scholarly journals Hypochlorite and superoxide radicals can act synergistically to induce fragmentation of hyaluronan and chondroitin sulphates

2004 ◽  
Vol 381 (1) ◽  
pp. 175-184 ◽  
Author(s):  
Martin D. REES ◽  
Clare L. HAWKINS ◽  
Michael J. DAVIES
Keyword(s):  
Metal Ions ◽  
Metal Ion ◽  
Transition Metal Ions ◽  
Chloride Ions ◽  
Superoxide Radicals ◽  
Thermal Source ◽  
Site Specific ◽  
Trace Metal Ions ◽  
Electron Reduction ◽  
Polymer Fragmentation

Activated phagocytes release the haem enzyme MPO (myeloperoxidase) and also generate superoxide radicals (O2•−), and hence H2O2, via an oxidative burst. Reaction of MPO with H2O2 in the presence of chloride ions generates HOCl (the physiological mixture of hypochlorous acid and its anion present at pH 7.4). Exposure of glycosaminoglycans to a MPO–H2O2–Cl− system or reagent HOCl generates long-lived chloramides [R-NCl-C(O)-R′] derived from the glycosamine N-acetyl functions. Decomposition of these species by transition metal ions gives polymer-derived amidyl (nitrogen-centred) radicals [R-N•-C(O)-R′], polymer-derived carbon-centred radicals and site-specific strand scission. In the present study, we have shown that exposure of glycosaminoglycan chloramides to O2•− also promotes chloramide decomposition and glycosaminoglycan fragmentation. These processes are inhibited by superoxide dismutase, metal ion chelators and the metal ion-binding protein BSA, consistent with chloramide decomposition and polymer fragmentation occurring via O2•−-dependent one-electron reduction, possibly catalysed by trace metal ions. Polymer fragmentation induced by O2•− [generated by the superoxide thermal source 1, di-(4-carboxybenzyl)hyponitrite] was demonstrated to be entirely chloramide dependent as no fragmentation occurred with the native polymers or when the chloramides were quenched by prior treatment with methionine. EPR spin-trapping experiments using 5,5-dimethyl1-pyrroline-N-oxide and 2-methyl-2-nitrosopropane have provided evidence for both O2•− and polymer-derived carbon-centred radicals as intermediates. The results obtained are consistent with a mechanism involving one-electron reduction of the chloramides to yield polymer-derived amidyl radicals, which subsequently undergo intramolecular hydrogen atom abstraction reactions to give carbon-centred radicals. The latter undergo fragmentation reactions in a site-specific manner. This synergistic damage to glycosaminoglycans induced by HOCl and O2•− may be of significance at sites of inflammation where both oxidants are generated concurrently.

scholarly journals Degradation of extracellular matrix and its components by hypobromous acid

2006 ◽  
Vol 401 (2) ◽  
pp. 587-596 ◽  
Author(s):  
Martin D. Rees ◽  
Tane N. McNiven ◽  
Michael J. Davies
Keyword(s):  
Extracellular Matrix ◽  
Metal Ion ◽  
Inflammatory Diseases ◽  
Transition Metal Ions ◽  
Dependent Manner ◽  
Hypobromous Acid ◽  
Polypeptide Backbone ◽  
Electron Reduction ◽  
Polymer Fragmentation

EPO (eosinophil peroxidase) and MPO (myeloperoxidase) are highly basic haem enzymes that can catalyse the production of HOBr (hypobromous acid). They are released extracellularly by activated leucocytes and their binding to the polyanionic glycosa-minoglycan components of extracellular matrix (proteoglycans and hyaluronan) may localize the production of HOBr to these materials. It is shown in the present paper that the reaction of HOBr with glycosaminoglycans (heparan sulfate, heparin, chondroitin sulfate and hyaluronan) generates polymer-derived N-bromo derivatives (bromamines, dibromamines, N-bromosulfon-amides and bromamides). Decomposition of these species, which can occur spontaneously and/or via one-electron reduction by low-valent transition metal ions (Cu+ and Fe2+), results in polymer fragmentation and modification. One-electron reduction of the N-bromo derivatives generates radicals that have been detected by EPR spin trapping. The species detected are consistent with metal ion-dependent polymer fragmentation and modification being initiated by the formation of nitrogen-centred (aminyl, N-bromoaminyl, sulfonamidyl and amidyl) radicals. Previous studies have shown that the reaction of HOBr with proteins generates N-bromo derivatives and results in fragmentation of the polypeptide backbone. The reaction of HOBr with extracellular matrix synthesized by smooth muscle cells in vitro induces the release of carbohydrate and protein components in a time-dependent manner, which is consistent with fragmentation of these materials via the formation of N-bromo derivatives. The degradation of extracellular matrix glycosaminoglycans and proteins by HOBr may contribute to tissue damage associated with inflammatory diseases such as asthma.

