Extent Of Protein Oxidation Research Articles

Insight into the oxidation mechanism of coconut globulin by atmospheric cold plasma focusing on side chain amino acids

Atmospheric cold plasma (ACP), a novel non-thermal processing technology, generates active substances that stimulate protein oxidation in protein-based foods. Nevertheless, the precise mechanism through which ACP initiates amino acid oxidation on protein side chains remains ambiguous. This study primarily aimed to elucidate the mechanism of ACP-induced oxidation of coconut globulin, focusing on the process of amino acid oxidation. Analysis of protein oxidation products indicated a positive correlation between the extent of protein oxidation and the voltage and duration of ACP treatment. By analyzing the composition of amino acids and active ingredients, the study identified that the most significant changes amino acids were methionine, cysteine, and arginine, and •OH was the primary free radicals. The findings from oxidation kinetics and dynamic simulation indicated that •OH predominantly oxidized methionine, followed by L-cysteine and L-arginine. These results offer theoretical framework for understanding protein oxidation by ACP and suggest potential applications in protein-based food.

Effect of three unsaturated fatty acids on the protein oxidation and structure of myofibrillar proteins from rainbow trout (Oncorhynchus mykiss)

In this study, the impact of three unsaturated fatty acids (Oleic acid: OA, Eicosapentaenoic acid: EPA, Docosahexaenoic acid: DHA) on the oxidation and structure of rainbow trout myofibrillar protein (MP) was explored. The findings revealed a notable increase in carbonyl content (P < 0.05) and a significant decrease in total sulfhydryl content (P < 0.05) of MP with the concentration increase of the three unsaturated fatty acids. Endogenous fluorescence spectroscopy and surface hydrophobicity analyses showed that unsaturated fatty acids can cause unfolding and exposure of hydrophobic groups in MP. In addition, SDS-PAGE showed that disulfide bonds were associated with MP cross-linking and aggregate size induced by unsaturated fatty acids. Overall, three unsaturated fatty acid treatments facilitated the oxidation of myofibrillar proteins, and the extent of protein oxidation was closely associated with the concentration of unsaturated fatty acids.

Effect of different extent of protein oxidation on the frozen storage stability of muscle protein in obscure pufferfish (Takifugu obscurus)

The objective of this study was to explore frozen storage stability of muscle protein of the obscure pufferfish using a semi-model system based on light exposure (LE), oxygen concentration (OC), and multiple freeze-thaw cycles (FTCs). The dorsal muscle of fifteen frozen fish was cut into small pieces (2 cm × 1.5 cm × 1 cm) and divided into 4 groups stored in differing conditions: one was stored in light with 0% oxygen (L-0), one in light with 20% oxygen (L-20), one in dark with 0% oxygen (D-0), and one in dark with 20% oxygen (D-20). All were subsequently subjected to five FTCs. Protein oxidation (PO) levels, protein structure, and water states were all assessed. The results showed that both LE and OC could significantly accelerate sulfhydryl and tryptophan loss, in the order of L-20 > L-0 and D-20 > D-0 during FTCs. Changes of protein structure were in line with the extent of PO indicated by surface hydrophobicity and UV absorbance. An increased PO also affected the water states, with higher PO resulting in immobilized water being more tightly trapped within the protein. However, thawing loss was shown to be independent of PO and the structural changes of myofibrillar protein.

Protein oxidation and tandem mass tag‐based proteomic analysis in the dorsal muscle of farmed obscure pufferfish subjected to multiple freeze–thaw cycles

The objective of this study was to determine the oxidative stability and proteome profile of dorsal muscle of frozen obscure pufferfish subjected to repeated freeze–thaw cycles (FTC). Twenty frozen fish were filleted (2 cm × 2 cm × 2 cm) and subjected to FTC. Protein oxidation, lipid oxidation, antioxidant enzyme activities (AEA), and proteome profile were assessed. The results showed that the carbonyl content and TBARS value increased (p < .05), while sulfhydryl content and AEA decreased (p < .05) as FTC increased. SDS-PAGE analysis revealed that FTC induced significant alterations in disulfide linkage and fragments. There were significant (p < .05) correlations between lipid oxidation, AEA, and protein oxidation. A total of 19 differentially abundant proteins were identified, of which L-lactate dehydrogenase and other proteins could be potential biomarkers for pufferfish subjected to FTC. Bioinformatic analysis revealed that these proteins are mainly involved in membrane structure, respiratory chain, and apoptosis. Practical applications Pufferfish is popular in many Asian countries for its palatable flavor and frozen storage is the most common way for its preservation. However, repeated freeze–thaw cycles (FTC) remain a core issue in frozen products, which lead to various changes in protein and consequently have a serious impact on food quality. In this study, the extent of protein oxidation (PO) and proteomic changes in pufferfish muscle subjected to FTC was investigated. The initiation of PO correlates with increased lipid oxidation and decreased antioxidant enzyme activity, which may be used to control the PO. The differentially abundant proteins identified may be used to distinguish the frozen products subjected to different FTC. Understanding the molecular mechanism of protein changes induced by FTC will enable us to achieve the target-control and to preserve the frozen aquatic products with better quality.

