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An Outbreak of Oxidative Stress in Pathogenesis of Alzheimer's Disease
Published in Suvardhan Kanchi, Rajasekhar Chokkareddy, Mashallah Rezakazemi, Smart Nanodevices for Point-of-Care Applications, 2022
Sourbh Suren Garg, Poojith Nuthalapati, Sruchi Devi, Atulika Sharma, Debasis Sahu, Jeena Gupta
Mitochondria, also known as the powerhouse of the cell, are the major site for the generation of free radicals in the body. Free radicals such as superoxide radicals are generated in the body during the cascade of electron transport [15]. Complex I and complex III are major sites in mitochondria to generate superoxide radicals [16]. NADPH dehydrogenase and ubiquinone cytochrome C reductase are other names for complex I and complex III, respectively. Briefly, there is the transport of electrons either from complex I or complex II to coenzyme Q. With this transfer, a reduced form of coenzyme (QH2) is generated which regenerates the coenzyme Q via semiquinone anion (•Q–). This reaction further continues with the transfer of electrons from semiquinone anion to oxygen leading to the formation of superoxide radicals in the mitochondria [17]. The generation of superoxide radicals in the body is responsible for a number of ailments. Mitochondrial superoxide dismutase is an enzyme responsible for the catalyzation of superoxide anion to other free radicals such as hydrogen peroxide [18] (H2O2).
Nigella sativa and its Characterization
Published in Devrim Balköse, Ana Cristina Faria Ribeiro, A. K. Haghi, Suresh C. Ameta, Tanmoy Chakraborty, Chemical Science and Engineering Technology, 2019
Coenzyme Q10 is a member of class of compounds that are characterized by their quinone moiety and lipophilic tail which could be in different composition and length as shown in Figure 7.2. The quinone group consists of benzene ring having two conjugated oxygen atoms, two methoxy groups, and a methyl group. The hydrophobic tail is made of isoprenoid chain with different lengths (n = 6–10). The characteristic quinone group can accept electrons from different biological sources and is converted into semiquinone group by a one electron transfer or to the more stable hydroquinone by two electrons. This feature makes Coenzyme Q10 cellular electron transfer molecule in the respiratory chain of mitochondria.
Symbols, Terminology, and Nomenclature
Published in W. M. Haynes, David R. Lide, Thomas J. Bruno, CRC Handbook of Chemistry and Physics, 2016
W. M. Haynes, David R. Lide, Thomas J. Bruno
where is the wavefunction, V is the potential energy expressed as a function of the spatial coordinates, E is an energy eigenvalue, 2 is the Laplacian operator, is Planck's constant divided by 2, and m is the mass. Second (s)* - The SI base unit of time. [1] Second radiation constant (c2)* - See First radiation constant. Secondary ion mass spectroscopy (SIMS) - See Techniques for Materials Characterization, page 12-1. Seebeck effect - The development of a potential difference in a circuit where two different metals or semiconductors are joined and their junctions maintained at different temperatures. It is the basis of the thermocouple. Selenides - Compounds having the structure RSeR (R not equal to H). They are thus selenium analogues of ethers. Also used for metal salts of H2Se. [5] Semicarbazones - Compounds having the structure R2C=NNHC(=O)NH2, formally derived by condensation of aldehydes or ketones with semicarbazide [NH2NHC(=O)NH2]. [5] Semiconductor - A material in which the highest occupied energy band (valence band) is completely filled with electrons at T = 0 K, and the energy gap to the next highest band (conduction band) ranges from 0 to 4 or 5 eV. With increasing temperature electrons are excited into the conduction band, leading to an increase in the electrical conductivity. Semiquinones - Radical anions having the structure -O-Z-O where Z is an ortho- or para-arylene group or analogous heteroarylene group; they are formally generated by the addition of an electron to a quinone. [5] SI units* - The International System of Units adopted in 1960 and recommended for use in all scientific and technical fields. [1] Siemens (S)* - The SI unit of electric conductance, equal to -1. [1] Sievert (Sv)* - The SI unit of dose equivalent (of radiation), equal to J/kg. [1] Silanes - Saturated silicon hydrides, analogues of the alkanes; i.e., compounds of the general formula SinH2n+2. Silanes may be subdivided into silane, oligosilanes, and polysilanes. Hydrocarbyl derivatives are often referred to loosely as silanes. [5] Silicones - Polymeric or oligomeric siloxanes, usually considered unbranched, of general formula [-OSiR2-]n (R not equal to H). [5] Siloxanes - Saturated silicon-oxygen hydrides with unbranched or branched chains of alternating silicon and oxygen atoms (each silicon atom is separated from its nearest silicon neighbors by single oxygen atoms). [5] Skin effect - The concentration of high frequency alternating currents near the surface of a conductor. Slater orbital - A particular mathematical expression for the radial part of the wave function of a single electron, which is used in quantum-mechanical calculations of the energy and other properties of atoms and molecules. Small angle neutron scattering (SANS) - See Techniques for Materials Characterization, page 12-1. Snell's law - The relation between the angle of incidence i and the angle of refraction r of a light beam which passes from a medium of refractive index n0 to a medium of index n1, viz., sin i/sin r = n1/n0. Solar constant* - The mean radiant energy flux from the sun on a unit surface normal to the direction of the rays at the mean
Genotoxicity of quinone: An insight on DNA adducts and its LC-MS-based detection
Published in Critical Reviews in Environmental Science and Technology, 2022
Yue Xiong, Han Yeong Kaw, Lizhong Zhu, Wei Wang
In the study of toxic metabolism mechanism, hydroxyl PCBs (OH-PCBs) and PCB-semiquinones have attracted a lot of attentions (Dhakal et al., 2018). Most of the higher chlorinated PCBs are inherently toxic and stable to persist in the environment. Yet, lower chlorinated PCBs tend to be metabolized to hydroxyl compounds, such as 2,5- and 3,4-dihydroxy substitutions. The hydroxy- and ortho- or para-dihydroxy-metabolites can be catalyzed by cytochrome P450s, and may undergo further oxidation to produce ortho- or para-quinone through peroxidases (Liu et al., 2020). PCB semiquinone radicals with high reactivity is generated by one-electron oxidation/reduction of hydroquinones and quinones (Song et al., 2008). Yang Song’s group unveiled that 2,3,5-trichloro-6-phenyl-[1,4]-benzoquinone (PCB29-pQ) promoted foam cell formation from macrophage which involved macrophage/monocyte polarization to CD163þ macrophage through Nrf2 signaling pathway (Liu et al., 2020; Yang et al., 2019). From the perspective of transcription factors, HMGB1 played a primary role at the dose of 5 μM PCB29-pQ, but p53 instead promoted autophagy in human hepatoma HepG2 cells at the dose of 15 μM PCB29-pQ (Shi et al., 2019). Further investigation showed PCB29-pQ induced breast cancer metastasis via ROS-dependent NF-κBMMP signaling in nude BALB/c mice, so overproduction of ROS by PCB29-pQ played significant roles in determining the toxicity (Wang et al., 2018).
