EPR study of the production of OH radicals in aqueous solutions of uranium irradiated by ultraviolet light

The aim of the study was to establish whether hydroxyl radicals (•OH) were produced in UV-irradiated aqueous solutions of uranyl salts. The production of •OH was studied in uranyl acetate and nitrate solutions by an EPR spin trap method over a wide pH range, with variation of the uranium concentrations. The production of •OH in uranyl solutions irradiated with UV was unequivocally demonstrated for the first time using the EPR spin-trapping method. The production of •OH can be connected to speciation of uranium species in aqueous solutions, showing a complex dependence on the solution pH. When compared with the results of radiative de-excitation of excited uranyl (*UO22+) by the quenching of its fluorescence, the present results indicate that the generation of hydroxyl radicals plays a major role in the fluorescence decay of *UO22+. The role of the presence of carbonates and counter ions pertinent to environmental conditions in biological systems on the production of hydroxyl radicals was also assessed in an attempt to reveal the mechanism of *UO22+ de-excitation. Various mechanisms, including •OH production, are inferred but the main point is that the generation of •OH in uranium containing solutions must be considered when assessing uranium toxicity

Applicability of neural networks in the estimation of brain iron content in the diagnosis of amyotrophic lateral sclerosis

Artificial Neural Networks, or simply ANN, are mathematical/computational model that are inspired by structure and functional aspects of biological neural networks. ANN, like man, learns by example. In the process of network training, network is supplied with set of data which represents examples of network’s proper behaviour. In the research we have done, neural network is created with the task to estimate the iron content in the brain of the Amyotrophic Lateral Sclerosis (ALS) patients. Network is created and trained using Neural Pattern Recognition Tool within the software package Matlab v7.10.0.499 (R2010a). Network is trained with set of data obtained from group of 50 ALS patients. Training set contains: (i) MRI signal of brain iron, (ii) EPR signal of hydroxyl radical from cerebrospinal fluid and (iii) score on ALS Functional Rating Scale (ALSFRS) for each patient individually. The results indicate that neural networks can be successfully used to predict the high content of iron in the brain, which in the perspective opens up the possibility of using this computer model as a standard tool in the diagnosis of ALS

Electrochemical and EPR investigation of spin probes acetoxymethoxycarbonyl- and carboxy-proxyl

Redox properties of one hydrophobic spin probe 3-(acetoxymethoxy)carbonyl-2,2,5,5-tetramethyl pyrrolidine-N-oxyl (AM-CxP) and corresponding water-soluble compound, 3-carboxy-2,2,5,5- tetramethyl-pyrrolidine-N-oxyl (3-CxP) were evaluated using electrochemical and EPR methods. The electrochemical behavior of two spin probes was investigated by cyclic voltammetry in phosphate buffer solution. The voltammograms of both compounds exhibited a single redox couple related to nitroxyl radical. EPR spectroscopy revealed that 3-CxP is less susceptible to reduction by Ascorbate than AM-CxP, nevertheless, both spin probes exhibit a great potential for in vivo application

Dependence of alumina/ascorbate oxidase biosensor electrocatalytic activity on alumina type

Biosensors have emerged as indispensable tools across various disciplines, facilitating real time monitoring of specific biomolecules. Within this context, a biosensor system integrates alumina, a versatile material, with ascorbate-oxidase, enabling the electrocatalytic detection of ascorbic acid. This study investigates the influence of different alumina types on the electrocatalytic activity of alumina/ascorbate-oxidase biosensors

The role of EPR spectroscopy in studies of the oxidative status of biological systems and the antioxidative properties of various compounds

In this era of intense study of free radicals and antioxidants, electron paramagnetic resonance (EPR) is arguably the best-suited technique for such research, particularly when considering biochemical and biological systems. No attempt was made to cover all the topics of EPR application but instead attention was restricted to two areas that are both novel and received less attention in previous reviews. In the first section, the application of EPR in assessing the oxidative status of various biological systems, using endogenous stabile paramagnetic species, such as the ascorbyl radical, semiquinone, melanin, and oxidized pigments, is addressed. The second section covers the use of EPR in the emerging field of antioxidant development, using EPR spin-trapping and spin-probing techniques. In both sections, in addition to giving an overview of the available literature, examples (mostly from the authors' recent work) are also presented in sufficient detail to illustrate how to explore the full potential of EPR. This review aims at encouraging biologists, chemists and pharmacologists interested in the redox metabolism of living systems, free radical chemistry or antioxidative properties of new drugs and natural products to take advantage of this technique for their investigations

Electrochemical and structural properties of Ni(II)-alumina composites as an annealing temperature function

