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A Brief Background
Published in Nathan Keighley, Miraculous Medicines and the Chemistry of Drug Design, 2020
Organic reactions can be classified as either acid-base reactions or redox reactions. The transfer of a hydrogen ion (a proton) identifies an acid-base reaction, while a change in functional group from reactants to products shows reduction-oxidation reactions. Processes that involve homolytic bond cleavage are called radical reactions. Processes that involve heterolytic bond breaking are called polar reactions. Polar reactions are the most common type of reaction of organic molecules and involve reactions between polar molecules and/or ions. There are three main classes of polar reactions. An addition reaction involves the combining of two molecules to yield a single product, while in an elimination reaction, one reactant molecule is converted into two product molecules. In a substitution reaction, one functional group on the molecule is replaced by another.
Energy Sources in Urology
Published in Anthony R. Mundy, John M. Fitzpatrick, David E. Neal, Nicholas J. R. George, The Scientific Basis of Urology, 2010
ESWL is well described in the fragmentation of urinary calculi, but its effect on both benign and malignant tissue has also been studied. The effects of ESWL on in vitro and in vivo tumor cell lines (55–57), and in particular, whether enhancement of chemotherapeutic effect occurs on ESWL-treated tissue, have been the subject of much study (58, 59). ESWL has been shown to cause cellular damage regardless of the cell’s doubling time. The mitochondria are most sensitive to its effect (59), although damage also occurs at the cell membrane, within the nucleus, along the endoplasmic reticulum, and in other cell organelles (such as lysosomes). Cellular damage may be mechanical or because of the generation of free radicals (60, 61) caused by homolytic cleavage of the molecule within the collapsing bubble. Extracorporeal shock wave techniques have been described in the treatment of Peyronie’s plaques (62) although outcomes are mixed.
Antimicrobial mechanisms of selected preservatives and the bacterial response
Published in Philip A. Geis, Cosmetic Microbiology, 2006
The mechanisms that generate these radicals have not yet been determined. Several potential routes are the widespread disruption of metabolism resulting in reductant imbalances, inhibition of mechanisms that detoxify radicals, aberrant functioning of biocide-modified enzymes, and (for some biocides) the homolytic scission of disulfides. Other mechanisms are certainly possible, although classic redox cycling seems unlikely due to the structure and reactivity of the biocides.
3-Nitrotyrosine: a versatile oxidative stress biomarker for major neurodegenerative diseases
Published in International Journal of Neuroscience, 2020
Maria Bandookwala, Pinaki Sengupta
Indeed, ONOO– as well as ONOOH is extremely potent and facilitates rapid oxidation and nitrations. In the body, they get reduced by donating their .NO group to biomolecules like proteins, lipids, DNA in turn oxidizing them [100]. Among proteins, L-Tyr is the most vulnerable target of nitration. This so-called protein nitration process follows an indirect path. The super-reactive ONOO– reacts with CO2-forming peroxycarbonate (ONOOCO2–) radical. Further homolysis of ONOOCO2– results into 2° carbonate radical (CO3– .) and •NO2 that subsequently manoeuvers Tyr nitration (reactions 7 and 8) [100,101].
Regulation of cytochrome P450 enzyme activity and expression by nitric oxide in the context of inflammatory disease
Published in Drug Metabolism Reviews, 2020
Edward T. Morgan, Cene Skubic, Choon-myung Lee, Kaja Blagotinšek Cokan, Damjana Rozman
Peroxynitrite, the product of the reaction between NO and superoxide anion, can nitrate tyrosine residues on proteins, resulting in the formation of 3-nitrotyrosine. It is now thought that peroxynitrite is not the major cellular nitrating species (Radi 2004; Lancaster 2006). Rather, nitration occurs via oxidation of tyrosine to the tyrosyl radical which then combines with the nitrating radical species .NO2. .NO2 can be formed by the homolysis of peroxynitrite, oxidation of nitrite in the presence of H2O2 and metal ions, and by myeloperoxidase (Radi 2004; Lancaster 2006). Regardless of the mechanism, high concentrations of NO in cells result in protein nitration, although there is no consensus sequence for nitration (Abello et al. 2009). Nitration is a relatively stable modification (cf. nitrosation, below), although denitration mechanisms have been identified (Abello et al. 2009).
Comparative Analysis of Mesenchymal Stem Cells from Bone Marrow, Adipose Tissue, and Dental Pulp as Sources of Cell Therapy for Zone of Stasis Burns
Published in Journal of Investigative Surgery, 2019
Ozan Luay Abbas, Orhan Özatik, Zeynep Burçin Gönen, Serdal Öğüt, Fikriye Yasemin Özatik, Hasan Salkın, Ahmet Musmul
At the molecular level, the over-production of free radicals resulting from activation of neutrophils may have contributed to progressive tissue destruction in the zone-of-stasis.37 The underlying mechanisms include lipid peroxidation of cell membranes and disruption of nucleic acids and proteins. Although the number of infiltrating neutrophils in the ASC-treated group was significantly less than either the BMSC- and DPMSC- treated groups, oxidative stress levels were found to be the same. We think that this could be associated with the fact that the cause of oxidative stress is multifactorial. For example, it has been shown that thermal injury is capable of directly producing free radicals through homolytic bond fusion.4 Additionally, recent studies have focused on increased nitric oxide after the burn as a source of oxidative stress.38