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The redox behaviors of macrocyclic molecules with an entirely π-conjugated system are of interest due to their unique optical, electronic, and magnetic properties. In this study, defect-free cyclic P3HT with a degree of polymerization (DPn) from 14 to 43 was synthesized based on our previously established method, and its unique redox behaviors arising from the cyclic topology were investigated. Cyclic voltammetry (CV) showed that the HOMO level of cyclic P3HT decreases from –4.86 eV (14 mer) to –4.89 eV (43 mer), in contrast to the linear counterparts increasing from –4.94 eV (14 mer) to –4.91 eV (43 mer). During the CV measurement, linear P3HT suffered from electro-oxidation at the chain ends, while cyclic P3HT was stable. ESR and UV–Vis–NIR spectroscopy suggested that cyclic P3HT has stronger dicationic properties due to the interactions between the polarons. On the other hand, linear P3HT showed characteristics of polaron pairs with multiple isolated polarons. Moreover, the dicationic properties of cyclic P3HT were more pronounced for the smaller macrocycles.

From the reaction of 2-hydroxy-6-methylpyridine (L) with iron(II) tetrafluoroborate, a new mononuclear iron(III) octahedral complex [FeL6](BF4)3 has been isolated. The color of the complex reversibly changed from red at room temperature to yellow-orange at the liquid nitrogen temperature. Magnetization measurements indicate that iron(III) in [FeL6](BF4)3 is in a high-spin state S = 5/2, from room temperature to 1.8 K. The high-spin ground state of iron(III) is also confirmed by DFT calculations. Although the spin-crossover of the complex is not observed, X-band and multifrequency high-field/high-frequency electron spin resonance (ESR) spectroscopy shows rather uncommon iron(III) spectra at room temperature and an unusual change with cooling. Spectral simulations reveal that the S = 5/2 ground state multiplet of the complex can be characterized by the temperature independent axial zero-field splitting parameter of |D| = +2 GHz (0.067 cm−1) while the value of the rhombic parameter E of the order of some tenths MHz increases on lowering the temperature. Single crystal X-ray diffraction (SCXRD) shows that the iron(III) coordination geometry does not change with temperature while supramolecular interactions are temperature dependent, influencing the iron(III) rhombicity. Additionally, the DFT calculations show temperature variation of the HOMO–LUMO gap, in agreement with the changes of color and ESR-spectra of the iron(III) complex with temperature.

Three new coordination compounds of copper(II) with glycine (HGly) and 2,2'-bipyridine (bipy) were synthesized by solution-based and mechanochemical methods: [Cu(Gly)(H2O)(bipy)][Cu(Gly)(SO4)(bipy)]·6H2O (1a·6H2O), [Cu(Gly)(H2O)(bipy)]2SO4 (1b), [Cu(Gly)(H2O) (bipy)]2SO4·H2O (1b·H2O). The amount of water in the reaction mixture influenced the product of crystallization. All compounds were characterized by X-ray diffraction methods and form 1D infinite chains or 2D sheets of complex ions connected by π-interactions. Compounds 1a·6H2O and 1b were characterized by X-band electron spin resonance (ESR) spectroscopy and the values of g-tensors for Cu(II) ions were determined. Compounds 1a·6H2O and 1b showed pronounced antiproliferative activity toward a panel of six human cell lines. The most impared was HepG2 cell line at 10−5 mol dm−3 concentration (74.5 % reduction of cell growth) followed by moderate activity toward KATO III, Caco-2, MDA-MB-231, PANC-1 and MRC-5 cells at 10−4 mol dm−3 concentration of compounds 1a·6H2O and 1b. Generally, both compounds express similar antiproliferative effect on evaluated cells.

International audience; Spin trapping with cyclic nitrones coupled to electron paramagnetic resonance (EPR) enables the detection and characterization of oxygen-derived free radicals, such as superoxide and hydroxyl radicals, in living cells. Detection is usually performed on cell suspensions introduced in glass capillaries, gas-permeable tubing, or flat cells, even when cells normally require attachment for growth. However, radical production may be influenced by cell adhesion, while enzymatic or mechanical cell harvesting may damage the cells and alter their metabolic rates. Here, we describe the detection on adherent cells attached to microscope coverslip glasses. This method preserves cell integrity, ensures near physiological conditions for naturally adherent cells, and is relatively simple to set up. Up to 12 conditions can be screened in half a day using a single batch of culture cells.

