The Redox Reactions Of Copper

Except for conditions of strong oxidative stress or high iron levels, the endogenous copper pool in cells and tissues is considered now as the determinant for the formation and decomposition of RS-NO in biosystems 1,3,13,20 . The redox couple Cu2+ Cu+ has a rather small redox potential Eo +0.15 V. Therefore, in principle, copper can catalyze the decomposition of RS-NO by shuttling between its two redox states according to the reaction as in Scheme 1. net reaction RS--NO+-> NO + (RS-SR) Scheme...

References

Biological actions and properties of endothelium-derived nitric oxide formed and released from artery and vein. Circ. Res. 1989 65 1-21. 2 Gladwin MT, Shelhamer JH, Schechter AN, Pease-Fye ME, Waclawiw MA, Panza JA, Ognibene FP, Cannon III RO. Role of circulating nitrite and S-nitrosohemoglobin in the regulation of regional blood flow in humans. Proc. Natl. Acad. Sci. USA 2000 97 11482-11487. 3 Rassaf T, Kleinbongard P, Preik M, Dejam A, Gharini P, Lauer T, Erckenbrecht J, Duschin...

Protein Mediators Of Biotransformation

Bioactivation of nitrates both to yield NO and to yield cGMP-independent bioactivity requires reduction and oxygen atom transfer. Therefore, an enzyme or protein mediator of bioactivation requires a functional group capable of supplying electrons and or accepting an oxygen atom the logical candidates are metaloproteins and protein thiols and sulfides. Several proteins have been identified that are capable of mediating the denitration of GTN, including Hb, Mb, XOR, old yellow enzyme, glutathione...

Xj

EPR spectra of control macrophage preparations 24 . Left panel unreduced preparations at 25 K (curve a), 16 K (curve b) and 30 K (curve c). Right panel preparations treated by dithionite (1 mM) + methyl viologen (5 mM), recorded at 40 K (curves d,e) and 23 K (curve f). Preparations treated with dithionite-methyl viologen after 5 min incubation with 10-7 M NO, recorded at 40 K (curves g,h) and 23 K (curve i). (Curve j) shows the EPR spectrum of mouse liver at 20 K. absorption near g 1.94...

Chemical Reactivity Of Nitrites

The chemistry of organic nitrites includes heterolytic and homolytic reactions, in addition to oxidation of haemoglobin 103 . There is an extensive literature on the dominant reaction pathway for nitrites in solution, transnitrosation, primarily reported by Williams and co-workers 104-107 . In parallel, these researchers studied the reaction of other nitroso compounds including nitrosothiols, although the fact that many studies were not carried out in pH 7.4 phosphate buffer has led to much of...

Nitrate Tolerance

In the clinical setting, tolerance to the antianginal and haemodynamic effects of nitrates is associated with continuous exposure to nitrates, and has led to the use of elliptical dosage regimens to provide a nitrate-free interval, during which recovery of sensitivity to the vasodilator effects of the nitrate can occur. A rebound phenomenon is clinically characterized, wherein increase in the frequency of anginal attacks or deterioration in exercise performance is observed. Tolerance to...

NO rs

NO+ RS- -> R NO+ RS- The cofacial stacking implies significant overlap between the axial dz2 orbitals of the adjacent iron atoms. The overlap causes antiferromagnetic spin-pairing that leaves the dimer diamagnetic 43,44 . We now consider the crystalline state of paramagnetic DNIC with thiol-containing lig-ands. As aforementioned diffraction experiments have revealed that the crystalline solid corresponds to iron in a tetrahedral crystal field 37,41,90,100-109 . In a tetrahedral crystal field,...

Nitrogen Monoxide Forms Intracellular Complexes With Iron

There is strong evidence that NO forms intracellular complexes that play important roles in biological processes. Apart from the formation of haem-NO complexes in guanylate cyclase, it is well-known that the cytotoxic effect of NO is, at least in part, due to its interaction * Author for Correspondence. E-mail d.richardson pathology.usyd.edu.au with Fe in a number of proteins, including (i) the rate-limiting enzyme in DNA synthesis, ribonucleotide reductase 12 (ii) the Fe storage protein,...

