Site-specific Hydroxyl Research Articles

A novel double kink-turn module in euryarchaeal RNase P RNAs.

RNase P is primarily responsible for the 5΄ maturation of transfer RNAs (tRNAs) in all domains of life. Archaeal RNase P is a ribonucleoprotein made up of one catalytic RNA and five protein cofactors including L7Ae, which is known to bind the kink-turn (K-turn), an RNA structural element that causes axial bending. However, the number and location of K-turns in archaeal RNase P RNAs (RPRs) are unclear. As part of an integrated approach, we used native mass spectrometry to assess the number of L7Ae copies that bound the RPR and site-specific hydroxyl radical-mediated footprinting to localize the K-turns. Mutagenesis of each of the putative K-turns singly or in combination decreased the number of bound L7Ae copies, and either eliminated or changed the L7Ae footprint on the mutant RPRs. In addition, our results support an unprecedented ‘double K-turn’ module in type A and type M archaeal RPR variants.

Antioxidative potential of Chenopodium botrys L. (Amaranthaceae)

Evaluation of the antioxidant potential of methanol extract of Chenopodium botrys L. (Amaranthaceae) collected from six different locations in Republic of Macedonia was performed. Several methods were used for testing the antioxidative activity: 1) 2,2-diphenyl1-picrylhydrazyl (DPPH) radical scavenging assay, 2) ferric reduction power assay (FRAP), 3) inhibition of H2 O2 activity, 4) non-sitespecific hydroxyl radical-catalyzed 2-deoxy-D-ribose degradation (NSSOH) and 5) site-specific hydroxyl radical-catalyzed 2-deoxy-D-ribose degradation (SSOH). The IC50 values ranged from 0.26-3.10 mg/mL, 3.01-12.71 mg/mL and 2.60-12.29 mg/mL, for DPPH, NSSOH and SSOH assays, respectively. The H2 O2 inhibition activity and the ferric reducing power capacity were from 28.84-46.56% and 26.14- 43.40%, respectively. The obtained data establish the antioxidant potency in concentration-dependent manner. Additionally, total phenols (TPC) and total flavonoid content (TFC) were determined. The estimated values ranged from 27.77-71.25 mg GAE/g DW and from 7.35- 16.33 mg QE/g DW, respectively

The L7Ae protein binds to two kink-turns in the Pyrococcus furiosus RNase P RNA.

The RNA-binding protein L7Ae, known for its role in translation (as part of ribosomes) and RNA modification (as part of sn/oRNPs), has also been identified as a subunit of archaeal RNase P, a ribonucleoprotein complex that employs an RNA catalyst for the Mg2+-dependent 5′ maturation of tRNAs. To better understand the assembly and catalysis of archaeal RNase P, we used a site-specific hydroxyl radical-mediated footprinting strategy to pinpoint the binding sites of Pyrococcus furiosus (Pfu) L7Ae on its cognate RNase P RNA (RPR). L7Ae derivatives with single-Cys substitutions at residues in the predicted RNA-binding interface (K42C/C71V, R46C/C71V, V95C/C71V) were modified with an iron complex of EDTA-2-aminoethyl 2-pyridyl disulfide. Upon addition of hydrogen peroxide and ascorbate, these L7Ae-tethered nucleases were expected to cleave the RPR at nucleotides proximal to the EDTA-Fe–modified residues. Indeed, footprinting experiments with an enzyme assembled with the Pfu RPR and five protein cofactors (POP5, RPP21, RPP29, RPP30 and L7Ae–EDTA-Fe) revealed specific RNA cleavages, localizing the binding sites of L7Ae to the RPR's catalytic and specificity domains. These results support the presence of two kink-turns, the structural motifs recognized by L7Ae, in distinct functional domains of the RPR and suggest testable mechanisms by which L7Ae contributes to RNase P catalysis.

