Thiol Groups

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Journal of Applied Pharmaceutical Science

Journal of Applied Pharmaceutical Science

This work was focused on the evaluation of parameters of oxidative stress (lipid peroxidation, total thiol groups, non-protein thiol groups, polyphenols and ascorbate) and endothelial adaptation by determining the nitric oxide (NO), high-sensitive C-reactive protein (HS-CRP) and ischemia-modified albumin (IMA) of patients with chronic renal insufficiency submitted to hemodialysis. It was seen a depletion of glutathione, polyphenols and reduced ascorbate, combined with the increase of oxidized ascorbate and lipid peroxidation stress. In addition, was verified the increase of levels of IMA in the plasma. NO showed an evident endothelial protective role due to reduction of levels of HS-CRP, however, did not contribute to increase the levels of IMA. Based on the results, it can be concluded that the patients evaluated in this study presented a clinical situation of oxidative stress. A new study focusing on the prevention of oxidative stress using different experimental models with antioxidants is valuable to improve the life quality of these patients.

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Key words

Key words

Photodynamic therapy (PDT) is an approved, minimally invasive and highly selective therapeu- tic approach to a variety of tumors [1]. It is based on the accumulation of specific photosensitizers in tumor tissue, followed by irradiation with visible light. The hydrophobic photosensitizer tends to lo- calize in the plasma and intracellular membranes, making these structures especially sensitive to pho- tooxidative damage. It concentrates specifically within the malignant tissue. The photochemical in- teractions of the photosensitizer, light and molecu- lar oxygen produce singlet oxygen and other forms of active oxygen [2, 3]. They induce the disintegra- tion of cellular structures and modulation of ge- netic information [4]. Cell death in PDT may occur by apoptosis or by necrosis [5, 6]. The reactions of free radicals with lipids and proteins in membranes may cause alterations of membrane function [7]. During oxidative stress, we observed high levels of protein carbonyls, a reduction in the concentration of protein thiol groups, and high levels of lipid per- oxides [8]. Antioxidant enzyme activity increases considerably to eliminate the initial radicals and also the more toxic products of spontaneous free- radical reaction. Two of the main antioxidant en- zymes are superoxide dismutase (SOD) and heme oxygenase (HO-1). SOD can even partially prevent the photodestruction caused by PDT [9, 10].

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Plasmatic antioxidant capacity as a possible marker of phytodrugs efficacy

Plasmatic antioxidant capacity as a possible marker of phytodrugs efficacy

Isobolograms derived from microsomal thiol oxidation are shown in Figure 2. The mixture of both extracts provoked a synergic inhibitory effect on microsomal thiol oxidation (Figure 2). In biological systems, thiol groups are the main cellular antioxidants; they exert their cellular redox activity via different mechanisms, some of which are similar to those exerted by polyphenols (free radical trapping and metal chelating) and others different, such as the capacity to reverse thiol oxidation. Therefore, it is possible that more than one of the mechanisms mentioned could be responsible for the synergic effect observed.

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MELATONIN MODULATES MERCURY INDUCED OXIDATIVE STRESS IN RAT LIVER

MELATONIN MODULATES MERCURY INDUCED OXIDATIVE STRESS IN RAT LIVER

Vitamin C (ascorbic acid) scavenges ROS by quick electron transfer and thus inhibits lipid peroxidation as well as reduces the oxidized tocopheroxyl radicals. Thus, it protects membrane lipids from damage. [49] It is well ascertained that the non-enzymatic antioxidants such as vitamin C concomitantly decreased along with thiol groups in heavy metal toxicity in support of our data. [50,40,48]

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Thiol Disulfide Homeostasis in Patients with Panic Disorder

Thiol Disulfide Homeostasis in Patients with Panic Disorder

The thiol groups are the primary targets of the reactive oxygen species. Thiol is an organic compound containing sulfhydryl (-SH) group which has a critical role in preventing the occurrence of oxidative stress. Thiol groups are oxidized by reactive oxygen species and reversible disulfide bonds are formed. This is the earliest sign of protein oxidation [5] [6] [7]. The most of thiols in plasma are formed by albumin, and the remaining part of the thiols consists of low molecu- lar weighted thiols such as homocysteine, methionine, cysteine, cysteinyl glycine, glutathione, and γ -glutamylcysteine [8]. Thiol groups of proteins are oxidized by oxidant molecules and reversibly converted to disulfide bond structure. Disul- fide bond structure can be again reduced to the thiol group. Maintenance of the thiol-disulfide homeostasis is kept by conversion of disulfide bond structure to the thiol group. When the native thiol levels decrease, disulfide levels increase [9].