Avoidance of protein oxidation correlates with the desiccation and radiation resistance of hot and cold desert strains of the cyanobacterium Chroococcidiopsis.

To investigate the relationship between desiccation and the extent of protein oxidation in desert strains of Chroococcidiopsis a selection of 10 isolates from hot and cold deserts and the terrestrial cyanobacterium Chroococcidiopsis thermalis sp. PCC 7203 were exposed to desiccation (air-drying) and analyzed for survival. Strain CCMEE 029 from the Negev desert and the aquatic cyanobacterium Synechocystis sp. PCC 6803 were further investigated for protein oxidation after desiccation (drying over silica gel), treatment with H2O2 up to 1M and exposure to γ-rays up to 25kGy. Then a selection of desert strains of Chroococcidiopsis with different survival rates after prolonged desiccation, as well as Synechocystis sp. PCC 6803 and Chroococcidiopsis thermalis sp. PCC 7203, were analyzed for protein oxidation after treatment with 10 and 100mM of H2O2. Results suggest that in the investigated strains a tight correlation occurs between desiccation and radiation tolerance and avoidance of protein oxidation.

High Fat Diet and Inflammation - Modulation of Haptoglobin Level in Rat Brain.

Obesity and dietary fats are well known risk factors for the pathogenesis of neurodegenerative diseases. The analysis of specific markers, whose brain level can be affected by diet, might contribute to unveil the intersection between inflammation/obesity and neurodegeneration. Haptoglobin (Hpt) is an acute phase protein, which acts as antioxidant by binding free haemoglobin (Hb), thus neutralizing its pro-oxidative action. We previously demonstrated that Hpt plays critical functions in brain, modulating cholesterol trafficking in neuroblastoma cell lines, beta-amyloid (Aβ) uptake by astrocyte, and limiting Aβ toxicity on these cells. A major aim of this study was to evaluate whether a long term (12 or 24 weeks) high-fat diet (HFD) influences Hpt and Hb expression in rat hippocampus. We also assessed the development of obesity-induced inflammation by measuring hippocampal level of TNF-alpha, and the extent of protein oxidation by titrating nitro-tyrosine (N-Tyr). Hpt concentration was lower (p < 0.001) in hippocampus of HFD rats than in control animals, both in the 12 and in the 24 weeks fed groups. HFD was also associated in hippocampus with the increase of Hb level (p < 0.01), inflammation and protein oxidative modification, as evidenced by the increase in the concentration of TNF-alpha and nitro-tyrosine. In fact, TNF-alpha concentration was higher in rats receiving HFD for 12 (p < 0.01) or 24 weeks (p < 0.001) compared to those receiving the control diet. N-Tyr concentration was more elevated in hippocampus of HFD than in control rats in both 12 weeks (p = 0.04) and 24 weeks groups (p = 0.01), and a positive correlation between Hb and N-Tyr concentration was found in each group. Finally, we found that the treatment of the human glioblastoma-astrocytoma cell line U-87 MG with cholesterol and fatty acids, such as palmitic and linoleic acid, significantly impairs (p < 0.001) Hpt secretion in the extracellular compartment. We hypothesize that the HFD-dependent decrease of Hpt in hippocampus, as associated with Hb increase, might enhance the oxidative stress induced by free Hb. Altogether our data, identifying Hpt as a molecule modulated in the brain by dietary fats, may represent one of the first steps in the comprehension of the molecular mechanisms underlying the diet-related effects in the nervous system.