Info

* Detection limit 1 nM. t 13 , ' 12 . * Detection limit 1 nM. t 13 , ' 12 . nitrite by certain bacterial strains in the gastrointestinal tract. (3) Finally, the oxidation of endogenous NO to nitrite. Some additional nitrite may also originate from exogenous sources like NO donors, organic nitrates or nitrites (cf Chapter 17). Nitrite levels in the vascular system are clearly strongly affected by the enzymatic activity of endothelial nitric oxide synthase (eNOS) 1,5 . Plasma nitrite levels were...

Dnic Capacity Of Inhibiting Platelet Aggregation

Investigations in the 1980s demonstrated that DNICs with various anion ligands (thio-sulfate, cysteine or phosphate) are capable of preventing platelet aggregation induced by diverse agents (ADP, collagen, thrombin or epinephrine) 18,19 . This activity was suggested to be mediated by NO release from the complexes. According to the earlier proposed mechanisms 51 , the activation of guanylate cyclase by NO radicals in platelets leads to the accumulation of guanosine 3',5'-cyclic monophosphate...

Protein degradation and apoptosis

Ubiquitination and proteasomal degradation represent the major protein degradation pathway in the cell. Two classes of ubiquitin enzymes, E2 ubiquitin-conjugating enzyme UbcH7 25 and the E3 ubiquitin ligase protein parkin 15,130 or HDM3 131 , were found to be S-nitrosated. S-nitrosation of the target protein may also change its sensitivity to ubiquitination and proteasomal degradation 132 . By contrast, S-nitrosation of iron regulatory protein 2 promotes its ubiquitination and proteasomal...

Nitrates As Nitric Oxide Mimetics

In experiments in blood vessels that exploited the sensitivity of ESR (electron spin resonance) detection using a tissue permeable spin trap, NO was measured from endogenous production and from addition of an exogenous nitrosothiol 47-49 . However, using the same methodology, NO was not detected from pharmacologically relevant concentrations of GTN and ISDN. At much higher, suprapharmacological concentrations of nitrates (> 10 M), detection of NO was possible. A second recent study failed to...

Chemical Reactivity Of Nitrates

The reactions of nitrates are sketched in Fig. 5. These are all heterolytic processes, except for the homolysis of the sulfenyl nitrite that may be formed from initial reaction of a nitrate with thiol. The bond dissociation energy for organic nitrate homolysis, 43 kcal mol, is substantially higher than that calculated for homolysis of nitrosothiols ( 32 kcal mol) 8,28,72 . Nitrate homolysis to NO2 is improbable as a thermal reaction relevant to biology, nevertheless, there is substantial...

Aqueous Reduction Pathways Of Nitrite

At physiological pH 7.0-7.4, nitrite anions are fairly stable in the absence of compounds like oxy-hemoglobin. In view of this stability, nitrite is often taken as an indirect measure for NO. Nitrite easily binds to many transition metal ions and decelerates their participation in redox reactions. This property is often used to cure meats or sausages by addition of nitrite. However, the presumed stability of nitrite should be approached with caution. As mentioned above, nitrite rapidly reacts...

Nitric Oxide Synthesis In Plants

In mammals, NO is generated primarily by nitric oxide synthase(s) (NOSs). NOSs are a group of evolutionarily conserved cytosolic or membrane-bound isoenzymes that convert L-arginine to L-citrulline and NO 16 . In plants, NOS activity has been detected in several plant species when mammalian NOS inhibitors have been used to inhibit NO production 17 . However, no gene or protein with a sequence similar to mammalian NOS has been found in the sequenced A. thaliana genome. Guo et al. (2003)...

GSNO infusion fcgmin

Drop in arterial blood pressure of preeclamptic pregnancies upon infusion of increasing doses of GSNO. (From Ref. 134 .) RSNO has been implicated in a number of respiratory diseases. In ammatory state as in pneumonia gives higher RSNO levels in the lungs. Asthmatic patients exhale high levels of NO but have depressed RSNO levels in the airways. The modulation of RSNO status for clinical therapy is only now being considered 66,70,135 . Injection of modest doses of GSNO has also been...

Xanthine Oxidasecatalyzed Nitrite Reduction

Xanthine oxidase (XO) is a ubiquitous enzyme in mammalian cells that plays important roles in both physiological and pathological conditions. It is involved in the catabolism of purine and pyrimidines, oxidizing hypoxanthine to xanthine and xanthine to uric acid. XO also reduces oxygen, to superoxide and hydrogen peroxide production, and is one of the key enzymes responsible for superoxide-mediated cellular injury. Although it has been established that XO can reduce nitrite to NO 4,5,37 ,...