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Synthesis of Novel Hexathiolated Squalene and Its Thiol Ene Photopolymerization with  Unsaturated Monomers

Synthesis of Novel Hexathiolated Squalene and Its Thiol Ene Photopolymerization with Unsaturated Monomers

pends on the substitution in the double bond group. The higher the electron density in the double bonds the higher the reactivity. Figure 4 shows the kinetics curves ob- tained by RT-FTIR of the photopolymerization of the photocurable system SQ6SH/TAC. It was observed that this photocurable system was rather reactive, with the double bonds groups being consumed more rapidly and with higher conversion than the thiol groups. As in the step-growth polymerization, both thiol and ene com- pounds must be consumed at the same time, it is clear that two polymerization mechanisms are occurring con- currently: the thiol-ene photopolymerization and the radi- cal homopolymerization of TAC. On one hand, although it has been reported that allylic bonds can homopolymer- ize to some extent [21], in our case, monomer TAC po- lymerize readily achieving 42% conversion in the first 20 seconds and 75% after 120 seconds. On the other hand, low conversion of thiol group (25%) was produced in the same run as a result of the multifuncionality of SQ6SH. As usual, in thiol-ene photopolymerizations, if multi- functional enes and thiols are used, crosslinked polymers are obtained. The higher the multifunctionality, the higher the crosslink density in the produced polythioether. Lower

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Cyanidin 3 rutinoside attenuates methylglyoxal induced protein glycation and DNA damage via carbonyl trapping ability and scavenging reactive oxygen species

Cyanidin 3 rutinoside attenuates methylglyoxal induced protein glycation and DNA damage via carbonyl trapping ability and scavenging reactive oxygen species

Methods: C3R (0.125 – 1 mM) was incubated with bovine serum albumin and MG (1 mM) for 2 weeks. The formation of fluorescent AGEs was measured by using spectrofluorometer and thiol group content were used to detect protein oxidative damage. Gel electrophoresis was used to determine whether C3R (0.125 – 1 mM) reduced DNA strand breakage in a glycation model comprising lysine, MG and/or Cu 2+ . The generation of superoxide anions and hydroxyl radicals were detected by the cytochrome c reduction assay and the thiobarbituric acid reactive substances assay. MG-trapping capacity was assessed by high performance liquid chromatography (HPLC). Results: C3R (0.25 – 1 mM) reduced the formation of fluorescent AGEs and depleted protein thiol groups in bovine serum albumin mediated by MG. At 1 mM C3R inhibited oxidative DNA damage in the glycation model (p < 0.05) and at 0.5 – 1 mM prevented Cu 2+ induced DNA strand breakage in the presence of lysine and MG. The findings showed that C3R reduced the formation of superoxide anion and hydroxyl radicals during the glycation reaction of MG with lysine. C3R directly trapped MG in a concentration and time dependent manner (both p < 0.001).

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Preparation and characterization of alkyl thiols monolayer on glass 
		substrates by
		
		microcontact printing

Preparation and characterization of alkyl thiols monolayer on glass substrates by microcontact printing

