

PubMed

Storr, S J; Woolston, C M; Martin, S G

2012-01-01

Control of redox homeostasis is crucial for a number of cellular processes with deregulation leading to a number of serious consequences including oxidative damage such induction of DNA base lesions. The DNA lesions caused by oxidative damage are principally repaired by the base excision repair (BER) pathway. Pharmacological inhibition of BER is becoming an increasingly active area of research with the emergence of PARP inhibitors in cancer therapy. The redox status of the cell is modulated by a number of systems, including a large number of anti-oxidant enzymes who function in the control of superoxide and hydrogen peroxide, and ultimately in the release of the damaging hydroxyl radical. Here we provide an overview of reactive oxygen species (ROS) production and its modulation by antioxidant enzymes. The review also discusses the effect of ROS on the BER pathway, particularly in relation to cancer. Finally, as the modulation of the redox environment is of interest in cancer therapy, with certain agents having the potential to reverse chemo- and radiotherapy resistance or treat therapy related toxicity, we discuss redox modulating agents currently under development.

Redox regulation of genome stability by effects on gene expression, epigenetic pathways and DNA damage/repair

PubMed Central

Mikhed, Yuliya; Görlach, Agnes; Knaus, Ulla G.; Daiber, Andreas

2015-01-01

Reactive oxygen and nitrogen species (e.g. H2O2, nitric oxide) confer redox regulation of essential cellular signaling pathways such as cell differentiation, proliferation, migration and apoptosis. In addition, classical regulation of gene expression or activity, including gene transcription to RNA followed by translation to the protein level, by transcription factors (e.g. NF-κB, HIF-1α) and mRNA binding proteins (e.g. GAPDH, HuR) is subject to redox regulation. This review will give an update of recent discoveries in this field, and specifically highlight the impact of reactive oxygen and nitrogen species on DNA repair systems that contribute to genomic stability. Emphasis will be placed on the emerging role of redox mechanisms regulating epigenetic pathways (e.g. miRNA, DNA methylation and histone modifications). By providing clinical correlations we discuss how oxidative stress can impact on gene regulation/activity and vise versa, how epigenetic processes, other gene regulatory mechanisms and DNA repair can influence the cellular redox state and contribute or prevent development or progression of disease. PMID:26079210

Synthesis of a new π-conjugated redox oligomer: Electrochemical and optical investigation

NASA Astrophysics Data System (ADS)

Blili, Saber; Zaâboub, Zouhour; Maaref, Hassen; Haj Said, Ayoub

2017-01-01

A new π-conjugated redox oligomer was prepared according a two-Step Synthesis. Firstly, an oligophenylene (OMPA) was obtained from the anodic oxidation of the (4-methoxyphenyl)acetonitrile. Then, the resulting material was chemically modified by the Knoevenagel condensation with the ferrocenecarboxaldehyde. This reaction led to a redox-conjugated oligomer the Fc-OMPA. The synthesized material was characterized using different spectroscopic techniques: NMR, FTIR, UV-vis and photoluminescence (PL) spectroscopy. The Fc-OMPA was used to modify a platinum electrode surface and the electrochemical response of the ferrocene redox-center was investigated by cyclic voltammetry. Moreover, the room temperature PL spectra of Fc-OMPA revealed that the ferrocene moiety, which acts as an electron donor, can effectively quench the oligomer luminescence. However, when ferrocene was oxidized to ferrocenium ion, the intramolecular charge transfer process was prevented which consequently enhanced the light emission. Thus, the oligomer light-emission can be, chemically or electrochemically tuned. The obtained results showed that the prepared material is a good candidate for the elaboration of electrochemical sensors and for the development of luminescent Redox-switchable devices.

Reduction Dynamics of Doped Ceria, Nickel Oxide, and Cermet Composites Probed Using In Situ Raman Spectroscopy

PubMed Central

Shearing, Paul R.; Brightman, Edward; Brett, Dan J. L.; Brandon, Nigel P.; Cohen, Lesley F.

2016-01-01

The redox properties of gadolinium doped ceria (CGO) and nickel oxide (NiO) composite cermets underpin the operation of solid oxide electrochemical cells. Although these systems have been widely studied, a full comprehension of the reaction dynamics at the interface of these materials is lacking. Here, in situ Raman spectroscopic monitoring of the redox cycle is used to investigate the interplay between the dynamic and competing processes of hydrogen spillover and water dissociation on the doped ceria surface. In order to elucidate these mechanisms, the redox process in pure CGO and NiO is studied when exposed to wet and dry hydrogen and is compared to the cermet behavior. In dry hydrogen, CGO reduces relatively rapidly via a series of intermediate phases, while NiO reduces via a single‐step process. In wet reducing atmospheres, however, the oxidation state of pure CGO is initially stabilized due to the dissociation of water by reduced Ce(III) and subsequent incorporation of oxygen into the structure. In the reduction process involving the composite cermet, the close proximity of the NiO improves the efficiency and speed of the composite reduction process. Although NiO is already incorporated into working cells, these observations suggest direct routes to further improve cell performance. PMID:27595058

Reduction Dynamics of Doped Ceria, Nickel Oxide, and Cermet Composites Probed Using In Situ Raman Spectroscopy.

PubMed

Maher, Robert C; Shearing, Paul R; Brightman, Edward; Brett, Dan J L; Brandon, Nigel P; Cohen, Lesley F

2016-01-01

The redox properties of gadolinium doped ceria (CGO) and nickel oxide (NiO) composite cermets underpin the operation of solid oxide electrochemical cells. Although these systems have been widely studied, a full comprehension of the reaction dynamics at the interface of these materials is lacking. Here, in situ Raman spectroscopic monitoring of the redox cycle is used to investigate the interplay between the dynamic and competing processes of hydrogen spillover and water dissociation on the doped ceria surface. In order to elucidate these mechanisms, the redox process in pure CGO and NiO is studied when exposed to wet and dry hydrogen and is compared to the cermet behavior. In dry hydrogen, CGO reduces relatively rapidly via a series of intermediate phases, while NiO reduces via a single-step process. In wet reducing atmospheres, however, the oxidation state of pure CGO is initially stabilized due to the dissociation of water by reduced Ce(III) and subsequent incorporation of oxygen into the structure. In the reduction process involving the composite cermet, the close proximity of the NiO improves the efficiency and speed of the composite reduction process. Although NiO is already incorporated into working cells, these observations suggest direct routes to further improve cell performance.

Redox-inflammatory synergy in the metabolic syndrome.

PubMed

Bryan, Sean; Baregzay, Boran; Spicer, Drew; Singal, Pawan K; Khaper, Neelam

2013-01-01

Metabolic syndrome (MetS) comprises interrelated disease states including obesity, insulin resistance and type 2 diabetes (T2DM), dyslipidemia, and hypertension. Essential to normal physiological function, and yet massively damaging in excess, oxidative stress and inflammation are pivotal common threads among the pathologies of MetS. Increasing evidence indicates that redox and inflammatory dysregulation parallels the syndrome's physiological, biochemical, and anthropometric features, leading many to consider the pro-oxidative, pro-inflammatory milieu an unofficial criterion in itself. Left unchecked, cross-promotion of oxidative stress and inflammation creates a feed-forward cycle that can initiate and advance disease progression. Such redox-inflammatory integration is evident in the pathogenesis of obesity, insulin resistance and T2DM, atherogenic dyslipidemia, and hypertension, and is thus hypothesized to be the "common soil" from which they develop. The present review highlights the synergistic contributions of redox-inflammatory processes to each of the components of the MetS.

Study to establish cost predictions for the production of Redox chemicals

NASA Technical Reports Server (NTRS)

Ammann, P. R.; Loreth, M.; Harvey, W. W.

1982-01-01

The chromium and iron chloride chemicals are significant first costs for NASA Redox energy storage systems. This study was performed to determine the lowest cost at which chromium and iron chlorides could be obtained for a complex of redox energy storage systems. In addition, since the solutions gradually become intermixed during the course of operation of Redox units, it was an objective to evaluate schemes for regeneration of the operating solutions. Three processes were evaluated for the production of chromium and iron chlorides. As a basis for the preliminary plant design and economic evaluation, it was assumed that the plant would produce about 25,000 tons of contained chromium as CrCl3 and an equivalent molar quantity of FeCl2. Preliminary plant designs, including materials and energy balances and sizing of major equipment, were prepared, and capital and operating costs were estimated.

Graphite felt modified with bismuth nanoparticles as negative electrode in a vanadium redox flow battery.

PubMed

Suárez, David J; González, Zoraida; Blanco, Clara; Granda, Marcos; Menéndez, Rosa; Santamaría, Ricardo

2014-03-01

A graphite felt decorated with bismuth nanoparticles was studied as negative electrode in a vanadium redox flow battery (VRFB). The results confirm the excellent electrochemical performance of the bismuth modified electrode in terms of the reversibility of the V(3+) /V(2+) redox reactions and its long-term cycling performance. Moreover a mechanism that explains the role that Bi nanoparticles play in the redox reactions in this negative half-cell is proposed. Bi nanoparticles favor the formation of BiHx , an intermediate that reduces V(3+) to V(2+) and, therefore, inhibits the competitive irreversible reaction of hydrogen formation (responsible for the commonly observed loss of Coulombic efficiency of VRFBs). Thus, the total charge consumed during the cathodic sweep in this electrode is used to reduce V(3+) to V(2+) , resulting in a highly reversible and efficient process. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

RAAS-mediated Redox effects in Chronic Kidney Disease

PubMed Central

Nistala, Ravi; Wei, Yongzhong; Sowers, James R; Whaley-Connell, Adam

2009-01-01

The renin-angiotensin-aldosterone-system (RAAS) is central to the pathogenesis of hypertension, cardiovascular and kidney disease. Emerging evidence support various pathways through which a local renal RAAS can affect kidney function, hypertension, and cardiovascular disease. A prominent mechanism appears to be loss of redox homeostasis and formation of excessive free radicals. Free radicals such as reactive oxygen species (ROS) are necessary in normal physiologic processes including development of nephrons, erythropoeisis and tubular sodium transport. However, loss of redox homeostasis contributes to pro-inflammatory and pro-fibrotic pathways in the kidney that in turn lead to reduced vascular compliance, podocyte pathology and proteinuria. Both blockade of the RAAS and oxidative stress produces salutary effects on hypertension and glomerular filtration barrier injury. Thus, the focus of current research is on understanding the pathophysiology of chronic kidney disease in the context of an elevated RAAS and unbalanced redox mechanisms. PMID:19218092

Imaging in real-time with FRET the redox response of tumorigenic cells to glutathione perturbations in a microscale flow†

PubMed Central

Lin, Chunchen; Kolossov, Vladimir L.; Tsvid, Gene; Trump, Lisa; Henry, Jennifer Jo; Henderson, Jerrod L.; Rund, Laurie A.; Kenis, Paul J.A.; Schook, Lawrence B.; Gaskins, H. Rex; Timp, Gregory

2012-01-01

Despite the potential benefits of selective redox-modulating strategies for cancer therapy, an efficacious methodology for testing therapies remains elusive because of the difficulty in measuring intracellular redox potentials over time. In this report, we have incorporated a new FRET-based biosensor to follow in real time redox-sensitive processes in cells transformed to be tumorigenic and cultured in a microfluidic channel. A microfluidic network was used to control micro-scale flow near the cells and at the same time deliver drugs exogenously. Subsequently, the response of a redox homeostasis circuit was tested, namely reduced glutathione (GSH)/oxidized glutathione(GSSG), to diamide, a thiol oxidant, and two drugs used for cancer therapies: BSO (l-buthionine-[SR]-sulfoximine) and BCNU (carmustine). The main outcome from these experiments is a comparison of the temporal depletion and recovery of GSH in single living cells in real-time. These data demonstrate that mammalian cells are capable of restoring a reduced intracellular redox environment in minutes after an acute oxidative insult is removed. This recovery is significantly delayed by (i) the inhibition of GSH biosynthesis by BSO; (ii) the inactivation of glutathione reductase by BCNU; and (iii) in tumorigenic cells relative to an isogenic non-tumorigenic control cell line. PMID:21183971

Effect of Redox Conditions on Bacterial Community Structure in Baltic Sea Sediments with Contrasting Phosphorus Fluxes

PubMed Central

Steenbergh, Anne K.; Bodelier, Paul L. E.; Slomp, Caroline P.; Laanbroek, Hendrikus J.

2014-01-01

Phosphorus release from sediments can exacerbate the effect of eutrophication in coastal marine ecosystems. The flux of phosphorus from marine sediments to the overlying water is highly dependent on the redox conditions at the sediment-water interface. Bacteria are key players in the biological processes that release or retain phosphorus in marine sediments. To gain more insight in the role of bacteria in phosphorus release from sediments, we assessed the effect of redox conditions on the structure of bacterial communities. To do so, we incubated surface sediments from four sampling sites in the Baltic Sea under oxic and anoxic conditions and analyzed the fingerprints of the bacterial community structures in these incubations and the original sediments. This paper describes the effects of redox conditions, sampling station, and sample type (DNA, RNA, or whole-cell sample) on bacterial community structure in sediments. Redox conditions explained only 5% of the variance in community structure, and bacterial communities from contrasting redox conditions showed considerable overlap. We conclude that benthic bacterial communities cannot be classified as being typical for oxic or anoxic conditions based on community structure fingerprints. Our results suggest that the overall structure of the benthic bacterial community has only a limited impact on benthic phosphate fluxes in the Baltic Sea. PMID:24667801

Intracellular Redox Compartmentation and ROS-Related Communication in Regulation and Signaling1[OPEN

PubMed Central

2016-01-01

Recent years have witnessed enormous progress in understanding redox signaling related to reactive oxygen species (ROS) in plants. The consensus view is that such signaling is intrinsic to many developmental processes and responses to the environment. ROS-related redox signaling is tightly wedded to compartmentation. Because membranes function as barriers, highly redox-active powerhouses such as chloroplasts, peroxisomes, and mitochondria may elicit specific signaling responses. However, transporter functions allow membranes also to act as bridges between compartments, and so regulated capacity to transmit redox changes across membranes influences the outcome of triggers produced at different locations. As well as ROS and other oxidizing species, antioxidants are key players that determine the extent of ROS accumulation at different sites and that may themselves act as signal transmitters. Like ROS, antioxidants can be transported across membranes. In addition, the intracellular distribution of antioxidative enzymes may be modulated to regulate or facilitate redox signaling appropriate to the conditions. Finally, there is substantial plasticity in organellar shape, with extensions such as stromules, peroxules, and matrixules playing potentially crucial roles in organelle-organelle communication. We provide an overview of the advances in subcellular compartmentation, identifying the gaps in our knowledge and discussing future developments in the area. PMID:27208308

Effect of redox conditions on bacterial community structure in Baltic Sea sediments with contrasting phosphorus fluxes.

PubMed

Steenbergh, Anne K; Bodelier, Paul L E; Slomp, Caroline P; Laanbroek, Hendrikus J

2014-01-01

Phosphorus release from sediments can exacerbate the effect of eutrophication in coastal marine ecosystems. The flux of phosphorus from marine sediments to the overlying water is highly dependent on the redox conditions at the sediment-water interface. Bacteria are key players in the biological processes that release or retain phosphorus in marine sediments. To gain more insight in the role of bacteria in phosphorus release from sediments, we assessed the effect of redox conditions on the structure of bacterial communities. To do so, we incubated surface sediments from four sampling sites in the Baltic Sea under oxic and anoxic conditions and analyzed the fingerprints of the bacterial community structures in these incubations and the original sediments. This paper describes the effects of redox conditions, sampling station, and sample type (DNA, RNA, or whole-cell sample) on bacterial community structure in sediments. Redox conditions explained only 5% of the variance in community structure, and bacterial communities from contrasting redox conditions showed considerable overlap. We conclude that benthic bacterial communities cannot be classified as being typical for oxic or anoxic conditions based on community structure fingerprints. Our results suggest that the overall structure of the benthic bacterial community has only a limited impact on benthic phosphate fluxes in the Baltic Sea.

Redox status and pro-survival/pro-apoptotic protein expression in the early cardiac hypertrophy induced by experimental hyperthyroidism.

PubMed

Fernandes, R O; Dreher, G J; Schenkel, P C; Fernandes, T R G; Ribeiro, M F M; Araujo, A S R; Belló-Klein, A

2011-10-01

This study was conducted to analyse the redox status and redox-sensitive proteins that may contribute to a non-genomic mechanism of cardiac hypertrophy induction by hyperthyroidism. Wistar rats, treated with L-thyroxine (T4) during 2 weeks (12 mg·l(-1) in drinking water), presented cardiac hypertrophy (68% higher than control), without signals of liver or lung congestion. Myocardial reduction of the reduced glutathione: oxidized glutathione (GSSG) ratio (45%) (redox status) and elevation in hydrogen peroxide concentration (H(2) O(2) ) (28%) were observed in hyperthyroid as compared with the control. No significant difference was found in thioredoxin (Trx), Trx reductase activity and Nrf2 (a transcriptional factor) protein expression between groups. Redox-sensitive proteins, quantified using Western blot, presented the following results: increased p-ERK: total extracellular-regulated kinase (ERK) (200%) and Bax:Bcl-2 (62%) ratios and reduced total-Akt (63%) and p-Akt (53%) expressions in the hyperthyroid rats as compared with the control. The redox imbalance, associated with increased immunocontent of a protein related to maladaptative growth (ERK) and reduced immunocontent of protein related to cytoprotection/survival (Akt), may suggest that the molecular scenario could favour the decompensation process of cardiac hypertrophy induced by experimental hyperthyroidism. Copyright © 2011 John Wiley & Sons, Ltd.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Small, Leo J.; Pratt, Harry D.; Staiger, Chad L.

We present a systematic approach for increasing the concentration of redox-active species in electrolytes for nonaqueous redox flow batteries (RFBs). Starting with an ionic liquid consisting of a metal coordination cation (MetIL), ferrocene-containing ligands and iodide anions are substituted incrementally into the structure. While chemical structures can be drawn for molecules with 10 m redox-active electrons (RAE), practical limitations such as melting point and phase stability constrain the structures to 4.2 m RAE, a 2.3× improvement over the original MetIL. Dubbed “MetILs 3,” these ionic liquids possess redox activity in the cation core, ligands, and anions. Throughout all compositions, infraredmore » spectroscopy shows the ethanolamine-based ligands primarily coordinate to the Fe 2+ core via hydroxyl groups. Calorimetry conveys a profound change in thermophysical properties, not only in melting temperature but also in suppression of a cold crystallization only observed in the original MetIL. Square wave voltammetry reveals redox processes characteristic of each molecular location. Testing a laboratory-scale RFB demonstrates Coulombic efficiencies >95% and increased voltage efficiencies due to more facile redox kinetics, effectively increasing capacity 4×. Application of this strategy to other chemistries, optimizing melting point and conductivity, can yield >10 m RAE, making nonaqueous RFB a viable technology for grid scale storage.« less

Intracellular Redox Compartmentation and ROS-Related Communication in Regulation and Signaling.

PubMed

Noctor, Graham; Foyer, Christine H

2016-07-01

Recent years have witnessed enormous progress in understanding redox signaling related to reactive oxygen species (ROS) in plants. The consensus view is that such signaling is intrinsic to many developmental processes and responses to the environment. ROS-related redox signaling is tightly wedded to compartmentation. Because membranes function as barriers, highly redox-active powerhouses such as chloroplasts, peroxisomes, and mitochondria may elicit specific signaling responses. However, transporter functions allow membranes also to act as bridges between compartments, and so regulated capacity to transmit redox changes across membranes influences the outcome of triggers produced at different locations. As well as ROS and other oxidizing species, antioxidants are key players that determine the extent of ROS accumulation at different sites and that may themselves act as signal transmitters. Like ROS, antioxidants can be transported across membranes. In addition, the intracellular distribution of antioxidative enzymes may be modulated to regulate or facilitate redox signaling appropriate to the conditions. Finally, there is substantial plasticity in organellar shape, with extensions such as stromules, peroxules, and matrixules playing potentially crucial roles in organelle-organelle communication. We provide an overview of the advances in subcellular compartmentation, identifying the gaps in our knowledge and discussing future developments in the area. © 2016 American Society of Plant Biologists. All Rights Reserved.

Copper phthalocyanine films deposited by liquid-liquid interface recrystallization technique (LLIRCT).

PubMed

Patil, K R; Sathaye, S D; Hawaldar, R; Sathe, B R; Mandale, A B; Mitra, A

2007-11-15

The simple recrystallization process is innovatively used to obtain the nanoparticles of copper phthalocyanine by a simple method. Liquid-liquid interface recrystallization technique (LLIRCT) has been employed successfully to produce small sized copper phthalocyanine nanoparticles with diameter between 3-5 nm. The TEM-SAED studies revealed the formation of 3-5 nm sized with beta-phase dominated mixture of alpha and beta copper phthalocyanine nanoparticles. The XRD, SEM, and the UV-vis studies were further carried out to confirm the formation of copper phthalocyanine thin films. The cyclic voltametry (CV) studies conclude that redox reaction is totally reversible one electron transfer process. The process is attributed to Cu(II)/Cu(I) redox reaction.

Redox Regulation of Plant Development

PubMed Central

Considine, Michael J.

2014-01-01

Abstract Significance: We provide a conceptual framework for the interactions between the cellular redox signaling hub and the phytohormone signaling network that controls plant growth and development to maximize plant productivity under stress-free situations, while limiting growth and altering development on exposure to stress. Recent Advances: Enhanced cellular oxidation plays a key role in the regulation of plant growth and stress responses. Oxidative signals or cycles of oxidation and reduction are crucial for the alleviation of dormancy and quiescence, activating the cell cycle and triggering genetic and epigenetic control that underpin growth and differentiation responses to changing environmental conditions. Critical Issues: The redox signaling hub interfaces directly with the phytohormone network in the synergistic control of growth and its modulation in response to environmental stress, but a few components have been identified. Accumulating evidence points to a complex interplay of phytohormone and redox controls that operate at multiple levels. For simplicity, we focus here on redox-dependent processes that control root growth and development and bud burst. Future Directions: The multiple roles of reactive oxygen species in the control of plant growth and development have been identified, but increasing emphasis should now be placed on the functions of redox-regulated proteins, along with the central roles of reductants such as NAD(P)H, thioredoxins, glutathione, glutaredoxins, peroxiredoxins, ascorbate, and reduced ferredoxin in the regulation of the genetic and epigenetic factors that modulate the growth and vigor of crop plants, particularly within an agricultural context. Antioxid. Redox Signal. 21, 1305–1326. PMID:24180689

Design of organic dyes and cobalt polypyridine redox mediators for high-efficiency dye-sensitized solar cells.

PubMed

Feldt, Sandra M; Gibson, Elizabeth A; Gabrielsson, Erik; Sun, Licheng; Boschloo, Gerrit; Hagfeldt, Anders

2010-11-24

Dye-sensitized solar cells (DSCs) with cobalt-based mediators with efficiencies surpassing the record for DSCs with iodide-free electrolytes were developed by selecting a suitable combination of a cobalt polypyridine complex and an organic sensitizer. The effect of the steric properties of two triphenylamine-based organic sensitizers and a series of cobalt polypyridine redox mediators on the overall device performance in DSCs as well as on transport and recombination processes in these devices was compared. The recombination and mass-transport limitations that, previously, have been found to limit the performance of these mediators were avoided by matching the properties of the dye and the cobalt redox mediator. Organic dyes with higher extinction coefficients than the standard ruthenium sensitizers were employed in DSCs in combination with outer-sphere redox mediators, enabling thinner TiO(2) films to be used. Recombination was reduced further by introducing insulating butoxyl chains on the dye rather than on the cobalt redox mediator, enabling redox couples with higher diffusion coefficients and more suitable redox potential to be used, simultaneously improving the photocurrent and photovoltage of the device. Optimization of DSCs sensitized with a triphenylamine-based organic dye in combination with tris(2,2'-bipyridyl)cobalt(II/III) yielded solar cells with overall conversion efficiencies of 6.7% and open-circuit potentials of more than 0.9 V under 1000 W m(-2) AM1.5 G illumination. Excellent performance was also found under low light intensity indoor conditions.

Monolayer to MTS: using SEM, HIM, TEM and SERS to compare morphology, nanosensor uptake and redox potential in MCF7 cells

NASA Astrophysics Data System (ADS)

Jamieson, L. E.; Bell, A. P.; Harrison, D. J.; Campbell, C. J.

2015-06-01

Cellular redox potential is important for the control and regulation of a vast number of processes occurring in cells. When the fine redox potential balance within cells is disturbed it can have serious consequences such as the initiation or progression of disease. It is thought that a redox gradient develops in cancer tumours where the peripheral regions are well oxygenated and internal regions, further from vascular blood supply, become starved of oxygen and hypoxic. This makes treatment of these areas more challenging as, for example, radiotherapy relies on the presence of oxygen. Currently techniques for quantitative analysis of redox gradients are limited. Surface enhanced Raman scattering (SERS) nanosensors (NS) have been used to detect redox potential in a quantitative manner in monolayer cultured cells with many advantages over other techniques. This technique has considerable potential for use in multicellular tumour spheroids (MTS) - a three dimensional (3D) cell model which better mimics the tumour environment and gradients that develop. MTS are a more realistic model of the in vivo cellular morphology and environment and are becoming an increasingly popular in vitro model, replacing traditional monolayer culture. Imaging techniques such as transmission electron microscopy (TEM), scanning electron microscopy (SEM) and helium ion microscopy (HIM) were used to investigate differences in morphology and NS uptake in monolayer culture compared to MTS. After confirming NS uptake, the first SERS measurements revealing quantitative information on redox potential in MTS were performed.

Thiol-redox signaling, dopaminergic cell death, and Parkinson's disease.

PubMed

Garcia-Garcia, Aracely; Zavala-Flores, Laura; Rodriguez-Rocha, Humberto; Franco, Rodrigo

2012-12-15

Parkinson's disease (PD) is characterized by the selective loss of dopaminergic neurons of the substantia nigra pars compacta, which has been widely associated with oxidative stress. However, the mechanisms by which redox signaling regulates cell death progression remain elusive. Early studies demonstrated that depletion of glutathione (GSH), the most abundant low-molecular-weight thiol and major antioxidant defense in cells, is one of the earliest biochemical events associated with PD, prompting researchers to determine the role of oxidative stress in dopaminergic cell death. Since then, the concept of oxidative stress has evolved into redox signaling, and its complexity is highlighted by the discovery of a variety of thiol-based redox-dependent processes regulating not only oxidative damage, but also the activation of a myriad of signaling/enzymatic mechanisms. GSH and GSH-based antioxidant systems are important regulators of neurodegeneration associated with PD. In addition, thiol-based redox systems, such as peroxiredoxins, thioredoxins, metallothioneins, methionine sulfoxide reductases, transcription factors, as well as oxidative modifications in protein thiols (cysteines), including cysteine hydroxylation, glutathionylation, and nitrosylation, have been demonstrated to regulate dopaminergic cell loss. In this review, we summarize major advances in the understanding of the role of thiol-redox signaling in dopaminergic cell death in experimental PD. Future research is still required to clearly understand how integrated thiol-redox signaling regulates the activation of the cell death machinery, and the knowledge generated should open new avenues for the design of novel therapeutic approaches against PD.

