Ariela Burg

Plausible Mechanisms of the Fenton-Like Reactions, M = Fe(II) and Co(II), in the Presence of RCO2– Substrates: Are OH• Radicals Formed in the Process?

DFT calculations concerning the plausible mechanism of Fenton-like reactions catalyzed by Fe(II) and Co(II) cations in the presence of carboxylate ligands suggest that hydroxyl radicals are not formed in these reactions. This conclusion suggests that the commonly accepted mechanisms of Fenton-like reactions induced oxidative stress and advanced oxidation processes have to be reconsidered.

The reaction mechanism of nitrosothiols with copper(I).

Abstract Copper and other transition metal ions and their complexes are catalysts for the decomposition of nitrosothiols. In this way they catalyze the biological functions of nitrosothiols. The kinetics and mechanism of the reaction of two nitrosothiols, S-nitrosothiolactic acid and S-nitrosoglutathione (GSNO), with copper(I) are reported. The kinetics of the reaction of Cu(MeCN)n+ (n=0–3) with the nitrosothiols were studied. The results indicate that Cu+aq is the active species in the GSNO system, with k(Cu+aq+GSNO)=(9.4 ±2.0)×107 dm3 mol−1 s−1 . The results also indicate that the Cu(MeCN)n+ (n=0–3) complexes react with S-nitrosothiolactic acid. Transient species are formed in these processes. The results suggest that these species contain copper(I) and thiol. The results shed light on the catalytic role of copper complexes in the decomposition of S-nitrosothiols.

Ligand Effects on the Reactivity of CuIL Complexes Towards Cl3CCO2

The effect of the nature of the ligand L on the mechanism and kinetics of the reaction of CuIL with Cl3CCO2− in aqueous solution is reported. The results demonstrate that the rate of the chlorine abstraction reaction, which is usually the rate-determining step in the process, is affected by: a) the redox potential of the CuII/IL couple, b) the hybridization on CuI in the CuIL complex, c) steric hindrance, d) electron density on the central CuI cation, at the binding site of the chlorine atom to be abstracted. Measurement of ΔV≠ for the chlorine abstraction step indicates that this reaction proceeds by the inner-sphere mechanism, as expected. When the redox potential of the CuII/IL couple is considerably cathodically shifted the transient complex LCuII−CCl2CO2− is relatively long-lived.

Fatty acid composition of breastmilk of Israeli mothers

We conducted this study to determine the fatty acid composition of breastmilk of Israeli women and compare it with baby milk substitutes. Samples of mature breast milk, from 29 lactating Israeli Jewish mothers were collected during feedings. Total milk lipids extracts were transmethylated and analyzed by using an improved gas-chromatographic method. About 72% of the total fatty acids in the investigated breast milk comprised oleic (18:1c; 31±4%), palmitic (16:0; 21±4%), and linoleic (18:2n-6; 20±4%) acids. Total saturated fatty acids represented 42±7% of total fatty acids. The monounsaturated fatty acids content was 33±5%, of which 94% was oleic acid, and the polyunsaturated fatty acids content was about 24±4%, of which 85% was linoleic acid. The α-linolenic acid level found in this study, 2.0±0.6%, was higher than the range of values reported for the world population (0.10–1.4%). The main fatty acids composition of the milk substitutes has very similar composition to the breast milk. Docosahexaenoic acid levels are particularly low among the population of Jewish nursing mothers in relation to the milk substitutes, containing docosahexaenoic acid in their formulations.

Labor Augmentation with Oxytocin Decreases Glutathione Level

Objective. To compare oxidative stress following spontaneous vaginal delivery with that induced by Oxytocin augmented delivery. Methods. 98 women recruited prior to labor. 57 delivered spontaneously, while 41 received Oxytocin for augmentation of labor. Complicated deliveries and high-risk pregnancies were excluded. Informed consent was documented. Arterial cord blood gases, levels of Hematocrit, Hemoglobin, and Bilirubin were studied. Glutathione (GSH) concentration was measured by a spectroscopic method. Plasma and red blood cell (RBC) levels of Malondialdehyde indicated lipid peroxidation. RBC uptake of phenol red denoted cell penetrability. SPSS data analysis was used. Results. Cord blood GSH was significantly lower in the Oxytocin group (2.3 ± 0.55 mM versus 2.55 ± 0.55 mM, P = .01). No differences were found in plasma or RBC levels of MDA or in uptake of Phenol red between the groups. Conclusion. Lower GSH levels following Oxytocin augmentation indicate an oxidative stress, though selected measures of oxidative stress demonstrate no cell damage.