Contents

Nitric oxide radicals and their reactions Ernst van Faassen and Anatoly F. Vanin 3 13 DNIC physico-chemical properties and biological activity Chapter 2. DNICs physico-chemical properties and their observations in cells and tissues Anatoly F. Vanin and Ernst van Faassen 19 Low-molecular-weight DNIC with thiol-containing ligands 20 Vibration spectroscopy of nitrosyl ligands in Mossbauer (y-resonance) properties of low-molecular DNICs with thiol-containing DNIC with sulfide and...

Biological formation

The cellular metabolism of S-nitrosothiols is complex and has not yet been fully elucidated. In general, the levels of S-nitrosothiols formed in vivo are determined by the NO flux, i.e., activity of NOS and availability of substrate rate of formation of the S-nitrosating species and competition of different thiols and other reactive motifs for reaction with the nitrosating species. We found that S-nitrosated proteins can form within endothelial cells from an exogenous S-nitrosothiol donor or...

Dnic May Be Used As A Biomarker For The Antimicrobial And Cytotoxic Actions Of Nitrite

The interaction of nitrite or NO with the iron-sulfur protein enzyme is closely implicated in nitrite treatment of biological systems as described in the previous sections. Dinitro-syl dithiolato iron complex (DNIC) formed through the interaction has been shown to be relatively stable paramagnetic molecule that exhibits a characteristic electron paramagnetic resonance (EPR) signal both in solution and the frozen state 46,74-78 . In nitrite-treated cells of clostridia 7-9 and E. coli O157 H7 79...

Nitrite and nitrosospecies in blood and tissue approaching the gap between bench and bedside

University Hospital Aachen, Medical Clinic I, Department of Medicine, Division of Cardiology and Pulmonary Diseases, Germany The continuous production and release of endothelium-derived nitric oxide (NO) plays an important role in vascular homeostasis and cardiac function 1 . For a long time, the signaling actions of NO in the vasculature have been thought to be short-lived as a result of its rapid reaction with oxy-hemoglobin and the immense concentration of the latter in blood. However, a...

Introduction

Dinitrosyl-iron complexes (DNICs) with thiol-containing ligands were discovered in cells and tissues with EPR spectroscopy. The EPR spectrum of these paramagnetic (S 1 2) complexes has a characteristic anisotropic lineshape centered at gav 2.03 (2.03 signal) which may be observed over a wide range of temperatures from liquid helium to room temperature. The g 2.03 signal was recorded and discussed for the first time in cultured yeast cells and subsequently in the tissues of some animals 1-3...

Nitric oxide and dinitrosyl iron complexes roles in plant iron sensing and metabolism

Magdalena Graziano and Lorenzo Lamattina* Instituto de Investigaciones Biol gicas, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, CC 1245, (7600) Mar del Plata, Argentina Nitric oxide (NO) is a signaling and physiologically active molecule in plants. However, the molecular mechanism s involved in transducing the NO signal between cells and tissues is are still unknown. The formation of low-molecular weight dinitrosyl iron complexes (DNICs) from internal NO...

Mdr1

The efflux of the MRP1 substrate, 3H -vincristine (3H-VCR), is greater from the MRPl-hyper-expressing cells, MCF7-VP, compared to control cells (MCF7-WT). (B,C) In contrast to other ABC transporters, only MRP1 is hyper-expressed in MCF7-VP cells relative to MCF7-WT. (A) 3H-VCR efflux from MCF7-WT and MCF7-VP cells. Cells were prelabelled with 3H-VCR (20 mM) for 30 min at 37 C, washed, and reincubated in the presence of non- radioactive VCR (20 mM). Released 3H-VCR was expressed as a...

Des R Richardson

Department of Pathology, Iron Metabolism and Chelation Program, Blackburn Building, University of Sydney, Sydney, New South Wales, 2031, Australia GENERAL INTRODUCTION NITROGEN MONOXIDE IS A VITAL MESSENGER MOLECULE AND CYTOTOXIC EFFECTOR Nitrogen monoxide (NO) is a crucial effector and messenger molecule that plays roles in a wide variety of biological processes in animals and plants 1,2 . In fact, NO has roles in neurotransmission, smooth muscle relaxation, blood clotting, iron (Fe)...