Spectroelectrochemistry of EuCl 3 in Four Molten Salt Eutectics; 3 LiCl−NaCl, 3 LiCl−2 KCl, LiCl−RbCl, and 3 LiCl−2 CsCl; at 873 K

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schroll, Cynthia A.; Chatterjee, Sayandev; Levitskaia, Tatiana

Key electrochemical properties affecting pyroprocessing of nuclear fuel were examined in four eutectic melts using using Eu3+/2+ as a representative probe. We report the electrochemical and spectroelectrochemical behavior of EuCl3 in four molten salt eutectics (3 LiCl – NaCl, 3 LiCl – 2 KCl, LiCl – RbCl and 3 LiCl – 2 CsCl) at 873 K. Cyclic voltammetry was used to determine the redox potential for Eu3+/2+ and the applied potentials for spectroelectrochemistry. Single step chronoabsorptometry and thin-layer spectroelectrochemistry were used to obtain the number of electrons transferred, redox potentials and diffusion coefficients for Eu3+ in each eutectic melt. Themore » redox potentials determined by thin-layer spectroelectrochemistry were extremely close to those obtained using cyclic voltammetry. The redox potential for Eu3+/2+ was most positive in the 3 LiCl - NaCl melt, showed a negative shift in the 3 LiCl - 2 KCl melt, and was the most negative in the LiCl - RbCl and 3 LiCl - 2 CsCl eutectics. The diffusion coefficient for Eu3+ followed this same trend; it was the largest in the 3 LiCl - NaCl melt and the smallest in the LiCl - RbCl and 3 LiCl - 2 CsCl melts. The basic one-electron reversible electron transfer for Eu3+/2+ was not changed by melt composition.« less

Electrode effects on temporal changes in electrolyte pH and redox potential for water treatment

PubMed Central

Ciblak, Ali; Mao, Xuhui; Padilla, Ingrid; Vesper, Dorothy; Alshawabkeh, Iyad; Alshawabkeh, Akram N.

2012-01-01

The performance of electrochemical remediation methods could be optimized by controlling the physicochemical conditions of the electrochemical redox system. The effects of anode type (reactive or inert), current density and electrolyte composition on the temporal changes in pH and redox potential of the electrolyte were evaluated in divided and mixed electrolytes. Two types of electrodes were used: iron as a reactive electrode and mixed metal oxide coated titanium (MMO) as an inert electrode. Electric currents of 15, 30, 45 and 60 mA (37.5 mA L−1, 75 mA L−1, 112.5 mA L−1 and 150 mA L−1) were applied. Solutions of NaCl, Na2SO4 and NaHCO3 were selected to mimic different wastewater or groundwater composition. Iron anodes resulted in highly reducing electrolyte conditions compared to inert anodes. Electrolyte pH was dependent on electrode type, electrolyte composition and current density. The pH of mixed-electrolyte was stable when MMO electrodes were used. When iron electrodes were used, the pH of electrolyte with relatively low current density (37.5 mA L−1) did not show significant changes but the pH increased sharply for relatively high current density (150 mA L−1). Sulfate solution showed more basic and relatively more reducing electrolyte condition compared to bicarbonate and chloride solution. The study shows that a highly reducing environment could be achieved using iron anodes in divided or mixed electrolytes and the pH and redox potential could be optimized by using appropriate current and polarity reversal. PMID:22416866

Technical Status and Progress of Lead Recycling of Battery

NASA Astrophysics Data System (ADS)

Li, Wei-feng; Jiang, Li-hua; Zhan, Jing; Zhang, Chuan-fu

The characteristics of various components in waste lead acid battery are analyzed in this paper. The present status and the study progress situation in industry production and research field of recycling of waste lead acid battery and lead paste used broken-separation technology are introduced. The comparison of advantages and disadvantages in different industry processes is carried. The advantages of redox bath smelting of lead concentrate and lead paste are analyzed. The method of redox bath smelting will be a low-carbon, environmentally friendly and efficient processes of secondary lead production and can be intensive to desulfurize for high temperature pool.

The Lincolnshire Limestone — Hydrogeochemical evolution over a ten-year period

NASA Astrophysics Data System (ADS)

Edmunds, W. M.; Walton, N. R. G.

1983-02-01

In the Lincolnshire (Jurassic) Limestone of Britain, a sequence of hydrogeochemical processes along a 28-km flow line was defined in 1969. These processes include solution, redox and ion-exchange reactions, sulphate reduction and mixing with saline formation water. Resampling of the aquifer profile after 10 years has confirmed the overall sequence, although downgradient increases in both sulphate and calcium, together with changes in redox system, can be recognised. These changes are related to the migration of agrichemical pollutants and the results demonstrate that the aquifer must have a significant capacity for in situ nitrate reduction.

Reactivity of bacterial and fungal laccases with lignin under alkaline conditions.

PubMed

Moya, Raquel; Saastamoinen, Päivi; Hernández, Manuel; Suurnäkki, Anna; Arias, Enriqueta; Mattinen, Maija-Liisa

2011-11-01

The ability of Streptomyces ipomoea laccase to polymerize secoisolariciresinol lignan and technical lignins was assessed. The reactivity of S. ipomoea laccase was also compared to that of low redox fungal laccase from Melanocarpus albomyces using low molecular mass p-coumaric, ferulic and sinapic acid as well as natural (acetosyringone) and synthetic 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) mediators as substrates. Oxygen consumption measurement, MALDI-TOF MS and SEC were used to follow the enzymatic reactions at pH 7, 8, 9 and 10 at 30°C and 50°C. Polymerization of lignins and lignan by S. ipomoea laccase under alkaline reaction conditions was observed, and was enhanced in the presence of acetosyringone almost to the level obtained with M. albomyces laccase without mediator. Reactivities of the enzymes towards acetosyringone and TEMPO were similar, suggesting exploitation of the compounds and low redox laccase in lignin valorization under alkaline conditions. The results have scientific impact on basic research of laccases. Copyright © 2011 Elsevier Ltd. All rights reserved.

Investigation of multi-state charge-storage properties of redox-active organic molecules in silicon-molecular hybrid devices for DRAM and Flash applications

NASA Astrophysics Data System (ADS)

Gowda, Srivardhan Shivappa

Molecular electronics has recently spawned a considerable amount of interest with several molecules possessing charge-conduction and charge-storage properties proposed for use in electronic devices. Hybrid silicon-molecular technology has the promise of augmenting the current silicon technology and provide for a transitional path to future molecule-only technology. The focus of this dissertation work has been on developing a class of hybrid silicon-molecular electronic devices for DRAM and Flash memory applications utilizing redox-active molecules. This work exploits the ability of molecules to store charges with single-electron precision at room temperature. The hybrid devices are fabricated by forming self-assembled monolayers of redox-active molecules on Si and oxide (SiO2 and HfO2) surfaces via formation of covalent linkages. The molecules possess discrete quantum states from which electrons can tunnel to the Si substrate at discrete applied voltages (oxidation process, cell write), leaving behind a positively charged layer of molecules. The reduction (erase) process, which is the process of electrons tunneling back from Si to the molecules, neutralizes the positively charged molecular monolayer. Hybrid silicon-molecular capacitor test structures were electrically characterized with an electrolyte gate using cyclic voltammetry (CyV) and impedance spectroscopy (CV) techniques. The redox voltages, kinetics (write/erase speeds) and charge-retention characteristics were found to be strongly dependent on the Si doping type and densities, and ambient light. It was also determined that the redox energy states in the molecules communicate with the valence band of the Si substrate. This allows tuning of write and read states by modulating minority carriers in n- and p-Si substrates. Ultra-thin dielectric tunnel barriers (SiO2, HfO2) were placed between the molecules and the Si substrate to augment charge-retention for Flash memory applications. The redox response was studied as a function of tunnel oxide thickness, dielectric permittivity and energy barrier, and modified Butler-Volmer expressions were postulated to describe the redox kinetics. The speed vs. retention performance of the devices was improved via asymmetric layered tunnel barriers. The properties of molecules can be tailored by molecular design and synthetic chemistry. In this work, it was demonstrated that an alternate route to tune/enhance the properties of the hybrid device is to engineer the substrate (silicon) component. The molecules were attached to diode surfaces to tune redox voltages and improve charge-retention characteristics. N+ pockets embedded in P-Si well were utilized to obtain multiple states from a two-state molecule. The structure was also employed as a characterization tool in investigating the intrinsic properties of the molecules such as lateral conductivity within the monolayer. Redox molecules were also incorporated on an ultra thin gate-oxide of Si MOSFETs with the intent of studying the interaction of redox states with Si MOSFETs. The discrete molecular states were manifested in the drain current and threshold voltage characteristics of the device. This work demonstrates the multi-state modulation of Si-MOSFETs' drain current via redox-active molecular monolayers. Polymeric films of redox-active molecules were incorporated to improve the charge-density (ON/OFF ratio) and these structures may be employed for multi-state, low-voltage Flash memory applications. The most critical aspect of this research effort is to build a reliable and high density solid state memory technology. To this end, efforts were directed towards replacement of the electrolytic gate, which forms an extremely thin insulating double layer (˜10 nm) at the electrolyte-molecule interface, with a combination of an ultra-thin high-K dielectric layer and a metal gate. Several interesting observations were made in the research approaches towards integration and provided valuable insights into the electrolyte-redox systems. In summary, this work provides fundamental insights into the interaction of redox-energy states with silicon substrate and realistic approaches for exploiting the unique properties of the molecules that may enable solutions for nanoscale high density, low-voltage, long retention and multiple bit memory applications.

Polyunsaturated fatty acids ameliorate aging via redox-telomere-antioncogene axis.

PubMed

Chen, Jingnan; Wei, Yan; Chen, Xinyu; Jiao, Jingjing; Zhang, Yu

2017-01-31

Polyunsaturated fatty acids (PUFA), a group of nourishing and health-promoting nutrients, ameliorate age-related chronic diseases. However, how PUFA especially n-3 PUFA exert anti-aging functions remains poorly understood. Here we link fish oil, docosahexaenoic acid (DHA) and arachidonic acid (AA) to the aging etiology via a redox-telomere-antioncogene axis based on D-galactose-induced aging mice. Both fish oil and PUFA enhanced hepatic superoxide dismutase (SOD) and catalase activities and cardiac SOD activities within the range of 18%-46%, 26%-65% and 19%-58%, respectively, whereas reduced cerebral monoamine oxidase activity, plasma F2-isoprostane level and cerebral lipid peroxidation level by 56%-90%, 20%-79% and 16%-54%, respectively. Thus, PUFA improve the in vivo redox and oxidative stress induced aging process, which however does not exhibit a dose-dependent manner. Notably, both PUFA and fish oil effectively inactivated testicular telomerase and inhibited c-Myc-mediated telomerase reverse transcriptase expression, whereas n-3 PUFA rather than n-6 PUFA protected liver and testes against telomere shortening within the range of 13%-25% and 25%-27%, respectively. Therefore, n-3 PUFA may be better at inhibiting the DNA damage induced aging process. Surprisingly, only DHA significantly suppressed cellular senescence pathway evidenced by testicular antioncogene p16 and p53 expression. This work provides evident support for the crosstalk between PUFA especially n-3 PUFA and the aging process via maintaining the in vivo redox homeostasis, rescuing age-related telomere attrition and down-regulating the antioncogene expression.

Tumor cell membrane-targeting pH-dependent electron donor-acceptor fluorescence systems with low background signals.

PubMed

Han, Liang; Liu, Mingming; Ye, Deyong; Zhang, Ning; Lim, Ed; Lu, Jing; Jiang, Chen

2014-03-01

Minimizing the background signal is crucial for developing tumor-imaging techniques with sufficient specificity and sensitivity. Here we use pH difference between healthy tissues and tumor and tumor targeting delivery to achieve this goal. We synthesize fluorophore-dopamine conjugate as pH-dependent electron donor-acceptor fluorescence system. Fluorophores are highly sensitive to electron-transfer processes, which can alter their optical properties. The intrinsic redox properties of dopamine are oxidation of hydroquinone to quinone at basic pH and reduction of quinone to hydroquinone at acidic pH. Quinone can accept electron then quench fluorescence. We design tumor cell membrane-targeting carrier for delivery. We demonstrate quenched fluorophore-quinone can be specially transferred to tumor extracellular environment and tumor-accumulated fluorophore can be activated by acidic pH. These tumor-targeting pH-dependent electron donor-acceptor fluorescence systems may offer new opportunity for developing tumor-imaging techniques. Copyright © 2014 Elsevier Ltd. All rights reserved.

The isotopic composition of authigenic chromium in anoxic marine sediments: A case study from the Cariaco Basin

NASA Astrophysics Data System (ADS)

Reinhard, Christopher T.; Planavsky, Noah J.; Wang, Xiangli; Fischer, Woodward W.; Johnson, Thomas M.; Lyons, Timothy W.

2014-12-01

Chromium (Cr) isotopes are an emerging proxy for tracking redox processes at the Earth's surface. However, there has been limited exploration of the Cr isotope record of modern and recent marine sediments. The basic inorganic chemistry of Cr suggests that anoxic marine basins should factor prominently in the global Cr cycle and that sediments deposited within anoxic basins may offer a valuable Cr isotope archive throughout Earth's history. Here, we present δ53Cr data from sediments of the Cariaco Basin, Venezuela-a 'type' environment for large, perennially anoxic basins with a relatively strong hydrological connection to the global oceans. We document a marked positive shift in bulk δ53Cr values following the termination of the Last Glacial Maximum, followed by relative stasis. Based on a suite of independent redox proxies, this transition marks a switch from oxic to persistently anoxic and sulfidic (euxinic) depositional conditions within the basin. We find good agreement between two independent approaches toward estimating the δ53Cr composition of authigenic Cr in euxinic Cariaco Basin sediments and that these estimates are very similar to the δ53Cr composition of modern open Atlantic Ocean seawater. These data, together with considerations of reaction kinetics and mass balance within the Cariaco Basin, are consistent with the hypothesis that anoxic marine settings can serve as a chemical archive of first-order trends in seawater δ53Cr composition. Additionally, the Cariaco Basin data suggest that there has been secular stability in the average δ53Cr value of Atlantic seawater over the last ∼15 kyr.

Impact of uranium (U) on the cellular glutathione pool and resultant consequences for the redox status of U.

PubMed

Viehweger, Katrin; Geipel, Gerhard; Bernhard, Gert

2011-12-01

Uranium (U) as a redox-active heavy metal can cause various redox imbalances in plant cells. Measurements of the cellular glutathione/glutathione disulfide (GSH/GSSG) by HPLC after cellular U contact revealed an interference with this essential redox couple. The GSH content remained unaffected by 10 μM U whereas the GSSG level immediately increased. In contrast, higher U concentrations (50 μM) drastically raised both forms. Using the Nernst equation, it was possible to calculate the half-cell reduction potential of 2GSH/GSSG. In case of lower U contents the cellular redox environment shifted towards more oxidizing conditions whereas the opposite effect was obtained by higher U contents. This indicates that U contact causes a consumption of reduced redox equivalents. Artificial depletion of GSH by chlorodinitrobenzene and measuring the cellular reducing capacity by tetrazolium salt reduction underlined the strong requirement of reduced redox equivalents. An additional element of cellular U detoxification mechanisms is the complex formation between the heavy metal and carboxylic functionalities of GSH. Because two GSH molecules catalyze electron transfers each with one electron forming a dimer (GSSG) two UO(2) (2+) are reduced to each UO(2) (+) by unbound redox sensitive sulfhydryl moieties. UO(2) (+) subsequently disproportionates to UO(2) (2+) and U(4+). This explains that in vitro experiments revealed a reduction to U(IV) of only around 33% of initial U(VI). Cellular U(IV) was transiently detected with the highest level after 2 h of U contact. Hence, it can be proposed that these reducing processes are an important element of defense reactions induced by this heavy metal.

Involvement of thiol-based mechanisms in plant development.

PubMed

Rouhier, Nicolas; Cerveau, Delphine; Couturier, Jérémy; Reichheld, Jean-Philippe; Rey, Pascal

2015-08-01

Increasing knowledge has been recently gained regarding the redox regulation of plant developmental stages. The current state of knowledge concerning the involvement of glutathione, glutaredoxins and thioredoxins in plant development is reviewed. The control of the thiol redox status is mainly ensured by glutathione (GSH), a cysteine-containing tripeptide and by reductases sharing redox-active cysteines, glutaredoxins (GRXs) and thioredoxins (TRXs). Indeed, thiol groups present in many regulatory proteins and metabolic enzymes are prone to oxidation, ultimately leading to post-translational modifications such as disulfide bond formation or glutathionylation. This review focuses on the involvement of GSH, GRXs and TRXs in plant development. Recent studies showed that the proper functioning of root and shoot apical meristems depends on glutathione content and redox status, which regulate, among others, cell cycle and hormone-related processes. A critical role of GRXs in the formation of floral organs has been uncovered, likely through the redox regulation of TGA transcription factor activity. TRXs fulfill many functions in plant development via the regulation of embryo formation, the control of cell-to-cell communication, the mobilization of seed reserves, the biogenesis of chloroplastic structures, the metabolism of carbon and the maintenance of cell redox homeostasis. This review also highlights the tight relationships between thiols, hormones and carbon metabolism, allowing a proper development of plants in relation with the varying environment and the energy availability. GSH, GRXs and TRXs play key roles during the whole plant developmental cycle via their antioxidant functions and the redox-regulation of signaling pathways. This article is part of a Special Issue entitled Redox regulation of differentiation and de-differentiation. Copyright © 2015 Elsevier B.V. All rights reserved.

Redox Fluctuations Increase the Contribution of Lignin to Soil Respiration

NASA Astrophysics Data System (ADS)

Hall, S. J.; Silver, W. L.; Timokhin, V.; Hammel, K.

2014-12-01

Lignin mineralization represents a critical flux in the terrestrial carbon (C) cycle, yet little is known about mechanisms and environmental factors controlling lignin breakdown in mineral soils. Hypoxia has long been thought to suppress lignin decomposition, yet variation in oxygen (O2) availability in surface soils accompanying moisture fluctuations could potentially stimulate this process by generating reactive oxygen species via coupled biotic and abiotic iron (Fe) redox cycling. Here, we tested the impact of redox fluctuations on lignin breakdown in humid tropical forest soils during ten-week laboratory incubations. We used synthetic lignins labeled with 13C in either of two positions (aromatic methoxyl and propyl Cβ) to provide highly sensitive and specific measures of lignin mineralization not previously employed in soils. Four-day redox fluctuations increased the percent contribution of methoxyl C to soil respiration, and cumulative methoxyl C mineralization was equivalent under static aerobic and fluctuating redox conditions despite lower total C mineralization in the latter treatment. Contributions of the highly stable Cβ to mineralization were also equivalent in static aerobic and fluctuating redox treatments during periods of O2 exposure, and nearly doubled in the fluctuating treatment after normalizing to cumulative O2 exposure. Oxygen fluctuations drove substantial net Fe reduction and oxidation, implying that reactive oxygen species generated during abiotic Fe oxidation likely contributed to the elevated contribution of lignin to C mineralization. Iron redox cycling provides a mechanism for lignin breakdown in soils that experience conditions unfavorable for canonical lignin-degrading organisms, and provides a potential mechanism for lignin depletion in soil organic matter during late-stage decomposition. Thus, close couplings between soil moisture, redox fluctuations, and lignin breakdown provide potential a link between climate variability and the biochemical composition of soil organic matter with important implications for soil C budgets.

Molecular inflammation: underpinnings of aging and age-related diseases.

PubMed

Chung, Hae Young; Cesari, Matteo; Anton, Stephen; Marzetti, Emanuele; Giovannini, Silvia; Seo, Arnold Young; Carter, Christy; Yu, Byung Pal; Leeuwenburgh, Christiaan

2009-01-01

Recent scientific studies have advanced the notion of chronic inflammation as a major risk factor underlying aging and age-related diseases. In this review, low-grade, unresolved, molecular inflammation is described as an underlying mechanism of aging and age-related diseases, which may serve as a bridge between normal aging and age-related pathological processes. Accumulated data strongly suggest that continuous (chronic) upregulation of pro-inflammatory mediators (e.g., TNF-alpha, IL-1beta, IL-6, COX-2, iNOS) are induced during the aging process due to an age-related redox imbalance that activates many pro-inflammatory signaling pathways, including the NF-kappaB signaling pathway. These pro-inflammatory molecular events are discussed in relation to their role as basic mechanisms underlying aging and age-related diseases. Further, the anti-inflammatory actions of aging-retarding caloric restriction and exercise are reviewed. Thus, the purpose of this review is to describe the molecular roles of age-related physiological functional declines and the accompanying chronic diseases associated with aging. This new view on the role of molecular inflammation as a mechanism of aging and age-related pathogenesis can provide insights into potential interventions that may affect the aging process and reduce age-related diseases, thereby promoting healthy longevity.

Molecular Inflammation: Underpinnings of Aging and Age-related Diseases

PubMed Central

Chung, Hae Young; Cesari, Matteo; Anton, Stephen; Marzetti, Emanuele; Giovannini, Silvia; Seo, Arnold Young; Carter, Christy; Yu, Byung Pal; Leeuwenburgh, Christiaan

2013-01-01

Recent scientific studies have advanced the notion of chronic inflammation as a major risk factor underlying aging and age-related diseases. In this review, low-grade, unresolved, molecular inflammation is described as an underlying mechanism of aging and age-related diseases, which may serve as a bridge between normal aging and age-related pathological processes. Accumulated data strongly suggest that continuous (chronic) up-regulation of pro-inflammatory mediators (e.g., TNF-α, IL-1β, 6, COX-2, iNOS) are induced during the aging process due to an age-related redox imbalance that activates many pro-inflammatory signaling pathways, including the NF-κB signaling pathway. These pro-inflammatory molecular events are discussed in relation to their role as basic mechanisms underlying aging and age-related diseases. Further, the anti-inflammatory actions of aging-retarding caloric restriction and exercise are reviewed. Thus, the purpose of this review is to describe the molecular roles of age-related physiological functional declines and the accompanying chronic diseases associated with aging. This new view on the role of molecular inflammation as a mechanism of aging and age-related pathogenesis can provide insights into potential interventions that may affect the aging process and reduce age-related diseases, thereby promoting healthy longevity. PMID:18692159

Design and engineering of photosynthetic light-harvesting and electron transfer using length, time, and energy scales.

PubMed

Noy, Dror; Moser, Christopher C; Dutton, P Leslie

2006-02-01

Decades of research on the physical processes and chemical reaction-pathways in photosynthetic enzymes have resulted in an extensive database of kinetic information. Recently, this database has been augmented by a variety of high and medium resolution crystal structures of key photosynthetic enzymes that now include the two photosystems (PSI and PSII) of oxygenic photosynthetic organisms. Here, we examine the currently available structural and functional information from an engineer's point of view with the long-term goal of reproducing the key features of natural photosystems in de novo designed and custom-built molecular solar energy conversion devices. We find that the basic physics of the transfer processes, namely, the time constraints imposed by the rates of incoming photon flux and the various decay processes allow for a large degree of tolerance in the engineering parameters. Moreover, we find that the requirements to guarantee energy and electron transfer rates that yield high efficiency in natural photosystems are largely met by control of distance between chromophores and redox cofactors. Thus, for projected de novo designed constructions, the control of spatial organization of cofactor molecules within a dense array is initially given priority. Nevertheless, constructions accommodating dense arrays of different cofactors, some well within 1 nm from each other, still presents a significant challenge for protein design.

The NASA Redox Storage System Development project, 1980

NASA Technical Reports Server (NTRS)

1982-01-01

The technical accomplishments pertaining to the development of Redox systems and related technology are outlined in terms of the task elements: prototype systems development, application analyses, and supporting technology. Prototype systems development provides for a major procurement to develop an industrial capability to take the current NASA Lewis technology and go on to the design, development, and commercialization of iron-chromium Redox storage systems. Application analyses provides for the definition of application concepts and technology requirements, specific definition studies, and the identification of market sectors and their penetration potential. Supporting technology includes both in house and contractual efforts that encompass implementation of technology improvements in membranes, electrodes, reactant processing, and system design. The status of all elements is discussed.

The NASA Redox Storage System Development project, 1980

NASA Astrophysics Data System (ADS)

1982-12-01

The technical accomplishments pertaining to the development of Redox systems and related technology are outlined in terms of the task elements: prototype systems development, application analyses, and supporting technology. Prototype systems development provides for a major procurement to develop an industrial capability to take the current NASA Lewis technology and go on to the design, development, and commercialization of iron-chromium Redox storage systems. Application analyses provides for the definition of application concepts and technology requirements, specific definition studies, and the identification of market sectors and their penetration potential. Supporting technology includes both in house and contractual efforts that encompass implementation of technology improvements in membranes, electrodes, reactant processing, and system design. The status of all elements is discussed.

Improving emerging organic compound degradation through chaotic advection in a Managed Aquifer Recharge: the case of benzotriazoles

NASA Astrophysics Data System (ADS)

Rodriguez-Escales, P.; Drechsel, J.; Fernandez-Garcia, D.; Sanchez-Vila, X.

2016-12-01

Improving emerging compound degradation in groundwater is still a challenge. The coupling of Managed Aquifer Recharge (MAR) with soil aquifer remediation (SAR) through a reactive layer placed at the bottom of the infiltration pond is a promising technology to improve the quality of both recharged water and groundwater. As the reactive layer is made up of organic matter, all the redox processes are enhanced, improving the degradation of emerging pollutants. The success of coupling the MAR-SAR is based on the assumption that recharged water and groundwater are well mixed. Nevertheless, it is well known that mixing is not an instantaneous process in porous media. One strategy to improve it is the enhancement of chaotic advection through extraction-injection engineering (EIE). The EIE enhances mixing and, thus, all the reactions of the system. Although the emerging pollutant degradation is not well understood, it is known that some compounds are preferably degraded either in oxic or in reduced conditions. For example, in the case of benzotriazoles different redox conditions are required depending on each compound. Promoting different redox conditions in a system will result in an enhancement in the actual degree of degradation expected for any given compound. Considering all of this, our work is aimed to evaluate how caothic advection can improve mixing during MAR-SAR, and thus, be capable of enhancing the spreading of redox conditions with the final aim of improving benzotriazoles degradation. To achieve this, we have developed a reactive transport model that describes how recharged water (rich in organic matter coming from a reactive layer) is mixed with groundwater, and how this organic matter is oxidized by different electron acceptors. We have included the degradation rates of each benzotriazole compound in function of its reactivity with redox condition. The model has been tested in different scenarios of recharge and injection-extraction sequences, both in homogenous and in heterogeneous media. The preliminary results show that EIE improves the mixing between the recharged water and groundwater and increases the spreading of the plume. Consequently, the redox zonation is found to be spread spatially, with the coexistence of different redox conditions and, consequently, enhancing benzotriazoles degradation.

Trinuclear ruthenium dioxolene complexes based on the bridging ligand hexahydroxytriphenylene: electrochemistry, spectroscopy, and near-infrared electrochromic behaviour associated with a reversible seven-membered redox chain.