Alumina powders, pure and doped with nickel, were synthetized by sol-gel method and calcined at 500, 900 and 1100°C in order to obtain mesoporous structures with a high specific surface area, well adapTab. to catalytic application. The characterization of samples was performed by XRD, EPR spectroscopy and electrochemical impedance spectroscopy (EIS). XRD analysis showed that the addition of Ni2+, as well as the annealing temperature, affects the structural properties of the obtained composites. EPR analysis revealed the traces of Fe3+ impurities, the presence of oxy defects in alumina and Ni2+ in tetrahedral position for samples calcined at 1100°C. The impedance of the Nafion/alumina modified GCE depended on combined effect of porous structure and surface properties of alumina samples. The electrochemical behavior of a glassy carbon electrode modified with Ni (II)-doped aluminas was studied in 0.5 M NaOH solution, with and without methanol. The electrochemical activity of nickel-doped alumina composites was dictated by the amount of present NiO impurity.Прахови алумине, без додатка и са додатком никла, синтетисани су сол-гел методом и жарени на 500, 900 и 1100 oC с циљем да се добију мезопорозне структуре са високом специфичном површином, применљиве у каталитичке сврхе. Карактеризација узорака вршена је са XRD, EPR и EIS спектроскопијом. XRD анализа показала је да и додатак Ni2+-јона, као и температура жарења, утичу на структурне особине добијених композита. EPR анализом утврђено је присуство Fe3+-јона у траговима, окси-дефеката у алумини и Ni2+-јона у тетраедарским позицијама у узорцима жареним на 1100 oC. Импеданса стакло-карбон електроде модификоване нафион/алумином, зависила је од комбинованог ефекта порозне структуре и површинских карактеристика узорака алумине. Електрохемијско понашање модификоване стакло-карбон електроде испитивано је у 0.5M раствору NaOH, без и са метанолом. Електрохемијска активност никл-алумина композита диктирана је присуством NiO фазе

Teorijsko ispitivanje antiradikalske aktivnosti delfinidina

Delphinidin, one of the natural anthocyanin pigments was theoretically (at M05-2X/6-311+G(d,p) level of theory) investigated for its ability scavange potentially highly damaging hydroxyl and superoxide anion radicals. Theoretical calculations point to HAT and SPLET mechanisms as operative for delphinidin in all solvents under investigations.Teoretski (na M05-2X/6-311+G(d,p) nivou teorije) je ispitivana sposobnost delfinidina, prirodnog antocijaninskog pigmenta, da reaguje sa potencijalno veoma štetnim hidroksi i superoksid anjon radikalima. Proračuni su pokazali da su HAT i SPLET mogući mehanizmi u svim rastvaračima

An EPR spin-probe and spin-trap study of the free radicals produced by plant plasma membranes

Plant plasma membranes are known to produce superoxide radicals, while the production of hydroxyl radical is thought to occur only in the cell wall. In this work it was demonstrated using combined spin-trap and spin-probe EPR spectroscopic techniques, that plant plasma membranes do produce superoxide and hydroxyl radicals but by kinetically different mechanisms. The results show that superoxide and hydroxyl radicals can be detected by DMPO spin-trap and that the mechanisms and location of their production call be differentiated using the reduction of spin-probes Tempone and 7-DS. It was shown that the mechanism of production of oxygen reactive species is NADH dependent and diphenylene iodonium inhibited. The kinetics of the reduction of Temponc, combined with scavengers or the absence of NADH indicates that hydroxyl radicals are produced by a mechanism independent of that of superoxide production. It was shown that a combination of the spill-probe and spin-trap technique can be used in free radical studies of biological systems, with a number of advantages inherent to them

Silicon facilitates manganese phytoextraction by cucumber (Cucumis sativus L.)

The effect of excess nutrient levels of manganese (Mn, 50 and 100 M) on the growth inhibition and the appearance of Mn-toxicity symptoms in the leaves was studied in cucumber plants (Cucumis sativus L. cv. Chinese long). Silicon (Si), when supplied as 1.5 mM silicic acid, clearly decreased symptoms of Mn-toxicity despite approximately the same total Mn content in the leaves. In treated plants, Si improves growth and biomass production compared with that of non Si treated plants. Inert deposition of Si in the leaf cell walls of cucumber (a Si-accumulating species) enhanced cell wall stability. The mechanism of Si protection is proposed to act by Si induced compartmentation of Mn hence increasing Mn2+ -binding sites in the cell wall (e.g. Mn silicate polymers) finally resulting in decreased toxic free Mn within the plant tissue rather than decrease of Mn uptake. These results suggest that Si nutrition can improve the phytoextraction potential of plants due to enhanced metal tolerance in leaf tissue