This article presents the results of a study of electrochemical transformations in aqueous and aprotic media of 5-methyl-6-nitro-7-oxo-4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidinide l-arginine monohydrate (1a, Triazid) obtained by electrochemical methods and ESR spectroscopy. The effect of pH on the current and the reduction potential of 1a in an aqueous Britton–Robinson buffer solution was studied. It was found that 1a is irreversibly reduced in aqueous acidic media on a glassy carbon electrode in one stage with the participation of six electrons and the formation of 5-methyl-6-amino-7-oxo-1,2,4-triazolo[1,5-a]pyrimidin. The electroreduction of 1a in DMF on a background of tetrabutylammonium salts proceeds in two stages, controlled by the kinetics of second-order reactions. In the first stage, the reduction of 1a is accompanied by protonation by the initial compound of the basic intermediate products formed in the electrode reaction (self-protonation mechanism). The second quasi-reversible stage of the electroreduction 1a corresponds to the formation of a dianion radical upon the reduction of the heterocyclic anion 5-methyl-6-nitro-7-oxo-4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidin, which is formed upon the potentials of the first peak. The ESR spectrum of the radical dianion was recorded upon electroreduction of Triazid in the presence of Bu4NOH. The effect of the formation of ion pairs on the reversibility of the second peak of the 1a transformation is shown. A change in the rate and regioselectivity of the protonation of the dianion radical in the presence of Na+ and Li+ ions is assumed. The results of studying the electroreduction of 1a by ESR spectroscopy with a TEMPO trap make it possible to assume the simultaneous formation of both a nitroxyl radical and a radical with the spin density localized on the nitrogen at the 4 position of the six-membered ring. © 2021 by the authors. Licensee MDPI, Basel, Switzerland. Funding: This work was supported by the Russian Foundation for Basic Research (RFBR, project No. 19-29-08015 mk).

Lingonberries contain high contents of bioactive compounds such as chlorogenic acids and anthocyanins. In addition to radical scavenging and antioxidant activities, these compounds can protect cells from DNA damage. For this reason, lingonberries might be well suited for nutraceuticals or natural biomedicines. To assess these applications, the present study characterized and identified the most effective extract, only consisting of anthocyanins, copigments or a mixture of both, obtained from a lingonberry juice concentrate. An extract was generated by using a XAD-7 column followed by fractionation into anthocyanins and copigments using adsorptive membrane chromatography. After identification of main polyphenols by HPLC–photodiode array–electrospray ionization–tandem mass spectrometry, free radical scavenging activity was analyzed by electron spin resonance spectroscopy using 2,2-diphenyl-1-picrylhydrazyl and galvinoxyl radicals. Furthermore, cyclic voltammetry analyses and the Trolox equivalent antioxidant capacity (TEAC) assay were applied. Finally, the reactive oxygen species (ROS) reducing effects of the lingonberry extract and its fractions were evaluated in HepG2 cells. While the combination of anthocyanins and copigments possessed the highest antioxidant activities, all samples (XAD-7 extract, anthocyanin and copigment fraction) protected cells from oxidative stress. Thus, synergistic effects between phenolic compounds may be responsible for the high antioxidant potential of lingonberries, enabling their use as nutraceuticals.

We synthesized two new organogold derivatives of a nitronyl nitroxide (NN) with phosphine ligands, namely NN-Au-PtBuPh2 and NN-Au-PtBu2Ph. They were characterized by X-ray diffraction analysis, cyclic voltammetry, and ESR, IR, and UV/Vis spectroscopy. The X-ray structural analysis revealed a tendency of the NN moiety to form a large number of short intermolecular contacts. This phenomenon is related to the anionic nature of the paramagnetic group NN, as evidenced by a significantly lower oxidation potential in comparison with purely organic derivatives of NN radicals. The cross-coupling reaction of NN-Au-PPh3, NN-Au-PtBuPh2, or NN-Au-PtBu2Ph with an activated bromoarene, namely, p-BrC6H4NO2, was investigated. It was shown that regardless of the presence of the bulky tert-butyl substituent, all gold derivatives have similar activities in the cross-coupling reaction and give a cross-coupling product, NN-C6H4NO2, with comparable yields.

We synthesized two new organogold derivatives of a nitronyl nitroxide (NN) with phosphine ligands, namely NN-Au-PtBuPh2 and NN-Au-PtBu2Ph. They were characterized by X-ray diffraction analysis, cyclic voltammetry, and ESR, IR, and UV/Vis spectroscopy. The X-ray structural analysis revealed a tendency of the NN moiety to form a large number of short intermolecular contacts. This phenomenon is related to the anionic nature of the paramagnetic group NN, as evidenced by a significantly lower oxidation potential in comparison with purely organic derivatives of NN radicals. The cross-coupling reaction of NN-Au-PPh3, NN-Au-PtBuPh2, or NN-Au-PtBu2Ph with an activated bromoarene, namely, p-BrC6H4NO2, was investigated. It was shown that regardless of the presence of the bulky tert-butyl substituent, all gold derivatives have similar activities in the cross-coupling reaction and give a cross-coupling product, NN-C6H4NO2, with comparable yields.