PubMed

Grange, Christopher S; Meijer, Anthony J H M; Ward, Michael D

2010-01-07

The trinuclear complexes [{(R2bipy)2Ru}3(mu3-HHTP)](PF6)3 [1(PF6)3, R = H; 2(PF6)3, R = 4-tBu] contain three {Ru(R2bipy)2}2+ fragments connected to the triangular tris-chelating ligand hexahydroxytriphenylene (H6HHTP). This bridging ligand contains three dioxolene-type binding sites, each of which can reversibly convert between dianionic catecholate (cat), monoanionic semiquinone (sq) or neutral quinone (q) redox states. The bridging ligand as a whole can therefore exist in seven different redox states from fully reduced [cat,cat,cat]6- through to fully oxidised, neutral [q,q,q]. Cyclic voltammetry of 1(PF6)3 in MeCN reveals six redox processes of which the three at more positive potentials (the sq/q couples) are reversible but the three at more negative potentials (the sq/cat couples) are irreversible with distorted wave shapes due to the insolubility of the reduced forms of the complex. In contrast, the more soluble complex 2(PF6)3 displays six reversible one-electron redox processes making all components of a seven-membered redox chain accessible. UV/Vis/NIR spectro-electrochemical studies reveal rich spectroscopic behaviour, with--in particular--very intense transitions in the near-IR region in many of the oxidation states associated with Ru(II)-->(dioxolene) MLCT and bridging ligand centred pi-pi* transitions. TDDFT calculations were used to analyse the electronic spectra in all seven oxidation states; the calculated spectra generally show very good agreement with experiment, which has allowed a fairly complete assignment of the low-energy transitions. The strong electrochromism of the complexes in the near-IR region has formed the basis of an optical window in which a thin film of 1(PF6)3 or 2(PF6)3 on a conductive glass surface can be reversibly and rapidly switched between redox states that alternate between strongly absorbing or near-transparent at 1100 nm, with--for 2(PF6)3--the switching being stable and reversible in water over thousands of cycles.

Chromated copper arsenate-treated fence posts in the agronomic landscape: soil properties controlling arsenic speciation and spatial distribution.

PubMed

Schwer Iii, Donald R; McNear, David H

2011-01-01

Soils adjacent to chromated copper arsenate (CCA)-treated fence posts along a fence line transecting different soil series, parent material, drainage classes, and slope were used to determine which soil properties had the most influence on As spatial distribution and speciation. Metal distribution was evaluated at macroscopic (total metal concentration contour maps) and microscopic scales (micro-synchrotron X-ray fluorescence maps), As speciation was determined using extended X-ray absorption fine structure spectroscopy, and redox status and a myriad of other basic soil properties were elucidated. All geochemical parameters measured point to a condition in which the mobilization of As becomes more favorable moving down the topographic gradient, likely resulting through competition (Meh-P, SOM), neutral or slightly basic pH, and redox conditions that are favorable for As mobilization (higher Fe(II) and total-Fe concentrations in water extracts). On the landscape scale, with hundreds of kilometers of fence, the arsenic loading into the soil can be substantial (∼8-12 kg km). Although a significant amount of the As is stable, extended use of CCA-treated wood has resulted in elevated As concentrations in the local environment, increasing the risk of exposure and ecosystem perturbation. Therefore, a move toward arsenic-free alternatives in agricultural applications for which it is currently permitted should be considered. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

High Energy Density Aqueous Electrochemical Capacitors with a KI-KOH Electrolyte.

PubMed

Wang, Xingfeng; Chandrabose, Raghu S; Chun, Sang-Eun; Zhang, Tianqi; Evanko, Brian; Jian, Zelang; Boettcher, Shannon W; Stucky, Galen D; Ji, Xiulei

2015-09-16

We report a new electrochemical capacitor with an aqueous KI-KOH electrolyte that exhibits a higher specific energy and power than the state-of-the-art nonaqueous electrochemical capacitors. In addition to electrical double layer capacitance, redox reactions in this device contribute to charge storage at both positive and negative electrodes via a catholyte of IOx-/I- couple and a redox couple of H2O/Had, respectively. Here, we, for the first time, report utilizing IOx-/I- redox couple for the positive electrode, which pins the positive electrode potential to be 0.4-0.5 V vs Ag/AgCl. With the positive electrode potential pinned, we can polarize the cell to 1.6 V without breaking down the aqueous electrolyte so that the negative electrode potential could reach -1.1 V vs Ag/AgCl in the basic electrolyte, greatly enhancing energy storage. Both mass spectroscopy and Raman spectrometry confirm the formation of IO3- ions (+5) from I- (-1) after charging. Based on the total mass of electrodes and electrolyte in a practically relevant cell configuration, the device exhibits a maximum specific energy of 7.1 Wh/kg, operates between -20 and 50 °C, provides a maximum specific power of 6222 W/kg, and has a stable cycling life with 93% retention of the peak specific energy after 14,000 cycles.

Preparation, Applications, and Digital Simulation of Carbon Interdigitated Array Electrodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Fei; Kolesov, Grigory; Parkinson, Bruce A.

2014-12-16

Carbon interdigitated array (IDA) electrodes with features sizes down to 1.2 μm were fabricated by controlled pyrolysis of patterned photoresist. Cyclic voltam-metry of reversible redox species produced the expected steady-state currents. The collection efficiency depends on the IDA electrode spacing, which ranged from around 2.7 to 16.5 μm, with the smaller dimensions achieving higher collection efficiencies of up to 98%. The signal amplification because of redox cycling makes it possible to detect species at relatively low concentrations (10–5 molar) and the small spacing allows detection of transient electrogenerated species with much shorter lifetimes (submillisecond). Digital simulation software that accounts formore » both the width and height of electrode elements as well as the electrode spacing was developed to model the IDA electrode response. The simulations are in quantitative agreement with experimental data for both a simple fast one electron redox reaction and an electron transfer with a following chemical reaction at the IDAs with larger gaps whereas currents measured for the smallest IDA electrodes, that were larger than the simulated currents, are attributed to convection from induced charge electrokinetic flow. This work was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the Department of Energy, Office of Science Office of Basic Energy Sciences.« less

Effects of N-acetyl-L-cysteine on redox status and markers of renal function in mice inoculated with Bothrops jararaca and Crotalus durissus terrificus venoms.

PubMed

Barone, Juliana Marton; Frezzatti, Rodrigo; Silveira, Paulo Flavio

2014-03-01

Renal dysfunction is an important aggravating factor in accidents caused by Crotalus durissus terrificus (Cdt) and Bothrops jararaca (Bj) bites. N-acetyl-l-cysteine (NAC) is well known as a nephroprotective antioxidant with low toxicity. The present study investigated the effects of NAC on redox status and markers of renal function in mice that received vehicle (controls) or venoms (v) of Cdt and Bj. In controls NAC promoted hypercreatinemia, hypouremia, hyperosmolality with decreased urea in urine, hyperproteinuria, decreased protein and increased dipeptidyl peptidase IV (DPPIV) in membrane-bound fraction (MF) from renal cortex (RC) and medulla (RM). NAC ameliorated or normalized altered creatinuria, proteinemia and aminopeptidase (AP) acid in MF, AP basic (APB) in soluble fraction (SF), and neutral AP in SF and MF from RC and RM in vBj envenomation. NAC ameliorated or normalized altered neutral AP in SF from RC and RM, and DPPIV and protein in MF from RC in vCdt envenomation. NAC ameliorated or restored renal redox status respectively in vCdt and vBj, and normalized uricemia in both envenomations. These data are promising perspectives that recommend the clinical evaluation of NAC as potential coadjuvant in the anti venom serotherapy for accidents with these snake's genera. Copyright © 2014 Elsevier Ltd. All rights reserved.

Energy metabolism and inflammation in brain aging and Alzheimer's disease.

PubMed

Yin, Fei; Sancheti, Harsh; Patil, Ishan; Cadenas, Enrique

2016-11-01

The high energy demand of the brain renders it sensitive to changes in energy fuel supply and mitochondrial function. Deficits in glucose availability and mitochondrial function are well-known hallmarks of brain aging and are particularly accentuated in neurodegenerative disorders such as Alzheimer's disease. As important cellular sources of H 2 O 2 , mitochondrial dysfunction is usually associated with altered redox status. Bioenergetic deficits and chronic oxidative stress are both major contributors to cognitive decline associated with brain aging and Alzheimer's disease. Neuroinflammatory changes, including microglial activation and production of inflammatory cytokines, are observed in neurodegenerative diseases and normal aging. The bioenergetic hypothesis advocates for sequential events from metabolic deficits to propagation of neuronal dysfunction, to aging, and to neurodegeneration, while the inflammatory hypothesis supports microglia activation as the driving force for neuroinflammation. Nevertheless, growing evidence suggests that these diverse mechanisms have redox dysregulation as a common denominator and connector. An independent view of the mechanisms underlying brain aging and neurodegeneration is being replaced by one that entails multiple mechanisms coordinating and interacting with each other. This review focuses on the alterations in energy metabolism and inflammatory responses and their connection via redox regulation in normal brain aging and Alzheimer's disease. Interaction of these systems is reviewed based on basic research and clinical studies. Copyright © 2016 Elsevier Inc. All rights reserved.

The Rate of Oxygen Utilization by Cells

PubMed Central

Wagner, Brett A.; Venkataraman, Sujatha; Buettner, Garry R.

2011-01-01

The discovery of oxygen is considered by some to be the most important scientific discovery of all time – from both physical-chemical/astrophysics and biology/evolution viewpoints. One of the major developments during evolution is the ability to capture dioxygen in the environment and deliver it to each cell in the multicellular, complex mammalian body -- on demand, i.e. just-in-time. Humans use oxygen to extract approximately 2550 Calories (10.4 MJ) from food to meet daily energy requirements. This combustion requires about 22 moles of dioxygen per day, or 2.5 × 10-4 mol s-1. This is an average rate of oxygen utilization of 2.5 × 10-18 mol cell-1 s-1, i.e. 2.5 amol cell-1 s-1. Cells have a wide range of oxygen utilization, depending on cell type, function, and biological status. Measured rates of oxygen utilization by mammalian cells in culture range from <1 to >350 amol cell-1 s-1. There is a loose positive linear correlation of the rate of oxygen consumption (OCR) by mammalian cells in culture with cell volume and cell protein. The use of oxygen by cells and tissues is an essential aspect of the basic redox biology of cells and tissues. This type of quantitative information is fundamental to investigations in quantitative redox biology, especially redox systems biology. PMID:21664270

Redox Stimulation of Human THP-1 Monocytes in Response to Cold Physical Plasma.

PubMed

Bekeschus, Sander; Schmidt, Anke; Bethge, Lydia; Masur, Kai; von Woedtke, Thomas; Hasse, Sybille; Wende, Kristian

2016-01-01

In plasma medicine, cold physical plasma delivers a delicate mixture of reactive components to cells and tissues. Recent studies suggested a beneficial role of cold plasma in wound healing. Yet, the biological processes related to the redox modulation via plasma are not fully understood. We here used the monocytic cell line THP-1 as a model to test their response to cold plasma in vitro. Intriguingly, short term plasma treatment stimulated cell growth. Longer exposure only modestly compromised cell viability but apparently supported the growth of cells that were enlarged in size and that showed enhanced metabolic activity. A significantly increased mitochondrial content in plasma treated cells supported this notion. On THP-1 cell proteome level, we identified an increase of protein translation with key regulatory proteins being involved in redox regulation (hypoxia inducible factor 2α), differentiation (retinoic acid signaling and interferon inducible factors), and cell growth (Yin Yang 1). Regulation of inflammation is a key element in many chronic diseases, and we found a significantly increased expression of the anti-inflammatory heme oxygenase 1 (HMOX1) and of the neutrophil attractant chemokine interleukin-8 (IL-8). Together, these results foster the view that cold physical plasma modulates the redox balance and inflammatory processes in wound related cells.

Redox Energy and Sulfur Chemistry in Prebiotic Polymer Synthesis and Replication

NASA Technical Reports Server (NTRS)

Weber, Arthur L.

1997-01-01

In the past year we have made significant progress in three research areas: (1) Most importantly, we discovered a new pathway of prebiotic amino acid synthesis in which formaldehyde and glycolaldehyde (substrates of the formose reaction) react with ammonia yielding alanine and homoserine in the presence of thiol catalysts. This thiol-dependent synthesis of amino acids undoubtedly occurs via amino acid thioester intermediates capable of forming peptides. This 'one-pot' reaction system operates under mild aqueous conditions, and like modern amino acid biosynthesis, uses sugar intermediates which are converted to amino acids by energy-yielding redox disproportionation. (2) Finally, in preparation for the analysis of Martian meteorite samples, we upgraded our HPLC system and developed an improved method capable of detecting a I femtomole of amino acid enantiomers. (3) We completed our analysis of the energetics of metabolism that revealed that life depends on biosynthetic processes driven by chemical energy made available by the redox disproportionation of carbon groups of sugars. We established that the favorable energy of redox disproportionation is based on the universal reduction potentials of carbon groups. We concluded that it is hard to imagine any other organic molecule besides sugars (formaldehyde oligomers) having the energy and reactivity needed to drive either modem biosynthesis or the chemical processes behind its origin.

Imposed glutathione-mediated redox switch modulates the tobacco wound-induced protein kinase and salicylic acid-induced protein kinase activation state and impacts on defence against Pseudomonas syringae.

PubMed

Matern, Sanja; Peskan-Berghoefer, Tatjana; Gromes, Roland; Kiesel, Rebecca Vazquez; Rausch, Thomas

2015-04-01

The role of the redox-active tripeptide glutathione in plant defence against pathogens has been studied extensively; however, the impact of changes in cellular glutathione redox potential on signalling processes during defence reactions has remained elusive. This study explored the impact of elevated glutathione content on the cytosolic redox potential and on early defence signalling at the level of mitogen-activated protein kinases (MAPKs), as well as on subsequent defence reactions, including changes in salicylic acid (SA) content, pathogenesis-related gene expression, callose depositions, and the hypersensitive response. Wild-type (WT) Nicotiana tabacum L. and transgenic high-glutathione lines (HGL) were transformed with the cytosol-targeted sensor GRX1-roGFP2 to monitor the cytosolic redox state. Surprisingly, HGLs displayed an oxidative shift in their cytosolic redox potential and an activation of the tobacco MAPKs wound-induced protein kinase (WIPK) and SA-induced protein kinase (SIPK). This activation occurred in the absence of any change in free SA content, but was accompanied by constitutively increased expression of several defence genes. Similarly, rapid activation of MAPKs could be induced in WT tobacco by exposure to either reduced or oxidized glutathione. When HGL plants were challenged with adapted or non-adapted Pseudomonas syringae pathovars, the cytosolic redox shift was further amplified and the defence response was markedly increased, showing a priming effect for SA and callose; however, the initial and transient hyperactivation of MAPK signalling was attenuated in HGLs. The results suggest that, in tobacco, MAPK and SA signalling may operate independently, both possibly being modulated by the glutathione redox potential. Possible mechanisms for redox-mediated MAPK activation are discussed. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology.

The Reactive Species Interactome: Evolutionary Emergence, Biological Significance, and Opportunities for Redox Metabolomics and Personalized Medicine.

PubMed

Cortese-Krott, Miriam M; Koning, Anne; Kuhnle, Gunter G C; Nagy, Peter; Bianco, Christopher L; Pasch, Andreas; Wink, David A; Fukuto, Jon M; Jackson, Alan A; van Goor, Harry; Olson, Kenneth R; Feelisch, Martin

2017-10-01

Oxidative stress is thought to account for aberrant redox homeostasis and contribute to aging and disease. However, more often than not, administration of antioxidants is ineffective, suggesting that our current understanding of the underlying regulatory processes is incomplete. Recent Advances: Similar to reactive oxygen species and reactive nitrogen species, reactive sulfur species are now emerging as important signaling molecules, targeting regulatory cysteine redox switches in proteins, affecting gene regulation, ion transport, intermediary metabolism, and mitochondrial function. To rationalize the complexity of chemical interactions of reactive species with themselves and their targets and help define their role in systemic metabolic control, we here introduce a novel integrative concept defined as the reactive species interactome (RSI). The RSI is a primeval multilevel redox regulatory system whose architecture, together with the physicochemical characteristics of its constituents, allows efficient sensing and rapid adaptation to environmental changes and various other stressors to enhance fitness and resilience at the local and whole-organism level. To better characterize the RSI-related processes that determine fluxes through specific pathways and enable integration, it is necessary to disentangle the chemical biology and activity of reactive species (including precursors and reaction products), their targets, communication systems, and effects on cellular, organ, and whole-organism bioenergetics using system-level/network analyses. Understanding the mechanisms through which the RSI operates will enable a better appreciation of the possibilities to modulate the entire biological system; moreover, unveiling molecular signatures that characterize specific environmental challenges or other forms of stress will provide new prevention/intervention opportunities for personalized medicine. Antioxid. Redox Signal. 00, 000-000.

Oxidative Stress, Redox Signaling, and Autophagy: Cell Death Versus Survival

PubMed Central

Navarro-Yepes, Juliana; Burns, Michaela; Anandhan, Annadurai; Khalimonchuk, Oleh; del Razo, Luz Maria; Quintanilla-Vega, Betzabet; Pappa, Aglaia; Panayiotidis, Mihalis I.

2014-01-01

Abstract Significance: The molecular machinery regulating autophagy has started becoming elucidated, and a number of studies have undertaken the task to determine the role of autophagy in cell fate determination within the context of human disease progression. Oxidative stress and redox signaling are also largely involved in the etiology of human diseases, where both survival and cell death signaling cascades have been reported to be modulated by reactive oxygen species (ROS) and reactive nitrogen species (RNS). Recent Advances: To date, there is a good understanding of the signaling events regulating autophagy, as well as the signaling processes by which alterations in redox homeostasis are transduced to the activation/regulation of signaling cascades. However, very little is known about the molecular events linking them to the regulation of autophagy. This lack of information has hampered the understanding of the role of oxidative stress and autophagy in human disease progression. Critical Issues: In this review, we will focus on (i) the molecular mechanism by which ROS/RNS generation, redox signaling, and/or oxidative stress/damage alter autophagic flux rates; (ii) the role of autophagy as a cell death process or survival mechanism in response to oxidative stress; and (iii) alternative mechanisms by which autophagy-related signaling regulate mitochondrial function and antioxidant response. Future Directions: Our research efforts should now focus on understanding the molecular basis of events by which autophagy is fine tuned by oxidation/reduction events. This knowledge will enable us to understand the mechanisms by which oxidative stress and autophagy regulate human diseases such as cancer and neurodegenerative disorders. Antioxid. Redox Signal. 21, 66–85. PMID:24483238

Predictive Framework and Experimental Tests of the Kinetic Isotope Effect at Redox-Active Interfaces

NASA Astrophysics Data System (ADS)

Kavner, A.; John, S.; Black, J. R.

2013-12-01

Electrochemical reactions provide a compelling framework to study kinetic isotope effects because redox-related processes are important for a wide variety of geological and environmental processes. In the laboratory, electrochemical reaction rates can be electronically controlled and measured in the laboratory using a potentiostat. This enables variation of redox reactions rates independent of changes in chemistry and, and the resulting isotope compositions of reactants and products can be separated and analyzed. In the past years, a series of experimental studies have demonstrated a large, light, and tunable kinetic isotope effect during electrodeposition of metal Fe, Zn, Li, Cu, and Mo from a variety of solutions (e.g. Black et al., 2009, 2010, 2011). A theoretical framework based on Marcus kinetic theory predicts a voltage-dependent kinetic isotope effect (Kavner et al., 2005, 2008), however while this framework was able to predict the tunable nature of the effect, it was not able to simultaneously predict absolute reaction rates and relative isotope rates. Here we present a more complete development of a statistical mechanical framework for simple interfacial redox reactions, which includes isotopic behavior. The framework is able to predict a kinetic isotope effect as a function of temperature and reaction rate, starting with three input parameters: a single reorganization energy which describes the overall kinetics of the electron transfer reaction, and the equilibrium reduced partition function ratios for heavy and light isotopes in the product and reactant phases. We show the framework, elucidate some of the predictions, and show direct comparisons against isotope fractionation data obtained during laboratory and natural environment redox processes. A. Kavner, A. Shahar, F. Bonet, J. Simon and E. Young (2005) Geochim. Cosmochim. Acta, 69(12), 2971-2979. A. Kavner, S. G. John, S. Sass, and E. A. Boyle (2008), Geochim. Cosmochim. Acta, vol 72, pp. 1731-1741. J. R. Black, Umeda, G., Dunn, B., McDonough, W. F. and A. Kavner. (2009), J. Amer. Chem. Soc., vol. 131, No.29 2009 pp. 9904-9905 DOI: 10.1021/ja903926x. J. R. Black, S. John, E.D. Young, and A. Kavner, (2010), Geochim. Cosmochim. Acta, vol 74 (18) pp. 5187-5201. J. R. Black, J. Crawford, S. John, and A. Kavner, (2011) Redox-driven stable isotope fractionation, in Aquatic Redox Chemistry ACS Symposium Series, Vol. 1071. Tratnyek, P.G., T. J. Grundl, and S. B. Haderlein, eds. Chapter 16, pp 345-359

Better than Nature: Nicotinamide Biomimetics That Outperform Natural Coenzymes

PubMed Central

2016-01-01

The search for affordable, green biocatalytic processes is a challenge for chemicals manufacture. Redox biotransformations are potentially attractive, but they rely on unstable and expensive nicotinamide coenzymes that have prevented their widespread exploitation. Stoichiometric use of natural coenzymes is not viable economically, and the instability of these molecules hinders catalytic processes that employ coenzyme recycling. Here, we investigate the efficiency of man-made synthetic biomimetics of the natural coenzymes NAD(P)H in redox biocatalysis. Extensive studies with a range of oxidoreductases belonging to the “ene” reductase family show that these biomimetics are excellent analogues of the natural coenzymes, revealed also in crystal structures of the ene reductase XenA with selected biomimetics. In selected cases, these biomimetics outperform the natural coenzymes. “Better-than-Nature” biomimetics should find widespread application in fine and specialty chemicals production by harnessing the power of high stereo-, regio-, and chemoselective redox biocatalysts and enabling reactions under mild conditions at low cost. PMID:26727612

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vijayakumar, M.; Nie, Zimin; Walter, Eric D.

Redox flow battery (RFB) is a promising candidate for energy storage component in designing resilient grid scale power supply due to the advantage of the separation of power and energy. However, poorly understood chemical and thermal stability issues of electrolytes currently limit the performance of RFB. Designing of high performance stable electrolytes requires comprehensive knowledge about the molecular level solvation structure and dynamics of their redox active species. The molecular level understanding of detrimental V2O5 precipitation process led to successful designing of mixed acid based electrolytes for vanadium redox flow batteries (VRFB). The higher stability of mixed acid based electrolytesmore » is attributed to the choice of hydrochloric acid as optimal co-solvent, which provides chloride anions for ligand exchange process in vanadium solvation structure. The role of chloride counter anion on solvation structure and dynamics of vanadium species were studied using combined magnetic resonance spectroscopy and DFT based theoretical methods. Finally, the solvation phenomenon of multiple vanadium species and their impact on VRFB electrolyte chemical stability were discussed.« less

Fluorescence analysis of ubiquinone and its application in quality control of medical supplies

NASA Astrophysics Data System (ADS)

Timofeeva, Elvira O.; Gorbunova, Elena V.; Chertov, Aleksandr N.

2017-02-01

The presence of antioxidant issues such as redox potential imbalance in human body is a very important question for modern clinical diagnostics. Implementation of fluorescence analysis into optical diagnostics of such wide distributed in a human body antioxidant as ubiquinone is one of the steps for development of the device with a view to clinical diagnostics of redox potential. Recording of fluorescence was carried out with spectrometer using UV irradiation source with thin band (max at 287 and 330 nm) as a background radiation. Concentrations of ubiquinone from 0.25 to 2.5 mmol/l in explored samples were used for investigation. Recording data was processed using correlation analysis and differential analytical technique. The fourth derivative spectrum of fluorescence spectrum provided the basis for a multicomponent analysis of the solutions. As a technique in clinical diagnostics fluorescence analysis with processing method including differential spectrophotometry, it is step forward towards redox potential calculation and quality control in pharmacy for better health care.

Reaction of N2O5 with H2O on carbonaceous surfaces

NASA Technical Reports Server (NTRS)

Brouwer, L.; Rossi, M. J.; Golden, D. M.

1986-01-01

The heterogeneous reaction of N2O5 with commercially available ground charcoal in the absence of H2O revealed a physisorption process (gamma = 0.003), together with a redox reaction generating mostly NO. Slow HNO3 formation was the result of the interaction of N2O5 with H2O that was still adsorbed after prolonged pumping at 0.0001 torr. In the presence of H2O, the same processes with gamma = 0.005 are observed. The redox reaction dominates in the early stages of the reaction, whereas the hydrolysis gains importance later at the expense of the redox reaction. The rate law for HNO3 generation was found to be d(HNO3)/dt = k(bi)(H2O)(N2O5) with k(bi), the effective bimolecular rate constants, for 10 mg of carbon being (1.6 + or - 0.3) x 10 to the -13th cu cm/s.

Self-assembling electroactive hydrogels for flexible display technology

NASA Astrophysics Data System (ADS)

Jones, Scott L.; Hou Wong, Kok; Thordarson, Pall; Ladouceur, François

2010-12-01

We have assessed the potential of self-assembling hydrogels for use in conformal displays. The self-assembling process can be used to alter the transparency of the material to all visible light due to scattering by fibres. The reversible transition is shown to be of low energy by differential scanning calorimetry. For use in technology it is imperative that this transition is controlled electrically. We have thus synthesized novel self-assembling hydrogelator molecules which contain an electroactive group. The well-known redox couple of anthraquinone/anthrahydroquinone has been used as the hydrophobic component for a series of small molecule gelators. They are further functionalized with peptide combinations of L-phenylalanine and glycine to provide the hydrophilic group to complete 'head-tail' models of self-assembling gels. The gelation and electroactive characteristics of the series were assessed. Cyclic voltammetry shows the reversible redox cycle to be only superficially altered by functionalization. Additionally, spectroelectrochemical measurements show a reversible transparency and colour change induced by the redox process.

Final Report - Crystal Settling, Redox, and High Temperature Properties of ORP HLW and LAW Glasses, VSL-09R1510-1, Rev. 0, dated 6/18/09

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kruger, Albert A.; Wang, C.; Gan, H.

2013-11-13

The radioactive tank waste treatment programs at the U. S. Department of Energy (DOE) have featured joule heated ceramic melter technology for the vitrification of high level waste (HLW). The Hanford Tank Waste Treatment and Immobilization Plant (WTP) employs this same basic technology not only for the vitrification of HLW streams but also for the vitrification of Low Activity Waste (LAW) streams. Because of the much greater throughput rates required of the WTP as compared to the vitrification facilities at the West Valley Demonstration Project (WVDP) or the Defense Waste Processing Facility (DWPF), the WTP employs advanced joule heated meltersmore » with forced mixing of the glass pool (bubblers) to improve heat and mass transport and increase melting rates. However, for both HLW and LAW treatment, the ability to increase waste loadings offers the potential to significantly reduce the amount of glass that must be produced and disposed and, therefore, the overall project costs. This report presents the results from a study to investigate several glass property issues related to WTP HLW and LAW vitrification: crystal formation and settling in selected HLW glasses; redox behavior of vanadium and chromium in selected LAW glasses; and key high temperature thermal properties of representative HLW and LAW glasses. The work was conducted according to Test Plans that were prepared for the HLW and LAW scope, respectively. One part of this work thus addresses some of the possible detrimental effects due to considerably higher crystal content in waste glass melts and, in particular, the impact of high crystal contents on the flow property of the glass melt and the settling rate of representative crystalline phases in an environment similar to that of an idling glass melter. Characterization of vanadium redox shifts in representative WTP LAW glasses is the second focal point of this work. The third part of this work focused on key high temperature thermal properties of representative WTP HLW and LAW glasses over a wide range of temperatures, from the melter operating temperature to the glass transition.« less

Chemical Disequilibria and Sources of Gibbs Free Energy Inside Enceladus

NASA Astrophysics Data System (ADS)

Zolotov, M. Y.

