scholarly journals Lipid radicals: properties and detection by spin trapping.

2000 ◽  
Vol 47 (4) ◽  
pp. 923-930 ◽  
Author(s):  
K Stolze ◽  
N Udilova ◽  
H Nohl
Keyword(s):  
Spin Trap ◽  
Lipid Phase ◽  
Linoleic Acid Hydroperoxide ◽  
Lipid Hydroperoxides ◽  
Acyl Radical ◽  
Alkoxyl Radical ◽  
Spin Traps ◽  
Unsaturated Lipids ◽  
High Concentrations ◽  
Lipid Radical

Unsaturated lipids are rapidly oxidized to toxic products such as lipid hydroperoxides, especially when transition metals such as iron or copper are present. In a Fenton-type reaction Fe2+ converts lipid hydroperoxides to the very short-lived lipid alkoxyl radicals. The reaction was started upon the addition of Fe2+ to an aqueous linoleic acid hydroperoxide (LOOH) emulsion and the spin trap in the absence of oxygen. Even when high concentrations of spin traps were added to the incubation mixture, only secondary radical adducts were detected, probably due to the rapid re-arrangement of the primary alkoxyl radicals. With the commercially available nitroso spin trap MNP we observed a slightly immobilized ESR spectrum with only one hydrogen splitting, indicating the trapping of a methinyl fragment of a lipid radical. With DMPO or 5-diethoxyphosphoryl-5-methyl-1-pyrroline N-oxide (DEPMPO) adducts were detected with carbon-centered lipid radical, with acyl radical, and with the hydroxyl radical. We also synthesized lipophilic derivatives of the spin trap DEPMPO in order to detect lipid radical species generated in the lipid phase. With all spin traps studied a lipid-derived carbon-centered radical was obtained in the anaerobic incubation system Fe2+/LOOH indicating the trapping of a lipid radical, possibly generated as a secondary reaction product of the primary lipid alkoxyl radical formed. Under aerobic conditions an SOD-insensitive oxygen-centered radical adduct was formed with DEPMPO and its lipophilic derivatives. The observed ESR parameters were similar to those of alkoxyl radical adducts, which were independently synthesized in model experiments using Fe3+-catalyzed nucleophilic addition of methanol or t-butanol to the respective spin trap.

scholarly journals Mechanism in the reaction of cytochrome c oxidase with organic hydroperoxides: an ESR spin-trapping investigation

2002 ◽  
Vol 365 (2) ◽  
pp. 461-469 ◽  
Author(s):  
Yeong-Renn CHEN ◽  
Ronald P. MASON
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Spin Trap ◽  
Spin Trapping ◽  
Initial Reaction ◽  
Radical Species ◽  
Alkoxyl Radical ◽  
Tyrosine Residues ◽  
Esr Spin Trapping ◽  
Organic Hydroperoxides

Organic hydroperoxides are of great utility in probing the reaction mechanism and the toxicological consequences of lipid peroxidation. In the present study, ESR spin-trapping was employed to investigate the peroxidation of mitochondrial cytochrome c oxidase (CcO) with t-butyl hydroperoxide (t-BuOOH) and cumene hydroperoxide (CumOOH). The spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO) was used to detect the radical species formed from the reaction of CcO with t-BuOOH. The presence of t-BuOOH-derived alkoxyl radical (t-BuO˙) as the primary radical indicates reductive scission of the O—O bond by CcO. The ESR signal of DMPO/˙Ot-Bu can be partially abolished by cyanide, implying that the reductive cleavage involved the haem a3CuB binuclear site of CcO. A nitroso spin trap, 2-methyl-2-nitrosopropane (MNP), was used to detect and identify radical species from the reaction of CcO with CumOOH. In addition to the t-BuOOH-derived methyl, hydroxylmethyl and tertiary carbon-centred radicals, a protein-derived radical was detected. The intensity of the ESR signal from the protein radical increased with the CumOOH concentration at low CumOOH/CcO ratios, with maximal intensity at a ratio of 100mol of CumOOH/mol of CcO. The immobilized protein radical adduct of MNP was stable and persistent after dialysis; it was also resistant to proteolytic digestion, suggesting that it was formed in the transmembrane region, a region that is not accessible to proteases. Its signal was greatly enhanced when CcO cysteine residues were chemically modified by N-ethylmaleimide, when the tryptophan residues in CcO were oxidized by N-bromosuccimide, and when tyrosine residues on the surface of CcO were iodinated, showing that a radical equilibrium was established among the cysteine, tryptophan and tyrosine residues of the protein-centred radical. Pre-treatment of CcO with cyanide prevented detectable MNP adduct formation, confirming that the haem a3-CuB binuclear centre was the initial reaction site. When the CcO was pre-treated with 10mM (100 equivalents) of CumOOH, the enzyme activity decreased by more than 20%. This inhibition was persistent after dialysis, suggesting that the detected protein-centred radical was, in part, involved in the irreversible inactivation by CumOOH. Visible spectroscopic analysis revealed that the haem a of CcO was not affected during the reaction. However, the addition of pyridine to the reaction mixture under alkaline conditions resulted in the destruction of the haem centre of CcO, suggesting that its protein matrix rather than its haem a is the target of oxidative damage by the organic hydroperoxide.