Effect of Ultrasonic Degradation on In Vitro Antioxidant Activity of Polysaccharides from Porphyra yezoensis (Rhodophyta)

This article aims to study the effect of ultrasonic degradation on antioxidant activity of polysaccharides from Porphyra yezoensis (Rhodophyta) (PSPY), and to look for the relationship between molecular structure of fractions (F1, F2, and F3) from ultrasonic-degraded PSPY (UDPSPY) and their activities of scavenging hydroxyl and superoxide anion radicals, chelating ability of iron ion and reducing power. Results of antioxidant assays indicated that the UDPSPY had higher antioxidant activity of scavenging superoxide anion radical and hydroxyl radical than that of the PSPY. As antioxidant activities of the fractions are concerned, this result might suggest that decreasing molecular weight and increasing sulfate group content in the molecule were vital and necessary factors for improving antioxidant activity of PSPY. Decrease of molecular weight was the dominant reason for increasing activities of scavenging non-site and site specific hydroxyl radical and reducing power of F1, F2, and F3, and increase of sulfate group content in the molecule was the dominant reason for increasing activities of scavenging superoxide anion radical and chelating ferrous ions of F1, F2, and F3. It was possible that ultrasonic treatment could be a new and effective method for enhancing PSPY's antioxidant activity.

Antioxidant activity of aqueous extract of a Tolypocladium sp . fungus isolated from wild Cordyceps sinensis

Tolypocladium sp. Ts-1 was isolated from the fruiting body of a wild Cordyceps sinensis, one of the best known traditional Chinese medicine and health foods. The antioxidant activities of hot-water extracts from cultured mycelia of Tolypocladium sp. were assessed in different in vitro systems. The extracts showed superoxide dismutase (SOD) activity of 35.6 U/mg protein and are effective in scavenging superoxide radical in a concentration dependent fashion with IC50 value of 1.3 mg/mL. As a reinforcement of the action, similar radical scavenging effects of the extracts were also discerned with both site-specific and non site-specific hydroxyl radical using the deoxyribose assay method. 1,1-Diphenyl-2-picrylhydracyl (DPPH) radical scavenging activities of the extracts reached more than 75.2% at the concentrations of 3-6 mg/mL. The extracts showed moderate reducing power and ferrous ion chelating activity. Moreover, the protective effects of the extracts against hydrogen peroxide (H2O2)-induced lesion to rat PC12 cell (pheochromocytoma cell line) was observed in a dose-dependent manner from 0.25 to 2.0 mg/mL. Our results suggest that the aqueous extract of Tolypocladium sp. mycelium has strong antioxidant activities and is a potential source of natural antioxidant products. This is the first report on antioxidant activity of Tolypocladium fungus isolated from wild C. sinensis, an endangered species. Key words: Aqueous extracts, antioxidant activity, free radicals, PC12 cells,Tolypocladium sp.

Evaluation of Antioxidant Activity of Some Common Mosses

The antioxidant activity of ethanol extracts of Atrichum undulatum, Polytrichum formosum (Polytrichaceae), Pleurozium schreberi (Entodontaceae) and Thuidium tamariscinum (Thuidiaceae) was evaluated by an electrochemical method (cyclic voltammetry) and standard photometric methods: Fe(III) to Fe(II) reducing power, nitric oxide scavenging (NO) assay and simulation of Fenton-type reaction by nonsite-specific (NSSOH) and site-specific (SSOH) hydroxyl radical-mediated 2-deoxy-D-ribose degradation inhibition. The total content of phenols was determined by the Folin-Ciocalteau reagent. All tested species showed antioxidant effects lower than the positive control, caffeic acid. The extracts of A. undulatum and P. formosum contained the highest content of phenols and were the most effective in Fe(III) to Fe(II) reducing power, cyclic voltammetry and SSOH assay. By contrast, only the extract of Pl. schreberi showed activity in the NSSOH assay. A. undulatum and T. tamariscinum extracts were the most active in the NO assay. The results suggest that the extracts of A. undulatum and P. formosum possess stronger antioxidant activity than those of Pl. scheberi and T. tamariscinum, but they affect the Fenton-type reaction mainly by iron chelation.

