Hemoglobin Oxidation Research Articles

Pathophysiology, clinical presentation, and treatment of coma and acute kidney injury complicating falciparum malaria.

Purpose of reviewCerebral impairment and acute kidney injury (AKI) are independent predictors of mortality in both adults and children with severe falciparum malaria. In this review, we present recent advances in understanding the pathophysiology, clinical features, and management of these complications of severe malaria, and discuss future areas of research.Recent findingsCerebral malaria and AKI are serious and well recognized complications of severe malaria. Common pathophysiological pathways include impaired microcirculation, due to sequestration of parasitized erythrocytes, systemic inflammatory responses, and endothelial activation. Recent MRI studies show significant brain swelling in both adults and children with evidence of posterior reversible encephalopathy syndrome-like syndrome although targeted interventions including mannitol and dexamethasone are not beneficial. Recent work shows association of cell-free hemoglobin oxidation stress involved in the pathophysiology of AKI in both adults and children. Paracetamol protected renal function likely by inhibiting cell-free-mediated oxidative stress. It is unclear if heme-mediated endothelial activation or oxidative stress is involved in cerebral malaria.SummaryThe direct causes of cerebral and kidney dysfunction remain incompletely understood. Optimal treatment involves prompt diagnosis and effective antimalarial treatment with artesunate. Renal replacement therapy reduces mortality in AKI but delayed diagnosis is an issue.

Oxidative Stress Caused by an SOD1 Deficiency Triggers the Accumulation of Oxidatively Modified Carbonic Anhydrase II in Erythrocytes

Red blood cells (RBCs) are continuously exposed to reactive oxygen species (ROS) that are largely produced from intrinsic sources such as the oxidation of hemoglobin. Since superoxide dismutase 1 (SOD1) is the sole superoxide-scavenging enzyme in RBCs, a deficiency leads to the development of hemolytic anemia in mice, suggesting that the underlying mechanism involves a massive, oxidative stress-induced destruction of RBCs. We recently reported a decreased proteasomal function and the accumulation of ubiquitinated proteins in RBCs in SOD1-knockout (KO) mice. Because proteasomes are responsible for the degradation of both ubiquitinated proteins and oxidatively-modified (oxidized) proteins without ubiquitination, their malfunction results in the accumulation of these proteins. In the current study, we examined the issue of how elevated ROS are involved in the destruction of RBCs and the onset of anemia from the point of view of the accumulation of oxidized proteins. The findings indicate that carbonic anhydrase II (CAII) was the major protein within RBCs that was oxidized and that high levels had accumulated in SOD1-KO RBCs. Using purified CAII, we demonstrated that oxidative modification decreased its enzymatic activity in a ROS-dependent manner. In addition, the oxidized CAII molecules appeared to be degraded by proteasomes in RBCs. Based on these findings, we conclude that oxidative stress caused by an SOD1 deficiency disrupts the scavenging activity of proteasomes and accelerates the accumulation of oxidized CAII, leading to RBCs having a shortened life span.

Methemoglobin reductase activity in intact fish red blood cells

Red blood cells (RBCs) possess methemoglobin reductase activity that counters the ongoing oxidation of hemoglobin (Hb) to methemoglobin (metHb), which in circulating blood is caused by Hb autoxidation or reactions with nitrite. We describe an assay for determining metHb reductase activity in intact RBCs in physiological saline at normal Pco2 and pH. After initial loading of oxygenated RBCs with nitrite (partly oxidizing Hb to metHb), the nitrite is removed by three washes of the RBCs in nitrite-free physiological saline to enable the detection of RBC metHb reductase activity in the absence of counteracting oxidation. This assay was used to compare metHb reduction in rainbow trout and carp RBCs under both oxygenated and deoxygenated conditions. Washing resulted in effective wash-out of nitrite to low and safe values (~2μM). The subsequent decline in [metHb] with time followed first-order kinetics, allowing characterization of metHb reductase activity through the first order rate constant k. In oxygenated RBCs at 25°C, the k values for rainbow trout and carp were slightly below or above 0.01min−1, respectively; which is double the value reported for mammals at 37°C. We conclude the higher metHb reductase activity in fish offsets their higher Hb autoxidation and higher likelihood of encountering elevated nitrite. Deoxygenation significantly raised the rates of RBC metHb reduction, and more so in rainbow trout than in carp. The temperature sensitivity of metHb reduction in rainbow trout RBCs was high (Q10 ~2.8) and instrumental in handling increased Hb autoxidation with temperature.