scholarly journals The activity of dopamine-stimulated adenylate cyclase from rat brain striatum is modulated by temperature and the bilayer-fluidizing agent, benzyl alcohol

1982 ◽  
Vol 206 (1) ◽  
pp. 89-95 ◽  
Author(s):  
Lindsey Needham ◽  
Miles D. Houslay
Keyword(s):  
Adenylate Cyclase ◽  
Rat Brain ◽  
Benzyl Alcohol ◽  
Break Point ◽  
Lipid Phase ◽  
Arrhenius Plots ◽  
Basal Activity ◽  
Fluidizing Agent ◽  
High Concentrations ◽  
Single Break

Benzyl alcohol achieved a marked activation of the adenylate cyclase activity in a partially purified membrane preparation from rat brain striata, although inhibition resulted at high concentrations. The degree of activation observed depended on the ligand used to stimulate the enzyme, with that observed in the presence of guanosine 5′-[β,γ-imido]triphosphate (p[NH]ppG) (5.8-fold)>dopamine+p[NH]ppG (5-fold)> GTP (3-fold)>dopamine+high GTP (2.25-fold)>dopamine (+low GTP)=basal (+low GTP) (1.7-fold). The differences in the concentration-dependence of both the activation and inhibition of dopamine-stimulated and basal activities of the enzyme meant that increasing benzyl alcohol concentrations caused a net elevation in the fold-stimulation of the basal activity by dopamine. Arrhenius plots of p[NH]ppG-, GTP-, fluoride-, dopamine-plus-high GTP- and dopamine-plus-p[NH]ppG-stimulated activities all exhibited a single break occurring at around 22°C. This break point was decreased to around 13°C when 50mm-benzyl alcohol was added to the assays. In the presence of dopamine (+low GTP), Arrhenius plots exhibited two distinct breaks, one at around 21°C and the other at around 11°C. When benzyl alcohol (50mm) was added to these assays of dopamine (+low GTP)-stimulated activity, a single break at around 14°C was observed. For the basal activity the Arrhenius plot exhibited a single break at around 15°C both in the presence and in the absence of 50mm-benzyl alcohol. It is suggested that the enzyme is activated by productive collisions between independent mobile entities and that the activity of the enzyme may be regulated by changes in membrane fluidity. The breaks in the Arrhenius plots of all of the ligand-stimulated activities, but not the basal activity, are attributed to lipid-phase separations occurring in either the inner or the outer halves of the bilayer.

scholarly journals l-carnosine (β-alanyl-l-histidine) and carcinine (β-alanylhistamine) act as natural antioxidants with hydroxyl-radical-scavenging and lipid-peroxidase activities