Antioxidant and free radical scavenging potential of Achillea santolina extracts

The antioxidative activities of hydroalcoholic extract of Achillea santolina were investigated employing various established in vitro systems including total antioxidant activity in linoleic acid emulsion system, 1,1-diphenyl-2-picrylhydrazyl (DPPH), superoxide and hydroxyl radicals scavenging, reducing power, and inhibitory effect on protein oxidation as well as the inhibition of Fe 2+/ascorbate induced lipid peroxidation in rat liver homogenate. Total phenolic and flavonoid content of A. santolina extract (ASE) was also determined by a colorimetric method. The results revealed that ASE has notable inhibitory activity on peroxides formation in linoleic acid emulsion system along with concentration-dependent quenching of DPPH and superoxide radicals. Furthermore, the extract showed both nonsite-specific (Fe 2+ + H 2O 2 + EDTA) and site-specific (Fe 2+ + H 2O 2) hydroxyl radical scavenging suggesting potent hydroxyl radical scavenging and chelating ability for iron ions in deoxyribose degradation model. A linear correlation between ASE and the reducing power was also observed ( r 2 = 0.9981). ASE prevents thiobarbituric acid reactive substances formation in Fe 2+/ascorbate induced lipid peroxidation in rat liver tissue in a dose-dependent manner. Moreover, free radical induced protein oxidation was suppressed significantly by the addition of ASE over a range of concentration. These results clearly demonstrated that A. santolina extract possess a marked antioxidant activity.

Studies on antioxidant potential of methanol extract/fractions of Acacia auriculiformis A. Cunn

Antioxidant activities of the methanol extract/fractions of Acacia auriculiformis A. Cunn were evaluated by three in vitro experiments, namely, DPPH, relative reducing power and hydroxyl radical (site specific and non site specific) assays. The differential activities of methanol extract/fractions could be correlated with their respective total phenolic contents and compared with standards (BHT and l-ascorbic acid.). The bark powder of the plant was extracted with different solvents of increasing and decreasing polarity by a maceration extraction method and then the methanol extract was further partitioned with ethyl acetate and water. The scavenging activity of extract was found to be enhanced on fractionating the extract. Moreover, among the two fractions (ethyl acetate and water fraction) and the crude extract, the water fraction exhibited good scavenging responses of 72.0%, (57.2%), 1.76 (1.52), 88.0% (82.6%) and 93.6% (83.47) in DPPH, reducing power, site specific and non-site specific hydroxyl radical scavenging assay in increasing and (decreasing) order of solvent polarity at maximum concentration, respectively. Studies are in progress to evaluate the effect of extracts/fractions in other antioxidant assays and to identify the factors responsible for the activity.

Chemical Composition and in Vitro Antioxidant Evaluation of Commercial Water-Soluble Willow Herb (Epilobium angustifolium L.) Extracts

Five commercially available water-soluble extracts prepared from the aerial parts of Epilobium angustifolium L. (Onagraceae) were screened for antioxidant-related properties in a battery of six in vitro assays. Total phenol content and qualitative-quantitative analyses were also carried out. The extracts demonstrated varying degrees of efficacy in each screen. Two extracts, denoted as nonfermented and Tver, were the most effective toward reducing iron(III), scavenging 1,1-diphenyl-2-picrylhydrazyl free radicals, inhibiting hydroxyl radical-catalyzed bovine brain-derived phospholipid degradation, and non-site- and site-specific hydroxyl radical-catalyzed 2-deoxy-D-ribose degradation. The activity profile of the extracts changed, however, when their iron(II) chelating ability was assessed. The nonfermented and Tver extracts were not as effective iron(II) chelators as the extract denoted as Lotos. All the extracts contained Folin-Ciocalteu-reactive substances, which was confirmed by the presence of predominantly polar phenolic analytes (i.e., hydroxylated benzoic acid derivatives and flavonoids).

Antioxidant activity of hot water extract from the fruit of the Doum palm, Hyphaene thebaica

A hot water extract from the fruit of Hyphaene thebaica was examined for its (i) hydrogen donating activity, (ii) Fe 2+-chelating activity, (iii) hydroxyl radical-scavenging activity, (iv) inhibition of substrate site-specific hydroxyl radical formation, (v) superoxide radical-scavenging activity, and (vi) reducing power. The total phenolic content of the fruit extract was also determined in order to quantitate antioxidant activity as gallic acid equivalent (GAE) per ml reaction. The total phenolic content of the Doum fruit is low, but the extract exhibited potent antioxidant activity in terms of GAE. The activities expressed as mmol pure compound equivalent per g GAE content of extract are: (i) 2.85 mmol ascorbic acid equivalent, (ii) 1.78 mmol ethylenediamine tetraacetic acid equivalent, (iii) 192 mmol gallic acid equivalent, (iv) 3.36 mmol gallic acid equivalent, (v) 1.78 mmol gallic acid equivalent and (vi) 3.93 mmol ascorbic acid equivalent. These values were of the same magnitude as antioxidant activity in black tea except for Fe 2+-chelating activity which was about 14 times more potent. The results show that the fruit of Hyphaene thebaica’s fruit is a source of potent antioxidants.