Chemical labeling

Jaffrey and colleagues recently published a sensitive chemical method in which thiols are first covalently blocked, after which S-nitrosothiols are gently reduced to thiols with ascorbate that react with a biotinylating reagent specific for sulfydryl groups 103 . As straightforward as this method appears, its success depends critically on the extent of blockade of protein thiols in the first step. Inefficiency in this reaction could lead to false-positive labeling of proteins, and, thus,...

Sj

The shape of the EPR spectra from 57Fe-(or 56Fe)-DNIC neocuproine (A,B). Doublet spectra above spectra A is low-field part of the latter recorded at higher amplification. The spectra were recorded at 77 K. (From Ref. 25 .) as 3d 7 and the iron center acquires the character of Fe+. In the absence of NO, the Fe2+ ions are not chelated by neocuproine because of rapid formation of water insoluble iron hydroxide complexes 25 . Bathocuproine disulfonate (BCS) is a highly soluble cuproine...

G

ESR spectra of selected DNIC. Spectra were recorded in 0.1 M phosphate buffer saturated with N2 (20 C). A stock solution of 0.1 M phosphate buffer (pH 7.20) saturated with NO gas ( 1.8 mM) was prepared by rst deoxygenating the medium with N2 for 20 min and then gassing with NO gas that was passed through a gas trap containing KOH. NO was produced by dropping sulfuric acid to sodium nitrite. Spectra 1 Fe(NH4)2(SO4)2 (0.2 mM) in the presence of cysteine (1 mM), DTT (5 mM), or...

Nitrosylheme Formation And Nitric Oxide Signaling During Brief Myocardial Ischemia

In addition to generation from specific nitric oxide (NO) synthases, we have observed that NO formation from nitrite occurs in the ischemic heart. While NO binding to heme-centers is the basis for NO-mediated signaling, as occurs through guanylate cyclase (GC), it was not known if this process is triggered with physiologically relevant periods of sublethal ischemia and if nitrite serves as a critical substrate. Therefore, EPR studies to measure nitrosyl-heme formation during the time course of...

Laboratory Synthesis Of Dnic With Lowmolecular Anionic Ligands

For laboratory synthesis of DNIC with low-molecular-weight thiol ligands, two facile pathways exist First, exposure of solutions with iron and thiols to gaseous NO 69 . Second, by mixing nitrosothiols with iron 46 . As a typical example of the first pathway, a Thunberg vial with two separate containers is prepared. The upper container holds 1 ml distillate water with 25 mM ferrous sulfate, the bottom container holds 4 ml 15 mM HEPES or Tris buffer, pH 7.4 with 100 mM thiol. After evacuation to...

A

EPR spectra of NO trapping in hearts labeled with Fe MGD. (A) Frozen tissue from a normally perfused heart (B) frozen tissue from a heart subjected to 30 min of ischemia. limited solubility in water, therefore, the ferrous iron complex of N-methyl-D-glucamine-dithiocarbamate (MGD), Fe2+ MGD2 (Fe MGD), was also developed and has been applied for measuring NO in living tissues 66 . Alterations in NO generation had been hypothesized to be a critical cause of injury in the ischemic heart...

Nitric oxide radicals and their reactions

Vanin2 1Debye Institute, Section Interface Physics, Ornstein Laboratory, Utrecht University, 3508 TA, Utrecht, The Netherlands 2Semenov Institute of Chemical Physics, Russian Academy of Sciences, Moscow, 119991, Nitric oxide is a peculiar radical species in many respects. It is a radical in the sense that its electronic configuration contains a half-occupied orbital that is occupied by a single electron only. In spite of this open electronic structure, its...

J i 111

EPR spectra at 77 K from liver of mice injected with bacterial lipopolysaccharide (LPS) 4 h earlier. (A) (1,2) ferrous-citrate complex and diethyldithiocarbamate (DETC) (B) (3) the ferrous-citrate complex or (4,5) the ferrous-citrate complex and thiosulfate. Spectra (2,5) were recorded in livers of mice which had been given NNLA at 2.5 h after the injection of LPS. The animals were euthanized in 15 min after injecting the ferrous-citrate complex, DETC or thiosulfate. (From Ref. 99 .)...