Surface modification is a fascinating method to tailor the surface of material properties such as hydrophilicity, roughness, surface charge and many more. The modification is not only limited to solid materials, but could be possibly extended to particular liquid surfaces. In this paper, surface modification of glass slides with self-assembled monolayers (SAMs) of (3-Mercaptopropyl) trimethoxysilane (MPTMS) was conducted by using a simple method of microcontact printing. Characterizations of the self-assembled monolayer were realized by 3 techniques; (1) Atomic Force Microscopy (AFM) to determine the height of self-assembled monolayer and obtain the topography image, (2) X-ray Photoelectron Spectroscopy (XPS) to further confirm the thiol groups were grafted on the surface and (3) Confocal Fluorescence Microscopy (CFM) to visualize the reaction between thiol terminal groups and fluorescent probe. From the experiment conducted, the result showed that the MPTMS was successfully stamped on glass substrates. AFM scanning images displayed the 0.8±0.2nm height of MPTMS, which matching the size of the MPTS molecules (0.7±0.05nm). XPS spectra indicated the appearance of the doublet structure in the S 2p region (S 2p3/2 and S 2p1/2 levels of the S energy levels) with two

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Graphene Oxide Polymer Composite Langmuir Films Constructed by Interfacial Thiol Ene Photopolymerization

Graphene Oxide Polymer Composite Langmuir Films Constructed by Interfacial Thiol Ene Photopolymerization

ized carbon bonds such as hydroxyl and/or epoxide bonds [51, 52]. It was reported that the D/G peak inten- sity ratio could be used as a measurement of the sp 2 do- main size of graphene sheets containing sp 3 and sp 2 bonds due to the origination of G and D bands [53, 54]. For the present system in Fig. 5b, the D/G ratio shifted from 1.09 for LB films from water surface to 1.18 for LB films from DA subphase by in situ thiol-ene photopoly- merization. The obvious change confirmed the success- ful photopolymerization reaction of polymeric DA molecules with thiol groups linked to GO sheet in the Langmuir films. In addition, the analysis of measured Raman spectra for the prepared GO-SH powder (Add- itional file 1: Figure S2) shows the calculated D/G ratio value of 1.05 in comparison with 0.91 and 0.92 for GO and GO–COOH materials.

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 Chitosans Versus Thiolated Chitosans As Polymers In Mucoadhesive Drug Delivery - A Comparitive Study

 Chitosans Versus Thiolated Chitosans As Polymers In Mucoadhesive Drug Delivery - A Comparitive Study

The improved mucoadhesive properties of thiolated chitosans are explained by the formation of covalent bonds between thiol groups of the polymer and cysteine rich sub domains of glycoprotein in the mucus layer. These covalent bonds are supposedly stronger than noncovalent bonds such as ionic interactions of chitosan with anionic substructures of the mucus layer. It was found that there is a positive correlation between the degree of modification with thiol bearing polymers polymers and their adhesive properties 1 . Permeation enhancing effect

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Lower Thiol, Glutathione, and Glutathione Peroxidase Levels in Prostate Cancer: A Meta- Analysis Study

Lower Thiol, Glutathione, and Glutathione Peroxidase Levels in Prostate Cancer: A Meta- Analysis Study

The first major finding of this meta-analysis is that PCa is characterized by lowered levels of -SH groups, GSH and GPx as compared with HC, while there were no significant differences in GR and GST, suggesting that antioxidant defenses are lowered in PCa patients and, thus, may play a role in the pathophysiology of PCa. Thiol groups have essential functions in ROS detoxification, regulation of enzymes, and cellular mechanisms, especially apoptotic signaling and, therefore, decreased -SH levels cause impaired antioxidant defense mechanism and may result in tissue damage 17,38 . Among non-protein thiols, GSH plays a key role in maintaining intracellular antioxidant defenses by scavenging ROS and regenerating other antioxidant molecules. In the cytoplasm, reduced GSH may dissociate hydrogen peroxides (H 2 O 2 ) resulting in increased oxidized GSH (GSSG) which, subsequently, may be recycled to

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Structure and interactions in α crystallin probed through thiol group reactivity

Structure and interactions in α crystallin probed through thiol group reactivity

-Crystallin is the major structural protein of eye lens of vertebrates. In human lens, the ratio of A- crystallin to B-crystallin was found to be 3:1. A- Crystallin contains two cysteine residues at positions 131 and 142, which are at the junction between the -crystallin domain and the C-terminal tail. We used the accessibility of the thiol groups by Ellman’s re- agent (DTNB) as a tool to gain information about the various structural perturbations of hinge region of -crystallin and during the binding with substrates. In the native condition, the cys-142 though reacted quite fast was not fully exposed. Several reagents were used to see the accessibility of cys-131. Rate constant for cys-131 was increased gradually with increase in the concentration of reagents. The bind- ings of substrates are affected by the accessibility of thiol indicating that the substrates bind to the hinge region of -crystallin. By blocking of cys-142, it was observed that the accessibility of one thiol depends on the other thiol, and they are not independent. The hinge region of -crystallin is very important as sub- strate binding site and from this study we have got various structural information about that region.