Son yıllarda, hızlı ve doğru biyodozimetri tekniği olarak tırnaklar üzerinde yapılan Elektron Spin Rezonans (ESR) çalışmalarının sayısı artmıştır. Bu çalışmaların en önemli sonucu, Fransız Radyasyondan Korunma ve Nükleer Güvenlik Enstitüsü (IRSN) tarafından tırnaklarda oluşan kararlı radyasyona bağlı ESR sinyalinin (RIS5) tanımlanmasıdır. Bir diğer önemli sonuç, Dartmouth ESR Merkezi aracılığıyla Amerikan Ulusal Sağlık Enstitüsü (NIH) tarafından desteklenen Sholom ve McKeever tarafından 2016’da yayımlanan çalışmada verilen doz belirleme protokolüdür. Bu çalışmada, tırnak dozimetrisi konusunda önerilen üç yaklaşımın sonuçları sunulmuştur: ikisi yukarıda anlatılan IRSN ve Dartmouth protokollerine dayanmaktadır, diğerinde ise klasik eklemeli doz yöntemi kullanılmıştır. Toplanan tırnak numuneleri Cs-137 gama kaynağında (0.5 kGy / saat) ışınlanmıştır. ESR ölçümleri, Bruker e-scan X-band EPR spektrometresi kullanılarak gerçekleştirilmiştir. 5 ve 10 Gy'lik adımlarla eklemeli doz-cevap eğrilerini oluşturmak için 25, 30, 85 ve 168 Gy dozlarına kadar ışınlanan örnekler kullanılmıştır. RIS5 ve merkez alan (yaklaşık g = 2.004) ESR sinyal şiddetleri, EPR sinyalinin tepeden-tepeye yüksekliği ölçülerek belirlenmiştir (Şekil 1 ve 4). 2016 yılında yayınlanan son protokolü test etmek için ise, tırnak örnekleri Co-60 gama kaynağında 2 ve 5 Gy kaza dozlarında ışınlanmıştır. ESR sinyal şiddetleri, bu protokolde verilen formülde kullanılmak üzere kaydedilmiştir. İlk protokolde, ışınlanmış ve ışınlanmamış örneklerin doyum noktaları arasındaki fark, birinci grup için 15 Gy ve ikinci grup için 10 Gy olarak bulunmuştur (Şekil 2 ve 3). Diğer yandan, ikinci protokolde ESR sinyal yoğunluğu eklenen doza bağlı olarak artmıştır. Deneysel olarak ölçülen ESR sinyal şiddeti değerleri en iyi polinom fonksiyonuna fit edilmiş ve dozlar, 10 ile 15 Gy kaza dozları için, sırasıyla, 13.89 ve 22.19 Gy olarak hesaplanmıştır (Şekil 5 ve 6). Son olarak, Dartmouth Merkezi protokolüne göre, 2 ve 5 Gy kaza dozlarında ışınlanmış örnekler için sırasıyla dozlar 2.18 ve 4.5 Gy olarak hesaplanmıştır. Özetle, RIS5 ESR sinyal şiddeti değişimini kullanan IRSN ve Dartmouth protokollerinin yüksek dozlara maruz kalmış tırnak örneklerinde kaza dozunun değerlendirilmesinde başarılı yöntemler olduğu görülmüşken, merkez alan ESR sinyal şiddeti değişimini kullanan klasik yaklaşımın yüzde 38.9 ve yüzde 47.9 hata ile kaza dozları vermesi sebebiyle bu yöntemin başarılı olmadığı tespit edilmiştir. IRSN ve Dartmouth yaklaşımlarının farklı bireylerden daha fazla örnek üzerinde daha düşük kaza dozları kullanılarak test edilmesi ve bu testlerin de kısa süre içerisinde yanıt verebilmesi yönünde ileri çalışmalar planlanmalıdır. In recent years, the number of Electron Spin Resonance (ESR) studies on nails have increased as a mean of rapid and accurate biodosimetry. The most important outcome of these studies is the identification of a stable radiation-induced signal (RIS5) component in nails reported by the French Radioprotection and Nuclear Safety Institute (IRSN). The other important result is the dose determination protocol publicated in 2016 proposed by Sholom and McKeever funding from Dartmouth ESR center, with American National Institute of Health (NIH) funding. In this study, the results of three approaches on nail dosimetry were presented: two of them were based on the described protocols of IRSN and Dartmouth and the other used the classical dose addition method. Nail samples were collected from a donor irradiated with 137Cs gamma rays (0.5 kGy/h). ESR measurements were carried out using a Bruker e-scan X-band ESR spectrometer. Samples irradiated up to the doses of 25, 30, 85 and 168 Gy were used to construct the added dose-response curves in steps of 5 and 10 Gy. The reported intensities of RIS5 and center field signal (near g = 2.004) were derived from peak-to-peak distance of the ESR signal (Figures 1 and 4). To test last protocol published in 2016 (Darthmouth protocol), nail samples were irradiated by Co-60 gamma rays at 2 and 5 Gy as accidental radiation doses. The ESR signal intensities were recorded to use in formula given in proposed protocol. By using the first protocol, differences between dose saturation points of exposed and unexposed samples which determine the accident doses were found as 15 Gy for the first group and 10 Gy for the second group (Figures 2 and 3). On the other hand, by the second protocol, the ESR signal intensity increased with increasing added doses. The experimentally measured ESR signal intensity values fitted well by polynomial function and the extrapolated doses were calculated as 13.89 and 22.19 Gy for 10 and 15 Gy accident doses, respectively (Figures 5 and 6). Lastly, according to Dartmouth center protocol, the mean accident doses were calculated as 2.18 and 4.5 Gy for 2 and 5 Gy accident doses, respectively. In summary, IRSN protocol evaluating the RIS5 component and Dartmouth protocol were found to be successful methods for the evaluation of dose to nails exposed high-doses. However, classical approach using center field ESR signal given extrapolated doses in error of 38.9 and 47.9 percent was found to be unsuccessful for dose assessment by nails. Further studies should be planned to test the IRSN and Dartmouth approaches for lower accident doses on more samples from different individuals, taking attention to get results in short time.