Nitrite acts as a colorant flavorant antioxidant and antibotulinal agent in cured meat

In ancient times, meat was preserved with saline desert sands and sea salts, both of which contain nitrate 5 . The reddening effect of nitrate in preserved meat was mentioned as far back as the late Roman era, but it wasn't until the early twentieth century that the bacterial reduction product, nitrite, was identified as the agent responsible for coloring and curing meat 5 . In meat curing, nitrate functions as a reservoir for nitrite, which acts not only to color meat, but also acts as a...

Cellular Iron Metabolism

Before describing in detail about the effects of NO on intracellular Fe pools, it is important to discuss the mechanisms involved in Fe metabolism. Iron is fundamental for life as it is a cofactor of enzymes such as cytochrome c and ribonucleotide reductase, which are essential for ATP production and DNA synthesis, respectively (for reviews see 11,35 ). The maintenance of mammalian iron (Fe) homeostasis begins with the ability to absorb and control dietary Fe from the gut via enterocytes (for...

Stability Of Rsno In Vivo

In biological systems, additional pathways exist for removal of RSNO. The consumption of S-nitrosogroups (S-denitrosation) by endogenous enzymes has not been often reported in the literature. Mammalian physiology does not seem to require a dedicated system to remove excess quantitites of RSNO. A modest capacity for S-denitrosation has been recently reported for the protein disul de isomerase enzyme 62 and for anaerobic xanthine oxidase 63 . Cu Zn superoxide dismutase was capable to denitrosate...

Products of the reaction of cytosolic and mitochondrial aconitases with nitric oxide

Antholine2 and Helmut Beinert3 1 Department of Chemistry, Gannon University, Erie, PA 16561, USA 2Biophysics Research Institute, Medical College of Wisconsin, Milwaukee, WI53226, USA 3Institute for Enzyme Research, University of Wisconsin Madison, 1710 University Avenue, Madison, Aconitases are enzymes that catalyze the stereospecific isomerization of citrate to isocitrate in the tricarboxylic cycle 1 . They are iron-sulfur proteins that contain 4Fe 4S clusters....

Iii11l

EPR spectra from 0.2 mM adrenodoxin (Adr) treated with 56Fe2+ (1.8 mM) + NO (curve a) followed by thiosulfate (curves b,c). Recordings were made at 77 K, microwave power 20 mW and modulation amplitude 0.5 mT (curves a,b) and 0.01 mT (curve c). To the right of the spectra, relative amplifications of the signals are shown. Reproduced with permission, from Ref. 21 the Biochemical Society. thiosulfate was added to the solution, a narrow isotropic signal at g 2.03 appeared that was...

Ironsulfur Clusters Can Be Reassembled To Replace Dnic

To re-assemble the FeS clusters, recombinant cysteine desulfurase (IscS protein) was prepared from E. coli 56 . IscS is a member of the recently identified FeS cluster assembly machinery 57 . The enzyme catalyzes desulfurization of L-cysteine and provides sulfide for the synthesis of FeS clusters 58 . When the ferredoxin DNIC (Fig. 4, trace a) was incubated with L-cysteine and IscS, the observed UV-visible absorption spectrum was typical for the ferredoxin 2Fe 2S clusters, with two absorption...

Origin Of Plasma Nitrite

The net concentration of nitrite in plasma is a result of its formation and consumption. Several routes of formation of nitrite exist in mammals. Nitrite is an oxidation product of endothelium-derived NO. Moreover, nitrite is present in food, especially in processed meat, in which nitrite is used to prevent botulism 95 . Furthermore, plasma nitrite increases after ingestion of large amounts of inorganic nitrate. This increase is entirely due to enterosali-vary circulation of nitrate (as much as...

Physiological distribution of Snitrosothiols

Protein S-nitrosothiols and low-molecular-weight S-nitrosothiol compounds like GSNO comprise two pools of intracellular S-nitrosothiols. Protein S-nitrosothiols tend to be more stable than low-molecular-weight S-nitrosothiols. GSNOR-deficient yeast or mice have higher protein S-nitrosothiol content, suggesting that GSNO exists in equilibrium with SNO-proteins 14,58 . The exchange of S-nitrosothiols between proteins and GSH occurs through trans-S-nitrosation in which a thiolate anion...