scholarly journals Experimental and Theoretical Investigations of a Ferrous / Ascorbate Complex

2021 ◽  
Author(s):  
◽  
Margaret Lockhart Dickson
Keyword(s):  
Metal Ions ◽  
Metal Ion ◽  
Theoretical Calculations ◽  
Transition Metal Ions ◽  
The Body ◽  
Trace Metal Ions ◽  
Transition Series ◽  
Theoretical Investigations ◽  
Vitamin B 12

<p>The importance of trace metal ions in biological processes has been known for some time, but the role of chelating molecules in the human body is a comparatively new and interesting field of research Schubert, j., 1966, Scientific American, 214, no. 5, 40. Among the important complexes occuring in the body are haemoglobin, containing iron, and vitamin B-12, containing cobalt, both essential to human health. Other well-known naturally occuring complexes include cytochrome oxidase, containing both iron and copper, and chlorophyll, containing magnesium. The transition metal ions of the First Transition Series are well-known for their ability to form complexes with suitable ligands, and in particular with chelate ligands which can seize the metal ion like a claw (chele means claw in Greek). Many of these complexes have been characterized experimentally, and their properties interpreted by theoretical calculations. However, the complexes arising from biological systems are much more difficult to study, partly because of their greater size and special properties.</p>

scholarly journals Experimental and Theoretical Investigations of a Ferrous / Ascorbate Complex

2021 ◽  
Author(s):  
◽  
Margaret Lockhart Dickson
Keyword(s):  
Metal Ions ◽  
Metal Ion ◽  
Theoretical Calculations ◽  
Transition Metal Ions ◽  
The Body ◽  
Trace Metal Ions ◽  
Transition Series ◽  
Theoretical Investigations ◽  
Vitamin B 12

<p>The importance of trace metal ions in biological processes has been known for some time, but the role of chelating molecules in the human body is a comparatively new and interesting field of research Schubert, j., 1966, Scientific American, 214, no. 5, 40. Among the important complexes occuring in the body are haemoglobin, containing iron, and vitamin B-12, containing cobalt, both essential to human health. Other well-known naturally occuring complexes include cytochrome oxidase, containing both iron and copper, and chlorophyll, containing magnesium. The transition metal ions of the First Transition Series are well-known for their ability to form complexes with suitable ligands, and in particular with chelate ligands which can seize the metal ion like a claw (chele means claw in Greek). Many of these complexes have been characterized experimentally, and their properties interpreted by theoretical calculations. However, the complexes arising from biological systems are much more difficult to study, partly because of their greater size and special properties.</p>

scholarly journals Coordination chemistry of glutathione.

1999 ◽  
Vol 46 (3) ◽  
pp. 567-580 ◽  
Author(s):  
A Krezel ◽  
W Bal
Keyword(s):  
Glutamic Acid ◽  
Metal Ions ◽  
Metal Ion ◽  
Reduced Glutathione ◽  
Transition Metal Ions ◽  
Oxidized Glutathione ◽  
Binding Modes ◽  
Glutamic Acid Residue ◽  
Reduced And Oxidized Glutathione ◽  
Soft Metal

The metal ion coordination abilities of reduced and oxidized glutathione are reviewed. Reduced glutathione (GSH) is a very versatile ligand, forming stable complexes with both hard and soft metal ions. Several general binding modes of GSH are described. Soft metal ions coordinate exclusively or primarily through thiol sulfur. Hard ones prefer the amino acid-like moiety of the glutamic acid residue. Several transition metal ions can additionally coordinate to the peptide nitrogen of the gamma-Glu-Cys bond. Oxidized glutathione lacks the thiol function. Nevertheless, it proves to be a surprisingly efficient ligand for a range of metal ions, coordinating them primarily through the donors of the glutamic acid residue.