2010-12-01

Non-photosynthetic organisms use chemical disequilibria in the environment to gain metabolic energy from enzyme catalyzed oxidation-reduction (redox) reactions. The presence of carbon dioxide, ammonia, formaldehyde, methanol, methane and other hydrocarbons in the eruptive plume of Enceladus [1] implies diverse redox disequilibria in the interior. In the history of the moon, redox disequilibria could have been activated through melting of a volatile-rich ice and following water-rock-organic interactions. Previous and/or present aqueous processes are consistent with the detection of NaCl and Na2CO3/NaHCO3-bearing grains emitted from Enceladus [2]. A low K/Na ratio in the grains [2] and a low upper limit for N2 in the plume [3] indicate low temperature (possibly < 273 K) of aqueous processes. Although many of the energetically favorable redox reactions are sluggish at low temperature, they could be catalyzed by enzymes if organisms were (are) present. The redox conditions in aqueous systems and amounts of available Gibbs free energy should have been affected by the production, consumption and escape of hydrogen. Aqueous oxidation of minerals (Fe-Ni metal, Fe-Ni phosphides, etc.) accreted on Enceladus should have led to H2 production, which is consistent with H2 detection in the plume [1]. Numerical evaluations based on concentrations of plume gases [1] reveal sufficient energy sources available to support metabolically diverse life at a wide range of activities (a) of dissolved H2 (log aH2 from 0 to -10). Formaldehyde, carbon dioxide [c.f. 4], HCN (if it is present), methanol, acetylene and other hydrocarbons have the potential to react with H2 to form methane. Aqueous hydrogenations of acetylene, HCN and formaldehyde to produce methanol are energetically favorable as well. Both favorable hydrogenation and hydration of HCN lead to formation of ammonia. Condensed organic species could also participate in redox reactions. Methane and ammonia are the final products of these putative redox transformations. Sulfates may have not formed in cold and/or short-term aqueous environments with a limited H2 escape. In contrast to Earth, Mars and Europa, the moon may have no (or very limited [4]) potential for sulfate reduction. Despite nutrient (C, N, P and S) and metal (e.g. Fe, Ni) rich environments and multiple sources of Gibbs free energy during aqueous episode(s), putative life on Enceladus [4] would have adapted to survive in low water activity alkaline brines rich in ammonia, methanol and organic liquids at temperature >150-170 K. The comet-like abundances of major plume gases and apparent redox disequilibria in aquatic systems are consistent with a minimal influence of aqueous processes on endogenic chemical reactions and may indicate abiotic interior. Alternatively, plume gases may represent never melted primordial parcels of the icy shell, while the deeper interior could contain altered species transformed in abiotic and/or biological processes. Refs: [1] Waite J. et al. (2009) Nature 460, 487-490. [2] Postberg F. et al. (2009) Nature 459, 1098-1101. [3] Hansen C. et al. (2010) 38th COSPAR Sci. Assembly. [4] McKay C. et al. (2008) Astrobiology 8, 909-919.

Redox-Responsive Fluorescent Probes with Different Design Strategies.

PubMed

Lou, Zhangrong; Li, Peng; Han, Keli

2015-05-19

In an aerobic organism, reactive oxygen species (ROS) are an inevitable metabolic byproduct. Endogenously produced ROS have a significant role in physiological processes, but excess ROS can cause oxidative stress and can damage tissue. Cells possess elaborate mechanisms to regulate their internal redox status. The intracellular redox homeostasis plays an essential role in maintaining cellular function. However, moderate alterations in redox balance can accompany major transitions in a cell's life cycle. Because of the role of ROS in physiology and in pathology, researchers need new tools to study redox chemistry in biological systems.In recent years, researchers have made remarkable progress in developing new, highly sensitive and selective fluorescent probes that respond to redox changes, and in this Account we highlight related research, primarily from our own group. We present an overview of the design, photophysical properties, and fluorescence transduction mechanisms of reported molecules that probe redox changes. We have designed and synthesized a series of fluorescent probes for redox cycles in biological systems relying on the active center of glutathione peroxidase (GPx). We have also constructed probes based on the oxidation and reduction of hydroquinone and of 2,2,6,6-tetramethylpiperidinooxy (TEMPO). Most of these probes exhibit high sensitivity and good selectivity, absorb in the near-infrared, and respond rapidly. Such probes are useful for confocal fluorescence microscopy, a dynamic imaging technique that could allow researchers to observe biologically important ROS and antioxidants in real time. This technique and these probes provide potentially useful tools for exploring the generation, transport, physiological function, and pathogenic mechanisms of ROS and antioxidants.We also describe features that could improve the properties of redox-responsive fluorescent probes: greater photostability; rapid, dynamic, cyclic and ratiometric responses; and broader absorption in the near-IR region. In addition, fluorescent probes that include organochalcogens such as selenium and tellurium show promise for a new class of fluorescent redox probes that are both chemically stable and robustly reversible. However, further investigations of the chemical and fluorescence transduction mechanisms of selenium-based probes in response to ROS are needed.

Synergistic oxygen atom transfer by ruthenium complexes with non-redox metal ions.

PubMed

Lv, Zhanao; Zheng, Wenrui; Chen, Zhuqi; Tang, Zhiming; Mo, Wanling; Yin, Guochuan

2016-07-28

Non-redox metal ions can affect the reactivity of active redox metal ions in versatile biological and heterogeneous oxidation processes; however, the intrinsic roles of these non-redox ions still remain elusive. This work demonstrates the first example of the use of non-redox metal ions as Lewis acids to sharply improve the catalytic oxygen atom transfer efficiency of a ruthenium complex bearing the classic 2,2'-bipyridine ligand. In the absence of Lewis acid, the oxidation of ruthenium(ii) complex by PhI(OAc)2 generates the Ru(iv)[double bond, length as m-dash]O species, which is very sluggish for olefin epoxidation. When Ru(bpy)2Cl2 was tested as a catalyst alone, only 21.2% of cyclooctene was converted, and the yield of 1,2-epoxycyclooctane was only 6.7%. As evidenced by electronic absorption spectra and EPR studies, both the oxidation of Ru(ii) by PhI(OAc)2 and the reduction of Ru(iv)[double bond, length as m-dash]O by olefin are kinetically slow. However, adding non-redox metal ions such as Al(iii) can sharply improve the oxygen transfer efficiency of the catalyst to 100% conversion with 89.9% yield of epoxide under identical conditions. Through various spectroscopic characterizations, an adduct of Ru(iv)[double bond, length as m-dash]O with Al(iii), Ru(iv)[double bond, length as m-dash]O/Al(iii), was proposed to serve as the active species for epoxidation, which in turn generated a Ru(iii)-O-Ru(iii) dimer as the reduced form. In particular, both the oxygen transfer from Ru(iv)[double bond, length as m-dash]O/Al(iii) to olefin and the oxidation of Ru(iii)-O-Ru(iii) back to the active Ru(iv)[double bond, length as m-dash]O/Al(iii) species in the catalytic cycle can be remarkably accelerated by adding a non-redox metal, such as Al(iii). These results have important implications for the role played by non-redox metal ions in catalytic oxidation at redox metal centers as well as for the understanding of the redox mechanism of ruthenium catalysts in the oxygen atom transfer reaction.

Testing the Role of Microbial Ecology, Redox-Mediated Deep Water Production and Hypersalinity on TEX86: Lipids and 16s Sequences from Archaea and Bacteria in the Water Column and Sediments of Orca Basin

NASA Astrophysics Data System (ADS)

Warren, C.; Romero, I.; Ellis, G.; Goddard, E.; Krishnan, S.; Nigro, L. M.; Super, J. R.; Zhang, Y.; Zhuang, G.; Hollander, D. J.; Pagani, M.

2014-12-01

Mesophilic marine archaea and bacteria are known to substantially contribute to the oceanic microbial biomass and play critical roles in global carbon, nitrogen and nutrient cycles. The Orca Basin, a 2400 meter deep bathymetric depression on the continental slope of the north-central Gulf of Mexico, is an ideal environment to examine how redox-dependent biochemical processes control the input and cycling of bacterial and archaea-derived lipid compounds from formation in near-surface water, through secondary recycling processes operating at the redox-transition in the water column, to sedimentary diagenetic processes operating in oxic to anoxic zones within the basin. The lowermost 180 meters of the Orca Basin is characterized by an anoxic, hypersaline brine that is separated from the overlying oxic seawater by a well-defined redox sequence associated with a systematic increasing in salinity from 35 - 250‰. While surface water conditions are viewed as normal marine with a seasonally productive water column, the sub-oxic to anoxic transition zones within the deep-water column and the sediment spans over 200 m allowing the unique opportunity for discrete sampling of resident organisms and lipids. Here we present 16s rRNA sequence data of Bacteria and Archaea collected parallel to GDGT lipid profiles and in situ environmental measurements from the sediment and overlying water column in the intermediate zone of the basin, where movements of chemical transition zones are preserved. We evaluated GDGTs and corresponding taxa across the surface water, chlorophyll maximum, thermocline, and the deep redox boundary, including oxygenation, denitrification, manganese, iron and sulfate reduction zones, to determine if GDGTs are being produced under these conditions and how surface-derived GDGT lipids and the TEX86 signal may be altered. The results have implications for the application of the TEX86 paleotemperature proxy.

Biredox ionic liquids: new opportunities toward high performance supercapacitors.

PubMed

Bodin, C; Mourad, E; Zigah, D; Le Vot, S; Freunberger, S A; Favier, F; Fontaine, O

2018-01-01

Nowadays commercial supercapacitors are based on purely capacitive storage at the porous carbons that are used for the electrodes. However, the limits that capacitive storage imposes on energy density calls to investigate new materials to improve the capacitance of the device. This new type of electrodes (e.g., RuO 2 , MnO 2 …) involves pseudo-capacitive faradaic redox processes with the solid material. Ion exchange with solid materials is, however, much slower than the adsorption process in capacitive storage and inevitably leads to significant loss of power. Faradaic process in the liquid state, in contrast can be similarly fast as capacitive processes due to the fast ion transport. Designing new devices with liquid like dynamics and improved specific capacitance is challenging. We present a new approach to increase the specific capacitance using biredox ionic liquids, where redox moieties are tethered to the electrolyte ions, allowing high redox concentrations and significant pseudo-capacitive storage in the liquid state. Anions and cations are functionalized with anthraquinone (AQ) and 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO) moieties, respectively. Glassy carbon, carbon-onion, and commercial activated carbon electrodes that exhibit different double layer structures and thus different diffusion dynamics were used to simultaneously study the electrochemical response of biredox ionic liquids at the positive and negative electrode.

FeS/S/FeS(2) redox system and its oxidoreductase-like chemistry in the iron-sulfur world.

PubMed

Wang, Wei; Yang, Bin; Qu, Youpeng; Liu, Xiaoyang; Su, Wenhui

2011-06-01

The iron-sulfur world (ISW) theory is an intriguing prediction regarding the origin of life on early Earth. It hypothesizes that life arose as a geochemical process from inorganic starting materials on the surface of sulfide minerals in the vicinity of deep-sea hot springs. During the last two decades, many experimental studies have been carried out on this topic, and some interesting results have been achieved. Among them, however, the processes of carbon/nitrogen fixation and biomolecular assembly on the mineral surface have received an inordinate amount of attention. To the present, an abiotic model for the oxidation-reduction of intermediates participating in metabolic pathways has been ignored. We examined the oxidation-reduction effect of a prebiotic FeS/S/FeS(2) redox system on the interconversion between several pairs of α-hydroxy acids and α-keto acids (i.e., lactate/pyruvate, malate/oxaloacetate, and glycolate/glyoxylate). We found that, in the absence of FeS, elemental sulfur (S) oxidized α-hydroxy acids to form corresponding keto acids only at a temperature higher than its melting point (113°C); in the presence of FeS, such reactions occurred more efficiently through a coupled reaction mechanism, even at a temperature below the phase transition point of S. On the other hand, FeS was shown to have the capacity to reversibly reduce the keto acids. Such an oxidoreductase-like chemistry of the FeS/S/FeS(2) redox system suggests that it can determine the redox homeostasis of metabolic intermediates in the early evolutionary phase of life. The results provide a possible pathway for the development of primordial redox biochemistry in the iron-sulfur world. Key Words: Iron-sulfur world-FeS/S/FeS(2) redox system-Oxidoreductase-like chemistry. Astrobiology 11, 471-476.

Mitochondrial Glutathione: Regulation and Functions.

PubMed

Calabrese, Gaetano; Morgan, Bruce; Riemer, Jan

2017-11-20

Mitochondrial glutathione fulfills crucial roles in a number of processes, including iron-sulfur cluster biosynthesis and peroxide detoxification. Recent Advances: Genetically encoded fluorescent probes for the glutathione redox potential (E GSH ) have permitted extensive new insights into the regulation of mitochondrial glutathione redox homeostasis. These probes have revealed that the glutathione pools of the mitochondrial matrix and intermembrane space (IMS) are highly reduced, similar to the cytosolic glutathione pool. The glutathione pool of the IMS is in equilibrium with the cytosolic glutathione pool due to the presence of porins that allow free passage of reduced glutathione (GSH) and oxidized glutathione (GSSG) across the outer mitochondrial membrane. In contrast, limited transport of glutathione across the inner mitochondrial membrane ensures that the matrix glutathione pool is kinetically isolated from the cytosol and IMS. In contrast to the situation in the cytosol, there appears to be extensive crosstalk between the mitochondrial glutathione and thioredoxin systems. Further, both systems appear to be intimately involved in the removal of reactive oxygen species, particularly hydrogen peroxide (H 2 O 2 ), produced in mitochondria. However, a detailed understanding of these interactions remains elusive. We postulate that the application of genetically encoded sensors for glutathione in combination with novel H 2 O 2 probes and conventional biochemical redox state assays will lead to fundamental new insights into mitochondrial redox regulation and reinvigorate research into the physiological relevance of mitochondrial redox changes. Antioxid. Redox Signal. 27, 1162-1177.

Effects of redox-active interlayer anions on the oxygen evolution reactivity of NiFe-layered double hydroxide nanosheets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Daojin; Cai, Zhao; Bi, Yongmin

Nickel-iron layered double hydroxide (NiFe-LDH) nanosheets have shown optimal oxygen evolution reaction (OER) performance; however, the role of the intercalated ions in the OER activity remains unclear. In this work, we show that the activity of the NiFe-LDHs can be tailored by the intercalated anions with different redox potentials. The intercalation of anions with low redox potential (high reducing ability), such as hypophosphites, leads to NiFe-LDHs with low OER overpotential of 240 mV and a small Tafel slope of 36.9 mV/dec, whereas NiFe-LDHs intercalated with anions of high redox potential (low reducing ability), such as fluorion, show a high overpotentialmore » of 370 mV and a Tafel slope of 80.8 mV/dec. The OER activity shows a surprising linear correlation with the standard redox potential. Density functional theory calculations and X-ray photoelectron spectroscopy analysis indicate that the intercalated anions alter the electronic structure of metal atoms which exposed at the surface. Anions with low standard redox potential and strong reducing ability transfer more electrons to the hydroxide layers. Finally, this increases the electron density of the surface metal sites and stabilizes their high-valence states, whose formation is known as the critical step prior to the OER process.« less

Effects of redox-active interlayer anions on the oxygen evolution reactivity of NiFe-layered double hydroxide nanosheets

DOE PAGES

Zhou, Daojin; Cai, Zhao; Bi, Yongmin; ...

2018-02-02

Nickel-iron layered double hydroxide (NiFe-LDH) nanosheets have shown optimal oxygen evolution reaction (OER) performance; however, the role of the intercalated ions in the OER activity remains unclear. In this work, we show that the activity of the NiFe-LDHs can be tailored by the intercalated anions with different redox potentials. The intercalation of anions with low redox potential (high reducing ability), such as hypophosphites, leads to NiFe-LDHs with low OER overpotential of 240 mV and a small Tafel slope of 36.9 mV/dec, whereas NiFe-LDHs intercalated with anions of high redox potential (low reducing ability), such as fluorion, show a high overpotentialmore » of 370 mV and a Tafel slope of 80.8 mV/dec. The OER activity shows a surprising linear correlation with the standard redox potential. Density functional theory calculations and X-ray photoelectron spectroscopy analysis indicate that the intercalated anions alter the electronic structure of metal atoms which exposed at the surface. Anions with low standard redox potential and strong reducing ability transfer more electrons to the hydroxide layers. Finally, this increases the electron density of the surface metal sites and stabilizes their high-valence states, whose formation is known as the critical step prior to the OER process.« less

Response of humic-reducing microorganisms to the redox properties of humic substance during composting.

PubMed

Zhao, Xinyu; He, Xiaosong; Xi, Beidou; Gao, Rutai; Tan, Wenbing; Zhang, Hui; Huang, Caihong; Li, Dan; Li, Meng

2017-12-01

Humic substance (HS) could be utilized by humus-reducing microorganisms (HRMs) as the terminal acceptors. Meanwhile, the reduction of HS can support the microbial growth. This process would greatly affect the redox conversion of inorganic and organic pollutants. However, whether the redox properties of HS lined with HRMs community during composting still remain unclear. This study aimed to assess the relationships between the redox capability of HS [i.e. humic acids (HA) and fulvic acids (FA)] and HRMs during composting. The results showed that the changing patterns of electron accepting capacity and electron donating capacity of HS were diverse during seven composting. Electron transfer capacities (ETC) of HA was significantly correlated with the functional groups (i.e. alkyl C, O-alkyl C, aryl C, carboxylic C, aromatic C), aromaticity and molecular weight of HA. Aromatic C, phenols, aryl C, carboxylic C, aromaticity and molecular weight of HS were the main structuralfeatures associated with the ETC of FA. Ten key genera of HRMs were found significantly determine these redox-active functional groups of HS during composting, thus influencing the ETC of HS in composts. In addition, a regulating method was suggested to enhance the ETC of HS during composting based on the relationships between the key HRMs and redox-active functional groups as well as environmental variables. Copyright © 2017 Elsevier Ltd. All rights reserved.

Bio-functionalization of conductive textile materials with redox enzymes

NASA Astrophysics Data System (ADS)

Kahoush, M.; Behary, N.; Cayla, A.; Nierstrasz, V.

2017-10-01

In recent years, immobilization of oxidoreductase enzymes on electrically conductive materials has played an important role in the development of sustainable bio-technologies. Immobilization process allows the re-use of these bio-catalysts in their final applications. In this study, different methods of immobilizing redox enzymes on conductive textile materials were used to produce bio-functionalized electrodes. These electrodes can be used for bio-processes and bio-sensing in eco-designed applications in domains such as medicine and pollution control. However, the main challenge facing the stability and durability of these electrodes is the maintenance of the enzymatic activity after the immobilization. Hence, preventing the enzyme’s denaturation and leaching is a critical factor for the success of the immobilization processes.

Hunting for low abundant redox proteins in plant plasma membranes.

PubMed

Lüthje, Sabine; Hopff, David; Schmitt, Anna; Meisrimler, Claudia-Nicole; Menckhoff, Ljiljana

2009-04-13

Nowadays electron transport (redox) systems in plasma membranes appear well established. Members of the flavocytochrome b family have been identified by their nucleotide acid sequences and characterized on the transcriptional level. For their gene products functions have been demonstrated in iron uptake and oxidative stress including biotic interactions, abiotic stress factors and plant development. In addition, NAD(P)H-dependent oxidoreductases and b-type cytochromes have been purified and characterized from plasma membranes. Several of these proteins seem to belong to the group of hypothetical or unknown proteins. Low abundance and the lack of amino acid sequence data for these proteins still hamper their functional analysis. Consequently, little is known about the physiological function and regulation of these enzymes. In recent years evidence has been presented for the existence of microdomains (so-called lipid rafts) in plasma membranes and their interaction with specific membrane proteins. The identification of redox systems in detergent insoluble membranes supports the idea that redox systems may have important functions in signal transduction, stress responses, cell wall metabolism, and transport processes. This review summarizes our present knowledge on plasma membrane redox proteins and discusses alternative strategies to investigate the function and regulation of these enzymes.

Artemisone and artemiside - potent pan-reactive antimalarial agents that also synergize redox imbalance in P. falciparum transmissible gametocyte stages.

PubMed

Coertzen, Dina; Reader, Janette; van der Watt, Mariëtte; Nondaba, Sindisiwe H; Gibhard, Liezl; Wiesner, Lubbe; Smith, Peter; D'Alessandro, Sarah; Taramelli, Donatella; Ning Wong, Ho; du Preez, Jan L; Wu, Ronald Wai Keung; Birkholtz, Lyn-Marie; Haynes, Richard K

2018-06-04

The emergence of resistance towards artemisinin combination therapies (ACTs) by the malaria parasite Plasmodium falciparum has the potential to severely compromise malaria control. Therefore, development of new artemisinins in combination with new drugs that impart activities towards both intraerythrocytic proliferative asexual and transmissible gametocyte stages, in particular those of resistant parasites, are urgently required. We define artemisinins as oxidant drugs through their ability to oxidize reduced flavin cofactors of flavin disulfide reductases critical for maintaining redox-homeostasis in the malaria parasite. Here we compare the activities of 10-amino artemisinin derivatives towards the asexual and gametocyte stages of P. falciparum parasites. Of these, artemisone and artemiside inhibited asexual and gametocyte stages, particularly stage V gametocytes in the low nM range. Further, treatment of both early and late gametocyte stages with artemisone or artemiside combined with the pro-oxidant redox partner methylene blue displays notable synergism. These data suggest that modulation of redox-homeostasis likely is an important druggable process, particularly in gametocytes, and thereby enhances the prospect of using combinations of oxidant and redox drugs for malaria control. Copyright © 2018 American Society for Microbiology.

Metabolic Dysfunction in Parkinson's Disease: Bioenergetics, Redox Homeostasis and Central Carbon Metabolism.

PubMed

Anandhan, Annadurai; Jacome, Maria S; Lei, Shulei; Hernandez-Franco, Pablo; Pappa, Aglaia; Panayiotidis, Mihalis I; Powers, Robert; Franco, Rodrigo

2017-07-01

The loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc) and the accumulation of protein inclusions (Lewy bodies) are the pathological hallmarks of Parkinson's disease (PD). PD is triggered by genetic alterations, environmental/occupational exposures and aging. However, the exact molecular mechanisms linking these PD risk factors to neuronal dysfunction are still unclear. Alterations in redox homeostasis and bioenergetics (energy failure) are thought to be central components of neurodegeneration that contribute to the impairment of important homeostatic processes in dopaminergic cells such as protein quality control mechanisms, neurotransmitter release/metabolism, axonal transport of vesicles and cell survival. Importantly, both bioenergetics and redox homeostasis are coupled to neuro-glial central carbon metabolism. We and others have recently established a link between the alterations in central carbon metabolism induced by PD risk factors, redox homeostasis and bioenergetics and their contribution to the survival/death of dopaminergic cells. In this review, we focus on the link between metabolic dysfunction, energy failure and redox imbalance in PD, making an emphasis in the contribution of central carbon (glucose) metabolism. The evidence summarized here strongly supports the consideration of PD as a disorder of cell metabolism. Copyright © 2017 Elsevier Inc. All rights reserved.

Carcinogenesis and Reactive Oxygen Species Signaling: Interaction of the NADPH Oxidase NOX1-5 and Superoxide Dismutase 1-3 Signal Transduction Pathways.

PubMed

Parascandolo, Alessia; Laukkanen, Mikko O

2018-04-05

Reduction/oxidation (redox) balance could be defined as an even distribution of reduction and oxidation complementary processes and their reaction end products. There is a consensus that aberrant levels of reactive oxygen species (ROS), commonly observed in cancer, stimulate primary cell immortalization and progression of carcinogenesis. However, the mechanism how different ROS regulate redox balance is not completely understood. Recent Advances: In the current review, we have summarized the main signaling cascades inducing NADPH oxidase NOX1-5 and superoxide dismutase (SOD) 1-3 expression and their connection to cell proliferation, immortalization, transformation, and CD34 + cell differentiation in thyroid, colon, lung, breast, and hematological cancers. Interestingly, many of the signaling pathways activating redox enzymes or mediating the effect of ROS are common, such as pathways initiated from G protein-coupled receptors and tyrosine kinase receptors involving protein kinase A, phospholipase C, calcium, and small GTPase signaling molecules. The clarification of interaction of signal transduction pathways could explain how cells regulate redox balance and may even provide means to inhibit the accumulation of harmful levels of ROS in human pathologies. Antioxid. Redox Signal. 00, 000-000.

Toxicity testing of sediment collected in the vicinity of effluent discharges from seafood processing plants in the maritimes.

PubMed

Lalonde, Benoit A; Jackman, Paula; Doe, Ken; Garron, Christine; Aubé, Jamie

2009-04-01

There are over 1100 fish-processing plants in Canada and the majority of them discharge untreated effluents directly to marine or estuarine receiving environments. The purpose of this study was to evaluate chemical and toxicological characteristics of sediments near fish-processing plant effluent discharges to assess potential impacts of seafood-processing effluents on receiving environments. Eighteen sediment samples were collected near effluent discharges of six seafood-processing plant outfalls in New Brunswick, Canada in the winter of 2006. Ammonia levels ranged from <0.2 to 3480 microg/g, sulfide levels ranged from <0.4 to 6970 microg/g, and redox ranged from -255 to 443 mV. Only one sample had a Microtox Solid-Phase Test IC(50) value below 1000 mg/kg, whereas three samples caused greater than 30% reduction to amphipod survival. Redox, sulfide, and ammonia concentrations were all found to be significantly related to both Eohaustorius estuarius survival and Microto (Vibrio fischeri) IC(50). An increase in sulfide (R (2) = 0.584; 0.750) and ammonia (R (2) = 0.478; 0.552) and a decrease in redox (R (2) = 0.485; 0.651) were associated with an increase in toxicity to E. estuarius and Microtox, respectively. The highest toxicity to both test organisms, and the most contaminated sediments based on physical/chemical characteristics measured, was observed in samples from Blacks Harbour.

Engineered Approaches to In Situ Bioremediation of Chlorinated Solvents: Fundamentals and Field Applications

DTIC Science & Technology

2000-07-01

scale system that consists of three injection wells currently is being installed at the site. The wells will deliver fructose corn syrup to the...aerobic reaction). The energy gained is stored as high energy compounds, such as ATP and low- energy compounds, such as nicotinamide adenine...processes at high redox potential values is limited; efficiency improves as the redox potential decreases. Pilot studies have been conducted at a variety of

Cofactor engineering for advancing chemical biotechnology.

PubMed

Wang, Yipeng; San, Ka-Yiu; Bennett, George N

2013-12-01

Cofactors provide redox carriers for biosynthetic reactions, catabolic reactions and act as important agents in transfer of energy for the cell. Recent advances in manipulating cofactors include culture conditions or additive alterations, genetic modification of host pathways for increased availability of desired cofactor, changes in enzyme cofactor specificity, and introduction of novel redox partners to form effective circuits for biochemical processes and biocatalysts. Genetic strategies to employ ferredoxin, NADH and NADPH most effectively in natural or novel pathways have improved yield and efficiency of large-scale processes for fuels and chemicals and have been demonstrated with a variety of microbial organisms. Copyright © 2013 Elsevier Ltd. All rights reserved.

Humus-reducing microorganisms and their valuable contribution in environmental processes.