Effluent arising from kraft or soda pulping section of a pulp and paper mill is difficult to treat due to the presence of recalcitrant organics such as lignin. In this study, FeCl3 pretreated pulping effluent was subjected to Fenton-like oxidation. Residual dissolved iron from pretreatment step and H2O2 were utilized as catalyst and oxidant, respectively while the initial wastewater pH was 4.0 (unadjusted). The maximum lignin and total organic carbon (TOC) removals of 85% and 48% could be achieved within 2 h of reaction. The oxidation reaction was mediated by hydroxyl radicals (HO center dot) which were detected by electron spin resonance (ESR) spectroscopy. Moreover, the addition of tertiary butyl alcohol and chloroform (both radical scavengers) as well hydroxyl amine (a ferrous ion recycler) affected TOC removal significantly. The TOC degradation data could adequately be fit in a lumped kinetic model (LKM) and the activation energy was calculated as 50.85 kJ/mol. The nature of chemical compounds in treated wastewater was also predicted using Fourier transforms infrared (FTIR) spectroscopy. (C) 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

In this work, we report some preliminary results regarding the analysis of electron spin resonance (ESR) response of soda-lime samples used for retrospective dosimetry. Six different soda-lime glass batches were evaluated after irradiation. We compared several dose reconstruction techniques: saturation method, subtraction method and g-effective, geff, approach. The differences were observed and discussed. ESR signal responses of soda-lime glass samples to different radiation doses for the triage application were investigated. Results confirmed that geff approach has potential for the identification and dosimetry of irradiated soda-lime glass samples using either additive dose method or only calibration curve.

Reaction of the bis(2-picolyl)amine (bpa) ligand with copper(II) results in formation of four complexes with a large structural variety: monomer, bromo-bridged dimer, a coordination polymer and a cyclic trimer that binds atmospheric CO2. Here we present an X-band electron spin resonance (ESR) study of the copper(II) complexes, from room down to liquid helium temperature. The spectral simulations were obtained using spin-Hamiltonian approach and EasySpin software [1]. The results obtained from the study will be discussed in terms of copper coordination geometries and magnetic interactions of copper spins S = 1/2 [2, 3].

JOURNAL OF CURRENT SCIENCE AND TECHNOLOGY, 9, 2, 141-147

The metal-organic frameworks (MOFs) are the subject of intensive research due to their promising applications in gas separation, ion exchange, sensors and catalysts.[1] However, exploring the magnetism of MOFs is a rather difficult task due to complexity of magnetic interactions.[2] Here we present a multi-frequency high-field electron spin resonance (HF-ESR) study, as well as X-band ESR and magnetization research, of magnetic properties of Ni-MOF-74 (Ni-MOF). Furthermore, we compare these results with those of a non-porous 1:1 (Ni:ligand) intermediate complex (Ni-INT) detected and isolated during the synthesis of the Ni-MOF material. Beside this, we investigate the properties of Ni-MOF when the pores or the coordination sphere of the metal sites were changed by removing the labile coordinated ligands (Ni-MOF-desolvated) and also the properties of the amorphous Ni-MOF with collapsed MOF architecture and non-existence of long-range ordering (Ni-MOF-amorph).

