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The Modification of Cystine — Cleavage of Disulfide Bonds
Published in Roger L. Lundblad, Chemical Reagents for Protein Modification, 2020
There are several approaches to the cleavage of disulfide bonds in proteins. The majority of studies involve the cleavage of the disulfide bond of cystine to the free thiol group of cysteine by reduction. Reduction has been generally accomplished with a mild reducing agent such as β-mercaptoethanol or cysteine. Gorin and co-workers1 have examined the rate of reaction of lysozyme with various thiols. At pH 10.0 (0.025 M borate), the relative rates of reaction were β-mercaptoethanol (2-mercaptoethanol), 0.2; dithiothreitol, 1.0; 3-mercaptopropionate, 0.4; and 2-aminoethanol, 0.01. The results with aminoethanethiol were somewhat surprising since the reaction (disulfide exchange) involves the thiolate anion and 2-aminoethanethiol would be more extensively ionized than the other mercaptans. Dithiothreitol has been a useful reagent in the reduction of disulfide bonds in proteins2 as introduced by Cleland. Dithiothreitol and the isomeric form, dithioerythritol, are each capable of the quantitative reduction of disulfide bonds in proteins. Furthermore, the oxidized form of dithiothreitol has an absorbance maximum at 283 nm (Δϵ = 273) which can be used to determine the extent of disulfide bond cleavage.2 The UV spectra of dithiothreitol and oxidized dithiothreitol are shown in Figure 1. Insolubilized dihydrolipoic acid has also been proposed for use in the quantitative reduction of disulfide bonds.4
Incapacitating Agents and Technologies: A Review *
Published in Brian J. Lukey, James A. Romano, Salem Harry, Chemical Warfare Agents, 2019
Contamination of persons with malodorous substances, such as mercaptans and amines, has been proposed as a means to deter less motivated rioters based on psychological and physiological effects such as olfactory repulsion and nausea (Whitten et al., 1970). They can be delivered by a frangible missile, and the addition of a thickening agent will prolong adhesiveness.
The Human Nail: Structure, Properties, Therapy and Grooming
Published in Heather A.E. Benson, Michael S. Roberts, Vânia Rodrigues Leite-Silva, Kenneth A. Walters, Cosmetic Formulation, 2019
Kenneth A. Walters, Majella E. Lane
Using human nail samples in a Franz cell setup, Malhotra and Zatz (2002b) screened a range of molecules with known ability to interact with keratin. The compounds studied included mercaptans (N-[2-mercaptopropionyl] glycine, zinc and sodium pyrithone, 8-mercaptomenthone, meso-2,3-dimercapto succinic acid), sodium metabisulphite, keratolytic agents (salicylic acid, urea, guanidine hydrochloride). Gels were prepared containing enhancers either alone, or in combination with each other, in a vehicle that was aqueous, hydroalcoholic or one containing dimethyl sulphoxide (DMSO). The results indicated that the chemical structure of the modifier is most important in determining its ability to enhance penetration. The best enhancement effect was obtained using N-(2-mercaptopropionyl) glycine in combination with urea. Mercaptan compounds contain sulphydryl groups (SH), and the primary mechanism for their enhancement of nail penetration is therefore reduction of disulphide linkages in the nail keratin matrix. Generally, the barrier integrity of nails was compromised irreversibly after treatment with effective chemical modifiers.
Protective mechanism of a novel aminothiol compound on radiation-induced intestinal injury
Published in International Journal of Radiation Biology, 2023
Xinxin Wang, Renbin Yuan, Longfei Miao, Xuejiao Li, Yuying Guo, Hongqi Tian
Although several research groups have found a variety of radiation protective agents, they are still in the early stages of development (Fischer et al. 2018). Amifostine is the first radiation protective agent approved by FDA for reducing the incidence of moderate to severe xerostomia in patients undergoing postoperative radiation treatment for head and neck cancer (Gula et al. 2013). However, its disadvantages, such as high toxicity and its short half-life, limit its clinical application (Korst et al. 1997). Our research group recently designed and synthesized a radiation protective agent known as compound 8, which is effective at protecting from radiation damages. In this study, the efficacies of the new amino-mercaptan compounds were evaluated, and the related mechanisms were studied. The results showed that the new small molecule amino-mercaptan compounds have a low initial dose and high safety.
Evaluation of thiol/disulfide homeostasis in patients with pityriasis rosea
Published in Cutaneous and Ocular Toxicology, 2019
Thiols are mercaptans containing sulfhydryl residues. Thiols are important reducing agents in the biological system and are mostly found in cysteine and cysteine-derived proteins3,5. Dynamic thiol-disulfide homeostasis has a critical role in antioxidant protection, detoxification, signal transduction, apoptosis, enzymatic activation, and regulation of cellular signaling mechanisms. It has been shown that abnormal thiol-disulfide homeostasis is involved in the pathogenesis of a wide range of diseases and conditions, including diabetes, cardiovascular diseases, cancer, rheumatoid arthritis, chronic kidney disease, acquired immunodeficiency syndrome, Parkinson’s disease, Alzheimer’s disease, Friedreich ataxia, multiple sclerosis, and amyotrophic lateral sclerosis6.
A novel biomarker explaining the role of oxidative stress in exercise and l -tyrosine supplementation: thiol/disulphide homeostasis
Published in Archives of Physiology and Biochemistry, 2018
Yildirim Kayacan, Hayrullah Yazar, Emin Can Kisa, Babak Elmi Ghojebeigloo
The thiols are organic compounds sometimes referred to as mercaptans. They are in the group of sulphydryls, formed when sulphur and oxygen are added to carbon atoms (Babademez et al. 2017). They possess versatile functions that play an important role in the defence against oxidants (Sen et al. 2000). Thiols can undergo an oxidation reaction via oxidants, causing them to form disulphide (Isik et al. 2017). When oxidative stress increases, oxidation of cysteine residues can lead to the formation of mixed disulphides of molecular weights between thiols and protein thiol groups. This formation is reversible, however. Disulphide bonds can also be reduced in thiol groups, thereby maintaining thiol/disulphide homeostasis (Guney et al. 2016). Homeostasis of dynamic thiol/disulphide plays an important part in cell signal mechanisms, transcription factors, regulation of enzymatic activations, apoptosis and signal transduction, antioxidant protection, and detoxification (Kemp et al. 2008, König et al. 2012).