The Formation of Persister Cells in Stationary-Phase Cultures of Escherichia Coli Is Associated with the Aggregation of Endogenous Proteins

Persister cells (persisters) are transiently tolerant to antibiotics and usually constitute a small part of bacterial populations. Persisters remain dormant but are able to re-grow after antibiotic treatment. In this study we found that the frequency of persisters correlated to the level of protein aggregates accumulated in E. coli stationary-phase cultures. When 3-(N-morpholino) propanesulfonic acid or an osmolyte (trehalose, betaine, glycerol or glucose) were added to the growth medium at low concentrations, proteins were prevented from aggregation and persister formation was inhibited. On the other hand, acetate or high concentrations of osmolytes enhanced protein aggregation and the generation of persisters. We demonstrated that in the E. coli stationary-phase cultures supplemented with MOPS or a selected osmolyte, the level of protein aggregates and persister frequency were not correlated with such physiological parameters as the extent of protein oxidation, culturability, ATP level or membrane integrity. The results described here may help to understand the mechanisms underlying persister formation.

Antioxidant Effects of Berry Phenolics Incorporated in Oil‐in‐Water Emulsions with Continuous Phase β‐Lactoglobulin

AbstractThe purpose of this study was to evaluate the effects of berry phenolics, in this case, black currant (Ribes nigrum) anthocyanins and raspberry (Rubus idaeus) ellagitannins, in the presence of continuous phase β‐lactoglobulin (β‐Lg), on the oxidative stability of Brij 35‐stabilized corn oil‐in‐water emulsions. The extent of lipid oxidation in emulsions was measured by determining the formation of lipid hydroperoxides and hexanal, and extent of protein oxidation by monitoring the loss of tryptophan and cysteine residues in the continuous phase β‐Lg. Berry phenolics at concentration levels of 20 and 50 μM were able to prevent lipid oxidation with and without β‐Lg in the aqueous phase. The results show that a combination of β‐Lg and berry phenolics was more efficient in inhibiting hexanal formation than either component alone. Synergistic effects on antioxidant activity toward hexanal were observed only at the 20 μM levels of berry phenolics in combination with continuous phase β‐Lg. The berry phenolics were also able to inhibit the oxidation of tryptophan and cysteine residues of β‐Lg. The results show that the amino acid residues were oxidized prior to the propagation of lipid oxidation. This suggests that these amino acids were able to inhibit fatty acid scission. The information gained from this study would be useful in protecting emulsion‐based food products from oxidative deterioration.

Chloroquine mediates specific proteome oxidative damage across the erythrocytic cycle of resistant Plasmodium falciparum

Resistance of Plasmodium falciparum to chloroquine hinders malaria control in endemic areas. Current hypotheses on the action mechanism of chloroquine evoke its ultimate interference with the parasite's oxidative defence systems. Through carbonyl derivatization by 2,4-dinitrophenylhydrazine and proteomics, we compared oxidatively modified proteins across the parasite's intraerythrocytic stages in untreated and transiently IC 50 chloroquine-treated cultures of the chloroquine-resistant P. falciparum strain Dd2. Functional plasmodial protein groups found to be most oxidatively damaged were among those central to the parasite's physiological processes, including protein folding, proteolysis, energy metabolism, signal transduction, and pathogenesis. While an almost constant number of oxidized proteins was detected across the P. falciparum life cycle, chloroquine treatment led to increases in both the extent of protein oxidation and the number of proteins oxidized as the intraerythrocytic cycle progressed to mature stages. Our data provide new insights into early molecular effects produced by chloroquine in the parasite, as well as into the normal protein-oxidation modifications along the parasite cycle. Oxidized proteins involved in the particular parasite drug-response suggest that chloroquine causes specific oxidative stress, sharing common features with eukaryotic cells. Targeting these processes might provide ways of combating chloroquine-resistance and developing new antimalarial drugs.

Occurrence of oxidative impairments, response of antioxidant defences and associated biochemical perturbations in male reproductive milieu in the Streptozotocin‐diabetic rat