Evaluation of the effect of brominated flame retardants on hemoglobin oxidation and hemolysis in human erythrocytes

Brominated flame retardants (BFRs) are widely used in many everyday products. Numerous studies have shown that BFRs can be released into the environment. Environmental pollution with these compounds raises concerns about their potentially adverse health effects. The aim of this study was to evaluate the effect of tetrabromobisphenol A (TBBPA), tetrabromobisphenol S (TBBPS), 2,4-dibromophenol (2,4-DBP), 2,4,6- tribromophenol (2,4,6-TBP) and pentabromophenol (PBP) on hemolysis induction and hemoglobin oxidation in human erythrocytes. The erythrocytes were incubated with selected BFRs in a wide concentrations ranging from 0.01 to 100 μg/ml for 24 h, 48 h and 72 h. All compounds studied, exhibited hemolytic potential and induced methemoglobin formation. Hemolytic and oxidative potential of BFRs increased along with the increasing concentrations of the compounds studied and elongation of the incubation time. Our study showed that both the number of aromatic rings and the number of bromine atoms in the molecule of the compounds examined influence hemoglobin oxidation and damage to the cellular membrane. Furthermore, we may conclude that 2,4-DBP is potentially most toxic compound because it causes statistically significant changes at the lowest concentration, while the highest toxicity at the highest concentrations was noted for TBBPA.

Characterization of a novel streptococcal heme-binding protein SntA and its interaction with host antioxidant protein AOP2

Efficient iron acquisition is critical for bacteria's survival, virulence and pathology of diseases. The largest reservoir of iron in mammals is incorporated into heme, which can be acquired by bacterial pathogens as a nutritional iron source. In this study, a cell wall protein SntA of Streptococcus suis serotype 2 (SS2) was characterized as a novel heme-binding protein by using the pyridine hemochrome assay and ICP-MS measurement. Yeast two-hybrid and pull-down assays revealed that the SntA protein could interact with the host antioxidant protein AOP2 (Antioxidant protein 2). The oxidation of hemoglobin could be promoted by adding the recombinant SntA into the hemolysates. Animal experiments demonstrated that SntA was associated with in vivo survival and pathogenesis of SS2. This is the first report that a streptococcal heme-binding protein can interact with a host antioxidant protein and consequently inhibit its antioxidant activity. These findings may provide new insights into bacterial cell wall functions and pathogen-host interactions.

Wireless Platform for the Fatigue Measurement of Workers Employed in Underground Mines

Human fatigue (tiredness) – identified as one of the major causes of injuries/accidents taking place in mines – can be easily determined and parameterized by examination of human pulse and haemoglobin oxidation level (SpO2). Two sensors, enabling continuous registration of the factors mentioned above, combined with a ZigBee radio module, have been integrated into a biosensor in the present study. The novelty of the solution is based on a small, pill-sized (and shaped) biosensor form conveniently attachable to a miner’s body for a constant reporting of his weariness level during regular work. Moreover, the biosensor is able to communicate with WLAN concentrators that, in turn, serve to convey each miner’s health readings, via multiple hops, to the monitoring centre for analysing incoming results on-the-fly. Individual miner’s fatigue control is expected to yield less accidents/injuries, which – beside the human aspect – will also considerably save costs of compensation paid to the injured miner/family and preserve the work continuity.DOI: http://dx.doi.org/10.5755/j01.eie.23.4.18718

Sodium meta-arsenite induced reactive oxygen species in human red blood cells: impaired antioxidant and membrane redox systems, haemoglobin oxidation, and morphological changes

Arsenic (As) is an air and water toxicant that causes cancer in multiple organs. Humans are exposed to As through contaminated water. We have examined the cytotoxicity of sodium meta-arsenite (SA), an As(III) compound, in human red blood cells (RBC) under in vitro conditions. Haemolysates were prepared from human RBC treated with different concentrations of SA (0.1–5.0 mM) for 5 h at 37 °C. SA treatment of RBC caused significant increase in methaemoglobin formation, protein and lipid oxidation, and nitric oxide levels. It also resulted in decrease in glutathione levels, methaemoglobin reductase activity and plasma membrane redox system. SA exposure also inhibited the pathways of glucose metabolism while increasing AMP deaminase and glyoxalase-I. It impaired the enzymatic and non-enzymatic antioxidant defence systems which resulted in decreased antioxidant power and a compromised ability to quench free radicals. SA exposure also damaged the membrane since it decreased the activity of membrane bound enzymes, increased the osmotic fragility of treated cells and induced gross morphological changes. This cytotoxicity was the result of oxidative damage since the production of reactive oxygen species (ROS) was increased in SA treated erythrocytes. Thus As(III) causes extensive damage to RBC which impairs their antioxidant system and alters the major cellular metabolic pathways. All this has the potential to lower the oxygen carrying capacity of RBC and reduce their lifespan in blood.