PubMed

Martinez, Claudia M; Alvarez, Luis H; Celis, Lourdes B; Cervantes, Francisco J

2013-12-01

Humus constitutes a very abundant class of organic compounds that are chemically heterogeneous and widely distributed in terrestrial and aquatic environments. Evidence accumulated during the last decades indicating that humic substances play relevant roles on the transport, fate, and redox conversion of organic and inorganic compounds both in chemically and microbially driven reactions. The present review underlines the contribution of humus-reducing microorganisms in relevant environmental processes such as biodegradation of recalcitrant pollutants and mitigation of greenhouse gases emission in anoxic ecosystems, redox conversion of industrial contaminants in anaerobic wastewater treatment systems, and on the microbial production of nanocatalysts and alternative energy sources.

Interior microelectrolysis oxidation of polyester wastewater and its treatment technology.

PubMed

Yang, Xiaoyi

2009-09-30

This paper has investigated the effects of interior microelectrolysis pretreatment on polyester wastewater treatment and analyzed its mechanism on COD and surfactant removal. The efficiency of interior microelectrolysis is mainly influenced by solution pH, aeration and reaction time. Contaminants can be removed not only by redox reaction and flocculation in the result of ferrous and ferric hydroxides but also by electrophoresis under electric fields created by electron flow. pH confirms the chemical states of surfactants, Fe(II)/Fe(III) ratio and the redox potential, and thus influences the effects of electrophoresis, flocculation and redox action on contaminant removal. Anaerobic and aerobic batch tests were performed to study the degradation of polyester wastewater. The results imply that interior microelectrolysis and anaerobic pretreatment are lacking of effectiveness if applied individually in treating polyester wastewater in spite of their individual advantages. The interior microelectrolysis-anaerobic-aerobic process was investigated to treat polyester wastewater with comparison with interior microelectrolysis-aerobic process and anaerobic-aerobic process. High COD removal efficiencies have been gotten by the combination of interior microelectrolysis with anaerobic technology and aerobic technology. The results also imply that only biological treatment was less effective in polyester wastewater treatment.

Natural attenuation of petroleum hydrocarbons-a study of biodegradation effects in groundwater (Vitanovac, Serbia).

PubMed

Marić, Nenad; Matić, Ivan; Papić, Petar; Beškoski, Vladimir P; Ilić, Mila; Gojgić-Cvijović, Gordana; Miletić, Srđan; Nikić, Zoran; Vrvić, Miroslav M

2018-01-20

The role of natural attenuation processes in groundwater contamination by petroleum hydrocarbons is of intense scientific and practical interest. This study provides insight into the biodegradation effects in groundwater at a site contaminated by kerosene (jet fuel) in 1993 (Vitanovac, Serbia). Total petroleum hydrocarbons (TPH), hydrochemical indicators (O 2 , NO 3 - , Mn, Fe, SO 4 2- , HCO 3 - ), δ 13 C of dissolved inorganic carbon (DIC), and other parameters were measured to demonstrate biodegradation effects in groundwater at the contaminated site. Due to different biodegradation mechanisms, the zone of the lowest concentrations of electron acceptors and the zone of the highest concentrations of metabolic products of biodegradation overlap. Based on the analysis of redox-sensitive compounds in groundwater samples, redox processes ranged from strictly anoxic (methanogenesis) to oxic (oxygen reduction) within a short distance. The dependence of groundwater redox conditions on the distance from the source of contamination was observed. δ 13 C values of DIC ranged from - 15.83 to - 2.75‰, and the most positive values correspond to the zone under anaerobic and methanogenic conditions. Overall, results obtained provide clear evidence on the effects of natural attenuation processes-the activity of biodegradation mechanisms in field conditions.

Kinetic modeling of a bi-enzymatic system for efficient conversion of lactose to lactobionic acid.

PubMed

Van Hecke, Wouter; Bhagwat, Aditya; Ludwig, Roland; Dewulf, Jo; Haltrich, Dietmar; Van Langenhove, Herman

2009-04-01

A model has been developed to describe the interaction between two enzymes and an intermediary redox mediator. In this bi-enzymatic process, the enzyme cellobiose dehydrogenase oxidizes lactose at the C-1 position of the reducing sugar moiety to lactobionolactone, which spontaneously hydrolyzes to lactobionic acid. 2,2'-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt is used as electron acceptor and is continuously regenerated by laccase. Oxygen is the terminal electron acceptor and is fully reduced to water by laccase, a copper-containing oxidase. Oxygen is added to the system by means of bubble-free oxygenation. Using the model, the productivity of the process is investigated by simultaneous solution of the rate equations for varying enzyme quantities and redox mediator concentrations, solved with the aid of a numerical solution. The isocharts developed in this work provide an easy-to-use graphical tool to determine optimal process conditions. The model allows the optimization of the employed activities of the two enzymes and the redox mediator concentration for a given overall oxygen mass transfer coefficient by using the isocharts. Model predictions are well in agreement with the experimental data.

Conducting Polyaniline Nanowire and Its Applications in Chemiresistive Sensing

PubMed Central

Song, Edward; Choi, Jin-Woo

2013-01-01

One dimensional polyaniline nanowire is an electrically conducting polymer that can be used as an active layer for sensors whose conductivity change can be used to detect chemical or biological species. In this review, the basic properties of polyaniline nanowires including chemical structures, redox chemistry, and method of synthesis are discussed. A comprehensive literature survey on chemiresistive/conductometric sensors based on polyaniline nanowires is presented and recent developments in polyaniline nanowire-based sensors are summarized. Finally, the current limitations and the future prospect of polyaniline nanowires are discussed. PMID:28348347

Redox potential of shallow groundwater by 1-month continuous in situ potentiometric measurements

NASA Astrophysics Data System (ADS)

Ioka, Seiichiro; Muraoka, Hirofumi; Suzuki, Yota

2017-10-01

One-month continuous in situ potentiometric measurements of redox potential (Eh) were used to investigate the dominant redox processes in the shallow groundwater (i.e., <10 m) of a Holocene aquifer, Aomori City, northern Japan. The Eh values, which were determined using a platinum electrode, were -163, -169 and -173 mV, respectively, for three monitoring campaigns. The temperatures and pH values of shallow groundwater during all three periods were approximately 12 °C and 6.6, respectively. Dissolved oxygen and sulfide ion concentrations were not detected. Chemical analyses showed that the shallow groundwater is Na-Fe-HCO3 type, and contains over 40 mg/L of Fe (the dominant cation) and over 200 mg/L of HCO3 - (the dominant anion). A good fit was found between measured Eh values and Eh values calculated using thermodynamic data of fine-grained goethite. This suggests that Fe redox system is related to the Eh values of shallow groundwater in the Aomori City aquifer.

Fluorescent in vivo imaging of reactive oxygen species and redox potential in plants.

PubMed

Ortega-Villasante, Cristina; Burén, Stefan; Blázquez-Castro, Alfonso; Barón-Sola, Ángel; Hernández, Luis E

2018-04-05

Reactive oxygen species (ROS) are by-products of aerobic metabolism, and excessive production can result in oxidative stress and cell damage. In addition, ROS function as cellular messengers, working as redox regulators in a multitude of biological processes. Understanding ROS signalling and stress responses requires methods for precise imaging and quantification to monitor local, subcellular and global ROS dynamics with high selectivity, sensitivity and spatiotemporal resolution. In this review, we summarize the present knowledge for in vivo plant ROS imaging and detection, using both chemical probes and fluorescent protein-based biosensors. Certain characteristics of plant tissues, for example high background autofluorescence in photosynthetic organs and the multitude of endogenous antioxidants, can interfere with ROS and redox potential detection, making imaging extra challenging. Novel methods and techniques to measure in vivo plant ROS and redox changes with better selectivity, accuracy, and spatiotemporal resolution are therefore desirable to fully acknowledge the remarkably complex plant ROS signalling networks. Copyright © 2018 Elsevier Inc. All rights reserved.

Redox-Active Nitroxide Radical Polymers: From Green Catalysts to Energy Storage Devices

NASA Astrophysics Data System (ADS)

Waskitoaji, Wihatmoko; Suga, Takeo; Nishide, Hiroyuki

2009-09-01

Robust but redox-active radical polymers bearing 2, 2, 6, 6-tetramethylpiperidin-N-oxy (TEMPO) were investigated as a metal-free, green mediator/catalyst for the oxidation of alcohol derivatives, and as a new electrode-active and charge-storage material. The TEMPO-mediated oxidation of the primary alcohol group of the natural cellulose improved the water-dispersivity of cellulose, and the polymer-supported catalysts or redox resins allow facile removal of catalysts from products by simple filtration. Other radical molecule (e.g. galvinoxyl) was also used as a mediator, which is coupled with the molecular oxygen. A reversible one-electron redox reaction of TEMPO allowed its application as an electrode-active material featuring high cyclability (>500 cycles), relatively high battery electrode capacity (100-135 mAh/g), and fast electrode kinetics, leading to the high power rate capability of the battery. The radical polymer-based electrodes also provided good processability and shape flexibility, which promised the paper-like and wearable energy-storage devices.

Rapid and Efficient Redox Processes within 2D Covalent Organic Framework Thin Films

DOE Office of Scientific and Technical Information (OSTI.GOV)

DeBlase, Catherine R.; Hernández-Burgos, Kenneth; Silberstein, Katharine E.

2015-03-24

Two-dimensional covalent organic frameworks (2D COFs) are ideally suited for organizing redox-active subunits into periodic, permanently porous polymer networks of interest for pseudocapacitive energy storage. Here we describe a method for synthesizing crystalline, oriented thin films of a redox-active 2D COF on Au working electrodes. The thickness of the COF film was controlled by varying the initial monomer concentration. A large percentage (80–99%) of the anthraquinone groups are electrochemically accessible in films thinner than 200 nm, an order of magnitude improvement over the same COF prepared as a randomly oriented microcrystalline powder. As a result, electrodes functionalized with oriented COFmore » films exhibit a 400% increase in capacitance scaled to electrode area as compared to those functionalized with the randomly oriented COF powder. These results demonstrate the promise of redox-active COFs for electrical energy storage and highlight the importance of controlling morphology for optimal performance.« less

Rapid and Efficient Redox Processes within 2D Covalent Organic Framework Thin Films

DOE Office of Scientific and Technical Information (OSTI.GOV)

DeBlase, Catherine R.; Hernández-Burgos, Kenneth; Silberstein, Katharine E.

2015-02-17

Two-dimensional covalent organic frameworks (2D COFs) are ideally suited for organizing redox-active subunits into periodic, permanently porous polymer networks of interest for pseudocapacitive energy storage. Here we describe a method for synthesizing crystalline, oriented thin films of a redox-active 2D COF on Au working electrodes. The thickness of the COF film was controlled by varying the initial monomer concentration. A large percentage (80–99%) of the anthraquinone groups are electrochemically accessible in films thinner than 200 nm, an order of magnitude improvement over the same COF prepared as a randomly oriented microcrystalline powder. As a result, electrodes functionalized with oriented COFmore » films exhibit a 400% increase in capacitance scaled to electrode area as compared to those functionalized with the randomly oriented COF powder. These results demonstrate the promise of redox-active COFs for electrical energy storage and highlight the importance of controlling morphology for optimal performance.« less

Redox signaling in acute pancreatitis

PubMed Central

Pérez, Salvador; Pereda, Javier; Sabater, Luis; Sastre, Juan

2015-01-01

Acute pancreatitis is an inflammatory process of the pancreatic gland that eventually may lead to a severe systemic inflammatory response. A key event in pancreatic damage is the intracellular activation of NF-κB and zymogens, involving also calcium, cathepsins, pH disorders, autophagy, and cell death, particularly necrosis. This review focuses on the new role of redox signaling in acute pancreatitis. Oxidative stress and redox status are involved in the onset of acute pancreatitis and also in the development of the systemic inflammatory response, being glutathione depletion, xanthine oxidase activation, and thiol oxidation in proteins critical features of the disease in the pancreas. On the other hand, the release of extracellular hemoglobin into the circulation from the ascitic fluid in severe necrotizing pancreatitis enhances lipid peroxidation in plasma and the inflammatory infiltrate into the lung and up-regulates the HIF–VEGF pathway, contributing to the systemic inflammatory response. Therefore, redox signaling and oxidative stress contribute to the local and systemic inflammatory response during acute pancreatitis. PMID:25778551

Endosomal Redox Signaling in the Antiphospholipid Syndrome.

PubMed

Lackner, Karl J; Manukyan, Davit; Müller-Calleja, Nadine

2017-04-01

It is well established that the antiphospholipid syndrome (APS) is caused by antiphospholipid antibodies (aPL). While several underlying mechanisms have been described in the past, many open questions remain. Here, we will review data on endosomal signaling and, in particular, redox signaling in APS. Endosomal redox signaling has been implicated in several cellular processes including signaling of proinflammatory cytokines. We have shown that certain aPL can activate endosomal NADPH-oxidase (NOX) in several cell types followed by induction of proinflammatory and procoagulant cellular responses in vitro. Involvement of endosomes in aPL signaling has also been reported by others. In wild-type mice but not in NOX-deficient mice, aPL accelerate venous thrombus formation underscoring the relevance of endosomal NOX. Furthermore, hydroxychloroquine (HCQ) inhibits activation of endosomal NOX and prevents thrombus formation in aPL-treated mice. Endosomal redox signaling is an important novel mechanism involved in APS pathogenesis. This makes endosomes a potential target for future treatment approaches of APS.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pezeshki, Alan M.; Sacci, Robert L.; Delnick, Frank M.

Here, an improved method for quantitative measurement of the charge transfer, finite diffusion, and ohmic overpotentials in redox flow batteries using electrochemical impedance spectroscopy is presented. The use of a pulse dampener in the hydraulic circuit enables the collection of impedance spectra at low frequencies with a peristaltic pump, allowing the measurement of finite diffusion resistances at operationally relevant flow rates. This method is used to resolve the rate-limiting processes for the V 2+/V 3+ redox couple on carbon felt and carbon paper electrodes in the vanadium redox flow battery. Carbon felt was limited by both charge transfer and ohmicmore » resistance, while carbon paper was limited by charge transfer, finite diffusion, and ohmic resistances. The influences of vanadium concentration and flow field design also are quantified.« less

Redox reactions of cytochrome c in isolated mitochondria exposed to blue or red lasers using resonance Raman spectroscopy

NASA Astrophysics Data System (ADS)

Denton, Michael L.; Gonzalez, Cherry C.; Noojin, Gary D.; Yakovlev, Vladislav V.

2018-02-01

Resonance Raman spectroscopy of cytochrome c was used to follow reduction/oxidation (redox) states of isolated mitochondria in response to blue or red laser exposure. Mitochondria were isolated from hTERT-RPE1 cells and were kept in a buffer formulation known to be conducive to electron transport chain (ETC) activity. Using either pyruvate or succinate as substrates for ETC, we found differences in the redox responses of cytochrome c for different exposure laser irradiance and excitation wavelength. We anticipate that the proposed new method will be valuable in the study of metabolic processes in mitochondria in response to low level laser exposure, and thus aid in elucidating the mechanism(s) of photobiomodulation.

Proton-Coupled Electron Transfer in Artificial Photosynthetic Systems.

PubMed

Mora, S Jimena; Odella, Emmanuel; Moore, Gary F; Gust, Devens; Moore, Thomas A; Moore, Ana L

2018-02-20

Artificial photosynthetic constructs can in principle operate more efficiently than natural photosynthesis because they can be rationally designed to optimize solar energy conversion for meeting human demands rather than the multiple needs of an organism competing for growth and reproduction in a complex ecosystem. The artificial photosynthetic constructs described in this Account consist primarily of covalently linked synthetic chromophores, electron donors and acceptors, and proton donors and acceptors that carry out the light absorption, electron transfer, and proton-coupled electron transfer (PCET) processes characteristic of photosynthetic cells. PCET is the movement of an electron from one site to another accompanied by proton transfer. PCET and the transport of protons over tens of angstroms are important in all living cells because they are a fundamental link between redox processes and the establishment of transmembrane gradients of proton electrochemical potential, known as proton-motive force (PMF), which is the unifying concept in bioenergetics. We have chosen a benzimidazole phenol (BIP) system as a platform for the study of PCET because with appropriate substitutions it is possible to design assemblies in which one or multiple proton transfers can accompany oxidation of the phenol. In BIP, oxidation of the phenol increases its acidity by more than ten pK a units; thus, electrochemical oxidation of the phenol is associated with a proton transfer to the imidazole. This is an example of a PCET process involving transfer of one electron and one proton, known as electron-proton transfer (EPT). When the benzimidazole moiety of BIP is substituted at the 4-position with good proton acceptor groups such as aliphatic amines, experimental and theoretical results indicate that two proton transfers occur upon one-electron oxidation of the phenol. This phenomenon is described as a one-electron-two-proton transfer (E2PT) process and results in translocation of protons over ∼7 Å via a Grotthuss-type mechanism, where the protons traverse a network of internally H-bonded sites. In the case of the E2TP process involving BIP analogues with amino group substituents, the thermodynamic price paid in redox potential to move a proton to the final proton acceptor is ∼300 mV. In this example, the decrease in redox potential limits the oxidizing power of the resulting phenoxyl radical. Thus, unlike the biological counterpart, the artificial construct is thermodynamically incapable of effectively advancing the redox state of a water oxidation catalyst. The design of systems where multiple proton transfer events are coupled to an oxidation reaction while a relatively high redox potential is maintained remains an outstanding challenge. The ability to control proton transfer and activity at defined distances and times is key to achieving proton management in the vicinity of catalysts operating at low overpotential in myriad biochemically important processes. Artificial photosynthetic constructs with well-defined structures, such as the ones described in this Account, can provide the means for discovering design principles upon which efficient redox catalysts for electrolysis and fuel cells can be based.

Redox Control For Hanford HLW Feeds VSL-12R2530-1, REV 0

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kruger, A. A.; Matlack, Keith S.; Pegg, Ian L.

2012-12-13

The principal objectives of this work were to investigate the effects of processing simulated Hanford HLW at the estimated maximum concentrations of nitrates and oxalates and to identify strategies to mitigate any processing issues resulting from high concentrations of nitrates and oxalates. This report provides results for a series of tests that were performed on the DM10 melter system with simulated C-106/AY-102 HLW. The tests employed simulated HLW feeds containing variable amounts of nitrates and waste organic compounds corresponding to maximum concentrations proj ected for Hanford HLW streams in order to determine their effects on glass production rate, processing characteristics,more » glass redox conditions, melt pool foaming, and the tendency to form secondary phases. Such melter tests provide information on key process factors such as feed processing behavior, dynamic effects during processing, processing rates, off-gas amounts and compositions, foaming control, etc., that cannot be reliably obtained from crucible melts.« less

Characteristics of the iodide/triiodide redox mediator in dye-sensitized solar cells.

PubMed

Boschloo, Gerrit; Hagfeldt, Anders

2009-11-17

Dye-sensitized solar cells (DSCs) have gained widespread interest because of their potential for low-cost solar energy conversion. Currently, the certified record efficiency of these solar cells is 11.1%, and measurements of their durability and stability suggest lifetimes exceeding 10 years under operational conditions. The DSC is a photoelectrochemical system: a monolayer of sensitizing dye is adsorbed onto a mesoporous TiO(2) electrode, and the electrode is sandwiched together with a counter electrode. An electrolyte containing a redox couple fills the gap between the electrodes. The redox couple is a key component of the DSC. The reduced part of the couple regenerates the photo-oxidized dye. The formed oxidized species diffuses to the counter electrode, where it is reduced. The photovoltage of the device depends on the redox couple because it sets the electrochemical potential at the counter electrode. The redox couple also affects the electrochemical potential of the TiO(2) electrode through the recombination kinetics between electrons in TiO(2) and oxidized redox species. This Account focuses on the special properties of the iodide/triiodide (I(-)/I(3)(-)) redox couple in dye-sensitized solar cells. It has been the preferred redox couple since the beginning of DSC development and still yields the most stable and efficient DSCs. Overall, the iodide/triiodide couple has good solubility, does not absorb too much light, has a suitable redox potential, and provides rapid dye regeneration. But what distinguishes I(-)/I(3)(-) from most redox mediators is the very slow recombination kinetics between electrons in TiO(2) and the oxidized part of the redox couple, triiodide. Certain dyes adsorbed at TiO(2) catalyze this recombination reaction, presumably by binding iodine or triiodide. The standard potential of the iodide/triiodide redox couple is 0.35 V (versus the normal hydrogen electrode, NHE), and the oxidation potential of the standard DSC-sensitizer (Ru(dcbpy)(2)(NCS)(2)) is 1.1 V. The driving force for reduction of oxidized dye is therefore as large as 0.75 V. This process leads to the largest internal potential loss in DSC devices. We expect that overall efficiencies above 15% might be achieved if half of this internal potential loss could be gained. The regeneration of oxidized dye with iodide leads to the formation of the diiodide radical (I(2)(-*)). The redox potential of the I(2)(-*)/I(-) couple must therefore be considered when determining the actual driving force for dye regeneration. The formed I(2)(-*) disproportionates to I(3)(-) and I(-), which leads to a large loss in potential energy.

The Reactive Species Interactome: Evolutionary Emergence, Biological Significance, and Opportunities for Redox Metabolomics and Personalized Medicine

PubMed Central

Koning, Anne; Kuhnle, Gunter G.C.; Nagy, Peter; Bianco, Christopher L.; Pasch, Andreas; Wink, David A.; Fukuto, Jon M.; Jackson, Alan A.; van Goor, Harry; Olson, Kenneth R.

2017-01-01

Abstract Significance: Oxidative stress is thought to account for aberrant redox homeostasis and contribute to aging and disease. However, more often than not, administration of antioxidants is ineffective, suggesting that our current understanding of the underlying regulatory processes is incomplete. Recent Advances: Similar to reactive oxygen species and reactive nitrogen species, reactive sulfur species are now emerging as important signaling molecules, targeting regulatory cysteine redox switches in proteins, affecting gene regulation, ion transport, intermediary metabolism, and mitochondrial function. To rationalize the complexity of chemical interactions of reactive species with themselves and their targets and help define their role in systemic metabolic control, we here introduce a novel integrative concept defined as the reactive species interactome (RSI). The RSI is a primeval multilevel redox regulatory system whose architecture, together with the physicochemical characteristics of its constituents, allows efficient sensing and rapid adaptation to environmental changes and various other stressors to enhance fitness and resilience at the local and whole-organism level. Critical Issues: To better characterize the RSI-related processes that determine fluxes through specific pathways and enable integration, it is necessary to disentangle the chemical biology and activity of reactive species (including precursors and reaction products), their targets, communication systems, and effects on cellular, organ, and whole-organism bioenergetics using system-level/network analyses. Future Directions: Understanding the mechanisms through which the RSI operates will enable a better appreciation of the possibilities to modulate the entire biological system; moreover, unveiling molecular signatures that characterize specific environmental challenges or other forms of stress will provide new prevention/intervention opportunities for personalized medicine. Antioxid. Redox Signal. 27, 684–712. PMID:28398072

Redox and Nitric Oxide-Mediated Regulation of Sensory Neuron Ion Channel Function

PubMed Central

2015-01-01

Abstract Significance: Reactive oxygen and nitrogen species (ROS and RNS, respectively) can intimately control neuronal excitability and synaptic strength by regulating the function of many ion channels. In peripheral sensory neurons, such regulation contributes towards the control of somatosensory processing; therefore, understanding the mechanisms of such regulation is necessary for the development of new therapeutic strategies and for the treatment of sensory dysfunctions, such as chronic pain. Recent Advances: Tremendous progress in deciphering nitric oxide (NO) and ROS signaling in the nervous system has been made in recent decades. This includes the recognition of these molecules as important second messengers and the elucidation of their metabolic pathways and cellular targets. Mounting evidence suggests that these targets include many ion channels which can be directly or indirectly modulated by ROS and NO. However, the mechanisms specific to sensory neurons are still poorly understood. This review will therefore summarize recent findings that highlight the complex nature of the signaling pathways involved in redox/NO regulation of sensory neuron ion channels and excitability; references to redox mechanisms described in other neuron types will be made where necessary. Critical Issues: The complexity and interplay within the redox, NO, and other gasotransmitter modulation of protein function are still largely unresolved. Issues of specificity and intracellular localization of these signaling cascades will also be addressed. Future Directions: Since our understanding of ROS and RNS signaling in sensory neurons is limited, there is a multitude of future directions; one of the most important issues for further study is the establishment of the exact roles that these signaling pathways play in pain processing and the translation of this understanding into new therapeutics. Antioxid. Redox Signal. 22, 486–504. PMID:24735331

FeS/S/FeS2 Redox System and Its Oxidoreductase-like Chemistry in the Iron-Sulfur World

NASA Astrophysics Data System (ADS)

Wang, Wei; Yang, Bin; Qu, Youpeng; Liu, Xiaoyang; Su, Wenhui

2011-06-01

The iron-sulfur world (ISW) theory is an intriguing prediction regarding the origin of life on early Earth. It hypothesizes that life arose as a geochemical process from inorganic starting materials on the surface of sulfide minerals in the vicinity of deep-sea hot springs. During the last two decades, many experimental studies have been carried out on this topic, and some interesting results have been achieved. Among them, however, the processes of carbon/nitrogen fixation and biomolecular assembly on the mineral surface have received an inordinate amount of attention. To the present, an abiotic model for the oxidation-reduction of intermediates participating in metabolic pathways has been ignored. We examined the oxidation-reduction effect of a prebiotic FeS/S/FeS2 redox system on the interconversion between several pairs of ±-hydroxy acids and ±-keto acids (i.e., lactate/pyruvate, malate/oxaloacetate, and glycolate/glyoxylate). We found that, in the absence of FeS, elemental sulfur (S) oxidized ±-hydroxy acids to form corresponding keto acids only at a temperature higher than its melting point (113°C); in the presence of FeS, such reactions occurred more efficiently through a coupled reaction mechanism, even at a temperature below the phase transition point of S. On the other hand, FeS was shown to have the capacity to reversibly reduce the keto acids. Such an oxidoreductase-like chemistry of the FeS/S/FeS2 redox system suggests that it can determine the redox homeostasis of metabolic intermediates in the early evolutionary phase of life. The results provide a possible pathway for the development of primordial redox biochemistry in the iron-sulfur world.

Early-Late Heterobimetallic Complexes Linked by Phosphinoamide Ligands. Tuning Redox Potentials and Small Molecule Activation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thomas, Christine M.

2015-08-01

Recent attention in the chemical community has been focused on the energy efficient and environmentally benign conversion of abundant small molecules (CO2, H2O, etc.) to useful liquid fuels. This project addresses these goals by examining fundamental aspects of catalyst design to ultimately access small molecule activation processes under mild conditions. Specifically, Thomas and coworkers have targetted heterobimetallic complexes that feature metal centers with vastly different electronic properties, dictated both by their respective positions on the periodic table and their coordination environment. Unlike homobimetallic complexes featuring identical or similar metals, the bonds between metals in early/late heterobimetallics are more polarized, withmore » the more electron-rich late metal center donating electron density to the more electron-deficient early metal center. While metal-metal bonds pose an interesting strategy for storing redox equivalents and stabilizing reactive metal fragments, the polar character of metal-metal bonds in heterobimetallic complexes renders these molecules ideally poised to react with small molecule substrates via cleavage of energy-rich single and double bonds. In addition, metal-metal interactions have been shown to dramatically affect redox potentials and promote multielectron redox activity, suggesting that metal-metal interactions may provide a mechanism to tune redox potentials and access substrate reduction/activation at mild overpotentials. This research project has provided a better fundamental understanding of how interactions between transition metals can be used as a strategy to promote and/or control chemical transformations related to the clean production of fuels. While this project focused on the study of homogeneous systems, it is anticipated that the broad conclusions drawn from these investigations will be applicable to heterogeneous catalysis as well, particularly on heterogeneous processes that occur at interfaces in multicomponent systems.« less

Reversible anionic redox chemistry in high-capacity layered-oxide electrodes.