Oxidative stress is implicated to play a vital role in the pathogenesis of various diabetic complications. While reproductive dysfunction is a well recognized consequence of diabetes mellitus, the underlying mechanisms are poorly understood. The present study aims to obtain insights into the incidence, extent and progression of oxidative impairments in testis and epididymal sperm (ES) in streptozotocin (STZ)-induced diabetic rat during early and progressive phase. Adult rats (CFT-Wistar strain) rendered diabetic by an acute dose of STZ (60 mg/kg bw, i.p.) were examined for induction of hyperglycaemia at 72 h, followed by the assessment of oxidative impairments in testis and ES over a 6-week period. Oxidative damage was ascertained by measuring the malondialdehyde levels, reactive oxygen species (ROS) generation, alterations in antioxidant defences and extent of protein oxidation. STZ induced a significant (2.5-fold) increase in blood glucose levels. In diabetic rats, both testis and ES showed enhanced status of lipid peroxidation measured as increased TBARS and ROS from week 2 onwards. These impairments in testis were consistent, progressive and accompanied by marked alterations in antioxidant defences and elevated protein carbonyls. Varying degree of reduction in the specific activities of antioxidant enzymes was evident in testis and ES, while the activity of glutathione-S-transferase (GST) was significantly elevated. Reduced glutathione (GSH) and vitamin E levels were consistently reduced in testis. Lipid dysmetabolism measured in terms of increased cholesterol, triglycerides and phospholipids was evident only beyond week 2 in diabetic testis. Taken together, these results indicate that the testis and ES are indeed subjected to significant oxidative stress in the STZ-diabetic rat both during early as well as progressive phase. It is hypothesized that oxidative impairments in testis which develop over time may at least in part contribute towards the development of testicular dysfunction eventually leading to testicular degeneration which culminates in reduced fertility during the progressive phase of STZ-induced diabetes in adult rats.

Oxidative Changes of Bronchoalveolar Proteins in Cystic Fibrosis

Chronic bacterial infection and severe, polymorphonuclear neutrophil-dominated endobronchial inflammation are characteristic hallmarks of cystic fibrosis (CF) lung disease. The free radicals generated can be deleterious for structure and function of many proteins. The goal of this study was to investigate the degree of oxidation of pulmonary epithelial lining fluid proteins. BAL fluid (BALF) from 55 children with CF and from 11 patients in a control group were investigated by dot-blot assay for content and by two-dimensional electrophoresis and Western blotting for the pattern of distribution of oxidized proteins. The highest level of oxidative stress, as assessed by the level of protein carbonyls, was found in patients with FEV1 < 80% of predicted or with highly elevated neutrophil counts. Compared to control subjects without lung disease, CF patients with normal lung function and CF patients with a normal neutrophil count in their BALF had significantly higher protein carbonyl levels. The extent of protein oxidation was directly related to the neutrophil granulocyte count and inversely to lung function. Our data support the hypothesis that oxidative damage of pulmonary proteins during chronic and excessive neutrophilic endobronchial inflammation may contribute to the decline of lung function in CF patients.

Oxidation of bovine serum albumin initiated by the Fenton reaction—effect of EDTA, tert-butylhydroperoxide and tetrahydrofuran

Oxidation of bovine serum albumin (BSA) was investigated using different oxidants: The water-soluble azo-initiator 2,2′azo-bis-(2-amidinopropane) hydrochloride (AAPH), a combination of FeCl3 and ascorbate or the Fenton oxidant consisting of FeCl2, H2O2 and EDTA. In addition, the effects of exogenous compounds such as tert-butyl hydroperoxide (tBuOOH) or solvents such as tetrahydrofuran (THF), often used in model systems, was evaluated. The extent of protein damage was studied by measuring protein carbonyl groups and protein hydroperoxides. The interaction between Fenton oxidant and EDTA, THF or tBuOOH was further characterized using spin trapping electron spin resonance (ESR) spectroscopy. The results showed that the extent of protein oxidation depended on the oxidant used. The Fenton oxidant was the most reactive of the initiators tested. However, in the absence of EDTA, the Fenton system produced protein carbonyl groups on BSA equivalent to that obtained with the other oxidants, however, significantly more protein hydroperoxide was produced. Surprisingly, it was also found that addition of tBuOOH or THF to BSA reduced protein damage when the oxidation was initiated with the Fenton oxidant. ESR investigation showed that EDTA played a key role in the generation of free radicals. It was also revealed that in an EDTA containing system both tBuOOH and THF were able to react with radicals without inducing protein damage in effect protecting BSA from oxidative damage.