Iron accelerates hemoglobin oxidation increasing mortality in vascular diseased guinea pigs following transfusion of stored blood.

Non-transferrin-bound iron (NTBI) and free hemoglobin (Hb) accumulate in circulation following stored RBC transfusions. This study investigated transfusion, vascular disease, and mortality in guinea pigs after stored RBC transfusion alone and following cotransfusion with apo-transferrin (apo-Tf) and haptoglobin (Hp). The effects of RBC exchange transfusion dose (1, 3, and 9 units), storage period (14 days), and mortality were evaluated in guinea pigs with a vascular disease phenotype. Seven-day mortality and the interaction between iron and Hb as cocontributors to adverse outcome were studied. Concentrations of iron and free Hb were greatest after transfusion with 9 units of stored RBCs compared with fresh RBCs or stored RBCs at 1- and 3-unit volumes. Nine units of stored RBCs led to mortality in vascular diseased animals, but not normal animals. One and 3 units of stored RBCs did not cause a mortality effect, suggesting the concomitant relevance of NTBI and Hb on outcome. Cotransfusion with apo-Tf or Hp restored survival to 100% following 9-unit RBC transfusions in vascular diseased animals. Our data suggest that increases in plasma NTBI and Hb contribute to vascular disease-associated mortality through iron-enhanced Hb oxidation and enhanced tissue injury.

Effects of Different Concentrations of Melatonin on the Time-course of Nitrite–induced Oxidation of Hemoglobin: In vitro Study

Melatonin is a potent scavenger of reactive oxygen species or free radicals like superoxide and hydroxyl radicals. The oxidation of hemoglobin to methemoglobin (meth-Hb) by oxidizing compounds has been widely studied. The present work was designed to evaluate the ability of different concentrations of melatonin to inhibit nitrite–induced oxidation of hemoglobin. Blood samples were obtained from apparently healthy individuals from which erythrocyte hemolysate was prepared. Different concentrations of melatonin (10-9-1.0 mg/ml) were incubated for 10 min with the hemolysate, then to the resultant mixture 1 ml of sodium nitrite (final concentration 0.6 mM) was added, and the formation of meth-Hb was measured by monitoring absorbance of light at 631 nm each min for 30 min. Control samples without melatonin were utilized for comparison. Nitrite caused rapid oxidation of hemoglobin to meth-Hb in control samples; in the presence of melatonin, the oxidation process was delayed in a dose–dependent manner. The effect of melatonin on the time course of nitrite-induced oxidation of Hb showed that melatonin has a protective effect initiated early after addition along with nitrite. Melatonin also affect the time required for the formation of meth-Hb, the time required to convert 50% of the available Hb to meth-Hb was 4 min in the absence of melatonin, and became 17, 22, 26, 30, 114 and 383 min with increasing melatonin concentrations (10-9, 10-6, 0.001, 0.01, 0.1, and 1.0 mg/ml respectively). In conclusion, melatonin in a concentration and time dependent manner can protect Hb from oxidation by nitrite; melatonin delays the onset of autocatalytic stage and the protective effect extended over long period of time.
 Key words: melatonin, erythrocytes oxidation

Concentration-Dependant Antioxidant Activity of Pentoxifylline in Nitrite-induced Hemoglobin Oxidation Model

Free radical formation in heme proteins is recognized as a factor in mediating the toxicity of many chemicals. The present study was designed to evaluate the dose-response relationship of the free radical scavenging properties of pentoxifylline in nitrite-induced Hb oxidation. Different concentrations of pentoxifylline were added at different time intervals of Hb oxidation in erythrocytes lysate, and formation of methemoglobin (MetHb) was monitored spectrophotometrically. The results showed that in this model, pentoxifylline successfully attenuates Hb oxidation after challenge with sodium nitrite; this protective effect was found to be not related to the catalytic stage of Hb oxidation, though such effect was reported to be more prominent when the compound was at the same time of induction of Hb oxidation with nitrite. In conclusion, pentoxifylline can effectively, in concentration-dependent pattern, attenuate sodium nitrite-induced Hb oxidation in vitro.
 Key words: pentoxifylline, radical scavenging, hemoglobin oxidation