How Many Dentates Of S2o3

1 Nalbandyan RM, Vanin AF, Blumenfeld LA. EPR signals of a new type in yeast cells.Abstracts of the Meeting Free radical processes in biological systems, Moscow, 1964 p. 18. 2 Vanin AF, Nalbandyan RM. Free radicals of a new type in yeast cells. Biofizika (Rus.) 1965 10 167-168. 3 Vanin AF, Blumenfeld LA, Chetverikov AG. Investigation of non-heme iron complexes in cells and tissues by the EPR method. Biofizika (Rus.) 1967 12 829-841. 4 Vithaythil AJ, Ternberg JL, Commoner B. Changes in electron...

Vibration Spectroscopy Of Nitrosyl Ligands In Dnic

As mentioned in Chapter 1, the frequency vno of the NO stretch vibration is strongly affected by the density of the unpaired electron in the half-occupied antibonding orbital of the nitrosyl ligand. Transfer of the unpaired electron from the antibonding orbital towards the iron stiffens the N O bond and raises vno. The DNIC represents a four-coordinate Fe(NO)2 n complex with n 7, 8 or 9. The orbital diagrams were discussed in Ref. 57 , which reviews the experimental data until 1974....

Nitrate Therapeutics

The importance of the discovery of NO biology was recognized by award of the Nobel Prize in 1998. In the first decade after the identification of NO as endothelium-derived relaxing factor and the expanding roles of NO in biology, medicinal chemists focused upon developing inhibitors of the NOS isoforms, because of the proposed contributions of NO to cellular cytotoxicity and tissue damage, most notably from inducible NOS (iNOS) in inflammation, neuronal NOS (nNOS) in CNS excitotoxicity, and the...

Dnic With Sulfide And Neocuproine Anionic Ligands

As well known, sulfide dianions S2- often appear in biological systems as inorganic sulfur bridges between iron ions in polynuclear iron-sulfur clusters 65 . Disruption of such multinuclear clusters is one mechanism by which nitric oxide may interact with iron-sulfur proteins (ISPs) 3,66 . More details of such reactions are given in Chapters 5 and 6. The disruption can lead to the formation of iron-nitrosyl complexes, but the inorganic sulfide ions may remain bound to the iron. Incorporation of...

Experiments On Endothelial Cell Cultures

The cell experiments were done with immortalized murine microvascular brain endothelial bEND.3 cells which have a good expression of endothelial nitric oxide synthase and good reproducibility from generation to generation. These cells were cultivated to confluence in 75 cm2 flasks at 37 C under a controlled atmosphere containing 5 CO2 and 20 O2. At confluence, the bottom of the flask was covered by a cellular monolayer consisting of ca 7.5 0.5 x 106 endothelial cells. Confluence and cell count...

Nitric Oxide And Red Blood Cells

By regulating blood vessel tone, inhibiting smooth muscle cell proliferation, blood cell adhesion and lipid oxidation, NO becomes fundamental for vascular homeostasis. Since NO is not only released abluminally to exert its effects on cells of the vascular wall, but also into the vessel lumen, a significant part of the NO produced by the endothelium is believed to come into direct contact with blood. Given the extremely short half-life of NO in blood and its rapid reaction with hemoglobin in...

I11

340 341 348 111T 320 340 360 nm Fig. 17. The left panel shows the EPR spectra from 1 mM solutions or bovine serum albumin (a) or horse hemoglobin (b) after addition of 1.0 mM DNIC with phosphate ligands. The spectra were recorded at ambient temperature. The right panel shows the optical absorptions of BSA (d) and horse Hb (d) after exposure for 5 min to a gas mixture of NO + air. The optical spectra were recorded with the reference cell filled with 1 mM albumin or hemoglobin solutions...

Stability Of Gsno In Vitro

Stability of RSNO is compromised by thermal decomposition, photolysis and the catalytic decomposition by trace metal ions like iron and copper. Although the various RSNO share the common C S N O motif, they show a big variation in intrinsic stability when in solution. The reason for this variation is not well understood. Given this instability, aqueous solutions of RSNO tend to release a certain quantity of gaseous NO and accumulate typical decomposition products like thiols, disul des and...