PubMed

Sathiya, M; Rousse, G; Ramesha, K; Laisa, C P; Vezin, H; Sougrati, M T; Doublet, M-L; Foix, D; Gonbeau, D; Walker, W; Prakash, A S; Ben Hassine, M; Dupont, L; Tarascon, J-M

2013-09-01

Li-ion batteries have contributed to the commercial success of portable electronics and may soon dominate the electric transportation market provided that major scientific advances including new materials and concepts are developed. Classical positive electrodes for Li-ion technology operate mainly through an insertion-deinsertion redox process involving cationic species. However, this mechanism is insufficient to account for the high capacities exhibited by the new generation of Li-rich (Li(1+x)Ni(y)Co(z)Mn(1-x-y-z)O₂) layered oxides that present unusual Li reactivity. In an attempt to overcome both the inherent composition and the structural complexity of this class of oxides, we have designed structurally related Li₂Ru(1-y)Sn(y)O₃ materials that have a single redox cation and exhibit sustainable reversible capacities as high as 230 mA h g(-1). Moreover, they present good cycling behaviour with no signs of voltage decay and a small irreversible capacity. We also unambiguously show, on the basis of an arsenal of characterization techniques, that the reactivity of these high-capacity materials towards Li entails cumulative cationic (M(n+)→M((n+1)+)) and anionic (O(2-)→O₂(2-)) reversible redox processes, owing to the d-sp hybridization associated with a reductive coupling mechanism. Because Li₂MO₃ is a large family of compounds, this study opens the door to the exploration of a vast number of high-capacity materials.

Chemical Processing Department monthly report, October 1962

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1962-11-21

This report, from the Chemical Processing Department at HAPO, for October, 1962 discusses the following: Production operation; Purex and Redox operation; Finished products operation; maintenance; Financial operations; facilities engineering; research; employee relations; and weapons manufacturing operation.

The extracellular redox state modulates mitochondrial function, gluconeogenesis, and glycogen synthesis in murine hepatocytes.

PubMed

Nocito, Laura; Kleckner, Amber S; Yoo, Elsia J; Jones Iv, Albert R; Liesa, Marc; Corkey, Barbara E

2015-01-01

Circulating redox state changes, determined by the ratio of reduced/oxidized pairs of different metabolites, have been associated with metabolic diseases. However, the pathogenic contribution of these changes and whether they modulate normal tissue function is unclear. As alterations in hepatic gluconeogenesis and glycogen metabolism are hallmarks that characterize insulin resistance and type 2 diabetes, we tested whether imposed changes in the extracellular redox state could modulate these processes. Thus, primary hepatocytes were treated with different ratios of the following physiological extracellular redox couples: β-hydroxybutyrate (βOHB)/acetoacetate (Acoc), reduced glutathione (GSH)/oxidized glutathione (GSSG), and cysteine/cystine. Exposure to a more oxidized ratio via extracellular βOHB/Acoc, GSH/GSSG, and cysteine/cystine in hepatocytes from fed mice increased intracellular hydrogen peroxide without causing oxidative damage. On the other hand, addition of more reduced ratios of extracellular βOHB/Acoc led to increased NAD(P)H and maximal mitochondrial respiratory capacity in hepatocytes. Greater βOHB/Acoc ratios were also associated with decreased β-oxidation, as expected with enhanced lipogenesis. In hepatocytes from fasted mice, a more extracellular reduced state of βOHB/Acoc led to increased alanine-stimulated gluconeogenesis and enhanced glycogen synthesis capacity from added glucose. Thus, we demonstrated for the first time that the extracellular redox state regulates the major metabolic functions of the liver and involves changes in intracellular NADH, hydrogen peroxide, and mitochondrial respiration. Because redox state in the blood can be communicated to all metabolically sensitive tissues, this work confirms the hypothesis that circulating redox state may be an important regulator of whole body metabolism and contribute to alterations associated with metabolic diseases.

The Extracellular Redox State Modulates Mitochondrial Function, Gluconeogenesis, and Glycogen Synthesis in Murine Hepatocytes

PubMed Central

Nocito, Laura; Kleckner, Amber S.; Yoo, Elsia J.; Jones IV, Albert R.; Liesa, Marc; Corkey, Barbara E.

2015-01-01

Circulating redox state changes, determined by the ratio of reduced/oxidized pairs of different metabolites, have been associated with metabolic diseases. However, the pathogenic contribution of these changes and whether they modulate normal tissue function is unclear. As alterations in hepatic gluconeogenesis and glycogen metabolism are hallmarks that characterize insulin resistance and type 2 diabetes, we tested whether imposed changes in the extracellular redox state could modulate these processes. Thus, primary hepatocytes were treated with different ratios of the following physiological extracellular redox couples: β-hydroxybutyrate (βOHB)/acetoacetate (Acoc), reduced glutathione (GSH)/oxidized glutathione (GSSG), and cysteine/cystine. Exposure to a more oxidized ratio via extracellular βOHB/Acoc, GSH/GSSG, and cysteine/cystine in hepatocytes from fed mice increased intracellular hydrogen peroxide without causing oxidative damage. On the other hand, addition of more reduced ratios of extracellular βOHB/Acoc led to increased NAD(P)H and maximal mitochondrial respiratory capacity in hepatocytes. Greater βOHB/Acoc ratios were also associated with decreased β-oxidation, as expected with enhanced lipogenesis. In hepatocytes from fasted mice, a more extracellular reduced state of βOHB/Acoc led to increased alanine-stimulated gluconeogenesis and enhanced glycogen synthesis capacity from added glucose. Thus, we demonstrated for the first time that the extracellular redox state regulates the major metabolic functions of the liver and involves changes in intracellular NADH, hydrogen peroxide, and mitochondrial respiration. Because redox state in the blood can be communicated to all metabolically sensitive tissues, this work confirms the hypothesis that circulating redox state may be an important regulator of whole body metabolism and contribute to alterations associated with metabolic diseases. PMID:25816337

Redox modulation of plant developmental regulators from the class I TCP transcription factor family.

PubMed

Viola, Ivana L; Güttlein, Leandro N; Gonzalez, Daniel H

2013-07-01

TEOSINTE BRANCHED1-CYCLOIDEA-PROLIFERATING CELL FACTOR1 (TCP) transcription factors participate in plant developmental processes associated with cell proliferation and growth. Most members of class I, one of the two classes that compose the family, have a conserved cysteine at position 20 (Cys-20) of the TCP DNA-binding and dimerization domain. We show that Arabidopsis (Arabidopsis thaliana) class I proteins with Cys-20 are sensitive to redox conditions, since their DNA-binding activity is inhibited after incubation with the oxidants diamide, oxidized glutathione, or hydrogen peroxide or with nitric oxide-producing agents. Inhibition can be reversed by treatment with the reductants dithiothreitol or reduced glutathione or by incubation with the thioredoxin/thioredoxin reductase system. Mutation of Cys-20 in the class I protein TCP15 abolished its redox sensitivity. Under oxidizing conditions, covalently linked dimers were formed, suggesting that inactivation is associated with the formation of intermolecular disulfide bonds. Inhibition of class I TCP protein activity was also observed in vivo, in yeast (Saccharomyces cerevisiae) cells expressing TCP proteins and in plants after treatment with redox agents. This inhibition was correlated with modifications in the expression of the downstream CUC1 gene in plants. Modeling studies indicated that Cys-20 is located at the dimer interface near the DNA-binding surface. This places this residue in the correct orientation for intermolecular disulfide bond formation and explains the sensitivity of DNA binding to the oxidation of Cys-20. The redox properties of Cys-20 and the observed effects of cellular redox agents both in vitro and in vivo suggest that class I TCP protein action is under redox control in plants.

Redox Modulation of Plant Developmental Regulators from the Class I TCP Transcription Factor Family1[W][OA

PubMed Central

Viola, Ivana L.; Güttlein, Leandro N.; Gonzalez, Daniel H.

2013-01-01

TEOSINTE BRANCHED1-CYCLOIDEA-PROLIFERATING CELL FACTOR1 (TCP) transcription factors participate in plant developmental processes associated with cell proliferation and growth. Most members of class I, one of the two classes that compose the family, have a conserved cysteine at position 20 (Cys-20) of the TCP DNA-binding and dimerization domain. We show that Arabidopsis (Arabidopsis thaliana) class I proteins with Cys-20 are sensitive to redox conditions, since their DNA-binding activity is inhibited after incubation with the oxidants diamide, oxidized glutathione, or hydrogen peroxide or with nitric oxide-producing agents. Inhibition can be reversed by treatment with the reductants dithiothreitol or reduced glutathione or by incubation with the thioredoxin/thioredoxin reductase system. Mutation of Cys-20 in the class I protein TCP15 abolished its redox sensitivity. Under oxidizing conditions, covalently linked dimers were formed, suggesting that inactivation is associated with the formation of intermolecular disulfide bonds. Inhibition of class I TCP protein activity was also observed in vivo, in yeast (Saccharomyces cerevisiae) cells expressing TCP proteins and in plants after treatment with redox agents. This inhibition was correlated with modifications in the expression of the downstream CUC1 gene in plants. Modeling studies indicated that Cys-20 is located at the dimer interface near the DNA-binding surface. This places this residue in the correct orientation for intermolecular disulfide bond formation and explains the sensitivity of DNA binding to the oxidation of Cys-20. The redox properties of Cys-20 and the observed effects of cellular redox agents both in vitro and in vivo suggest that class I TCP protein action is under redox control in plants. PMID:23686421

Adenine nucleotide-dependent and redox-independent control of mitochondrial malate dehydrogenase activity in Arabidopsis thaliana.

PubMed

Yoshida, Keisuke; Hisabori, Toru

2016-06-01

Mitochondrial metabolism is important for sustaining cellular growth and maintenance; however, the regulatory mechanisms underlying individual processes in plant mitochondria remain largely uncharacterized. Previous redox-proteomics studies have suggested that mitochondrial malate dehydrogenase (mMDH), a key enzyme in the tricarboxylic acid (TCA) cycle and redox shuttling, is under thiol-based redox regulation as a target candidate of thioredoxin (Trx). In addition, the adenine nucleotide status may be another factor controlling mitochondrial metabolism, as respiratory ATP production in mitochondria is believed to be influenced by several environmental stimuli. Using biochemical and reverse-genetic approaches, we addressed the redox- and adenine nucleotide-dependent regulation of mMDH in Arabidopsis thaliana. Recombinant mMDH protein formed intramolecular disulfide bonds under oxidative conditions, but these bonds did not have a considerable effect on mMDH activity. Mitochondria-localized o-type Trx (Trx-o) did not facilitate re-reduction of oxidized mMDH. Determination of the in vivo redox state revealed that mMDH was stably present in the reduced form even in Trx-o-deficient plants. Accordingly, we concluded that mMDH is not in the class of redox-regulated enzymes. By contrast, mMDH activity was lowered by adenine nucleotides (AMP, ADP, and ATP). Each adenine nucleotide suppressed mMDH activity with different potencies and ATP exerted the largest inhibitory effect with a significantly lower K(I). Correspondingly, mMDH activity was inhibited by the increase in ATP/ADP ratio within the physiological range. These results suggest that mMDH activity is finely controlled in response to variations in mitochondrial adenine nucleotide balance. Copyright © 2016 Elsevier B.V. All rights reserved.

Redox regulation and pro-oxidant reactions in the physiology of circadian systems.

PubMed

Méndez, Isabel; Vázquez-Martínez, Olivia; Hernández-Muñoz, Rolando; Valente-Godínez, Héctor; Díaz-Muñoz, Mauricio

2016-05-01

Rhythms of approximately 24 h are pervasive in most organisms and are known as circadian. There is a molecular circadian clock in each cell sustained by a feedback system of interconnected "clock" genes and transcription factors. In mammals, the timing system is formed by a central pacemaker, the suprachiasmatic nucleus, in coordination with a collection of peripheral oscillators. Recently, an extensive interconnection has been recognized between the molecular circadian clock and the set of biochemical pathways that underlie the bioenergetics of the cell. A principle regulator of metabolic networks is the flow of electrons between electron donors and acceptors. The concomitant reduction and oxidation (redox) reactions directly influence the balance between anabolic and catabolic processes. This review summarizes and discusses recent findings concerning the mutual and dynamic interactions between the molecular circadian clock, redox reactions, and redox signaling. The scope includes the regulatory role played by redox coenzymes (NAD(P)+/NAD(P)H, GSH/GSSG), reactive oxygen species (superoxide anion, hydrogen peroxide), antioxidants (melatonin), and physiological events that modulate the redox state (feeding condition, circadian rhythms) in determining the timing capacity of the molecular circadian clock. In addition, we discuss a purely metabolic circadian clock, which is based on the redox enzymes known as peroxiredoxins and is present in mammalian red blood cells and in other biological systems. Both the timing system and the metabolic network are key to a better understanding of widespread pathological conditions such as the metabolic syndrome, obesity, and diabetes. Copyright © 2015 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.

Electronic connection between the quinone and cytochrome C redox pools and its role in regulation of mitochondrial electron transport and redox signaling.

PubMed

Sarewicz, Marcin; Osyczka, Artur

2015-01-01

Mitochondrial respiration, an important bioenergetic process, relies on operation of four membranous enzymatic complexes linked functionally by mobile, freely diffusible elements: quinone molecules in the membrane and water-soluble cytochromes c in the intermembrane space. One of the mitochondrial complexes, complex III (cytochrome bc1 or ubiquinol:cytochrome c oxidoreductase), provides an electronic connection between these two diffusible redox pools linking in a fully reversible manner two-electron quinone oxidation/reduction with one-electron cytochrome c reduction/oxidation. Several features of this homodimeric enzyme implicate that in addition to its well-defined function of contributing to generation of proton-motive force, cytochrome bc1 may be a physiologically important point of regulation of electron flow acting as a sensor of the redox state of mitochondria that actively responds to changes in bioenergetic conditions. These features include the following: the opposing redox reactions at quinone catalytic sites located on the opposite sides of the membrane, the inter-monomer electronic connection that functionally links four quinone binding sites of a dimer into an H-shaped electron transfer system, as well as the potential to generate superoxide and release it to the intermembrane space where it can be engaged in redox signaling pathways. Here we highlight recent advances in understanding how cytochrome bc1 may accomplish this regulatory physiological function, what is known and remains unknown about catalytic and side reactions within the quinone binding sites and electron transfers through the cofactor chains connecting those sites with the substrate redox pools. We also discuss the developed molecular mechanisms in the context of physiology of mitochondria. Copyright © 2015 the American Physiological Society.

Electronic Connection Between the Quinone and Cytochrome c Redox Pools and Its Role in Regulation of Mitochondrial Electron Transport and Redox Signaling

PubMed Central

Sarewicz, Marcin; Osyczka, Artur

2015-01-01

Mitochondrial respiration, an important bioenergetic process, relies on operation of four membranous enzymatic complexes linked functionally by mobile, freely diffusible elements: quinone molecules in the membrane and water-soluble cytochromes c in the intermembrane space. One of the mitochondrial complexes, complex III (cytochrome bc1 or ubiquinol:cytochrome c oxidoreductase), provides an electronic connection between these two diffusible redox pools linking in a fully reversible manner two-electron quinone oxidation/reduction with one-electron cytochrome c reduction/oxidation. Several features of this homodimeric enzyme implicate that in addition to its well-defined function of contributing to generation of proton-motive force, cytochrome bc1 may be a physiologically important point of regulation of electron flow acting as a sensor of the redox state of mitochondria that actively responds to changes in bioenergetic conditions. These features include the following: the opposing redox reactions at quinone catalytic sites located on the opposite sides of the membrane, the inter-monomer electronic connection that functionally links four quinone binding sites of a dimer into an H-shaped electron transfer system, as well as the potential to generate superoxide and release it to the intermembrane space where it can be engaged in redox signaling pathways. Here we highlight recent advances in understanding how cytochrome bc1 may accomplish this regulatory physiological function, what is known and remains unknown about catalytic and side reactions within the quinone binding sites and electron transfers through the cofactor chains connecting those sites with the substrate redox pools. We also discuss the developed molecular mechanisms in the context of physiology of mitochondria. PMID:25540143

Simulation of electron-proton coupling with a Monte Carlo method: application to cytochrome c3 using continuum electrostatics.

PubMed Central

Baptista, A M; Martel, P J; Soares, C M

1999-01-01

A new method is presented for simulating the simultaneous binding equilibrium of electrons and protons on protein molecules, which makes it possible to study the full equilibrium thermodynamics of redox and protonation processes, including electron-proton coupling. The simulations using this method reflect directly the pH and electrostatic potential of the environment, thus providing a much closer and realistic connection with experimental parameters than do usual methods. By ignoring the full binding equilibrium, calculations usually overlook the twofold effect that binding fluctuations have on the behavior of redox proteins: first, they affect the energy of the system by creating partially occupied sites; second, they affect its entropy by introducing an additional empty/occupied site disorder (here named occupational entropy). The proposed method is applied to cytochrome c3 of Desulfovibrio vulgaris Hildenborough to study its redox properties and electron-proton coupling (redox-Bohr effect), using a continuum electrostatic method based on the linear Poisson-Boltzmann equation. Unlike previous studies using other methods, the full reduction order of the four hemes at physiological pH is successfully predicted. The sites more strongly involved in the redox-Bohr effect are identified by analysis of their titration curves/surfaces and the shifts of their midpoint redox potentials and pKa values. Site-site couplings are analyzed using statistical correlations, a method much more realistic than the usual analysis based on direct interactions. The site found to be more strongly involved in the redox-Bohr effect is propionate D of heme I, in agreement with previous studies; other likely candidates are His67, the N-terminus, and propionate D of heme IV. Even though the present study is limited to equilibrium conditions, the possible role of binding fluctuations in the concerted transfer of protons and electrons under nonequilibrium conditions is also discussed. The occupational entropy contributions to midpoint redox potentials and pKa values are computed and shown to be significant. PMID:10354425

Chasing stress signals - Exposure to extracellular stimuli differentially affects the redox state of cell compartments in the wild type and signaling mutants of Botrytis cinerea.

PubMed

Marschall, Robert; Schumacher, Julia; Siegmund, Ulrike; Tudzynski, Paul

2016-05-01

Reactive oxygen species (ROS) are important molecules influencing intracellular developmental processes as well as plant pathogen interactions. They are produced at the infection site and affect the intracellular redox homeostasis. However, knowledge of ROS signaling pathways, their connection to other signaling cascades, and tools for the visualization of intra- and extracellular ROS levels and their impact on the redox state are scarce. By using the genetically encoded biosensor roGFP2 we studied for the first time the differences between the redox states of the cytosol, the intermembrane space of mitochondria and the ER in the filamentous fungus Botrytis cinerea. We showed that the ratio of oxidized to reduced glutathione inside of the cellular compartments differ and that the addition of hydrogen peroxide (H2O2), calcium chloride (CaCl2) and the fluorescent dye calcofluor white (CFW) have a direct impact on the cellular redox states. Dependent on the type of stress agents applied, the redox states were affected in the different cellular compartments in a temporally shifted manner. By integrating the biosensor in deletion mutants of bcnoxA, bcnoxB, bctrx1 and bcltf1 we further elucidated the putative roles of the different proteins in distinct stress-response pathways. We showed that the redox states of ΔbcnoxA and ΔbcnoxB display a wild-type pattern upon exposure to H2O2, but appear to be strongly affected by CaCl2 and CFW. Moreover, we demonstrated the involvement of the light-responsive transcription factor BcLtf1 in the maintenance of the redox state in the intermembrane space of the mitochondria. Finally, we report that CaCl2 as well as cell wall stress-inducing agents stimulate ROS production and that ΔbcnoxB produces significantly less ROS than the wild type and ΔbcnoxA. Copyright © 2016 Elsevier Inc. All rights reserved.

Redox regulation of mitochondrial function with emphasis on cysteine oxidation reactions☆

PubMed Central

Mailloux, Ryan J.; Jin, Xiaolei; Willmore, William G.

2013-01-01

Mitochondria have a myriad of essential functions including metabolism and apoptosis. These chief functions are reliant on electron transfer reactions and the production of ATP and reactive oxygen species (ROS). The production of ATP and ROS are intimately linked to the electron transport chain (ETC). Electrons from nutrients are passed through the ETC via a series of acceptor and donor molecules to the terminal electron acceptor molecular oxygen (O2) which ultimately drives the synthesis of ATP. Electron transfer through the respiratory chain and nutrient oxidation also produces ROS. At high enough concentrations ROS can activate mitochondrial apoptotic machinery which ultimately leads to cell death. However, if maintained at low enough concentrations ROS can serve as important signaling molecules. Various regulatory mechanisms converge upon mitochondria to modulate ATP synthesis and ROS production. Given that mitochondrial function depends on redox reactions, it is important to consider how redox signals modulate mitochondrial processes. Here, we provide the first comprehensive review on how redox signals mediated through cysteine oxidation, namely S-oxidation (sulfenylation, sulfinylation), S-glutathionylation, and S-nitrosylation, regulate key mitochondrial functions including nutrient oxidation, oxidative phosphorylation, ROS production, mitochondrial permeability transition (MPT), apoptosis, and mitochondrial fission and fusion. We also consider the chemistry behind these reactions and how they are modulated in mitochondria. In addition, we also discuss emerging knowledge on disorders and disease states that are associated with deregulated redox signaling in mitochondria and how mitochondria-targeted medicines can be utilized to restore mitochondrial redox signaling. PMID:24455476

Genetic and biochemical investigations of the role of MamP in redox control of iron biomineralization in Magnetospirillum magneticum.

PubMed

Jones, Stephanie R; Wilson, Tiffany D; Brown, Margaret E; Rahn-Lee, Lilah; Yu, Yi; Fredriksen, Laura L; Ozyamak, Ertan; Komeili, Arash; Chang, Michelle C Y

2015-03-31

Magnetotactic bacteria have evolved complex subcellular machinery to construct linear chains of magnetite nanocrystals that allow the host cell to sense direction. Each mixed-valent iron nanoparticle is mineralized from soluble iron within a membrane-encapsulated vesicle termed the magnetosome, which serves as a specialized compartment that regulates the iron, redox, and pH environment of the growing mineral. To dissect the biological components that control this process, we have carried out a genetic and biochemical study of proteins proposed to function in iron mineralization. In this study, we show that the redox sites of c-type cytochromes of the Magnetospirillum magneticum AMB-1 magnetosome island, MamP and MamT, are essential to their physiological function and that ablation of one or both heme motifs leads to loss of function, suggesting that their ability to carry out redox chemistry in vivo is important. We also develop a method to heterologously express fully heme-loaded MamP from AMB-1 for in vitro biochemical studies, which show that its Fe(III)-Fe(II) redox couple is set at an unusual potential (-89 ± 11 mV) compared with other related cytochromes involved in iron reduction or oxidation. Despite its low reduction potential, it remains competent to oxidize Fe(II) to Fe(III) and mineralize iron to produce mixed-valent iron oxides. Finally, in vitro mineralization experiments suggest that Mms mineral-templating peptides from AMB-1 can modulate the iron redox chemistry of MamP.

Redox Modulation of Flavin and Tyrosine Determines Photoinduced Proton-coupled Electron Transfer and Photoactivation of BLUF Photoreceptors

PubMed Central

Mathes, Tilo; van Stokkum, Ivo H. M.; Stierl, Manuela; Kennis, John T. M.

2012-01-01

Photoinduced electron transfer in biological systems, especially in proteins, is a highly intriguing matter. Its mechanistic details cannot be addressed by structural data obtained by crystallography alone because this provides only static information on a given redox system. In combination with transient spectroscopy and site-directed manipulation of the protein, however, a dynamic molecular picture of the ET process may be obtained. In BLUF (blue light sensors using FAD) photoreceptors, proton-coupled electron transfer between a tyrosine and the flavin cofactor is the key reaction to switch from a dark-adapted to a light-adapted state, which corresponds to the biological signaling state. Particularly puzzling is the fact that, although the various naturally occurring BLUF domains show little difference in the amino acid composition of the flavin binding pocket, the reaction rates of the forward reaction differ quite largely from a few ps up to several hundred ps. In this study, we modified the redox potential of the flavin/tyrosine redox pair by site-directed mutagenesis close to the flavin C2 carbonyl and fluorination of the tyrosine, respectively. We provide information on how changes in the redox potential of either reaction partner significantly influence photoinduced proton-coupled electron transfer. The altered redox potentials allowed us furthermore to experimentally describe an excited state charge transfer intermediately prior to electron transfer in the BLUF photocycle. Additionally, we show that the electron transfer rate directly correlates with the quantum yield of signaling state formation. PMID:22833672

The Central Role of Amino Acids in Cancer Redox Homeostasis: Vulnerability Points of the Cancer Redox Code

PubMed Central

Vučetić, Milica; Cormerais, Yann; Parks, Scott K.; Pouysségur, Jacques

2017-01-01

A fine balance in reactive oxygen species (ROS) production and removal is of utmost importance for homeostasis of all cells and especially in highly proliferating cells that encounter increased ROS production due to enhanced metabolism. Consequently, increased production of these highly reactive molecules requires coupling with increased antioxidant defense production within cells. This coupling is observed in cancer cells that allocate significant energy reserves to maintain their intracellular redox balance. Glutathione (GSH), as a first line of defense, represents the most important, non-enzymatic antioxidant component together with the NADPH/NADP+ couple, which ensures the maintenance of the pool of reduced GSH. In this review, the central role of amino acids (AAs) in the maintenance of redox homeostasis in cancer, through GSH synthesis (cysteine, glutamate, and glycine), and nicotinamide adenine dinucleotide (phosphate) production (serine, and glutamine/glutamate) are illustrated. Special emphasis is placed on the importance of AA transporters known to be upregulated in cancers (such as system xc-light chain and alanine-serine-cysteine transporter 2) in the maintenance of AA homeostasis, and thus indirectly, the redox homeostasis of cancer cells. The role of the ROS varies (often described as a “two-edged sword”) during the processes of carcinogenesis, metastasis, and cancer treatment. Therefore, the context-dependent role of specific AAs in the initiation, progression, and dissemination of cancer, as well as in the redox-dependent sensitivity/resistance of the neoplastic cells to chemotherapy are highlighted. PMID:29312889

Redox regulation of mitochondrial function with emphasis on cysteine oxidation reactions.

PubMed

Mailloux, Ryan J; Jin, Xiaolei; Willmore, William G

2014-01-01

Mitochondria have a myriad of essential functions including metabolism and apoptosis. These chief functions are reliant on electron transfer reactions and the production of ATP and reactive oxygen species (ROS). The production of ATP and ROS are intimately linked to the electron transport chain (ETC). Electrons from nutrients are passed through the ETC via a series of acceptor and donor molecules to the terminal electron acceptor molecular oxygen (O2) which ultimately drives the synthesis of ATP. Electron transfer through the respiratory chain and nutrient oxidation also produces ROS. At high enough concentrations ROS can activate mitochondrial apoptotic machinery which ultimately leads to cell death. However, if maintained at low enough concentrations ROS can serve as important signaling molecules. Various regulatory mechanisms converge upon mitochondria to modulate ATP synthesis and ROS production. Given that mitochondrial function depends on redox reactions, it is important to consider how redox signals modulate mitochondrial processes. Here, we provide the first comprehensive review on how redox signals mediated through cysteine oxidation, namely S-oxidation (sulfenylation, sulfinylation), S-glutathionylation, and S-nitrosylation, regulate key mitochondrial functions including nutrient oxidation, oxidative phosphorylation, ROS production, mitochondrial permeability transition (MPT), apoptosis, and mitochondrial fission and fusion. We also consider the chemistry behind these reactions and how they are modulated in mitochondria. In addition, we also discuss emerging knowledge on disorders and disease states that are associated with deregulated redox signaling in mitochondria and how mitochondria-targeted medicines can be utilized to restore mitochondrial redox signaling.