Sweet cherries from Fundão possess antidiabetic potential and protect human erythrocytes against oxidative damage

Cherries are one of the most appreciated summer fruits due to their attractive colour, sweet taste, high water content, low level of calories and composition in bioactive compounds which, in turn, are important to prevent some pathologies like diabetes, cardiovascular diseases and cancer. In this work we evaluated the phenolic profile and biological potential of 5 varieties of sweet cherries from Fundão region (Portugal) (Saco, Sweetheart, Satin, Maring and Hedelfinger). A total of 23 phenolic compounds were identified by LC-DAD and distributed by the several classes: 6 anthocyanins, 1 hydroxybenzoic acid, 8 hydroxycinnamic acids, 3 flavan-3-ols and 5 flavonols. Maring revealed higher contents in anthocyanins, while Hedelfinger was the richest in non-coloured phenolics. The antioxidant capacity was evaluated against DPPH and nitric oxide radicals. Hedelfinger was the most active against DPPH• (IC50=12.1μg/mL) and Maring against nitric oxide (IC50=140.9μg/mL). Afterwards, antidiabetic capacity was evaluated through the inhibition of α-glucosidase activity, pointing Hedelfinger as the most active (IC50=10.3μg/mL). The capacity of Saco extracts to inhibit the hemoglobin oxidation and the hemolysis of human erythrocytes was also evaluated. Both assays revealed a concentration-dependent inhibitory effect (IC50=38.6μg/mL and IC50=73.0μg/mL, respectively). The results obtained in this study allow us to conclude that sweet cherries possess a great biological potential, and further investigation should be done to promote commercialization and encourage its use in food supplements and in new pharmaceutical and nutraceutical applications.

Evaluation of glucose-6-phosphate dehydrogenase enzyme deficiency and methemoglobin concentration in blood donors in a Nigerian Tertiary hospital-based blood bank

Background: Glucose-6-phosphate dehydrogenase (G6PD) enzyme deficiency and methemoglobinemia adversely impact on blood transfusion safety by significantly increasing blood storage lesion. Objective: To determine G6PD enzyme deficiency and methemoglobin levels among blood donors in a tertiary hospital-based blood bank in Nigeria. Subjects and Methods: One hundred blood donors who met the criteria for blood donation were prospectively studied. Two milliliters of venous blood was collected from each participant into potassium-ethylenediaminetetraacetic acid specimen containers and analyzed for G6PD status and methemoglobin levels by spectrophotometry, on the same day of sample collection. Results: Among the donors, 43% had normal G6PD activity (9.32 ± 2.26 U/gHb), 44% had partially enzyme deficiency (4.92 ± 1.33 U/gHb), while 13% had total deficiency (0.47 ± 3.49 U/gHb); these were statistically different (P < 0.001). Methemoglobin concentration was elevated in 25% of study participants (3.05 ± 2.30%), while it was normal in 75% (0.99% ± 0.60%); these differences were statistically different (P < 0.001). Conclusion: A significant proportion of our blood donor set has G6PD enzyme deficiency (partial or total) as well as evidence of oxidation of hemoglobin; these findings have adverse implications on transfusion safety.

Comparative Studies on the Effects of Ethyl Nitrite and Hexyl Nitrite Induced Hemoglobin Oxidation of Diabetics Blood and Normal Blood

Comparative Studies on the Effects of Ethyl Nitrite and Hexyl Nitrite Induced Hemoglobin Oxidation of Diabetics Blood and Normal Blood

Interactions between peroxiredoxin 2, hemichrome and the erythrocyte membrane

Peroxiredoxin 2 (Prx2) is an abundant antioxidant protein in erythrocytes that protects against hemolytic anemia resulting from hemoglobin oxidation and Heinz body formation. A small fraction of Prx2 is bound to the cell membrane, but the mechanism and relevance of binding are not clear. We have investigated Prx2 interactions with the erythrocyte membrane and oxidized hemoglobin and whether these interactions are dependent on Prx2 redox state. Membrane binding of Prx2 in erythrocytes decreased when the cells were treated with H2O2, but studies with purified Prx2 and isolated ghosts showed that the interaction was independent of Prx2 redox state. Hemoglobin oxidation leads to the formation of hemichrome, a denatured form of the protein that binds to Band3 protein in the cell membrane as part of the senescence process and is a precursor of Heinz bodies. Hemichrome competed with Prx2 and decreased Prx2 binding to the membrane, potentially explaining the decreased binding in oxidant-exposed cells. The increased membrane binding of Prx2 seen with increasing intracellular calcium was less sensitive to H2O2 or hemichrome, suggesting an alternative mode of binding. Prx2 was also shown to exhibit chaperone-like activity by retarding the precipitation of pre-formed hemichrome. Our results suggest that Prx2, by restricting membrane binding of hemichrome, could impede Band3 clustering and exposure of senescence antigens. This mechanism, plus the observed chaperone activity for oxidized hemoglobin, may help protect against hemolytic anemia.