Immuno-spin trapping of hemoglobin and myoglobin radicals derived from nitrite-mediated oxidation

The reaction of nitrite with hemoglobin has become of increasing interest due to the realization that plasma nitrite may act as an NO congener that is activated by interaction with red blood cells. Using a combination of spectrophotometry, immuno-spin trapping, and EPR, we have examined the formation of radicals during the oxidation of oxyhemoglobin (oxyHb) and oxymyoglobin (oxyMb) by inorganic nitrite. The proposed intermediacy of ferryl species during this oxidation was confirmed by spectrophotometry using multiple linear regression analysis of kinetic data. Using EPR/spin trapping, a protein radical was observed in the case of oxyMb, but not oxyHb, and was inhibited by catalase. When DMPO spin trapping was combined with Western blot analysis using an anti-DMPO–nitrone antibody, globin/DMPO adducts of both oxyHb and oxyMb were detected, and their formation was inhibited by catalase. Catalase effects confirm the intermediacy of hydrogen peroxide as a heme oxidant in this system. Spectrophotometric kinetic studies revealed that the presence of DMPO elongated the lag phase and decreased the maximal rate of oxidation of both oxyHb and oxyMb, which suggests that the globin radical plays an active role in the mechanism of autocatalysis. Interestingly, the oxidation of oxyHb or oxyMb by nitrite, but not by hydrogen peroxide, produced a diffusible radical that was able to generate spin adducts on a bystander protein. This indicates that the oxidation of oxyhemeproteins by nitrite may cause more widespread oxidative damage than the corresponding oxidation by hydrogen peroxide. The immuno-spin trapping technique represents an important new development for the study of the range and extent of protein oxidation by free radicals and oxidants.

Protein Oxidation by Chronic Pulmonary Diseases in Children

The oxidation of proteins may play an important role in the pathogenesis of chronic inflammatory lung diseases, and may contribute to lung damage. However, the extent of oxidation and the distribution among proteins are not known for most pediatric lung diseases. In this work, protein oxidation was assessed as protein carbonyls. Bronchoalveolar lavages (BAL) from children with chronic lung diseases were investigated by dot-blot assay for content and for pattern of distribution of oxidized proteins by two-dimensional (2D) electrophoresis and Western blotting. Significantly higher levels of protein oxidation than in healthy controls were determined in groups of patients with interstitial lung disease, gastro-esophageal reflux disease, and pulmonary alveolar proteinosis. The proteins most sensitive to oxidation were serum albumin, surfactant protein A, and alpha1-antitrypsin. Our data show increased oxidative stress in lungs of children with chronic pulmonary diseases, with significant interindividual variations. The extent of protein oxidation was proportional to the count of neutrophilic granulocytes in BAL fluid. These findings strongly support the concept that an abundance of reactive oxygen species produced during neutrophilic inflammation may be a deleterious factor, leading to pulmonary damage in these patients.

Anthocyanin Antioxidant Activity and Partition Behavior in Whey Protein Emulsion

The antioxidant activities of anthocyanins and anthocyanin fractions isolated from blackcurrants, raspberries, and lingonberries were investigated in whey protein-stabilized emulsion. The extent of protein oxidation was measured by determining the loss of tryptophan fluorescence and formation of protein carbonyl compounds and that of lipid oxidation by conjugated diene hydroperoxides and hexanal analyses. The antioxidant activity of berry anthocyanins increased with an increase in concentration. Blackcurrant anthocyanins were the most potent antioxidants toward both protein and lipid oxidation at all concentrations due to the beneficial combination of delphinidin and cyanidin glycosides. Most berry anthocyanins (69.4-72.8%) partitioned into the aqueous phase of the emulsion, thus being located favorably for antioxidant action toward protein oxidation. The presence of the lipid decreased the share of anthocyanin in the aqueous phase. Thus, the structure of food affects the antioxidant activity by influencing the partitioning of the antioxidant.

Inhibition of Protein and Lipid Oxidation in Liposomes by Berry Phenolics

The antioxidant activity of berry phenolics (at concentrations of 1.4, 4.2, and 8.4 mug of purified extracts/mL of liposome sample) such as anthocyanins, ellagitannins, and proanthocyanidins from raspberry (Rubus idaeus), bilberry (Vaccinium myrtillus), lingonberry (Vaccinium vitis-idaea), and black currant (Ribes nigrum) was investigated in a lactalbumin-liposome system. The extent of protein oxidation was measured by determining the loss of tryptophan fluorescence and formation of protein carbonyl compounds and that of lipid oxidation by conjugated diene hydroperoxides and hexanal analyses. The antioxidant protection toward lipid oxidation was best provided by lingonberry and bilberry phenolics followed by black currant and raspberry phenolics. Bilberry and raspberry phenolics exhibited the best overall antioxidant activity toward protein oxidation. Proanthocyanidins, especially the dimeric and trimeric forms, in lingonberries were among the most active phenolic constituents toward both lipid and protein oxidation. In bilberries and black currants, anthocyanins contributed the most to the antioxidant effect by inhibiting the formation of both hexanal and protein carbonyls. In raspberries, ellagitannins were responsible for the antioxidant activity. While the antioxidant effect of berry proanthocyanidins and anthocyanins was dose-dependent, ellagitannins appeared to be equally active at all concentrations. In conclusion, berries are rich in monomeric and polymeric phenolic compounds providing protection toward both lipid and protein oxidation.