Development of an Electrochemistry Teaching Sequence using a Phenomenographic Approach

NASA Astrophysics Data System (ADS)

Rodriguez-Velazquez, Sorangel

Electrochemistry is the area of chemistry that studies electron transfer reactions across an interface. Chemistry education researchers have acknowledged that difficulties in electrochemistry instruction arise due to the level of abstraction of the topic, lack of adequate explanations and representations found in textbooks, and a quantitative emphasis in the application of concepts. Studies have identified conceptions (also referred to as misconceptions, alternative conceptions, etc.) about the electrochemical process that transcends academic and preparation levels (e.g., students and instructors) as well as cultural and educational settings. Furthermore, conceptual understanding of the electrochemical process requires comprehension of concepts usually studied in physics such as electric current, resistance and potential and often neglected in introductory chemistry courses. The lack of understanding of physical concepts leads to students. conceptions with regards to the relation between the concepts of redox reactions and electric circuits. The need for instructional materials to promote conceptual understanding of the electrochemical process motivated the development of the electrochemistry teaching sequence presented in this dissertation. Teaching sequences are educational tools that aim to bridge the gap between student conceptions and the scientific acceptable conceptions that instructors expect students to learn. This teaching sequence explicitly addresses known conceptions in electrochemistry and departs from traditional instruction in electrochemistry to reinforce students. previous knowledge in thermodynamics providing the foundation for the explicit relation of redox reactions and electric circuits during electrochemistry instruction. The scientific foundations of the electrochemical process are explained based on the Gibbs free energy (G) involved rather than on the standard redox potential values (E° ox/red) of redox half-reactions. Representations of the core concepts from discipline-specific models and theories serve as visual tools to describe reversible redox half-reactions at equilibrium, predict the spontaneity of the electrochemical process and explain interfacial equilibrium between redox species and electrodes in solution. The integration of physics concepts into electrochemistry instruction facilitated describing the interactions between the chemical system (e.g., redox species) and the external circuit (e.g., voltmeter). The "Two worlds" theoretical framework was chosen to anchor a robust educational design where the world of objects and events is deliberately connected to the world of theories and models. The core concepts in Marcus theory and density of states (DOS) provided the scientific foundations to connect both worlds. The design of this teaching sequence involved three phases; the selection of the content to be taught, the determination of a coherent and explicit connection among concepts and the development of educational activities to engage students in the learning process. The reduction-oxidation and electrochemistry chapters of three of the most popular general chemistry textbooks were revised in order to identify potential gaps during instruction, taking into consideration learning and teaching difficulties. The electrochemistry curriculum was decomposed into manageable sections contained in modules. Thirteen modules were developed and each module addresses specific conceptions with regard to terminology, redox reactions in electrochemical cells, and the function of the external circuit in electrochemical process. The electrochemistry teaching sequence was evaluated using a phenomenographic approach. This approach allows describing the qualitative variation in instructors' consciousness about the teaching of electrochemistry. A phenomenographic analysis revealed that the most relevant aspect of variation came from instructors' expertise. Participant A expertise (electrochemist) promoted in-depth discussions of fundamental theories and models that explain the electrochemical process while participant B expertise (general chemistry instruction) emphasized a coherent and explicit presentation of such theories and models to students. Other categories of variation were identified as: recognizing students' conceptions, the use of teaching resources and instructors' expectations for the teaching sequence. For example, while Participant B depended heavily on representations and explanations found in textbooks, participant A recognized misleading representations and oversimplified statements in general chemistry textbooks. Participant A was also more inclined to question the significance of some conceptions such as the correlation between the use of the term circuit and students' conceptions related to the movement of electrons in solution in an electrochemical cell. The electrochemistry teaching sequence in this dissertation fulfils each of the instructors' expectations with regards to the content that incorporated discipline-specific theories and models, explicit connections and flow among concepts, and addressing students' conceptions via the educational activities developed.

The impact of sublethal concentrations of Cu, Pb and Cd on honey bee redox status, superoxide dismutase and catalase in laboratory conditions.

PubMed

Nikolić, Tatjana V; Kojić, Danijela; Orčić, Snežana; Batinić, Darko; Vukašinović, Elvira; Blagojević, Duško P; Purać, Jelena

2016-12-01

In this study, laboratory bioassays were performed to investigate the impact of sublethal concentrations of Cu (CuCl 2 : 1000, 100, 10 mg L -1 ), Pb (PbCl 2 : 10, 1, 0.1 mg L -1 ) and Cd (CdCl 2 : 0.1, 0.01, 0.001 mg L -1 ) on honey bee redox status and the activity of the main antioxidative enzymes and their gene expression. Our results show that exposure to these metals led to significant changes of gene expression, the levels of enzyme activity and redox status, but the effects are metal and dose dependent. In general, exposure of 48 h to given concentrations of Cu, Cd and Pb did not change the activity of antioxidative enzymes and the level of lipid peroxidation, with the exception of decreased activity of catalase at the lowest concentration of cadmium. Only lead produced increases in glutathione and thiol groups. Expression of genes for catalase and superoxide dismutase changed with exposure to cadmium and copper, whilst lead induced only expression of superoxide dismutase genes. The results from this study provide basic data for future research regarding the impacts of metal pollution on Apis mellifera and will be an important step towards a comprehensive risk assessment of the environmental stressors on honey bees. Copyright © 2016 Elsevier Ltd. All rights reserved.

Teaching the basics of reactive oxygen species and their relevance to cancer biology: Mitochondrial reactive oxygen species detection, redox signaling, and targeted therapies.

PubMed

Kalyanaraman, Balaraman; Cheng, Gang; Hardy, Micael; Ouari, Olivier; Bennett, Brian; Zielonka, Jacek

2018-05-01

Reactive oxygen species (ROS) have been implicated in tumorigenesis (tumor initiation, tumor progression, and metastasis). Of the many cellular sources of ROS generation, the mitochondria and the NADPH oxidase family of enzymes are possibly the most prevalent intracellular sources. In this article, we discuss the methodologies to detect mitochondria-derived superoxide and hydrogen peroxide using conventional probes as well as newly developed assays and probes, and the necessity of characterizing the diagnostic marker products with HPLC and LC-MS in order to rigorously identify the oxidizing species. The redox signaling roles of mitochondrial ROS, mitochondrial thiol peroxidases, and transcription factors in response to mitochondria-targeted drugs are highlighted. ROS generation and ROS detoxification in drug-resistant cancer cells and the relationship to metabolic reprogramming are discussed. Understanding the subtle role of ROS in redox signaling and in tumor proliferation, progression, and metastasis as well as the molecular and cellular mechanisms (e.g., autophagy) could help in the development of combination therapies. The paradoxical aspects of antioxidants in cancer treatment are highlighted in relation to the ROS mechanisms in normal and cancer cells. Finally, the potential uses of newly synthesized exomarker probes for in vivo superoxide and hydrogen peroxide detection and the low-temperature electron paramagnetic resonance technique for monitoring oxidant production in tumor tissues are discussed. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Challenges and Opportunities for Small-Molecule Fluorescent Probes in Redox Biology Applications.

PubMed

Jiang, Xiqian; Wang, Lingfei; Carroll, Shaina L; Chen, Jianwei; Wang, Meng C; Wang, Jin

2018-02-16

The concentrations of reactive oxygen/nitrogen species (ROS/RNS) are critical to various biochemical processes. Small-molecule fluorescent probes have been widely used to detect and/or quantify ROS/RNS in many redox biology studies and serve as an important complementary to protein-based sensors with unique applications. Recent Advances: New sensing reactions have emerged in probe development, allowing more selective and quantitative detection of ROS/RNS, especially in live cells. Improvements have been made in sensing reactions, fluorophores, and bioavailability of probe molecules. In this review, we will not only summarize redox-related small-molecule fluorescent probes but also lay out the challenges of designing probes to help redox biologists independently evaluate the quality of reported small-molecule fluorescent probes, especially in the chemistry literature. We specifically highlight the advantages of reversibility in sensing reactions and its applications in ratiometric probe design for quantitative measurements in living cells. In addition, we compare the advantages and disadvantages of small-molecule probes and protein-based probes. The low physiological relevant concentrations of most ROS/RNS call for new sensing reactions with better selectivity, kinetics, and reversibility; fluorophores with high quantum yield, wide wavelength coverage, and Stokes shifts; and structural design with good aqueous solubility, membrane permeability, low protein interference, and organelle specificity. Antioxid. Redox Signal. 00, 000-000.

Rational Design of Na(Li1/3 Mn2/3 )O2 Operated by Anionic Redox Reactions for Advanced Sodium-Ion Batteries.

PubMed

Kim, Duho; Cho, Maenghyo; Cho, Kyeongjae

2017-09-01

In an effort to develop high-energy-density cathodes for sodium-ion batteries (SIBs), low-cost, high capacity Na(Li 1/3 Mn 2/3 )O 2 is discovered, which utilizes the labile O 2p-electron for charge compensation during the intercalation process, inspired by Li 2 MnO 3 redox reactions. Na(Li 1/3 Mn 2/3 )O 2 is systematically designed by first-principles calculations considering the Li/Na mixing enthalpy based on the site preference of Na in the Li sites of Li 2 MnO 3 . Using the anionic redox reaction (O 2- /O - ), this Mn-oxide is predicted to show high redox potentials (≈4.2 V vs Na/Na + ) with high charge capacity (190 mAh g -1 ). Predicted cathode performance is validated by experimental synthesis, characterization, and cyclic performance studies. Through a fundamental understanding of the redox reaction mechanism in Li 2 MnO 3 , Na(Li 1/3 Mn 2/3 )O 2 is designed as an example of a new class of promising cathode materials, Na(Li 1/3 M 2/3 )O 2 (M: transition metals featuring stabilized M 4+ ), for further advances in SIBs. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photosynthetic activity of cotyledons is critical during post-germinative growth and seedling establishment.

PubMed

Ojeda, Valle; Nájera, Victoria A; González, Maricruz; Pérez-Ruiz, Juan M; Cejudo, Francisco J

2017-09-02

Thioredoxins (Trxs) play a relevant role in thiol-dependent redox regulation, which allows the rapid adaptation of chloroplast metabolism to unpredictable environmental conditions. In chloroplasts, Trxs use reducing equivalents provided by photoreduced ferredoxin (Fdx) via the action of a ferredoxin-thioredoxin reductase (FTR), thus linking redox regulation to light. In addition, these organelles contain an NADPH-thioredoxin reductase, NTRC, with a Trx domain at the C-terminus. NTRC efficiently reduces 2-Cys peroxiredoxins (Prxs), hence having antioxidant function. However, NTRC also participates in the redox regulation of processes, such as starch and chlorophyll biosynthesis, which are known to be regulated by Trxs. Thus, the question arising is whether there is a cross-talk between the 2 redox systems. Arabidopsis mutants simultaneously devoid of NTRC and Trx x or Trxs f show a dramatic growth inhibition phenotype, indicating that NTRC is required for the function of these unrelated Trxs. Remarkably, both the ntrc-trxx double mutant and, to a higher extent, the ntrc-trxf1f2 triple mutant show high mortality at the seedling stage, which is rescued by sucrose. These findings show the relevant role of redox regulation for chloroplast performance and uncover the key function of cotyledons chloroplasts at the transition to autotrophic metabolism during seedling establishment.

Energy transducing redox steps of the Na+-pumping NADH:quinone oxidoreductase from Vibrio cholerae

PubMed Central

Juárez, Oscar; Morgan, Joel E.; Nilges, Mark J.; Barquera, Blanca

2010-01-01

Na+-NQR is a unique respiratory enzyme that couples the free energy of electron transfer reactions to electrogenic pumping of sodium across the cell membrane. This enzyme is found in many marine and pathogenic bacteria where it plays an analogous role to the H+-pumping complex I. It has generally been assumed that the sodium pump of Na+-NQR operates on the basis of thermodynamic coupling between reduction of a single redox cofactor and the binding of sodium at a nearby site. In this study, we have defined the coupling to sodium translocation of individual steps in the redox reaction of Na+-NQR. Sodium uptake takes place in the reaction step in which an electron moves from the 2Fe-2S center to FMNC, while the translocation of sodium across the membrane dielectric (and probably its release into the external medium) occurs when an electron moves from FMNB to riboflavin. This argues against a single-site coupling model because the redox steps that drive these two parts of the sodium pumping process do not have any redox cofactor in common. The significance of these results for the mechanism of coupling is discussed, and we proposed that Na+-NQR operates through a novel mechanism based on kinetic coupling, mediated by conformational changes. PMID:20616050

Cysteine Oxidative Post-translational Modifications: Emerging Regulation in the Cardiovascular System

PubMed Central

Chung, Heaseung S.; Wang, Sheng-Bing; Venkatraman, Vidya; Murray, Christopher I.; Van Eyk, Jennifer E.

2014-01-01

In the cardiovascular system, changes in the oxidative balance can affect many aspects of cellular physiology through redox-signaling. Depending on the magnitude, fluctuations in the cell's production of reactive oxygen and nitrogen species can regulate normal metabolic processes, activate protective mechanisms, or be cytotoxic. Reactive oxygen and nitrogen species can have many effects including the post-translational modification of proteins at critical cysteine (Cys) thiols. A subset can act as redox-switches, which elicit functional effects in response to changes in oxidative state. While the general concepts of redox-signaling have been established, the identity and function of many regulatory switches remains unclear. Characterizing the effects of individual modifications is the key to understanding how the cell interprets oxidative signals under physiological and pathological conditions. Here, we review the various Cys oxidative post-translational modifications (Ox-PTMs) and their ability to function as redox-switches that regulate the cell's response to oxidative stimuli. In addition, we discuss how these modifications have the potential to influence other post-translational modifications' signaling pathways though cross-talk. Finally, we review the growing number of tools being developed to identify and quantify the various Cys Ox-PTMs and how this will advance our understanding of redox-regulation. PMID:23329793

Revisiting the BaO2/BaO redox cycle for solar thermochemical energy storage.

PubMed

Carrillo, A J; Sastre, D; Serrano, D P; Pizarro, P; Coronado, J M

2016-03-21

The barium peroxide-based redox cycle was proposed in the late 1970s as a thermochemical energy storage system. Since then, very little attention has been paid to such redox couples. In this paper, we have revisited the use of reduction-oxidation reactions of the BaO2/BaO system for thermochemical heat storage at high temperatures. Using thermogravimetric analysis, reduction and oxidation reactions were studied in order to find the main limitations associated with each process. Furthermore, the system was evaluated through several charge-discharge stages in order to analyse its possible degradation after repeated cycling. Through differential scanning calorimetry the heat stored and released were also determined. Oxidation reaction, which was found to be slower than reduction, was studied in more detail using isothermal tests. It was observed that the rate-controlling step of BaO oxidation follows zero-order kinetics, although at high temperatures a deviation from Arrhenius behaviour was observed probably due to hindrances to anionic oxygen diffusion caused by the formation of an external layer of BaO2. This redox couple was able to withstand several redox cycles without deactivation, showing reaction conversions close to 100% provided that impurities are previously eliminated through thermal pre-treatment, demonstrating the feasibility of this system for solar thermochemical heat storage.

S-Glutathionylation and Redox Protein Signaling in Drug Addiction

PubMed Central

Womersley, Jacqueline S.; Uys, Joachim D.

2016-01-01

Drug addiction is a chronic relapsing disorder that comes at a high cost to individuals and society. Therefore understanding the mechanisms by which drugs exert their effects is of prime importance. Drugs of abuse increase the production of reactive oxygen and nitrogen species resulting in oxidative stress. This change in redox homeostasis increases the conjugation of glutathione to protein cysteine residues; a process called S-glutathionylation. Although traditionally regarded as a protective mechanism against irreversible protein oxidation, accumulated evidence suggests a more nuanced role for S-glutathionylation, namely as a mediator in redox-sensitive protein signaling. The reversible modification of protein thiols leading to alteration in function under different physiologic/pathologic conditions provides a mechanism whereby change in redox status can be translated into a functional response. As such, S-glutathionylation represents an understudied means of post-translational protein modification that may be important in the mechanisms underlying drug addiction. This review will discuss the evidence for S-glutathionylation as a redox-sensing mechanism and how this may be involved in the response to drug-induced oxidative stress. The function of S-glutathionylated proteins involved in neurotransmission, dendritic spine structure, and drug-induced behavioral outputs will be reviewed with specific reference to alcohol, cocaine, and heroin. PMID:26809999

TiO2 Photocatalysis in Aromatic "Redox Tag"-Guided Intermolecular Formal [2 + 2] Cycloadditions.

PubMed

Okada, Yohei; Maeta, Naoya; Nakayama, Kaii; Kamiya, Hidehiro

2018-05-04

Since the pioneering work by Macmillan, Yoon, and Stephenson, homogeneous photoredox catalysis has occupied a central place in new reaction development in the field of organic chemistry. While heterogeneous semiconductor photocatalysis has also been studied extensively, it has generally been recognized as a redox option in inorganic chemistry where such "photocatalysis" is most often used to catalyze carbon-carbon bond cleavage and not in organic chemistry where bond formation is usually the focal point. Herein, we demonstrate that titanium dioxide photocatalysis is a powerful redox option to construct carbon-carbon bonds by using intermolecular formal [2 + 2] cycloadditions as models. Synergy between excited electrons and holes generated upon irradiation is expected to promote the overall net redox neutral process. Key for the successful application is the use of a lithium perchlorate/nitromethane electrolyte solution, which exhibits remarkable Lewis acidity to facilitate the reactions of carbon-centered radical cations with carbon nucleophiles. The reaction mechanism is reasonably understood based on both intermolecular and intramolecular single electron transfer regulated by an aromatic "redox tag". Most of the reactions were completed in less than 30 min even in aqueous and/or aerobic conditions without the need for sacrificial reducing or oxidizing substrates generally required for homogeneous photoredox catalysis.

S-Glutathionylation and Redox Protein Signaling in Drug Addiction.

PubMed

Womersley, Jacqueline S; Uys, Joachim D

2016-01-01

Drug addiction is a chronic relapsing disorder that comes at a high cost to individuals and society. Therefore understanding the mechanisms by which drugs exert their effects is of prime importance. Drugs of abuse increase the production of reactive oxygen and nitrogen species resulting in oxidative stress. This change in redox homeostasis increases the conjugation of glutathione to protein cysteine residues; a process called S-glutathionylation. Although traditionally regarded as a protective mechanism against irreversible protein oxidation, accumulated evidence suggests a more nuanced role for S-glutathionylation, namely as a mediator in redox-sensitive protein signaling. The reversible modification of protein thiols leading to alteration in function under different physiologic/pathologic conditions provides a mechanism whereby change in redox status can be translated into a functional response. As such, S-glutathionylation represents an understudied means of post-translational protein modification that may be important in the mechanisms underlying drug addiction. This review will discuss the evidence for S-glutathionylation as a redox-sensing mechanism and how this may be involved in the response to drug-induced oxidative stress. The function of S-glutathionylated proteins involved in neurotransmission, dendritic spine structure, and drug-induced behavioral outputs will be reviewed with specific reference to alcohol, cocaine, and heroin. Copyright © 2016. Published by Elsevier Inc.

About the dangers, costs and benefits of living an aerobic lifestyle.

PubMed

Knoefler, Daniela; Leichert, Lars I O; Thamsen, Maike; Cremers, Claudia M; Reichmann, Dana; Gray, Michael J; Wholey, Wei-Yun; Jakob, Ursula

2014-08-01

The era in which ROS (reactive oxygen species) were simply the 'bad boys of biology' is clearly over. High levels of ROS are still rightfully considered to be toxic to many cellular processes and, as such, contribute to disease conditions and cell death. However, the high toxicity of ROS is also extremely beneficial, particularly as it is used to kill invading micro-organisms during mammalian host defence. Moreover, a transient, often more localized, increase in ROS levels appears to play a major role in signal transduction processes and positively affects cell growth, development and differentiation. At the heart of all these processes are redox-regulated proteins, which use oxidation-sensitive cysteine residues to control their function and by extension the function of the pathways that they are part of. Our work has contributed to changing the view about ROS through: (i) our characterization of Hsp33 (heat-shock protein 33), one of the first redox-regulated proteins identified, whose function is specifically activated by ROS, (ii) the development of quantitative tools that reveal extensive redox-sensitive processes in bacteria and eukaryotes, and (iii) the discovery of a link between early exposure to oxidants and aging. Our future research programme aims to generate an integrated and system-wide view of the beneficial and deleterious effects of ROS with the central goal to develop more effective antioxidant strategies and more powerful antimicrobial agents.

Interim glycol flowsheet reduction/oxidation (redox) model for the Defense Waste Processing Facility (DWPF)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jantzen, C. M.; Williams, M. S.; Zamecnik, J. R.

Control of the REDuction/OXidation (REDOX) state of glasses containing high concentrations of transition metals, such as High Level Waste (HLW) glasses, is critical in order to eliminate processing difficulties caused by overly reduced or overly oxidized melts. Operation of a HLW melter at Fe +2/ΣFe ratios of between 0.09 and 0.33, a range which is not overly oxidizing or overly reducing, helps retain radionuclides in the melt, i.e. long-lived radioactive 99Tc species in the less volatile reduced Tc 4+ state, 104Ru in the melt as reduced Ru +4 state as insoluble RuO 2, and hazardous volatile Cr 6+ in themore » less soluble and less volatile Cr +3 state in the glass. The melter REDOX control balances the oxidants and reductants from the feed and from processing additives such as antifoam. Currently, the Defense Waste Processing Facility (DWPF) is running a formic acid-nitric acid (FN) flowsheet where formic acid is the main reductant and nitric acid is the main oxidant. During decomposition formate and formic acid releases H 2 gas which requires close control of the melter vapor space flammability. A switch to a nitric acid-glycolic acid (GN) flowsheet is desired as the glycolic acid flowsheet releases considerably less H 2 gas upon decomposition. This would greatly simplify DWPF processing. Development of an EE term for glycolic acid in the GN flowsheet is documented in this study.« less

A Heterobimetallic W-Ni Complex Containing a Redox-Active W[SNS]2 Metalloligand.

PubMed

Rosenkoetter, Kyle E; Ziller, Joseph W; Heyduk, Alan F

2016-07-05

The tungsten complex W[SNS]2 ([SNS]H3 = bis(2-mercapto-4-methylphenyl)amine) was bound to a Ni(dppe) [dppe = 1,2-bis(diphenylphosphino)ethane] fragment to form the new heterobimetallic complex W[SNS]2Ni(dppe). Characterization of the complex by single-crystal X-ray diffraction revealed the presence of a short W-Ni bond, which renders the complex diamagnetic despite formal tungsten(V) and nickel(I) oxidation states. The W[SNS]2 unit acts as a redox-active metalloligand in the bimetallic complex, which displays four one-electron redox processes by cyclic voltammetry. In the presence of the organic acid 4-cyanoanilinium tetrafluoroborate, W[SNS]2Ni(dppe) catalyzes the electrochemical reduction of protons to hydrogen coincident with the first reduction of the complex.

Environmental Electrophiles: Protein Adducts, Modulation of Redox Signaling, and Interaction with Persulfides/Polysulfides.

PubMed

Kumagai, Yoshito; Abiko, Yumi

2017-01-17

Included among the many environmental electrophiles are aromatic hydrocarbon quinones formed during combustion of gasoline, crotonaldehyde in tobacco smoke, methylmercury accumulated in fish, cadmium contaminated in rice, and acrylamide in baked foods. These electrophiles can modify nucleophilic functions such as cysteine residues in proteins forming adducts and in the process activate cellular redox signal transduction pathways such as kinases and transcription factors. However, higher concentrations of electrophiles disrupt such signaling by nonselective covalent modification of cellular proteins. Persulfide/polysulfides produced by various enzymes appear to capture environmental electrophiles because of the formation of their sulfur adducts without electrophilicity. We therefore speculate that persulfide/polysulfides are candidates for the regulation of redox signal transduction pathways (e.g., cell survival, cell proliferation, and adaptive response) and toxicity during exposure to environmental electrophiles.

Redox-mediated signal transduction by cardiovascular Nox NADPH oxidases.

PubMed

Brandes, Ralf P; Weissmann, Norbert; Schröder, Katrin

2014-08-01

The only known function of the Nox family of NADPH oxidases is the production of reactive oxygen species (ROS). Some Nox enzymes show high tissue-specific expression and the ROS locally produced are required for synthesis of hormones or tissue components. In the cardiovascular system, Nox enzymes are low abundant and function as redox-modulators. By reacting with thiols, nitric oxide (NO) or trace metals, Nox-derived ROS elicit a plethora of cellular responses required for physiological growth factor signaling and the induction and adaptation to pathological processes. The interactions of Nox-derived ROS with signaling elements in the cardiovascular system are highly diverse and will be detailed in this article, which is part of a Special Issue entitled "Redox Signalling in the Cardiovascular System". Copyright © 2014 Elsevier Ltd. All rights reserved.

Robust and conductive two-dimensional metal-organic frameworks with exceptionally high volumetric and areal capacitance

DOE PAGES

Feng, Dawei; Lei, Ting; Lukatskaya, Maria R.; ...

2018-01-01

For miniaturized capacitive energy storage, volumetric and areal capacitances are more important metrics than gravimetric ones because of the constraints imposed by device volume and chip area. Typically used in commercial supercapacitors, porous carbons, although they provide a stable and reliable performance, lack volumetric performance because of their inherently low density and moderate capacitances. In this paper, we report a high-performing electrode based on conductive hexaaminobenzene (HAB)-derived two-dimensional metal-organic frameworks (MOFs). In addition to possessing a high packing density and hierarchical porous structure, these MOFs also exhibit excellent chemical stability in both acidic and basic aqueous solutions, which is inmore » sharp contrast to conventional MOFs. Submillimetre-thick pellets of HAB MOFs showed high volumetric capacitances up to 760 F cm -3 and high areal capacitances over 20 F cm -2. Furthermore, the HAB MOF electrodes exhibited highly reversible redox behaviours and good cycling stability with a capacitance retention of 90% after 12,000 cycles. In conclusion, these promising results demonstrate the potential of using redox-active conductive MOFs in energy-storage applications.« less

Quality changes in refrigerated stored minced pork wrapped with plastic cling film and the effect of glucose supplementation.

PubMed

Del Blanco, Alba; Caro, Irma; Quinto, Emiliano J; Mateo, Javier

2017-04-01

Meat spoilage greatly depends on meat composition and storage conditions. Microbial and biochemical changes in minced pork (100-g portions) wrapped with a polyvinyl chloride film during a 4-day refrigerated storage were studied. As glucose is the first substrate used by spoilage bacteria and when it is depleted bacteria could generate undesirable volatiles, the effect of the addition of glucose to minced meat was also studied. Three treatments were used: control (C), without added glucose, and low and high glucose concentration (L and H), 150mg and 750mg of glucose in 100g of meat, respectively. Spoilage bacteria, pH, redox potential, colour, basic volatile nitrogen, glucose, organic acids, and volatiles were analyzed in both recently prepared and stored pork samples. Storage resulted in increased levels of lactic acid bacteria and glucose-derived short chain alkyl volatiles, and a decrease in redox potential and volatile aldehyde levels. The addition of glucose to meat did not affect the biochemical characteristics of stored minced pork. Copyright © 2016 Elsevier Ltd. All rights reserved.