The Mechanism For Assembly Of Dnic With Thiolcontaining Ligands

The two pathways described in the previous section yield DNIC complexes with Fe(NO)2 7 configuration. The mechanism for the assembly of this complex is not just simple liganding of nitrosyl and thiol ligands to the iron, but must necessarily involve some redox transformation of the constituents. The experimental evidence for redox activity is clear The synthesis proceeds in the absence of oxygen and starts with ferrous iron in d6 state (non-heme ferric iron is not capable of NO binding)....

Endogenous Nitrates And Nitrites

In mammalian systems, nitrates and nitrites theoretically may be formed as products of the reactions of RNOS nitrates may be produced by nitrating RNOS or by the action of nitrosating and nitroxidizing RNOS nitrites may be produced by nitrosating RNOS. Nitrates and nitrites have been proposed as endogenous products of the reactions of NO, peroxynitrite, or NO2 with lipids, and other biomolecules, under oxidative and nitrosative stress. In particular, nitrite and nitrate derivatives of lipids...

Lowmolecularweight Dnic With Thiolcontaining Ligands

The first description of EPR spectra of low-molecular DNIC with various anionic ligands (phosphate, pyrophosphate, arsenate, molybdate, carbonate, maleate, mercaptane, cysteine, Fig. 2. 2.03 signals from the livers of mice maintained on drinking water with nitrite + 57Fe-citrate complex (curve a) or nitrite + 56Fe-citrate complex (curve b). EPR signals of DNIC with cysteine, containing 57Fe (curves c,f) or 56Fe (curves d,g). Recordings were made at 77 K (curves a-d) or ambient temperature...

The Experiments With Neocuproine Show That Decomposition And Synthesis Of Rsno Are Catalyzed By Copper As Well As Iron

Experiments have shown that neocuproine 2,9-dimethyl phenanthroline blocks the decomposition of RS-NO in cells and tissues. Neocuproine which is often considered to be a selective chelating agent for Cu and its effect is often interpreted as proof that the presence of monovalent Cu dominates the decomposition of nitrosothiols 20,22 . However, as discussed in Chapter 2, neocuproine interacts with the pool of loosely bound iron as well. EPR spectroscopy has demonstrated that the combination of...

The Mechanism Of Rsno Synthesis Catalyzed By Iron

In principle, one could expect that ferric iron catalyzes the synthesis of RS-NO from thiols and NO through the oxidative pathways similar to those shown for Cu2 ions in Schemes 3 and 4. However, cells and tissues contain mM levels of glutathione. With GSH GS-SG 100 firmly on the reduced side, one would expect that endogenous iron be kept dominantly ferrous state. In buffered solutions, the redox state of iron is easily determined but the situation in biological systems is not clear, and the...

Detc

Detection of NO stores by the BP response to DETC in conscious rats, of baseline values. Upper panel a 5 h after DNIC with glutathione injection b control. Bottom panel 1 baseline 2 BP response to DETC in untreated rats and 3 BP response to DETC in rats pretreated with DNIC. Significant difference from baseline, p lt 0.05 32 . Fig. 11. Detection of NO stores by the BP response to DETC in conscious rats, of baseline values. Upper panel a 5 h after DNIC with glutathione injection b...

Biological Reactivity Of Nitrates And Bioactivation

Mediation of the vasodilator response to GTN by NO requires the efficiency of bioactivation to NO to be high, since GTN induces tissue relaxation with nanomolar potency and bioactive concentrations of NO are also nanomolar 119-121 . However, inspection of the chemical reactions of nitrates, depicted in Fig. 5, indicates that there is no direct pathway for the 3e-reduction to NO. On the basis of chemical reactivity, the most facile reactions of nitrates in vivo are predicted to be 1. Formation...

Photolysischemiluminescence

Photolytic cleavage of S-nitrosothiols generates nitric oxide, which then can be detected by the chemiluminescence of its reaction product with ozone or directly electrochemically by a nitric oxide-selective electrode. Alternatively, NO can be released from S-nitrosothiols in the presence of copper and cysteine 94,95 or acidic triiodide 96,97 . As low as 10-13 M can be detected by chemiluminescence methods, compared to 10-9 M electrochemically. Owing to the sensitivity,...