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Dynamic Thiol Disulphide Homeostasis in Patients with Multiple Sclerosis

Dynamic Thiol Disulphide Homeostasis in Patients with Multiple Sclerosis

Thiols contain functional sulfhydryl group (-SH) which is consist of hydrogen and sulfur atom bound to a carbon atom [16]. Plasma thiol pool consists of albumin, protein, cysteine, homocysteine, glutathione, γ -glutam- ylcysteine and cysteinylglycine [17]. When oxidative stress is increased, thiol groups of proteins get into oxidant reactions through oxidants and turn into disulphide bonds. Formed disulphide bonds can be reduced to thiol groups. In this way, dynamic thiol-disulphide homeostasis is maintained [18]. This balance has an important role in antioxidant defense, detoxification, apoptosis, signal transduction, regulation of enzymatic activity, transcrip- tion and intracellular signaling mechanisms [19] [20].

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Total Thiols: Biomedical Importance And Their Alteration In Various Disorders

Total Thiols: Biomedical Importance And Their Alteration In Various Disorders

Under conditions of moderate oxidative stress, oxida- tion of Cys residues can lead to the reversible forma- tion of mixed disulfides between protein thiol groups and low–molecular-mass thiols (S-thiolation), particu- larly with GSH (S-glutathionylation). Protein S-gluta- thionylation can directly alter or regulate protein func- tion (redox regulation) and may also have a role in protection from irreversible (terminal) oxidation. S- glutathiolation of protein cysteine residues protects against higher oxidation states of the protein thiol, thereby preserving the reversibility of this type of modification. Second, reduced protein thiols can be re- generated from their S-glutathiolated forms enzymatic- ally through the action of protein disulfide isomerase, mitochondrial glutaredoxin, or thioredoxin. Protein S- glutathiolation has also been implicated in the control of ubiquitination, the binding of transcription factor c- Jun to DNA, and sarcoplasmic Ca 2- -ATPase activity. 39

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Effect of Atrazine on Glutathione Levels, Glutathione S-Transferase and Glutathione Reductase Activities in Pea and Wheat Plants

Effect of Atrazine on Glutathione Levels, Glutathione S-Transferase and Glutathione Reductase Activities in Pea and Wheat Plants

(Figure 1A). Similarly, atrazine increased the con- tent of oxidised glutathione (Figure 1C). On the last day of the stress programme, the GSSG/TG ratio in younger leaves of treated plants was lower than that in the control plants (data not shown). The opposite tendency was found with older leaves, where the GSSG/TG ratio was higher in the control plants. The herbicide treatment did not provoke significant changes in the activity of GST in pea plants (Figure 2A). GR activity (Figure 2C) gradually increased in the treated plants, and the effect was more pronounced in the upper leaf nodes. The absolute values of glu- tathione levels and enzyme activities during the period studied decreased in both experimental groups, which were better expressed by older leaves (2 nd ).

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Chemical modification of Bombyx mori silk fibers with vinyl groups for thiol-ene click chemistry

Chemical modification of Bombyx mori silk fibers with vinyl groups for thiol-ene click chemistry

To attach thiol-containing molecules to the MOI-modi- fied SF fibers, each sample was contacted with 0.5 ml of a neat PFDT liquid. A quartz coverslip (0.5 mm thickness, Ted Pella) was placed on the sample to ensure homoge- neous coverage of the organic liquid across the sample surface and was illuminated with a 40 W light-emitting diode (LED) UV lamp (UVSP1-A, ShenZhen YuXi- anDe Science and Technology Ltd., China) with 365 nm wavelength. Each sample was placed 20  mm below the LED UV lamp. Samples were then sonicated in ethanol to remove nonspecifically adsorbed PFDT molecules, rinsed with ultrapure water, and dried under a stream of nitrogen prior to analysis.