1994 ◽  
Vol 304 (2) ◽  
pp. 509-516 ◽  
Author(s):  
M A Babizhayev ◽  
M C Seguin ◽  
J Gueyne ◽  
R P Evstigneeva ◽  
E A Ageyeva ◽  
...  
Keyword(s):  
Linoleic Acid ◽  
Direct Reduction ◽  
Radical Scavenging ◽  
Thiobarbituric Acid ◽  
Natural Antioxidants ◽  
Peroxyl Radicals ◽  
Lipid Phase ◽  
Oh Radicals ◽  
Thiobarbituric Acid Reactive Substance ◽  
Lipid Hydroperoxides

Carnosine (beta-alanyl-L-histidine) and carcinine (beta-alanylhistamine) are natural imidazole-containing compounds found in the non-protein fraction of mammalian tissues. Carcinine was synthesized by an original procedure and characterized. Both carnosine and carcinine (10-25 mM) are capable of inhibiting the catalysis of linoleic acid and phosphatidylcholine liposomal peroxidation (LPO) by the O2(-.)-dependent iron-ascorbate and lipid-peroxyl-radical-generating linoleic acid 13-monohydroperoxide (LOOH)-activated haemoglobin systems, as measured by thiobarbituric-acid-reactive substance. Carcinine and carnosine are good scavengers of OH. radicals, as detected by iron-dependent radical damage to the sugar deoxyribose. This suggests that carnosine and carcinine are able to scavenge free radicals or donate hydrogen ions. The iodometric, conjugated diene and t.l.c. assessments of lipid hydroperoxides (13-monohydroperoxide linoleic acid and phosphatidylcholine hydroperoxide) showed their efficient reduction and deactivation by carnosine and carcinine (10-25 mM) in the liberated and bound-to-artificial-bilayer states. This suggests that the peroxidase activity exceeded that susceptible to direct reduction with glutathione peroxidase. Imidazole, solutions of beta-alanine, or their mixtures with peptide moieties did not show antioxidant potential. Free L-histidine and especially histamine stimulated iron (II) salt-dependent LPO. Due to the combination of weak metal chelating (abolished by EDTA), OH. and lipid peroxyl radicals scavenging, reducing activities to liberated fatty acid and phospholipid hydroperoxides, carnosine and carcinine appear to be physiological antioxidants able to efficiently protect the lipid phase of biological membranes and aqueous environments.

scholarly journals A coupled surface-Cahn–Hilliard bulk-diffusion system modeling lipid raft formation in cell membranes

2016 ◽  
Vol 26 (06) ◽  
pp. 1149-1189 ◽  
Author(s):  
Harald Garcke ◽  
Johannes Kampmann ◽  
Andreas Rätz ◽  
Matthias Röger
Keyword(s):  
Numerical Simulations ◽  
Lipid Raft ◽  
System Modeling ◽  
Bulk Diffusion ◽  
Lipid Phase ◽  
Qualitative Behavior ◽  
Time Behavior ◽  
Relaxation Dynamics ◽  
Unsaturated Lipids ◽  
Long Time

We propose and investigate a model for lipid raft formation and dynamics in biological membranes. The model describes the lipid composition of the membrane and an interaction with cholesterol. To account for cholesterol exchange between cytosol and cell membrane we couple a bulk-diffusion to an evolution equation on the membrane. The latter describes the relaxation dynamics for an energy which takes lipid–phase separation and lipid–cholesterol interaction energy into account. It takes the form of an (extended) Cahn–Hilliard equation. Different laws for the exchange term represent equilibrium and nonequilibrium models. We present a thermodynamic justification, analyze the respective qualitative behavior and derive asymptotic reductions of the model. In particular we present a formal asymptotic expansion near the sharp interface limit, where the membrane is separated into two pure phases of saturated and unsaturated lipids, respectively. Finally we perform numerical simulations and investigate the long-time behavior of the model and its parameter dependence. Both the mathematical analysis and the numerical simulations show the emergence of raft-like structures in the nonequilibrium case whereas in the equilibrium case only macrodomains survive in the long-time evolution.

scholarly journals Nitrones: not only extraordinary spin traps, but also good nitric oxide sources in vivo