Fish lipids are comprised of considerable quantities of polyunsaturated acids and are prone to oxidation, producing reactive oxygen species and hydroperoxides. This study aimed to evaluate the biochemical and structural alterations in Caco-2 cells following exposure to 100 &mu, g/mL methyl linoleate or fish oil, and then radiated for 24, 48 or 72 h. Electron spin resonance spectroscopy detected free radicals in the lipid membrane, Raman microscopy observed biochemical alterations and atomic force microscopy identified changes in morphology, such as the breakdown of DNA bonds. The study showed that bioimaging and biochemical techniques can be effective at detecting and diagnosing cellular injuries incurred by lipid peroxidation.

The accumulation of radical anions from 3,4-disubstituted 1,2,5-thiadiazole S,S-dioxides (1) in solution of organic solvents is achieved by electrochemical, chemical and photoinduced pathways. Electrolytic and chemical reduction of 1 produces the radical anions (1•–) in high molar yields (> ca. 80%). The survival of 1•– is measured for ca. three months. The stability of the reduced state depends on its structure and the composition (solvent, reducing agent, and supporting electrolyte) of the medium in which it is generated by the chemical and electrochemical routes. In solution of polar aprotic solvents, 1•– persists even in the presence of water or oxygen. Irradiation with 254 nm light generates 1•– but only in DMF solution; the proposed reaction mechanism involves the participation of the solvent. Radical anions are characterized by cyclic voltammetry, UV-Vis spectrophotometry and electron spin resonance spectroscopy. The chemical stability and the properties of 1/1•– make them suitable for the development of novel materials for technological applications. Fil: Caram, José Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina Fil: Jiménez Macías, Julyleth Paola. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina Fil: Rodriguez Arroyo, Nelson. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina Fil: Martinez Suarez, Jaime Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina Fil: Gennaro, Ana Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; Argentina Fil: Echeverría, Gustavo Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina Fil: Piro, Oscar Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina Fil: Mirifico, Maria Virginia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina

Reaction of 2-hydroxy-6-methylpyridine (L) with iron(II) tetrafluoroborate results in the isolation of [FeL6](BF4)3 a mononuclear iron(III) octahedral complex. X -ray diffraction studies have confirmed the existence of iron (III). Polycrystalline sample of the complex has been investigated by X-ray diffraction, magnetization and electron spin resonance (HF-ESR) spectroscopy. Beside commercially available X-band ESR, we used also multi-frequency (up to 318 GHz) high-field (up to 16 T) HF-ESR spectroscopy (Fig. 1). The obtained results will be discussed in terms of magneto-structural correlations. [1, 2] [1] P. Gamez et al. Dalton Trans. 2009, 7845-7853 [2] L. Wang et al. Chem. Eur. J. 10.1002/chem.201705989

Background Nucleophosmin-1 (NPM1) is an abundant multifunctional protein, implicated in a variety of biological processes and in the pathogenesis of several human malignancies. Its C-terminal domain (CTD) is endowed with a three helix bundle and we demonstrated that several regions within it, associated with acute myeloid leukemia (AML), have a strong tendency to form beta amyloid-like assemblies toxic for cells. The central helix of the bundle (H2) resulted the most amyloidgenic region; here we aim to model the cytoxicity processes of the H2 sequence and getting clues of a potential involvement in toxicity of the interaction between CTDs and cellular membranes. Methods We investigated the interaction of CTD-NPM1 regions with model membranes through fluorescence, SPR, CD and ESR spectroscopies and the localization of NPM1 by immune-fluorescence in leukemic cells. Results Our findings indicate that investigated regions are able to interact with membranes with different mechanisms and outlined the importance of the presence of cholesterol. Conclusions H2 showed a preference of interaction with membrane containing cholesterol determining a sensitive fluidification of the bilayer, while N-term H2 causes a stiffening of central and outer regions of the lipid system. Noticeably, NPM1 mut A demonstrated to thicken at the plasma membrane, differently from wt. These findings were corroborated by diverse mechanisms of interaction of CTDs toward membrane models in vitro. General significance This study suggests that the direct interaction of several regions of NPM1CTD with cellular membranes could be implicated in diseases where NPM1 is mutated and/or where its overexpression is cytoxic.