Usnic acid attenuates genomic instability in Chinese hamster ovary (CHO) cells as well as chemical-induced preneoplastic lesions in rat colon
Published in Journal of Toxicology and Environmental Health, Part A, 2019
Nayane Moreira Machado, Arthur Barcelos Ribeiro, Heloiza Diniz Nicolella, Saulo Duarte Ozelin, Lucas Henrique Domingos Da Silva, Ana Paula Prado Guissone, Francisco Rinaldi-Neto, Igor Lizo Limonti Lemos, Ricardo Andrade Furtado, Wilson Roberto Cunha, Alexandre Azenha Alves De Rezende, Mário Antônio Spanó, Denise Crispim Tavares
In an attempt to contribute to the understanding of MOA underlying the antigenotoxic effect previously reported by Leandro et al. (2013), the influence of UA was investigated on genotoxicity induced by mutagens with differing MOA such as DXR, H2O2, and VP-16. DXR, an anthracycline antibiotic, is a key chemotherapeutic drug employed for cancer treatment, although its use is limited by chronic and acute adverse effects (Quiles et al. 2002). Anthracyclines such as DXR are DNA topoisomerase II inhibitors. This enzyme is involved in fundamental biological processes, including DNA replication, transcription, DNA repair, and chromatin remodeling. DXR binds to DNA topoisomerase II and stabilizes an intermediate reaction in which the DNA strands are cut and covalently linked to tyrosine residues of DNA topoisomerase II, creating a ternary DXR–DNA–DNA topoisomerase II complex that alters DNA structure and impedes its synthesis (Minotti et al. 2004). Further, the quinone present in the molecular structure of DXR may be oxidized to a semiquinone radical. Semiquinone radicals react rapidly with oxygen to generate superoxide (O2−) and H2O2 that are converted to highly reactive hydroxyl radicals, inducing DNA damage (Finn, Findley, and Kemp 2011; Injac and Strukelj 2008; Venkatesh et al. 2007).
Electrochemical reduction of halogenated organic contaminants using carbon-based cathodes: A review
Published in Critical Reviews in Environmental Science and Technology, 2023
Jacob F. King, William A. Mitch
The other critical property of carbon-based electrodes is their ability to transfer electrons. The two pathways identified for electron transport in carbon materials involve either reversible oxidation-reduction of oxygenated functional groups or transport through conductive graphene regions. The first pathway is illustrated by the reversible and sequential reduction of quinones to semiquinones and hydroquinones (Scheme 1). The importance of this scheme was first demonstrated for quinones in dissolved organic matter (DOM) mediating the transfer of electrons from sulfides to nitroaromatics and polyhalogenated alkanes (Dunnivant et al., 1992; Schwarzenbach et al., 1990). Sulfide reduction of nitroaromatics mediated by rice straw-derived black carbon was also attributed to sulfide radicals formed by electron transfer from sulfides to quinones (Wei et al., 2020). Because of the reversibility of quinone reduction, these groups behave as a battery, accepting and storing electrons, and then releasing them by reducing neighboring contaminants. Using an electrochemical approach, Klüpfel et al. (2014) quantified the electron exchange capacity (EEC) in biochars attributable to such reactions and demonstrated their reversibility. The EEC increased with pyrolysis temperature from ∼0.15 mmol e-/gchar at 200 °C to 0.46-1.6 mmol e-/gchar at 400 °C, but then declined for higher pyrolysis temperatures up through 700 °C (Table 1), matching the pattern observed for quinoid content (Table 1) (Klüpfel et al., 2014). Biochars produced at 300-700 °C also exhibit a high prevalence of persistent free radicals, potentially including semiquinones, that increases with temperature initially (∼1019 spin/gchar at 550 °C) (G. Fang et al., 2014) before decreasing at higher temperatures (∼1017 spin/gchar) (Qin et al., 2017). Activated carbons, on the other hand, typically have lower quantities of oxygenated surface groups (Pignatello et al., 2017), which enhances sorption of halogenated organics by reducing the polarity of the surface.