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Abnormal redox status of membrane protein thiols in sickle erythrocytes

Abnormal redox status of membrane protein thiols in sickle erythrocytes

Although sickle erythrocytes (RBC) undergo excessive autooxidation, investigators have not found evidence for abnormal oxidation of protein thiols in sickle RBC membranes (e.g., protein aggregates linked by intermolecular disulfide bonds). However, the conventional techniques heretofore used cannot detect more subtle changes in thiol status such as abnormal intramolecular disulfide bonds. We examined RBC membranes using thiol- disulfide exchange chromatography which partitions sodium dodecyl sulfate-solubilized proteins on the basis of reactive thiols, yielding gel-bound (reduced-thiol) and filtrate (oxidized/blocked-thiol) fractions. Membranes from normal RBC partition so that only 13.6 +/- 1.4% of all membrane protein is found in the filtrate fraction. An abnormally increased amount of membrane protein from sickle RBC (21.5 +/- 4.3%) partitions into the filtrate fraction (P less than 0.001). Since sickle RBC do not have high molecular weight

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Metallothioneins, Caspase-3 and Oxidative Stress Responses in the Multi-Marker Study of Freshwater Mussel Inhabiting Sites of Various Human Impact

Metallothioneins, Caspase-3 and Oxidative Stress Responses in the Multi-Marker Study of Freshwater Mussel Inhabiting Sites of Various Human Impact

At site F, the studied indices reflect the sustainable environmental quality. The level of GSH and RI GSH was rather high and caspase-3 activity lower compared between the three groups. Elevated MT-Cd concentration in summer did not contradict this conclusion, because the effective ability to accumulate Cd from the surroundings could attest to the adequacy of the MTs functioning. Besides that, the ratio of Cd in the composition of MTs was very low. The elevated level of Cd in the mussels and their MTs in this area was shown previously, despite other markers characterizing this area as a reference site (Falfushynska et al., 2009). MTs are able to accumulate metals from the environment with particular sensitivity for Cd (Hamza-Chaffai et al., 2000; Amiard et al., 2006). MTs usually bind about 80-90% of Cd in the cells, for example in freshwater bivalves Pyganodongrandis living along a Cd concentration gradient (Giguère et al., 2003). In comparison, at site A in autumn, mussels accumulated

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Dynamic Thiol/Disulphide Homeostasis in Patients with Vaginitis

Dynamic Thiol/Disulphide Homeostasis in Patients with Vaginitis

The present study explored whether the systemic thiol/disulphide balance was different in women with vaginitis compared to women without vaginitis. To our knowledge, this is the first study to assess the relationship between vaginitis and thiol metabolism. Herein it was demonstrated that there was an increase in disulphide levels indicative of oxidative stress in the systemic circulation system of women with vaginitis, a local infection. Again, the disulphide rate in the group with vaginitis was determined to be higher when compared with the control group. The native thiol/total thiol ratios, on the other hand, proved to be higher in the control group.

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Thermal Stability of alpha-Lactalbumin

Thermal Stability of alpha-Lactalbumin

explain the general trend of increasing solubility. First, the net negative protein surface charge increases slightly from –4 to –6 (approximately) when the pH is increased from pH 6 to 7 (Robbins, Andreott, Holmes & Kronman, 1967). This would result in increased intermolecular electrostatic repulsion that would prevent close approach required for hydrophobic interactions and thiol-disulfide interchange. The intramolecular repulsion would drive more complete unfolding with the major restriction being the 4 disulfide bonds that cause α-La to retain its compact structure even under denaturing conditions (Dolgikh et al., 1985). As the pH approaches the thiol pKa (~8.0-8.5 in proteins (Creighton, 1993), the thiol/disulfide reactions would increase in rate. Disulfide bond reduction is critical to molecular unfolding that would disrupt the native hydrophobic clusters and diminish their role in the development of large, insoluble protein aggregates.

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