International audience; The imidoylnitrene 8, N-methyl-C-phenylimidoylnitrene, has been generated by laser photolysis of 1-methyl-5-phenyltetrazole 6 at 5 K and characterized by its ESR spectrum ( D/hc = 0.9602, E/hc = 0.0144 cm-1). In addition, the triplet excited states of 6 and of 2-methyl-5-phenyltetrazole 11 were also observed by ESR spectroscopy in the 5 K matrices (6: D/hc = 0.123 cm-1, E/hc = 0.0065 cm-1, 11: D/hc = 0.126 cm-1, E/hc = 0.0056 cm-1). The imidoylnitrene 8 is unstable both thermally (disappearing at 80 K) and photochemically (disappearing on continued irradiation at 266 nm). Methyl(phenyl)carbodiimide is the end product of photolysis

Three 2´-deoxynucleosides containing semi-flexible spin labels, namely TA, UA and UC, were prepared and incorporated into deoxyoligonucleotides using the phosphoramidite method. All three nucleosides contain 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) connected to the exocyclic amino group; TA directly and UA as well as UC through a urea linkage. TA and UC showed a minor destabilization of a DNA duplex, as registered by a small decrease in the melting temperature, while UA destabilized the duplex by more than 10 °C. Circular dichroism (CD) measurements indicated that all three labels were accommodated in B-DNA duplex. The mobility of the spin label TA varied with different base-pairing partners in duplex DNA, with the TA•T pair being the least mobile. Furthermore, TA showed decreased mobility under acidic conditions for the sequences TA•C and TA•G, to the extent that the EPR spectrum of the latter became nearly superimposable to that of TA•T. The reduced mobility of the TA•C and TA•G mismatches at pH 5 is consistent with the formation of TAH+•C and TAH+•G, in which protonation of N1 of A allows the formation of an additional hydrogen bond to N3 of C and N7 of G, respectively, with G in a syn-conformation. The urea-based spin labels UA and UC were more mobile than TA, but still showed a minor variation in their EPR spectra when paired with A, G, C or T in a DNA duplex. UA and UC had similar mobility order for the different base pairs, with the lowest mobility when paired with C and the highest when paired with T.

Morphology-controlled titania nanocrystals (NCs) are indicated as promising building blocks for the generation of new photocatalytic materials, where precise tailoring of particle size and exposed crystal surfaces enables to fulfill specific reactivity requirements. In fact, beyond the dimensions, the presence of different TiO2 facets dramatically affects its photoactivity. This has been recently connected to the peculiar electronic band structures of specific surfaces and to their ability in promoting the concentration of different photogenerated defects. The most mature methods for the synthesis of shape-controlled TiO2 utilize organic surfactants, which commonly remain anchored to the NCs surfaces, often precluding their final use in photocatalytic applications. Although several alternatives have been provided (e.g., ligand exchange), there is still an urgent need to identify approaches for controlling morphology by also granting tunable surface functionalities, easy scalable procedures, and applicability in "friendly" materials (e.g., pellet, membranes, or flexible substrates). Bearing these challenges in mind, this chapter briefly presents the basic synthesis strategies for tuning morphology and surfaces of TiO2 NCs, focusing on those that may guarantee a transfer of the NCs intrinsic features to technological applicable photocatalytic materials. A brief state of art of the microscopic and spectroscopic techniques utilized for verify and study their morphology-dependent functionalities will be described. In this context and aiming to suggest implementation of TiO2 reactivity, a special attention will be devoted to spectroscopies (mainly ESR) allowing to monitor quasi "in situ" the photocatalytic mechanism. Finally, some perspectives for the inclusion of shape-controlled TiO2 NCs in smart materials will be proposed.

Here we present the synthesis and characterization of a new mononuclear iron(II) octahedral complex. Reaction of 2-hydroxy-6-methylpyridine (L) with iron(II) tetrafluoroborate results in the isolation of [FeL6](BF4)2. Polycrystalline sample of the complex has been investigated by X-band electron spin resonance (ESR) spectroscopy (microwave frequency ν ≈ 9.7 GHz). The measurements have been performed from room down to liquid helium temperature. The recorded spectra show very complex structure. The obtained results will be discussed in terms of the iron coordination and interaction between iron spins. The magneto-structural correlations will be established and comparison with similar compounds will be presented.

Single-crystal studies on anisotropic ESR-active materials can be conveniently carried out using torque-detected (TD) ESR, a novel technique which brings to ESR the sensitivity typical of torque magnetometry (TM). This method, which is easily operated in high magnetic fields and in a wide range of frequencies, was applied to investigate magnetic anisotropy in crystals of a tetrairon(III) single-molecule magnet with an S=5 ground state. TDESR was supported by TM measurements carried out in situ and provided an accurate estimate of the second-order axial anisotropy parameter D and of the longitudinal fourth-order contribution B(4)(0). The results were validated through a parallel angle-resolved investigation by traditional high-frequency ESR on the same material.