Chapter 7 – The chemistry of monovalent copper in aqueous solutions

Abstract Copper complexes are catalysts of a variety of biological and industrial processes, especially redox processes. Cu(I) complexes are key intermediates in most of these processes. This review discusses ligand properties required for the stabilization of Cu(I) in aqueous solutions, obtaining copper complexes with desired redox potentials, obtaining Cu(I) complexes that are kinetically stabile and have desired chemical reactivity. The factors affecting the effects of ligands on the mechanisms of electron transfer reactions involving Cu(I) complexes are discussed. The role of copper complexes in processes leading to the formation of radicals and the mechanisms of reaction of copper complexes with radicals is analyzed.

Role of Radicals in the Lipid Peroxidation Products of Commercial Infant Milk Formula

Four commercial brands of infant milk formula were investigated, and the amount of shelf lipid peroxidation was determined by measuring malondialdehyde (MDA) or, more exactly, thiobarbituric acid reactive substance (TBARS) levels, which are the end products of lipid peroxidation. TBARS level, indicated by MDA concentration, was higher in the vegetarian brands. The vegetarian brands are, as expected, more prone to oxidation than dairy brands, as they contain more unsaturated fats. The introduction of formate anion diminishes the peroxide amounts initially present in the milk samples as well as those induced by radiation-induced oxidation.

Salt Effect on the Antioxidant Activity of Red Microalgal Sulfated Polysaccharides in Soy-Bean Formula

Sulfated polysaccharides produced by microalgae, which are known to exhibit various biological activities, may potentially serve as natural antioxidant sources. To date, only a few studies have examined the antioxidant bioactivity of red microalgal polysaccharides. In this research, the effect of different salts on the antioxidant activities of two red microalgal sulfated polysaccharides derived from Porphyridium sp. and Porphyridium aerugineum were studied in a soy bean-based infant milk formula. Salt composition and concentration were both shown to affect the polysaccharides’ antioxidant activity. It can be postulated that the salt ions intefer with the polysaccharide chains’ interactions and alter their structure, leading to a new three-dimensional structure that better exposes antiooxidant sites in comparison to the polysaccharide without salt supplement. Among the cations that were studied, Ca2+ had the strongest enhancement effect on antioxidant activities of both polysaccharides. Understanding the effect of salts on polysaccharides’ stucture, in addition to furthering knowledge on polysaccharide bioactivities, may also shed light on the position of the antioxidant active sites.

The reaction between the peroxide VO(η2-O2)(pyridine-2-carboxylate)·2H2O and FeIIaq is not a Fenton-like reaction

Abstract The reduction of VO(η2-O2)(pyridine-2-carboxylate) by Fe(H2O)62+ proceeds via formation of the transient complex (pyridine-2-carboxylate)(O)VV(μ-η2 : η2-O2)FeII(H2O)32+ that is transformed via intramolecular electron transfer into (pyridine-2-carboxylate)(O)VIV(μ-η2 : η2-O2)FeIII(H2O)32+. The latter transient reacts with another Fe(H2O)62+ to yield 2Fe(H2O)63+ + VVO(OH)(pyridine-2-carboxylate)+. These results point out that: (1) VV does not activate the η2 bound peroxide toward the Fenton-like reaction. In this aspect, VV differs from FeIII in (H2O)5Fe–OOH2+ and (2) transients of the type LmMn(μ-η2 : η2-O2)M′L″l have to be considered in the reductions of complexes of η2-bound peroxides.

Polyoxometalates entrapped in sol–gel matrices for reducing electron exchange column applications

Abstract Electron exchange columns were developed by utilizing the redox properties of polyoxometalates (POMs) entrapped in silica matrices via the sol–gel route. The properties of the columns strongly depend on the composition of the precursors used to prepare the matrices. The columns exhibit good reversibility and are the first ‘reducing’ electron exchange columns ever prepared. They are also the first columns where both the matrix and the entrapped redox agent are inorganic compounds. This increases their stability. However, the redox properties of the entrapped POMs in the matrices are affected by the composition of the matrices.