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The Modification of Cysteine
Published in Roger L. Lundblad, Chemical Reagents for Protein Modification, 2020
The reaction of chloroacetic acid and chloroacetamide with papain has also yielded interesting results.11,12 In studies with chloroacetamide, the active-site sulfhydryl group of papain reacts at a rate more than tenfold faster than free cysteine (5.78 M−1 s−1 vs. 0.429 M−1 s−1).11 As was the situation with streptococcal proteinase, there are dramatic differences in the rate of reaction of papain with chloroacetic acid and chloroacetamide. The reaction with chloroacetic acid has a pH optimum of approximately 7 while the optimum for reaction with chloroacetamide is at a pH greater than 9. A comparison of the effect of pH on the reaction of papain with chloroacetic acid and chloroacetamide is shown in Figure 6. This investigation notes the influence of the neighboring histidyl residue as has been discussed for streptococcal proteinase. These data further emphasize the importance of neighboring functional group effects on cysteinyl reactivity in proteins as well as the importance of rigorous evaluation of the effect of pH on the rate of the modification reaction.
Nasal Cavity Carcinogens: Possible Routes of Metabolic Activation
Published in D. V. M. Gerd Reznik, Sherman F. Stinson, Nasal Tumors in Animals and Man, 2017
Stephen S. Hecht, Andre Castonguay, Dietrich Hoffmann
Vinyl chloride (1), (Figure 13), is metabolized by microsomal mixed-function oxidases to chloroethylene oxide (2) which rearranges to chloroacetaldehyde (3). The latter can be oxidized to chloroacetic acid (4). Chloroethylene oxide, chloroacetaldehyde, and chloroacetic acid react directly with glutathione or enzymatically via glutathione S-transferase to form S-formylmethyl glutathione (5) or S-carboxymethylglutathione (6), respectively. Urinary excretion products include N-acetyl-S-(2-hydroxyethyl)cysteine (10), S-(carboxyme-thyl)cysteine (9), and thiodiglycolic acid (H).200-203
Chemical hazards *
Published in Jamie Bartram, Rachel Baum, Peter A. Coclanis, David M. Gute, David Kay, Stéphanie McFadyen, Katherine Pond, William Robertson, Michael J. Rouse, Routledge Handbook of Water and Health, 2015
Lisa Smeester, Andrew E. Yosim, Rebecca C. Fry
Because chlorine is the most cost-effective and widely used disinfectant, it is not surprising that its THM by-products bromodichloromethane, bromoform, chloroform and dibromochloromethane are the most commonly monitored in drinking water. While the WHO does not address an overall guideline value, regulatory limits for total THMs have been set by the US EPA (80 ug/L), the European Union and Canada (100 ug/L) (WHO, 2005b). The WHO guidelines levels for each of the THM by-products can be found in Table 10.1. HAAs are the second most common group of DBPs formed after disinfection with chlorine (Hua and Reckhow, 2007). The US EPA currently regulates five HAAs (known as the HAA5) at a limit of 0.06 mg/L, measured as the sum of the concentrations of five monitored HAA species: chloroacetic acid, dichloroacetic acid, trichloroacetic acid, bromoacetic acid and dibromoacetic acid. Many municipal bodies are switching to chloramine as a chlorine alternative, as chloramination produces lower concentrations of THMs compared to chlorination. However, chloramine is associated with increased formation of nitrogenated and iodinated DBPs (Richardson and Postigo, 2012).
Anti-breast cancer sinomenine derivatives via mechanisms of apoptosis induction and metastasis reduction
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2022
Xiang Gao, Baojia Sun, Yonglian Hou, Lilin Liu, Jianan Sun, Fanxing Xu, Dahong Li, Huiming Hua
The synthetic process for compounds 1–4, 5A–F, 6A–F(a–c) and 7A–F(a–c) were summarised in Scheme 1. Thiophenol was acidified to 2-phenylsulfanylacetic acid via chloroacetic acid at a high level of heat. Two steps of oxidation subsequently carried out by hydrogen peroxide and fuming nitric acid in room temperature and ice water respectively afforded 1,2,5-oxadiazole with two (phenylsulfonyl)acetic acid fusing together. One phenylsulfonyl group of compound 4 was replaced by a corresponding diol in the alkaline environment under an ice bath for a simple one-step reaction. Intermediary compounds were further extended through the esterification of the corresponding anhydride linked to the hydroxy group in the presence of TEA and DMAP. Target compounds were synthesised by binding sinomenine with intermediary acids 6A–F(a–c) at room temperature. The structures of target hybrids were confirmed by 1H NMR, 13 C NMR and HR-MS.
Expression of estrogen receptor alpha in response to stress and estrogen antagonist tamoxifen in the shell gland of Gallus gallus domesticus: involvement of anti-oxidant system and estrogen
Published in Stress, 2021
Mukesh Kumar Niranjan, Raj Kumar Koiri, Rashmi Srivastava
Glutathione peroxidase (GPx) assay: 10 µl of tissue supernatant was added in the reaction mixture containing 30 mM of potassium phosphate buffer, 10 mM of sodium azide, 4 mM reduced glutathione, 2.5 mM of H2O2, and 6 ml of triple distilled water. The reaction mixture was incubated at 37 °C for 3 min. After incubation 0.5 ml of 10% (w/v) tri-chloroacetic acid (TCA) was added for protein precipitation. Then the reaction mixture was centrifuged at 3000 rpm for 5 min at room temperature. After centrifugation, pellet was discarded and 1 ml of 0.3 M di-potassium hydrogen phosphate was added in 1 ml of supernatant. About 1 ml of Elman’s reagent was added in the reaction mixture, mixed well, and kept for 3 min. Then absorbance was taken at 412 nm by spectrophotometer (Rotruck et al., 1973).
Synthesis and biological evaluation of benzothiazin-4-ones: a possible new class of acetylcholinesterase inhibitors
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2019
Gabriele A. Berwaldt, Daniela P. Gouvêa, Daniel S. da Silva, Adriana M. das Neves, Mayara S. P. Soares, Juliana H. Azambuja, Geonir M. Siqueira, Roselia M. Spanevello, Wilson Cunico
Benzothiazinones derivatives have attracted continuing interest over the years because of their diverse biological activities12. A literature survey reveals that several benzothiazin-4-ones have been prepared based on different synthetic routes: a) from classic primary amine, aldehyde or ketone and thiosalicylic acid as reported by Zarghi et al.17 using p-toluenesulfonic acid catalyst in toluene reflux or as reported by Kamel et al.20 using sodium sulfate in dioxane or as reported by Kitsiou et al.21 and Silverberg et al.11 using propylphosphonic acid anhydride (T3P) as catalyst; b) from 2-aminothiophenol and chloroacetic acid as reported by Shaikh et al.16; c) from aromatic carboxylic acid with ammonium isothiocyanate as reported by Peng et al.22