Robust and conductive two-dimensional metal-organic frameworks with exceptionally high volumetric and areal capacitance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, Dawei; Lei, Ting; Lukatskaya, Maria R.

For miniaturized capacitive energy storage, volumetric and areal capacitances are more important metrics than gravimetric ones because of the constraints imposed by device volume and chip area. Typically used in commercial supercapacitors, porous carbons, although they provide a stable and reliable performance, lack volumetric performance because of their inherently low density and moderate capacitances. In this paper, we report a high-performing electrode based on conductive hexaaminobenzene (HAB)-derived two-dimensional metal-organic frameworks (MOFs). In addition to possessing a high packing density and hierarchical porous structure, these MOFs also exhibit excellent chemical stability in both acidic and basic aqueous solutions, which is inmore » sharp contrast to conventional MOFs. Submillimetre-thick pellets of HAB MOFs showed high volumetric capacitances up to 760 F cm -3 and high areal capacitances over 20 F cm -2. Furthermore, the HAB MOF electrodes exhibited highly reversible redox behaviours and good cycling stability with a capacitance retention of 90% after 12,000 cycles. In conclusion, these promising results demonstrate the potential of using redox-active conductive MOFs in energy-storage applications.« less

Could Magnetic Fields Affect the Circadian Clock Function of Cryptochromes? Testing the Basic Premise of the Cryptochrome Hypothesis (ELF Magnetic Fields).

PubMed

Vanderstraeten, Jacques; Burda, Hynek; Verschaeve, Luc; De Brouwer, Christophe

2015-07-01

It has been suggested that weak 50/60 Hz [extremely low frequency (ELF)] magnetic fields (MF) could affect circadian biorhythms by disrupting the clock function of cryptochromes (the "cryptochrome hypothesis," currently under study). That hypothesis is based on the premise that weak (Earth strength) static magnetic fields affect the redox balance of cryptochromes, thus possibly their signaling state as well. An appropriate method for testing this postulate could be real time or short-term study of the circadian clock function of retinal cryptochromes under exposure to the static field intensities that elicit the largest redox changes (maximal "low field" and "high field" effects, respectively) compared to zero field. Positive results might encourage further study of the cryptochrome hypothesis itself. However, they would indicate the need for performing a similar study, this time comparing the effects of only slight intensity changes (low field range) in order to explore the possible role of the proximity of metal structures and furniture as a confounder under the cryptochrome hypothesis.

Robust and conductive two-dimensional metal-organic frameworks with exceptionally high volumetric and areal capacitance

NASA Astrophysics Data System (ADS)

Feng, Dawei; Lei, Ting; Lukatskaya, Maria R.; Park, Jihye; Huang, Zhehao; Lee, Minah; Shaw, Leo; Chen, Shucheng; Yakovenko, Andrey A.; Kulkarni, Ambarish; Xiao, Jianping; Fredrickson, Kurt; Tok, Jeffrey B.; Zou, Xiaodong; Cui, Yi; Bao, Zhenan

2018-01-01

For miniaturized capacitive energy storage, volumetric and areal capacitances are more important metrics than gravimetric ones because of the constraints imposed by device volume and chip area. Typically used in commercial supercapacitors, porous carbons, although they provide a stable and reliable performance, lack volumetric performance because of their inherently low density and moderate capacitances. Here we report a high-performing electrode based on conductive hexaaminobenzene (HAB)-derived two-dimensional metal-organic frameworks (MOFs). In addition to possessing a high packing density and hierarchical porous structure, these MOFs also exhibit excellent chemical stability in both acidic and basic aqueous solutions, which is in sharp contrast to conventional MOFs. Submillimetre-thick pellets of HAB MOFs showed high volumetric capacitances up to 760 F cm-3 and high areal capacitances over 20 F cm-2. Furthermore, the HAB MOF electrodes exhibited highly reversible redox behaviours and good cycling stability with a capacitance retention of 90% after 12,000 cycles. These promising results demonstrate the potential of using redox-active conductive MOFs in energy-storage applications.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stechel, Ellen Beth; Ambrosini, Andrea; Coker, Eric Nicholas

The Sunshine to Petrol effort at Sandia aims to convert carbon dioxide and water to precursors for liquid hydrocarbon fuels using concentrated solar power. Significant advances have been made in the field of solar thermochemical CO{sub 2}-splitting technologies utilizing yttria-stabilized zirconia (YSZ)-supported ferrite composites. Conceptually, such materials work via the basic redox reactions: Fe{sub 3}O{sub 4} {yields} 3FeO + 0.5O{sub 2} (Thermal reduction, >1350 C) and 3FeO + CO{sub 2} {yields} Fe{sub 3}O{sub 4} + CO (CO{sub 2}-splitting oxidation, <1200 C). There has been limited fundamental characterization of the ferrite-based materials at the high temperatures and conditions present in thesemore » cycles. A systematic study of these composites is underway in an effort to begin to elucidate microstructure, structure-property relationships, and the role of the support on redox behavior under high-temperature reducing and oxidizing environments. In this paper the synthesis, structural characterization (including scanning electron microscopy and room temperature and in-situ x-ray diffraction), and thermogravimetric analysis of YSZ-supported ferrites will be reported.« less

Redox signaling and stress tolerance in plants: a focus on vitamin E.

PubMed

Miret, Javier A; Munné-Bosch, Sergi

2015-03-01

Plants are subject to specific redox processes, in which photosynthesis plays a prominent role. Chloroplasts function in light at high oxygen tensions and are enormous generators of reactive oxygen species, mainly singlet oxygen. This side product of photosynthesis inflicts damage to thylakoid membranes at high concentrations, but at the same time it is an essential component of cellular signaling. Detoxification of singlet oxygen is achieved by different means, including quenching and scavenging by tocopherols, responsible for controlling singlet oxygen levels, and the extent of lipid peroxidation in chloroplasts. Here, environmental conditions leading to excess light in chloroplasts will be used to show the importance of singlet oxygen, tocopherols, and lipid peroxidation in cell signaling. Defects in antioxidant protection (e.g., tocopherol deficiency) can lead to increased photo-oxidative damage, but also to the activation of defense pathways, illustrating the phenotypic plasticity evolved by plants to withstand stress. Most importantly, these studies show how redox signaling processes are integrated within the cell and illustrate the great capacity of plants to adapt to their environment. © 2015 New York Academy of Sciences.

Warfarin traps human vitamin K epoxide reductase in an intermediate state during electron transfer

PubMed Central

Shen, Guomin; Cui, Weidong; Zhang, Hao; Zhou, Fengbo; Huang, Wei; Liu, Qian; Yang, Yihu; Li, Shuang; Bowman, Gregory R.; Sadler, J. Evan; Gross, Michael L.; Li, Weikai

2017-01-01

Although warfarin is the most widely used anticoagulant worldwide, the mechanism by which warfarin inhibits its target, human vitamin K epoxide reductase (hVKOR), remains unclear. Here we show that warfarin blocks a dynamic electron-transfer process in hVKOR. A major fraction of cellular hVKOR is at an intermediate redox state of this process containing a Cys51-Cys132 disulfide, a characteristic accommodated by a four-transmembrane-helix structure of hVKOR. Warfarin selectively inhibits this major cellular form of hVKOR, whereas disruption of the Cys51-Cys132 disulfide impairs warfarin binding and causes warfarin resistance. Relying on binding interactions identified by cysteine alkylation footprinting and mass spectrometry coupled with mutagenesis analysis, we are able to conduct structure simulations to reveal a closed warfarin-binding pocket stabilized by the Cys51-Cys132 linkage. Understanding the selective warfarin inhibition of a specific redox state of hVKOR should enable the rational design of drugs that exploit the redox chemistry and associated conformational changes in hVKOR. PMID:27918545

Simultaneous and spectroscopic redox molecular imaging of multiple free radical intermediates using dynamic nuclear polarization-magnetic resonance imaging.

PubMed

Hyodo, Fuminori; Ito, Shinji; Yasukawa, Keiji; Kobayashi, Ryoma; Utsumi, Hideo

2014-08-05

Redox reactions that generate free radical intermediates are essential to metabolic processes. However, their intermediates can produce reactive oxygen species, which may promote diseases related to oxidative stress. We report here the use of dynamic nuclear polarization-magnetic resonance imaging (DNP-MRI) to conduct redox molecular imaging. Using DNP-MRI, we obtained simultaneous images of free radical intermediates generated from the coenzyme Q10 (CoQ10), flavin mononucleotide (FMN), and flavin adenine dinucleotide (FAD) involved in the mitochondrial electron transport chain as well as the radicals derived from vitamins E and K1. Each of these free radicals was imaged in real time in a phantom comprising a mixture of free radicals localized in either lipophilic or aqueous environments. Changing the frequency of electron spin resonance (ESR) irradiation also allowed each of the radical species to be distinguished in the spectroscopic images. This study is the first to report the spectroscopic DNP-MRI imaging of free radical intermediates that are derived from endogenous species involved in metabolic processes.

Approaching the limits of cationic and anionic electrochemical activity with the Li-rich layered rocksalt Li3IrO4

NASA Astrophysics Data System (ADS)

Perez, Arnaud J.; Jacquet, Quentin; Batuk, Dmitry; Iadecola, Antonella; Saubanère, Matthieu; Rousse, Gwenaëlle; Larcher, Dominique; Vezin, Hervé; Doublet, Marie-Liesse; Tarascon, Jean-Marie

2017-12-01

The Li-rich rocksalt oxides Li2MO3 (M = 3d/4d/5d transition metal) are promising positive-electrode materials for Li-ion batteries, displaying capacities exceeding 300 mAh g-1 thanks to the participation of the oxygen non-bonding O(2p) orbitals in the redox process. Understanding the oxygen redox limitations and the role of the O/M ratio is therefore crucial for the rational design of materials with improved electrochemical performances. Here we push oxygen redox to its limits with the discovery of a Li3IrO4 compound (O/M = 4) that can reversibly take up and release 3.5 electrons per Ir and possesses the highest capacity ever reported for any positive insertion electrode. By quantitatively monitoring the oxidation process, we demonstrate the material's instability against O2 release on removal of all Li. Our results show that the O/M parameter delineates the boundary between the material's maximum capacity and its stability, hence providing valuable insights for further development of high-capacity materials.

Estimation of the number of biophotons involved in the visual perception of a single-object image: biophoton intensity can be considerably higher inside cells than outside.

PubMed

Bókkon, I; Salari, V; Tuszynski, J A; Antal, I

2010-09-02

Recently, we have proposed a redox molecular hypothesis about the natural biophysical substrate of visual perception and imagery [1,6]. Namely, the retina transforms external photon signals into electrical signals that are carried to the V1 (striatecortex). Then, V1 retinotopic electrical signals (spike-related electrical signals along classical axonal-dendritic pathways) can be converted into regulated ultraweak bioluminescent photons (biophotons) through redox processes within retinotopic visual neurons that make it possible to create intrinsic biophysical pictures during visual perception and imagery. However, the consensus opinion is to consider biophotons as by-products of cellular metabolism. This paper argues that biophotons are not by-products, other than originating from regulated cellular radical/redox processes. It also shows that the biophoton intensity can be considerably higher inside cells than outside. Our simple calculations, within a level of accuracy, suggest that the real biophoton intensity in retinotopic neurons may be sufficient for creating intrinsic biophysical picture representation of a single-object image during visual perception. Copyright (c) 2010 Elsevier B.V. All rights reserved.

A computational reinvestigation of the formation of N-alkylpyrroles via intermolecular redox amination.

PubMed

Xue, Xiaosong; Yu, Ao; Cai, Yu; Cheng, Jin-Pei

2011-11-18

A detailed mechanism of N-alkylpyrrole formation from 3-pyrroline and 2-phenylpropanal in the presence of a Brønsted acid catalyst was investigated in depth using the MP2 and DFT theories. The two mechanisms proposed earlier in recent literatures for this internal redox process were evaluated and were found not to account perfectly for the transition state and the energetic barrier of its formation. Based on the present calculations, a new mechanism was put forth.

Redox potential - field measurements - meassured vs. expected values

NASA Astrophysics Data System (ADS)

Stavělová, Monika; Kovář, Martin

2016-04-01

Oxidation and reduction (redox) potential is an important and theoretically very well defined parameter and can be calculated accurately. Its value is determinative for management of many electrochemical processes, chemical redox technologies as well as biotechnologies. To measure the redox value that would correspond with the accuracy level of theoretical calculations in field or operational conditions is however nearly impossible. Redox is in practice measured using combined argentochloride electrode with subsequent value conversion to standard hydrogen electrode (EH). Argentochloride electrode does not allow for precise calibration. Prior to the measurement the accuracy of measurement of particular electrode can only be verified in comparative/control solution with value corresponding with oxic conditions (25°C: +220 mV argentochloride electrode, i.e.. +427 mV after conversion to EH). A commercial product of stabile comparative solution for anoxic conditions is not available and therefore not used in every day practice - accuracy of negative redox is not verified. In this presentation results of two tests will be presented: a) monitoring during dynamic groundwater sampling from eight monitoring wells at a site contaminated by chlorinated ethenes (i.e. post-oxic to anoxic conditions) and b) laboratory test of groundwater contaminated by arsenic from two sites during reaction with highly oxidized compounds of iron (ferrates) - i.e. strongly oxic conditions. In both tests a simultaneous measurement by four argentochloride electrodes was implemented - all four electrodes were prior to the test maintained expertly. The redox values of testing electrodes in a comparative solution varied by max. 6 mV. The redox values measured by four electrodes in both anoxic and oxic variant varied by tens to a hundred mV, while with growing time of test the variance of measured redox values increased in both oxic and anoxic variant. Therefore the interpretation of measured redox data must be approached keeping in mind that their accuracy does not correspond with theoretical calculations and their values must be assessed in combination with other parameters - e.g. in case of interpretations of measured redox during remediation of contaminated sites it is appropriate to assess these values together with determined concentrations of significant terminal electron acceptors (TEA) whose laboratory determination is more accurate (NO3-, NO2-, Fe2+,Mn2+ , SO42-, H2S+S2-,CH4….). Acknowledgement: This study has been funded by the Technology Agency of the Czech Republic within the research project Nanobiowat (No. TE01010218), and by AECOM CZ, s.r.o.

Chemistry Cube Game - Exploring Basic Principles of Chemistry by Turning Cubes.

PubMed

Müller, Markus T

2018-02-01

The Chemistry Cube Game invites students at secondary school level 1 and 2 to explore basic concepts of chemistry in a playful way, either as individuals or in teams. It consists of 15 different cubes, 9 cubes for different acids, their corresponding bases and precursors, and 6 cubes for different reducing and oxidising agents. The cubes can be rotated in those directions indicated. Each 'allowed' vertical or horizontal rotation of 90° stands for a chemical reaction or a physical transition. Two different games and playing modes are presented here: First, redox chemistry is introduced for the formation of salts from elementary metals and non-metals. Second, the speciation of acids and bases at different pH-values is shown. The cubes can be also used for games about environmental chemistry such as the carbon and sulphur cycle, covering the topic of acid rain, or the nitrogen cycle including ammoniac synthesis, nitrification and de-nitrification.

Multiple Redox Modes in the Reversible Lithiation of High-Capacity, Peierls-Distorted Vanadium Sulfide

DOE PAGES

Britto, Sylvia; Leskes, Michal; Hua, Xiao; ...

2015-06-08

Vanadium sulfide VS 4 in the patronite mineral structure, is a linear chain compound comprising vanadium atoms coordinated by disulfide anions [S 2] 2–. 51V NMR shows that the material, despite having V formally in the d 1 configuration, is diamagnetic, suggesting potential dimerization through metal-metal bonding associated with a Peierls distortion of the linear chains. This is supported by density functional calculations, and is also consistent with the observed alternation in V-V distances of 2.8 Å and 3.2 Å along the chains. Partial lithiation results in reduction of the disulfide ions to sulfide S 2–, including via an internalmore » redox process whereby an electron from V 4+ is transferred to [S 2] 2– resulting in oxidation of V 4+ to V 5+ and reduction of the [S 2] 2– to S 2- to form Li 3VS 4 containing tetrahedral [VS 4] 3– anions. On further lithiation this is followed by reduction of the V 5+ in Li 3VS 4 to form Li 3+xVS 4 (x=0.5-1), a mixed valent V 4+/V 5+ compound. Eventually reduction to Li 2S plus elemental V occurs. Despite the complex redox processes involving both the cation and the anion occurring in this material, the system is found to be partially reversible between 0 and 3 V. In conclusion, the unusual redox processes in this system are elucidated using a suite of short range characterization tools including 51V Nuclear Magnetic Resonance spectroscopy (NMR), S Kedge X-ray Absorption Near Edge Spectroscopy (XANES) and Pair Distribution Function (PDF) Analysis of X-ray data.« less

Carbonyl Stress in Aging Process: Role of Vitamins and Phytochemicals as Redox Regulators

PubMed Central

Ergin, Volkan; Hariry, Reza Ebrahimi; Karasu, Çimen

2013-01-01

There is a growing scientific agreement that the cellular redox regulators such as antioxidants, particularly the natural polyphenolic forms, may help lower the incidence of some pathologies, including metabolic diseases like diabetes and diabesity, cardiovascular and neurodegenerative abnormalities, and certain cancers or even have anti-aging properties. The recent researches indicate that the degree of metabolic modulation and adaptation response of cells to reductants as well as oxidants establish their survival and homeostasis, which is linked with very critical balance in imbalances in cellular redox capacity and signaling, and that might be an answer the questions why some antioxidants or phytochemicals potentially could do more harm than good, or why some proteins lose their function by increase interactions with glyco- and lipo-oxidation mediates in the cells (carbonyl stress). Nonetheless, pursue of healthy aging has led the use of antioxidants as a means to disrupt age-associated physiological dysfunctions, dysregulated metabolic processes or prevention of many age-related diseases. Although it is still early to define their exact clinical benefits for treating age-related disease, a diet rich in polyphenolic or other forms of antioxidants does seem to offer hope in delaying the onset of age-related disorders. It is now clear that any deficiency in antioxidant vitamins, inadequate enzymatic antioxidant defenses can distinctive for many age-related disease, and protein carbonylation can used as an indicator of oxidative stress associated diseases and aging status. This review examines antioxidant compounds and plant polyphenols as redox regulators in health, disease and aging processes with hope that a better understanding of the many mechanisms involved with these distinct compounds, which may lead to better health and novel treatment approaches for age-related diseases. PMID:24124633

Distribution of dissolved manganese in the Peruvian Upwelling and Oxygen Minimum Zone

NASA Astrophysics Data System (ADS)

Vedamati, Jagruti; Chan, Catherine; Moffett, James W.

2015-05-01

The geochemistry of manganese (Mn) in seawater is dominated by its redox chemistry, as Mn(II) is soluble and Mn(IV) forms insoluble oxides, and redox transformations are mediated by a variety of processes in the oceans. Dissolved Mn (DMn) accumulates under reducing conditions and is depleted under oxidizing conditions. Thus the Peruvian upwelling region, characterized by highly reducing conditions over a broad continental shelf and a major oxygen minimum zone extending far offshore, is potentially a large source of Mn to the eastern Tropical South Pacific. In this study, DMn was determined on cruises in October 2005 and February 2010 in the Peruvian Upwelling and Oxygen Minimum Zone, to evaluate the relationship between Mn, oxygen and nitrogen cycle processes. DMn concentrations were determined using simple dilution and matrix-matched external standardization inductively coupled mass spectrometry. Surprisingly, DMn was depleted under the most reducing conditions along the Peruvian shelf. Concentrations of dissolved Mn in surface waters increased offshore, indicating that advection of Mn offshore from the Peruvian shelf is a minor source. Subsurface Mn maxima were observed within the oxycline rather than within the oxygen minimum zone (OMZ), indicating they arise from remineralization of organic matter rather than reduction of Mn oxides. The distribution of DMn appears to be dominated by non-redox processes and inputs from the atmosphere and from other regions associated with specific water masses. Lower than expected DMn concentrations on the shelf probably reflect limited fluvial inputs from the continent and efficient offshore transport. This behavior is in stark contrast to Fe, reported in a companion study which is very high on the shelf and undergoes dynamic redox cycling.

Carbonyl stress in aging process: role of vitamins and phytochemicals as redox regulators.

PubMed

Ergin, Volkan; Hariry, Reza Ebrahimi; Karasu, Cimen

2013-10-01

There is a growing scientific agreement that the cellular redox regulators such as antioxidants, particularly the natural polyphenolic forms, may help lower the incidence of some pathologies, including metabolic diseases like diabetes and diabesity, cardiovascular and neurodegenerative abnormalities, and certain cancers or even have anti-aging properties. The recent researches indicate that the degree of metabolic modulation and adaptation response of cells to reductants as well as oxidants establish their survival and homeostasis, which is linked with very critical balance in imbalances in cellular redox capacity and signaling, and that might be an answer the questions why some antioxidants or phytochemicals potentially could do more harm than good, or why some proteins lose their function by increase interactions with glyco- and lipo-oxidation mediates in the cells (carbonyl stress). Nonetheless, pursue of healthy aging has led the use of antioxidants as a means to disrupt age-associated physiological dysfunctions, dysregulated metabolic processes or prevention of many age-related diseases. Although it is still early to define their exact clinical benefits for treating age-related disease, a diet rich in polyphenolic or other forms of antioxidants does seem to offer hope in delaying the onset of age-related disorders. It is now clear that any deficiency in antioxidant vitamins, inadequate enzymatic antioxidant defenses can distinctive for many age-related disease, and protein carbonylation can used as an indicator of oxidative stress associated diseases and aging status. This review examines antioxidant compounds and plant polyphenols as redox regulators in health, disease and aging processes with hope that a better understanding of the many mechanisms involved with these distinct compounds, which may lead to better health and novel treatment approaches for age-related diseases.

Nitric-glycolic flowsheet reduction/oxidation (redox) model for the defense waste processing facility (DWPF)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jantzen, C. M.; Williams, M. S.; Edwards, T. B.

Control of the REDuction/OXidation (REDOX) state of glasses containing high concentrations of transition metals, such as High Level Waste (HLW) glasses, is critical in order to eliminate processing difficulties caused by overly reduced or overly oxidized melts. Operation of a HLW melter at Fe +2/ΣFe ratios of between 0.09 and 0.33, retains radionuclides in the melt and thus the final glass. Specifically, long-lived radioactive 99Tc species are less volatile in the reduced Tc 4+ state as TcO 2 than as NaTcO 4 or Tc 2O 7, and ruthenium radionuclides in the reduced Ru 4+ state are insoluble RuO 2 inmore » the melt which are not as volatile as NaRuO 4 where the Ru is in the +7 oxidation state. Similarly, hazardous volatile Cr 6+ occurs in oxidized melt pools as Na 2CrO 4 or Na 2Cr 2O 7, while the Cr +3 state is less volatile and remains in the melt as NaCrO 2 or precipitates as chrome rich spinels. The melter REDOX control balances the oxidants and reductants from the feed and from processing additives such as antifoam.« less

The effects of metamorphism on iron mineralogy and the iron speciation redox proxy

NASA Astrophysics Data System (ADS)

Slotznick, Sarah P.; Eiler, John M.; Fischer, Woodward W.

2018-03-01

As the most abundant transition metal in the Earth's crust, iron is a key player in the planetary redox budget. Observations of iron minerals in the sedimentary record have been used to describe atmospheric and aqueous redox environments over the evolution of our planet; the most common method applied is iron speciation, a geochemical sequential extraction method in which proportions of different iron minerals are compared to calibrations from modern sediments to determine water-column redox state. Less is known about how this proxy records information through post-depositional processes, including diagenesis and metamorphism. To get insight into this, we examined how the iron mineral groups/pools (silicates, oxides, sulfides, etc.) and paleoredox proxy interpretations can be affected by known metamorphic processes. Well-known metamorphic reactions occurring in sub-chlorite to kyanite rocks are able to move iron between different iron pools along a range of proxy vectors, potentially affecting paleoredox results. To quantify the effect strength of these reactions, we examined mineralogical and geochemical data from two classic localities where Silurian-Devonian shales, sandstones, and carbonates deposited in a marine sedimentary basin with oxygenated seawater (based on global and local biological constraints) have been regionally metamorphosed from lower-greenschist facies to granulite facies: Waits River and Gile Mountain Formations, Vermont, USA and the Waterville and Sangerville-Vassalboro Formations, Maine, USA. Plotting iron speciation ratios determined for samples from these localities revealed apparent paleoredox conditions of the depositional water column spanning the entire range from oxic to ferruginous (anoxic) to euxinic (anoxic and sulfidic). Pyrrhotite formation in samples highlighted problems within the proxy as iron pool assignment required assumptions about metamorphic reactions and pyrrhotite's identification depended on the extraction techniques utilized. The presence of diagenetic iron carbonates in many samples severely affected the proxy even at low grade, engendering an interpretation of ferruginous conditions in all lithologies, but particularly in carbonate-bearing rocks. Increasing metamorphic grades transformed iron in carbonates into iron in silicate minerals, which when combined with a slight increase in the amount of pyrrhotite, drove the proxy toward more oxic and more euxinic conditions. Broad-classes of metamorphic reactions (e.g. decarbonation, silicate formation) occurred at distinct temperatures-pressures in carbonates versus siliciclastics, and could be either abrupt between metamorphic facies or more gradual in nature. Notably, these analyses highlighted the importance of trace iron in phases like calcite, which otherwise might not be included in iron-focused research i.e. ore-system petrogenesis, metamorphic evolution, or normative calculations of mineral abundance. The observations show that iron is mobile and reactive during diagenesis and metamorphism, and these post-depositional processes can readily overprint primary redox information held by iron speciation. However, in principle, additional mineralogical and petrographic approaches can be combined with iron speciation data to help untangle many of these post-depositional processes and arrive at more accurate estimates of paleoenvironmental redox conditions and processes, even for metamorphosed samples.

Mutually exclusive redox forms of HMGB1 promote cell recruitment or proinflammatory cytokine release

PubMed Central

Venereau, Emilie; Casalgrandi, Maura; Schiraldi, Milena; Antoine, Daniel J.; Cattaneo, Angela; De Marchis, Francesco; Liu, Jaron; Antonelli, Antonella; Preti, Alessandro; Raeli, Lorenzo; Shams, Sara Samadi; Yang, Huan; Varani, Luca; Andersson, Ulf; Tracey, Kevin J.; Bachi, Angela; Uguccioni, Mariagrazia

2012-01-01

Tissue damage causes inflammation, by recruiting leukocytes and activating them to release proinflammatory mediators. We show that high-mobility group box 1 protein (HMGB1) orchestrates both processes by switching among mutually exclusive redox states. Reduced cysteines make HMGB1 a chemoattractant, whereas a disulfide bond makes it a proinflammatory cytokine and further cysteine oxidation to sulfonates by reactive oxygen species abrogates both activities. We show that leukocyte recruitment and activation can be separated. A nonoxidizable HMGB1 mutant in which serines replace all cysteines (3S-HMGB1) does not promote cytokine production, but is more effective than wild-type HMGB1 in recruiting leukocytes in vivo. BoxA, a HMGB1 inhibitor, interferes with leukocyte recruitment but not with activation. We detected the different redox forms of HMGB1 ex vivo within injured muscle. HMGB1 is completely reduced at first and disulfide-bonded later. Thus, HMGB1 orchestrates both key events in sterile inflammation, leukocyte recruitment and their induction to secrete inflammatory cytokines, by adopting mutually exclusive redox states. PMID:22869893