Dandelion (Taraxacum officinale) flower extract suppresses both reactive oxygen species and nitric oxide and prevents lipid oxidation in vitro

Flavonoids and coumaric acid derivatives were identified from dandelion flower (Taraxacum officinale). Characteristics of chain-breaking antioxidants, such as extended lag phase and reduced propagation rate, were observed in oxidation of linoleic acid emulsion with the addition of dandelion flower extract (DFE). DFE suppressed both superoxide and hydroxyl radical, while the latter was further distinguished by both site-specific and non-specific hydroxyl radical inhibition. DPPH-radical-scavenging activity and a synergistic effect with alpha-tocopherol were attributed to the reducing activity derived from phenolic content of DFE. A significant (p < 0.05) and concentration-dependent, reduced nitric oxide production from acterial-lipopolysaccharide-stimulated mouse macrophage RAW264.7 cells was observed with the addition of DFE. Moreover, peroxyl-radical-induced intracellular oxidation of RAW264.7 cells was inhibited significantly (p < 0.05) by the addition of DFE over a range of concentrations. These results showed that the DFE possessed marked antioxidant activity in both biological and chemical models. Furthermore, the efficacy of DFE in inhibiting both reactive oxygen species and nitric oxide were attributed to its phenolic content.

Free radical scavenging and antioxidant activities of EPS2, an exopolysaccharide produced by a marine filamentous fungus Keissleriella sp. YS 4108

The reactive oxygen species (ROS) and free radical-initiated reactions are ascertained to play multiple roles in degenerative or pathological events such as aging, cancer, heart dysfunction and Alzheimer’s disease. EPS2 with a mean molecular weight of 1.3 × 10 5 was characterized as an antioxidant exopolysaccharide from the broth of a marine filamentous fungus Keissleriella sp. YS 4108. Compositionally, it is composed of galactose, glucose, rhamnose, mannose and glucuronic acid in an approximate proportion of 50:8:1:1:0.4. The radical eliminating and antioxidant actions of the glycan was assessed in different in vitro systems showing that EPS2 exhibited profound scavenging activities in superoxide radical. As a reinforcement of the action, similar radical scavenging effects of EPS2 were also discerned with both site-specific and non site-specific hydroxyl radical using the deoxyribose assay method. Moreover, EPS2 effectively blocked as well the non site-specific strand-breaking of DNA induced by the Fenton reaction at concentrations of 0.1 and 1 mg/mL. Further investigation of the effect of EPS2 on human low density lipoprotein (LDL) system demonstrated that it significantly inhibited copper-mediated oxidation of LDL in a dose-dependent manner. These results suggest that EPS2, possessing pronounced free radical scavenging and antioxidant activities, could be of considerable preventive and therapeutic significance to some life-threatening health problems such as cancer, atherogenesis and Alzheimer’s disease which pathologically initiated by the presence of free radicals leading to the inevitable peroxidation of important biomolecules.

Free radical scavenging and antioxidant activities of EPS2, an exopolysaccharide produced by a marine filamentous fungus Keissleriella sp. YS 4108

The reactive oxygen species (ROS) and free radical-initiated reactions are ascertained to play multiple roles in degenerative or pathological events such as aging, cancer, heart dysfunction and Alzheimer’s disease. EPS2 with a mean molecular weight of 1.3 × 105 was characterized as an antioxidant exopolysaccharide from the broth of a marine filamentous fungus Keissleriella sp. YS 4108. Compositionally, it is composed of galactose, glucose, rhamnose, mannose and glucuronic acid in an approximate proportion of 50:8:1:1:0.4. The radical eliminating and antioxidant actions of the glycan was assessed in different in vitro systems showing that EPS2 exhibited profound scavenging activities in superoxide radical. As a reinforcement of the action, similar radical scavenging effects of EPS2 were also discerned with both site-specific and non site-specific hydroxyl radical using the deoxyribose assay method. Moreover, EPS2 effectively blocked as well the non site-specific strand-breaking of DNA induced by the Fenton reaction at concentrations of 0.1 and 1 mg/mL. Further investigation of the effect of EPS2 on human low density lipoprotein (LDL) system demonstrated that it significantly inhibited copper-mediated oxidation of LDL in a dose-dependent manner. These results suggest that EPS2, possessing pronounced free radical scavenging and antioxidant activities, could be of considerable preventive and therapeutic significance to some life-threatening health problems such as cancer, atherogenesis and Alzheimer’s disease which pathologically initiated by the presence of free radicals leading to the inevitable peroxidation of important biomolecules.