2015 ◽  
Vol 65 (4) ◽  
pp. 413-426 ◽  
Author(s):  
Mircea Dumitru Croitoru ◽  
Hermina Iulia Petkes ◽  
Ibolya Fülöp ◽  
Remus Cotârlan ◽  
Oana Elena Şerban ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Spin Trap ◽  
Nitrate Concentration ◽  
Plasma Concentrations ◽  
Hepatic Metabolism ◽  
Nitric Oxide Production ◽  
Spin Traps ◽  
Oxide Production

Abstract Free radicals are involved in the development of reperfusion injuries. Using a spin trap, the intensity of such lesions can be reduced. Nitrones (effective in vivo spin traps) were tried in this work as in vivo nitric oxide donors. Nitrite and nitrate concentration values (rabbit blood) were used as biomarkers of nitric oxide production. Most nitrones did not increase plasma concentrations of nitrite and nitrate; on the contrary, reduced plasma concentrations of these indicators were noted. However, glyoxal isopropyldinitrone, in a dose of 50 mg kg-1, was highly effective in increasing nitric oxide production. At the same time, nitrones do not react with hepatic homogenates, proving that the release of nitric oxide takes place in the tissues and is not related to hepatic metabolism. Before using nitrones in vivo, they were tested in vitro for the ability to release nitric oxide following a reaction with the hydroxyl radical.

Spin trapping in photochemistry of coordination compounds

1982 ◽  
Vol 60 (12) ◽  
pp. 1565-1573 ◽  
Author(s):  
Detlef Rehorek ◽  
Horst Hennig
Keyword(s):  
Coordination Compounds ◽  
Spin Trap ◽  
Spin Trapping ◽  
Photochemical Reactions ◽  
Paramagnetic Species ◽  
Side Reactions ◽  
Limited Extent ◽  
Solvated Electrons ◽  
Spin Traps ◽  
Spin Trapping Technique

The application of spin-trapping technique to detect short-lived paramagnetic species formed during photochemical reactions of coordination compounds is reviewed. Interference of radical recombinations by scavenging action of spin traps has been pointed out to be important at high spin-trap concentrations only. Due to only a limited extent of side reactions, nitrosodurene and phenyl N-tert-butyl nitrone were found to be excellent spin traps for the study of photoreactions of metal complexes in nonpolar solutions, whereas 5,5-dimethyl pyrroline-1-oxide is recommended for aqueous solutions. Using these spin traps, both organic and inorganic radicals, e.g. H, Cl, N3, CN, OH, O2−, as well as solvated electrons and metal-centered free radicals have been detected during the photolysis of coordination compounds. The detection of singlet oxygen by reaction with 2,2,6,6-tetramethyl piperidine is briefly discussed.

scholarly journals Characterization of microsomal choloyl-coenzyme A synthetase

1977 ◽  
Vol 163 (2) ◽  
pp. 357-362 ◽  
Author(s):  
D A Vessey ◽  
D Zakim
Keyword(s):  
Bile Salts ◽  
Substrate Inhibition ◽  
Active Form ◽  
Microsomal Membrane ◽  
Lipid Phase ◽  
Bivalent Cation ◽  
Absolute Requirement ◽  
High Concentrations ◽  
Triton X ◽  
Membrane Treatment

Choloyl-CoA synthetase (EC 6.2.1.7) was characterized for the first time under appropriated assay conditions. The p/ optimum for the reaction is pH 7.2.-7.3. The reaction has an absolute requirement for bivalent cation. Several different metal ions fulfil this requirement, but Mn2+ and Mg2+ were the most effective. The KAppm (apparent Km) for CoA, extrapolated from kinetic data, is 50 micronM, but in fact the rate of reaction is increased little by concentrations of CoA above 25 micronM. The KAppm for ATP is 600 micronM. High concentrations of ATP appear to cause substrate inhibition. The KAppm for cholate was 6 micronM. The enzyme was inhibited by treating the microsomal fraction with N-ethylmaleimide. The inclusion of various conjugated and unconjugated bile salts in the assay also inhibited the enzyme. Unconjugated bile salts were more potent inhibitors than the conjugated bile salts. High concentrations of oleic acid inhibited the enzyme. The properties of choloyl-CoA synthetase were not modified by alterations of the properties of the lipid phase of the microsomal membrane. Treatment with phospholipase A did not alter activity directly. Triton N-101 and Triton X-100 also were without effect on activity, and the enzyme was insensitive to temperature-induced phase transitions within the lipid portion of the membrane. The enzyme can be solubilized from the microsomal membrane in an active form by treatment with Triton N-101.