scholarly journals The Role of Metals in the Reaction Catalyzed by Metal-Ion-Independent Bacillary RNase

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Yulia Sokurenko ◽  
Vera Ulyanova ◽  
Pavel Zelenikhin ◽  
Alexey Kolpakov ◽  
Dmitriy Blokhin ◽  
...  
Keyword(s):  
Metal Ions ◽  
Rna Structure ◽  
Metal Ion ◽  
Extracellular Enzymes ◽  
Bacillus Pumilus ◽  
Transition Metal Ions ◽  
The Body ◽  
Intestinal Microbiome ◽  
Phosphodiester Bond

Extracellular enzymes of intestinal microbiota are the key agents that affect functional activity of the body as they directly interact with epithelial and immune cells. Several species of theBacillusgenus, likeBacillus pumilus, a common producer of extracellular RNase binase, can populate the intestinal microbiome as a colonizing organism. Without involving metal ions as cofactors, binase depolymerizes RNA by cleaving the 3′,5′-phosphodiester bond and generates 2′,3′-cyclic guanosine phosphates in the first stage of a catalytic reaction. Maintained in the reaction mixture for more than one hour, such messengers can affect the human intestinal microflora and the human body. In the present study, we found that the rate of 2′,3′-cGMP was growing in the presence of transition metals that stabilized the RNA structure. At the same time, transition metal ions only marginally reduced the amount of 2′,3′-cGMP, blocking binase recognition sites of guanine at N7 of nucleophilic purine bases.

2,2î-Bipyridine Catalyzed Bleaching of Cotton Fibers with Peracetic Acid

1988 ◽  
Vol 58 (4) ◽  
pp. 198-210 ◽  
Author(s):  
James W. Rucker ◽  
David M. Cates
Keyword(s):  
Transition Metal ◽  
Metal Ions ◽  
Peracetic Acid ◽  
Metal Ion ◽  
Solution Treatment ◽  
Transition Metal Ions ◽  
Ferrous Ion ◽  
Cotton Fibers ◽  
Lauryl Sulfate ◽  
Ferrous Ions

Peracetic acid can be catalyzed to bleach cotton fibers at temperatures as low as 30°C by incorporating 2,2î-bipyridine in the bleach solution. Treatment of the fibers with HCl prior to bleaching reduces bleaching effectiveness by removing trace transition metal ions from the fibers. Sorption of individual ions (Cr+3 Mn+2, Fe+2, Fe+3 Co+2, Ni+2, Cu+2, and Zn+2) by HCl treated cotton fibers prior to bleaching indicates that the ferrous ion produces the greatest catalytic effect, and it is only effective when the metal ion is in the fiber as opposed to in solution. Ferrous ions in the fibers sorb 2,2î-bipyridine from solution to form the tris-2,2î-bipyridine ferrous ion complex that is associated with the fibers, and it is the trischelate associated with the fibers that catalyzes bleaching. The effects of pH, temperature, and concentrations of 2,2î-bipyridine, sodium lauryl sulfate, and transition metal ions (in the fibers and in solution) on bleaching effectiveness and peracetic acid decomposition have been studied, and a bleaching mechanism is proposed.

scholarly journals Copper Complexing Capacity and Trace Metal Content in Common and Balsamic Vinegars: Impact of Organic Matter

Molecules ◽  
2020 ◽  
Vol 25 (4) ◽  
pp. 861
Author(s):  
Sotirios Karavoltsos ◽  
Aikaterini Sakellari ◽  
Vassilia J. Sinanoglou ◽  
Panagiotis Zoumpoulakis ◽  
Marta Plavšić ◽  
...  
Keyword(s):  
Organic Matter ◽  
Metal Ions ◽  
Metal Ion ◽  
Metal Speciation ◽  
Anodic Stripping Voltammetry ◽  
Stripping Voltammetry ◽  
Differential Pulse ◽  
Transition Metal Ions ◽  
Electrochemical Technique ◽  
Mass Unit