The rapid degradation of organic photovoltaic (OPV) devices compared to conventional inorganic solar cells is one of the critical issues that have to be solved in order to make OPV a competitive commercial technology. The understanding of the fundamental mechanisms that reduce the power conversion efficiency (PCE) over time is beneficial for the design of new materials with enhanced stability. This paper focuses on bulk heterojunction organic solar cells based on thieno [3,4-b] thiophene-alt-benzodithiophene (PTB7) mixed with [6,6]-phenyl-C71-butyric acid methyl esther ([70]PCBM). In spite of being promising in terms of PCE, devices based on this blend are unstable and have a short lifetime. When exposed to light in inert atmosphere, the PCE drops by 15% in less than 1 h and by 35% in 8 h; this degradation is induced by the ultraviolet (UV) part of the spectrum. This paper analyzes the effect induced by UV light on the transport of charges in PTB7:[70] PCBM. Contrary to expectations, the electron transport shows evidence of trapping, while the transport of holes appears unaffected. Furthermore, it is proven that the loss of PCE is due to a reaction between PTB7 and [70] PCBM, while the intrinsic instability of the polymer plays a marginal role.

CAPES FACEPE O sítio arqueológico Lagoa Uri de Cima é uma lagoa intermitente, hoje seca, localizada no município de Salgueiro, estado de Pernambuco, Brasil. Durante as escavações realizadas no local entre os anos de 2010 e 2013, ossadas de mamíferos de grande porte, atualmente extintos, conhecidos como animais da megafauna, típicos do período quaternário,foram encontradas nas camadas mais profundas da lagoa. Este trabalho apresenta os resultados das datações por espectroscopia por ressonância paramagnética eletrônica (RPE) realizadas em amostras de dentes, provenientes das ossadas da megafauna encontradas na Lagoa Uri de Cima: 1 dente da espécie Hippidion bonaerensis, 2 dentes da família Toxodontidae, e 2 dentes de espécie Haplomastodon waring. Sedimentos em diferentes níveis estratigráficos da lagoa também foram analisados e datados pela técnica de luminescência opticamente estimulada (LOE). As doses acumuladas nas amostras de dentes e sedimentos foram determinadas, respectivamente, através dos métodos de doses aditavas e doses regenerativas. A taxa de dose anual foi estimada através da determinação dos teores de urânio, tório e potássio presentes nas amostras de dentes analisadas, bem como nos sedimentos do local. Para as amostras de dentes, as taxas de dose anual e idades foram estimadas através dos programas ROSY e DATA, que levam em consideração fatores como umidade e forma como o urânio foi incorporado pelos tecidos dentários, através dos modelos de captação: precoce (CP), linear (CL) e combinado (CC). Para as amostras de sedimentos, foi utilizado o programa AGE. Em relação a datação dos dentes, valores semelhantes de taxas de dose anual e idades para cada amostra foram obtidos através dos dois programas. As maiores e menores idades estimadas foram, respectivamente, para a espécie Hippidion bonaerensis: 20 ± 0,90mil anos (CP), 22 ± 0,70mil anos (CL),20± 0,80 mil anos (CC); e Haplomastodon waring: 13 ± 0,70mil anos (CP), 15 ± 0,80mil anos (CL),13 ± 0,80 kanos (CC). Em relação à datação dos sedimentos, os resultados obtidos estão dentro das perspectivas dos arqueólogos que estudam a formação geológica do sítio Lagoa do Uri de Cima, tendo sido estimado para o nível mais superficial da lagoa a idade de 3,6 ± 0,60mil anos e para o nível mais profundo 152 ± 16mil anos. Levandose em consideração os níveis estratigráficos em que os dentes da megafauna foram coletados, as idades estimadas para os dentes mostram uma coerência com as idades estimadas para os sedimentos coletados nos diferentes níveis estratigráficos da lagoa através da técnica de datação por LOE, permitindo uma maior confiabilidade para a datação dos sedimentos. Além disso, este trabalho contribuiu para a implantação da técnica de datação de dentes por espectroscopia RPE no laboratório do Grupo de Metrologia Arqueológica e Patrimonial (MAP) da Universidade Federal de Pernambuco (UFPE), o que permitirá auxiliar outras pesquisas arqueológicas e geológicas realizadas em outros sítios, além das realizadas no sítio Lagoa Uri de Cima. the municipality of Salgueiro, in Pernambuco state, Brazil. During the excavations at this site, between the years 2010 and 2013, fossils of large mammal, presently extinct, also known as megafauna animals, typical of the quaternary period, were found in the lower layers on bottom of this lake. This study presents the results of electron spin resonance (ESR) spectroscopy dating performed on samples of teeth from megafauna fossils found in "Lagoa Uri de Cima" site: a Hippidion bonaerensis tooth, two Toxodontidae teeth, and two Haplomastodon waring teeth. Sediments from different stratigraphic levels of the lake were also analyzed and dated by optically stimulated luminescence (OSL). Cumulative doses from the teeth and sediments samples were determined, respectively, by additive doses and regenerative doses methods. The annual dose rate was estimated by the determination of the levels of uranium, thorium and potassium present in the teeth samples as well in the surrounding sediments. For the teeth samples, annual dose rates and ages were estimated via ROSY and DATA softwares, which take into account factors such as humidity and how uranium was incorporated by dental tissues through the uptake models: early (EU), linear (LU) and combined (CU). For sediments, the AGE software was used. Concerning the teeth dating, similar values from annual dose rates and ages were obtained from both programs. The highest and lowest estimated ages were, respectively, for the species Hippidion bonaerensis: 20 ± 0,90 thousand years (EU), 22 ± 0,70 thousand years (LU), 20 ± 0,80 thousand years (CU); and Haplomastodon waring: 13 ± 0,70 thousand years (EU), 15 ± 0,80 thousand years (LU), 13 ± 0,80thousand years (CU).. Regarding the dating of the sediments, the results are within the perspectives of the archaeologists that study the geological formation of the “Lagoa Uri de Cima” site, having been estimated for the most superficial level of the lagoon an age of3,6 ± 0,60 thousand years and for the most deeper level an age of 152 ± 16 thousand years. Taking into account the stratigraphic levels in which the megafauna teeth were collected, the estimated ages for these teeth show a consistency with the estimated ages for the sediment collected at different stratigraphic levels of the lagoon, through the LOE dating method, allowing a greater reliability for the dating of the sediments. Furthermore, this work contributed to the implementation of the RPE dating for teeth by the group of “Metrologia Arqueológica e Patrimonial” (MAP) at the “Universidade Federal de Pernambuco” (UFPE), which will support other archaeological and geological researches, in other sites, beyond the researches performed at "Lagoa Uri de Cima" site.