Antioxidant Properties of Aqueous Extracts from Selected Lamiaceae Species Grown in Turkey

Water-soluble extracts from black thyme (Thymbra spicata L.), savory (Satureja cuneifolia Ten.), Spanish oregano (Coridothymus capitatus (L.) Reichb. f.), sweet marjoram (Majorana hortensis Moench), Syrian oregano (Origanum syriacum L.), Toka oregano (Origanum minutiflorum O. Schwarz et P. H. Davis), and Turkish oregano (Origanum onites L.) were screened for antioxidant properties in a battery of six in vitro assays. Total phenol content and qualitative-quantitative compositional analyses were also carried out. The extracts demonstrated varying degrees of efficacy in each screen. The savory extract was the most effective at reducing iron(III), scavenging 1,1-diphenyl-2-picrylhydrazyl radicals, inhibiting ascorbate-iron(III)-catalyzed hydroxyl radical-mediated brain phospholipid peroxidation, and site-specific hydroxyl radical-mediated 2-deoxy-d-ribose degradation. The Syrian oregano extract was the most effective chelator of iron(II), while Spanish and Turkish oregano extracts were the most effective inhibitors of nonsite-specific hydroxyl radical-mediated 2-deoxy-d-ribose degradation. All the extracts contained Folin-Ciocalteu reagent-reactive substances, which was confirmed by the presence of polar phenolic analytes (i.e., hydroxybenzoates, hydroxycinnamates, and flavonoids).

Antioxidant, prooxidant, and cytotoxic activities of solvent-fractionated dandelion (Taraxacum officinale) flower extracts in vitro.

This study was conducted to investigate the chemical antioxidant and bioactive properties of the water (WF) and ethyl acetate fractions (EAF) derived from dandelion (Taraxacum officinale) flower extract (DFE). HPLC analysis showed the presence of both luteolin and luteolin 7-glucoside in the DFE, which contributed to noted in vitro antioxidant and Caco-2 cell cytotoxic activities. Both WF and EAF of DFE exhibited free radical scavenging activities in a stable 2,2-diphenyl-1-picrylhydrazyl radical model and reduced the breakage of supercoiled DNA strand induced by both non-site-specific and site-specific hydroxyl radical. Oxidation of structured phosphatidylcholine liposome induced by peroxyl radical was reduced in the presence of both EAF and WF. EAF had greater (p < 0.05) affinity to scavenge peroxyl radical than WF, as measured by the formation of conjugated diene. At low concentration, prooxidant activity of both fractions was observed in Cu(2+)-induced structured liposome and hLDL oxidation models, thus indicating that the reducing power of the DFE had resulted in generation of reactive cuprous ion. However, at high concentrations the EAF did not promote oxidation in the presence of Cu(2+), suggesting that the free radical scavenging activity of this fraction was sufficient to minimize the potential oxidative mechanism attributed to the metal ion reducing activity associated with prooxidant activity.

Ferrous Ion Strongly Promotes the Ring Opening of the Hydrolysis Intermediates of the Antioxidant Cardioprotective Agent Dexrazoxane (ICRF-187)

The ferrous- and ferric-ion-promoted hydrolysis of the doxorubicin cardioprotective agent dexrazoxane (ICRF-187) has been studied spectrophotometrically and by HPLC. While dexrazoxane itself did not undergo any iron-promoted ring-opening hydrolysis, both ferrous ( t 1/2 0.4 min) and ferric ( t 1/2 170 min) ions promoted, by factors of up to 6000 and 8, respectively, the hydrolysis of the one-ring open intermediates of dexrazoxane to yield the strongly metal-ion-chelating form. The pH dependence of both the ferrous- and ferric-ion-promoted hydrolysis of one of the one-ring open intermediates was studied and was consistent with base-catalyzed hydrolysis. In each case, due to the problem of proton ambiguity in the rate law, a bimolecular reaction with external hydroxide could not be distinguished from an intramolecular reaction of hydroxide bound to iron. The mechanism of the cardioprotective effects of dexrazoxane may involve enzymatic or nonenzymatic hydrolysis to the one-ring open intermediates. Thus, these intermediates may be the active forms of the drug that may be acting by either displacing iron from the iron-doxorubicin complex or chelating loosely bound iron and then undergoing a rapid metal-ion-promoted hydrolysis to their strongly chelating forms. Thus, the ability of iron to participate in site-specific hydroxyl radical damage may be reduced.