Complex formation is among the mechanisms affecting metal bioaccessibility. Hence, the quantification of organic metal complexation in food items is of interest. Organic ligands in solutions of environmental and/or food origin function as buffering agents against small changes in dissolved metal concentrations, being able to maintain free metal ion concentrations below the toxicity threshold. Organic matter in vinegars consists of bioactive compounds, such as polyphenols, Maillard reaction endproducts, etc., capable of complexing metal ions. Furthermore, transition metal ions are considered as micronutrients essential for living organisms exerting a crucial role in metabolic processes. In this study, differential pulse anodic stripping voltammetry (DPASV), a sensitive electrochemical technique considered to be a powerful tool for the study of metal speciation, was applied for the first time in vinegar samples. The concentrations of Cu complexing ligands (LT) in 43 vinegars retailed in Greece varied between 0.05 and 52 μM, with the highest median concentration determined in balsamic vinegars (14 μM), compared to that of common vinegars (0.86 μM). In 21% of the vinegar samples examined, LT values were exceeded by the corresponding total Cu concentrations, indicating the presence of free Cu ion and/or bound within labile inorganic/organic complexes. Red grape balsamic vinegars exhibited the highest density of Cu ligands per mass unit of organic matter compared to other foodstuffs such as herbal infusions, coffee brews, and beers. Among the 16 metals determined in vinegars, Pb is of particular importance from a toxicological point of view, whereas further investigation is required regarding potential Rb biomagnification.

Metal ion complexation by soft nanoparticles: the effect of Ca2+ on electrostatic and chemical contributions to the Eigen-type reaction rate

2015 ◽  
Vol 12 (2) ◽  
pp. 130 ◽  
Author(s):  
Raewyn M. Town
Keyword(s):  
Humic Acid ◽  
Trace Metal ◽  
Metal Ions ◽  
Electrostatic Field ◽  
Metal Binding ◽  
Metal Ion ◽  
Bulk Solution ◽  
Trace Metal Ions ◽  
Charged Nanoparticles ◽  
Soft Nanoparticles

Environmental context The speciation of trace metals in the environment is often dominated by complexation with natural organic matter such as humic acid. Humic acid is a negatively charged soft nanoparticle and its electrostatic properties play an important role in its reactivity with metal ions. The presence of major cations, such as Ca2+, can decrease the effective negative charge in the humic acid particle body and thus modify the chemodynamics of its interactions with trace metal ions. Abstract The effect of Ca2+ on the chemodynamics of PbII complexation by humic acid (HA) is interpreted in terms of theory for permeable charged nanoparticles. The effect of the electrostatic field of a negatively charged nanoparticle on its rate of association with metal cations is governed by the interplay of (i) conductive enhancement of the diffusion of cations from the medium to the particle and (ii) ionic Boltzmann equilibration with the bulk solution leading to accumulation of cations in the particle body. Calcium ions accumulate electrostatically within the HA body and thus lower the magnitude of the negative potential in the particle. For the case where trace metal complexation takes place in a medium in which the particulate electrostatic field is set by pre-equilibration in the electrolyte, the lability of Pb-HA complexes is found to be significantly increased in Ca2+-containing electrolyte, consistent with the predicted change in particle potential. Furthermore, the rate-limiting step changes from diffusive supply to the particle body in a 1–1 electrolyte, to inner-sphere complexation in a 2–1 electrolyte. The results provide insights into the electrostatic and covalent contributions to the thermodynamics and kinetics of trace metal binding by soft nanoparticles.

Intermediate-stage transition metal ion exchange in a zeolite X

1982 ◽  
Vol 35 (7) ◽  
pp. 1335 ◽  
Author(s):  
M Chatterjee ◽  
D Ganguli
Keyword(s):  
Ion Exchange ◽  
Transition Metal ◽  
Metal Ions ◽  
Metal Ion ◽  
Intermediate Stage ◽  
Transition Metal Ions ◽  
Zeolite X ◽  
Counter Ions ◽  
Metal Ion Exchange ◽  
Exchange Behaviour

The exchange behaviour of some divalent transition metal ions M2+ (Zn2+, Cu2+, Ni2+, Co2+, Mn2+) in a zeolite NaX (SiO2/Al2O3 2.75) was studied at intermediate stages before equilibrium. The equivalent counter ion supply in the solution, given by the equivalent ratio of the two counter ions 2M2+/Na+, was found to be critical in determining the saturation level of exchange. The series of relative abilities of exchange was very similar to the well known selectivity series at equilibrium. It is suggested that water exchange of the metal ions in solution could be one of the factors controlling the relative ease of ion exchange.

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