Haemoglobin Oxidation: A possible mechanism of crude oil toxicity in fish

Haemoglobin Oxidation: A possible mechanism of crude oil toxicity in fish

Oxidative stress and hemoglobin–cholesterol adduct in renal patients with different LDL phenotypes

Unfavorable lipid profile is a major risk factor for cardiovascular disease in renal pathology. In this study, we compared chronic renal patients and healthy controls with different LDL phenotypes (A or B) in respect of various biochemical parameters related to cardiovascular disease. Oxidative stress and anti-oxidative defense parameters [thiobarbituric acid-reacting substances (TBARS), total oxidative status (TOS), total anti-oxidative status (TAS), total protein sulfhydryl (-SH) groups], as well as red blood cell cholesterol distribution were assessed in 40 renal patients and 40 control subjects by standardized assays. LDL particle diameters were determined by polyacrylamide gradient gel electrophoresis. LDL particles are subdivided according to their size into large LDL A phenotype (diameter >25.5nm) and small LDL B phenotype (diameter ≤25.5nm). Renal patients with LDL A phenotype had increased oxidative stress (TOS: p<0.01, and TBARS: p<0.001) and decreased total SH- groups (p<0.001) compared to controls with the same LDL phenotype. A notable decrease in hemoglobin-cholesterol adduct was detected in patients with LDL A phenotype (p<0.001) and LDL B phenotype (p<0.05) compared with appropriate controls. LDL B phenotype was characterized with increased TBARS (p<0.05) compared with LDL A phenotype in control group. Increased oxidative stress, decreased anti-oxidative defense followed with unfavorable changes in hemoglobin-cholesterol binding capacity, could have important influence on cardiovascular disease risk in renal patients regardless of LDL phenotype.

Oxidative hemoglobin reactions: Applications to drug metabolism

Hb is a protein with multiple functions, acting as an O2 transport protein, and having peroxidase and oxidase activities with xenobiotics that lead to substrate radicals. However, there is a lack of evidence for intermediates involved in these reactions of Hb with redox-active compounds, including those with xenobiotics such as drugs, chemical carcinogens, and sulfides. In particular, questions exist as to what intermediates participate in reactions of either metHb or oxyHb with sulfides.The studies presented here elaborate kinetics and intermediates involved in the reactions of Hb with oxidants (H2O2 and mCPBA), and they demonstrate the formation of high valent intermediates, providing insights into mechanistic issues of sulfur and drug oxidations. Overall, we propose generalized mechanisms that include peroxidatic reactions using H2O2 generated from the autooxidation of oxyHb, with involvement of substrate radicals in reactions of Hb with oxidizable drugs such as metyrapone or 2,4-dinitrophenylhydrazine and with sulfides. We identify ferryl intermediates (with a Soret band at 407 nm) in oxidative reactions with all of the above-mentioned reactions. These spectral properties are consistent with a protonated ferryl heme, such as Cpd II or Cpd ES-like species (Spolitak et al., JIB, 2006, 100, 2034–2044). Mechanism(s) of Hb oxidative reactions are discussed.

The metabolites of glutamine prevent hydroxyl radical-induced apoptosis through inhibiting mitochondria and calcium ion involved pathways in fish erythrocytes