N,N'-bis-dibenzyl ethylenediaminediacetic acid (DBED): a site-specific hydroxyl radical scavenger acting as an "oxidative stress activatable" iron chelator in vitro.

During oxidative stress, iron traces are supposed to be released from normal storage sites and to catalyse oxidative damage by Fenton-type reactions. This type of damage is difficult to prevent in vivo except by the use of strong iron chelators such as deferoxamine (affinity constant for Fe(III): log K = 30.8). However, strong iron chelating agents are also suspected to mobilize iron from various storage and transport proteins thereby leading to toxic effects. In contrast, N,N'-bis-dibenzyl ethylenediaminediacetic acid (DBED) is an iron chelator with relatively low affinity for iron (affinity constant for Fe(III): log K < 15). In the present paper, we show that, in situations mimicking oxidative stress in vitro, DBED is site-specifically oxidized into new species with strong iron binding capacity. Indeed, in the presence of ascorbate as a reductant, the iron chelate of DBED reacts with H2O2 in aqueous solution to yield a purple chromophore with minor release of free HO. in the medium, as measured by aromatic hydroxylation assay. The formation of these purple species is not suppressed by the presence of HO. scavengers at high concentration. The visible spectrum of these species is consistent with a charge transfer band from a phenolate ligand to iron. N-2-hydroxybenzyl N'-benzyl ethylenediaminediacetic acid (HBBED) was identified in the medium as one of the oxidation products of DBED. Therefore, these results suggest that the iron chelate of DBED undergoes an intramolecular aromatic hydroxylation by HO. leading to 2-OH derivatives and hence that DBED is a site-specific HO. scavenger. Moreover, since the measured affinity for Fe(III) of HBBED (log K = 28) is at least 13 orders of magnitude higher than that of DBED and since ferric HBBED chelate is not a catalyst of Fenton chemistry, DBED may be looked as an "oxidative stress activatable" iron chelator, e.g. which increase in affinity for iron is triggered in the presence of H2O2 and an electron donor. Therefore it is proposed that DBED and related derivatives may be interesting as protective compounds against oxygen radicals toxicity, especially for chronic use.

NADPH-cytochrome-P450 reductase promotes hydroxyl radical production by the iron complex of ADR-925, the hydrolysis product of ICRF-187 (dexrazoxane).

ICRF-187 (dexrazoxane) is currently in clinical trials as a cardioprotective agent for the prevention of doxorubicin-induced cardiotoxicity. ICRF-187 likely acts through its strongly metal ion-binding rings-opened hydrolysis product ADR-925 by removing iron from its complex with doxorubicin or by chelating free iron. The ability of NADPH-cytochrome-P450 reductase to promote hydroxyl radical formation by iron complexes of ADR-925 and EDTA was compared by EPR spin trapping. The iron-EDTA complex produced hydroxyl radicals at six times the rate that the iron-ADR-925 complex did. The aerobic oxidation of ferrous complexes of ADR-925, its tetraacid analog, EDTA and DTPA was followed spectrophotometrically. The iron(II)-ADR-925 complex was aerobically oxidized 700 times slower than was the EDTA complex. It is concluded that even though ADR-925 does not completely eliminate iron-based hydroxyl radical production, it likely protects by preventing site-specific hydroxyl radical damage by the iron-doxorubicin complex.

A role for metals and free radicals in the induction of apoptosis in thymocytes

Recent reports have implicated a possible but undefined role for reactive oxygen species in the induction and mediation of apoptosis. In the present study, the role of free radicals and metal ions in apoptosis induced in rat thymocytes by dexamethasone and etoposide was examined. Copper chelators, but not iron specific chelators, inhibited apoptosis induced by both these stimuli. Several antioxidants also possessed potent inhibitory effects. We therefore propose that diverse agents may induce apoptosis in thymocytes by a common mechanism involving a copper mediated Fenton reaction, generating site specific hydroxyl radicals, possibly as a result of activation of the redox sensitive transcription factor NF-ϰB.

“Crypto”- and site-specific hydroxyl radicals: New data and conceptions

“Crypto”- and site-specific hydroxyl radicals: New data and conceptions