Photodynamic treatment and H2O2-induced oxidative stress result in different patterns of cellular protein oxidation.

Photodynamic treatment (PDT) is an emerging therapeutic procedure for the management of cancer, based on the use of photosensitizers, compounds that generate highly reactive oxygen species (ROS) on irradiation with visible light. The ROS generated may oxidize a variety of biomolecules within the cell, loaded with a photosensitizer. The high reactivity of these ROS restricts their radius of action to 5-20 nm from the site of their generation. We studied oxidation of intracellular proteins during PDT using the ROS-sensitive probe acetyl-tyramine-fluorescein (acetylTyr-Fluo). This probe labels cellular proteins, which become oxidized at tyrosine residues under the conditions of oxidative stress in a reaction similar to dityrosine formation. The fluorescein-labeled proteins can be visualized after gel electrophoresis and subsequent Western blotting using the antibody against fluorescein. We found that PDT of rat or human fibroblasts, loaded with the photosensitizer Hypocrellin A, resulted in labeling of a set of intracellular proteins that was different from that observed on treatment of the cells with H2O2. This difference in labeling patterns was confirmed by 2D electrophoresis, showing that a limited, yet distinctly different, set of proteins is oxidized under either condition of oxidative stress. By matching the Western blot with the silver-stained protein map, we infer that alpha-tubulin and beta-tubulin are targets of PDT-induced protein oxidation. H2O2 treatment resulted in labeling of endoplasmic reticulum proteins. Under conditions in which the extent of protein oxidation was comparable, PDT caused massive apoptosis, whereas H2O2 treatment had no effect on cell survival. This suggests that the oxidative stress generated by PDT with Hypocrellin A activates apoptotic pathways, which are insensitive to H2O2 treatment. We hypothesize that the pattern of protein oxidation observed with Hypocrellin A reflects the intracellular localization of the photosensitizer. The application of acetylTyr-Fluo may be useful for characterizing protein targets of oxidation by PDT with various photosensitizers.

Repression of ferritin expression increases the labile iron pool, oxidative stress, and short-term growth of human erythroleukemia cells

AbstractThe role of ferritin expression on the labile iron pool of cells and its implications for the control of cell proliferation were assessed. Antisense oligodeoxynucleotides were used as tools for modulating the expression of heavy and light ferritin subunits of K562 cells. mRNA and protein levels of each subunit were markedly reduced by 2-day treatment with antisense probes against the respective subunit. Although the combined action of antisense probes against both subunits reduced their protein expression, antisense repression of one subunit led to an increased protein expression of the other. Antisense treatment led to a rise in the steady-state labile iron pool, a rise in the production of reactive oxygen species after pro-oxidative challenges and in protein oxidation, and the down-regulation of transferrin receptors. When compared to the repression of individual subunits, co-repression of each subunit evoked a more than additive increase in the labile iron pool and the extent of protein oxidation. These treatments had no detectable effects on the long-term growth of cells. However, repression of ferritin synthesis facilitated the renewal of growth and the proliferation of cells pre-arrested at the G1/S phase. Renewed cell growth was significantly less dependent on external iron supply when ferritin synthesis was repressed and its degradation inhibited by lysosomal antiproteases. This study provides experimental evidence that links the effect of ferritin repression on growth stimulation to the expansion of the labile iron pool.

Quinolinic aminoxyl protects albumin against peroxyl radical mediated damage.

A study of peroxyl radical-mediated bovine serum albumin oxidation in the presence of the quinolinic aminoxyl 1,2-dihydro-2,2-diphenyl-4-ethoxy-quinoline-1-oxyl (QAO) was carried out in order to test its efficiency as a protein antioxidant. Albumin oxidation was induced by the tert-butylhydroperoxide/PbO2 system. The extent of protein oxidation, measured by monitoring the formation of carbonyl groups, was considerably reduced in the presence of QAO. ESR measurements were carried out to confirm the consumption of the nitroxide during oxidation and its incorporation in the protein. The data obtained indicate that the quinolinic aminoxyl function can be used as an effective antioxidant in biological systems.