The present study explored the apoptosis pathways in hydroxyl radicals (∙OH)-induced carp erythrocytes. Carp erythrocytes were treated with the caspase inhibitors in physiological carp saline (PCS) or Ca2+-free PCS in the presence of 40μM FeSO4/20μM H2O2. The results showed that the generation of reactive oxygen species (ROS), the release of cytochrome c and DNA fragmentation were caspase-dependent, and Ca2+ was involved in calpain activation and phosphatidylserine (PS) exposure in ∙OH-induced carp erythrocytes. Moreover, the results suggested that caspases were involved in PS exposure, and Ca2+ was involved in DNA fragmentation in ∙OH-induced fish erythrocytes. These results demonstrated that there might be two apoptosis pathways in fish erythrocytes, one is the caspase and cytochrome c-dependent apoptosis that is similar to that in mammal nucleated cells, the other is the Ca2+-involved apoptosis that was similar to that in mammal non-nucleated erythrocytes. So, fish erythrocytes may be used as a model for studying oxidative stress and apoptosis in mammal cells. Furthermore, the present study investigated the effects of glutamine (Gln)’s metabolites [alanine (Ala), citrulline (Cit), proline (Pro) and their combination (Ala10Pro4Cit1)] on the pathways of apoptosis in fish erythrocytes. The results displayed that Ala, Cit, Pro and Ala10Pro4Cit1 effectively suppressed ROS generation, cytochrome c release, activation of caspase-3, caspase-8 and caspase-9 at the physiological concentrations, prevented Ca2+ influx, calpain activation, PS exposure, DNA fragmentation and the degradation of the cytoskeleton and oxidation of membrane and hemoglobin (Hb) and increased activity of anti-hydroxyl radical (AHR) in ∙OH-induced carp erythrocytes. Ala10Pro4Cit1 produced a synergistic effect of inhibited oxidative stress and apoptosis in fish erythrocytes. These results demonstrated that Ala, Cit, Pro and their combination can protect mammal erythrocytes and nucleated cells against oxidative stress and apoptosis. The studies supported the use of Gln, Ala, Cit and Pro as oxidative stress and apoptosis inhibitors in mammal cells and the hypothesis that the inhibited effects of Gln on oxidative stress and apoptosis are at least partly dependent on that of its metabolites in mammalian.

Extraction of Phospholipids from Human Erythrocyte Membranes by Hemoglobin Oxidation Products.

This investigation examines oxidation conditions under which hemoglobin extracts membrane phospholipid from erythrocytes and model membranes. In erythrocytes made echinocytic with exogenous phospholipid, addition of hemoglobin oxidized with hydrogen peroxide (H2O2) or Vitamin C (conditions that result in the formation of significant quantities of choleglobin), but not ferricyanide (which produces predominantly methemoglobin), induced dose-dependent shape reversion to less echinocytic forms, consistent with extraction of phospholipids from the exofacial side of the membrane. Erythrocytes preloaded with radiolabeled phosphatidylcholine or NBD-labeled phosphatidylcholine, phosphatidylglycerol or phosphatidic acid, exhibited greatest extraction of radiolabel or fluorescence signal with exogenous hemoglobin oxidized via H2O2 or Vitamin C, but not ferricyanide. However, with NBD-phosphatidylserine (a preferential inner monolayer intercalator), significantly less extraction of labeled lipid occurred with oxidized hemoglobin prepared under all three oxidizing conditions. In dimyristoylphosphatidylcholine liposomes containing radiolabeled phosphatidylcholine, phosphatidylserine or phosphatidylethanolamine, subsequent addition of hemoglobin oxidized with H2O2 or Vitamin C extracted radiolabeled lipid with significantly greater efficiency than ferricyanide-treated hemoglobin, with enhanced extraction detectable at levels approaching physiological plasma oxidant concentrations. Radiolabeled lipid extraction was comparable for phospholipids containing saturated acyl chains between 12 and 18 carbons but diminished significantly for oleoyl-containing phospholipids. Hemoglobin dimerization occurred at very low levels with H2O2 treatment, and even lower levels with Vitamin C treatment, and thus did not correlate to the high efficiency and consistent levels of lipid extraction observed with these treatments. These findings indicate that choleglobin extracts lipids from cell membranes regardless of headgroup or acyl chain length, through a process of direct hydrophobic interaction with the membrane surface.

The modification of structural and functional properties of human hemoglobin induced by nitroglycerin under different oxygen regime conditions

Human oxyhemoglobin exhibits high resistance to nitroglycerin during incubation of the protein with this compound for 0.3-3 h. Prolonged exposure (24 h) leads to activation of methemoglobin production. In the presence of nitroglycerin hemoglobin molecules undergo rapid oxidation during deoxygenation with formation of methemoglobin as the terminal product of human oxyhemoglobin interaction with nitroglycerin. The scheme of interaction processes of oxyhemoglobin with nitroglycerin in different conditions of oxygen regime is proposed. Partially deliganded hemoglobin plays the leading role in the initiation of hemoglobin oxidation processes.