From early spin-trapping experiments to acyl nitroxide chemistry: synthesis of and spin trapping with a water-soluble nitrosopyrazole derivative

1982 ◽  
Vol 60 (12) ◽  
pp. 1587-1593 ◽  
Author(s):  
M John Perkins ◽  
Harparkash Kaur
Keyword(s):  
Spin Trap ◽  
Preliminary Investigation ◽  
Spin Trapping ◽  
Water Soluble ◽  
Nitroso Compounds ◽  
Nitroxide Radicals ◽  
Personal View ◽  
Spin Traps ◽  
Subsequent Investigation

A personal view of early experiments which led to the use of C-nitroso-compounds as spin traps is presented, and it is shown how these experiments resulted in the first isolation, and subsequent investigation, of acyl nitroxide radicals: the use of 1-methyl-4-nitroso-3,5-diphenylpyrazole as a spin trap, and the preparation and preliminary investigation of its water-soluble analogue (1) are described.

Free radical production during phenylhydrazine-induced hemolysis

1982 ◽  
Vol 60 (12) ◽  
pp. 1528-1531 ◽  
Author(s):  
H. A. O. Hill ◽  
P. J. Thornalley
Keyword(s):  
Spin Trap ◽  
Spin Adduct ◽  
Phenyl Radical ◽  
Erythrocyte Suspension ◽  
Phenyl Radicals ◽  
Spin Traps ◽  
Free Radical Production ◽  
Radical Trapping ◽  
Radical Production ◽  
Moderate Yield

The production of phenyl radicals during phenylhydrazine-induced hemolysis has been demonstrated by the use of the spin traps, DMPO, M4PO, and LINPyBN. The phenyl spin adducts of DMPO and M4PO were produced in moderate yield by an oxygenated 1% erythrocyte suspension. With the lipid soluble spin trap LINPyBN, a dramatic increase (400%) in the yield of phenyl spin adduct was observed despite little increase in the rate of phenyl radical trapping. The production of phenyl spin adducts was decreased when phenylhydrazine-4-sulphonic acid or carbonmonoxyhemoglobin-containing erythrocytes were used. These results suggest that the reaction of phenylhydrazine with oxyhemoglobin leads to the formation of phenyl radicals that are preferentially trapped in the erythrocyte membrane.

EFFECTS OF OVARIAN STEROID HORMONES ON HISTOCHEMICALLY DEMONSTRABLE LIPIDS IN THE RAT UTERINE EPITHELIUM

1973 ◽  
Vol 56 (1) ◽  
pp. 59-67 ◽  
Author(s):  
D. P. BOSHIER ◽  
HILARY HOLLOWAY
Keyword(s):  
Steroid Hormones ◽  
Medroxyprogesterone Acetate ◽  
Neutral Lipids ◽  
Uterine Epithelium ◽  
Oestrous Cycle ◽  
Ovarian Steroid ◽  
Plasma Progesterone ◽  
Unsaturated Lipids ◽  
High Concentrations

SUMMARY Histochemical studies showed that during the rat oestrous cycle, uterine epithelial lipids were at their highest levels during dioestrus and pro-oestrus. In ovariectomized mature animals given oestradiol-17β, either by itself or in combination with medroxyprogesterone acetate, neutral lipids and unsaturated lipids were below control levels, while phospholipids were increased. Medroxyprogesterone acetate, however, increased levels of neutral lipids and unsaturated lipids, and decreased phospholipids. It is suggested that during the oestrous cycle of the rat, high concentrations of uterine epithelial lipid during late dioestrus and pro-oestrus reflect the increased plasma progesterone of early dioestrus acting in a low plasma oestrogen environment.

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