WOS: 000382221100008 1H-Benzo[ b] pyrrole samples were irradiated in the air with gamma source at 0.969 kGy per hour at room temperature for 24, 48 and 72 h. After irradiation, electron spin resonance, thermogravimetry analysis (TGA) and differential thermal analysis (DTA) measurements were immediately carried out on the irradiated and unirradiated samples. The ESR measurements were performed between 320 and 400 K. ESR spectra were recorded from the samples irradiated for 48 and 72 h. The obtained spectra were observed to be dependent on temperature. Two radical-type centres were detected on the sample. Detected radiation-induced radicals were attributed to R-+center dot NH and R=(center dot)CC2H2. The g-values and hyperfine constants were calculated by means of the experimental spectra. It was also determined from TGA spectrum that both the unirradiated and irradiated samples were decomposed at one step with the rising temperature. Moreover, a theoretical study was presented. Success of the machine learning methods was tested. It was found that bagging techniques, which are widely used in the machine learning literature, could optimise prediction accuracy noticeably. Alanya Alaaddin Keykubat University; Gebze Technical UniversityGebze Teknik University; Scientific Research Projects Coordination Center of Selcuk University, Antalya, Kocaeli, Konya/Turkey This study was partially supported by Alanya Alaaddin Keykubat, and Gebze Technical Universities, and the Scientific Research Projects Coordination Center of Selcuk University, Antalya, Kocaeli, Konya/Turkey.

Background: We have previously reported that alkaline extract of Sasa senanensis leaves (SE) showed potent anti-HIV, anti-UV and radical scavenging activity. In the present study, we investigated the biological activities of SE-10, a granulated powder of SE supplemented with lactose, lactitol, trehalose and tea extract. Materials and Methods: Cell viability of mock-infected, HIV-infected, and UV-irradiated cells was determined by the 3-(4,5- dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) method. Scavenging activity of superoxide anion and hydroxyl radicals was determined by electron-spin resonance spectroscopy. Cytochrome P-450 (CYP)3A4 activity was measured by β-hydroxylation of testosterone in human recombinant CYP3A4. Results: SE-10 had slightly higher anti-HIV and anti-UV activities, but slightly lower radical-scavenging and CYP3A4-inhibitory activities, as compared with SE. Conclusion: The present study demonstrates that the biological activities of SE were well preserved during the manufacturing process of SE-10.

A solid film of Nafion has been prepared on the inner wall of a quartz tube. After pulsed photoexcitation, time-resolved electron spin resonance (TR-ESR) spectra have been recorded in the temperature range of 290–15 K. The spectra exhibit strongly electron-spin polarized signals in full absorption arising from the excited triplet state of Nafion. The absence of any resolved spectral features and the unusual narrowing of the TR-ESR signal linewidth with decreasing temperature are discussed in terms of the spin Hamiltonian of an excited triplet state with dynamic dipole–dipole interactions between the two unpaired electron spins. The existence of a triplet–triplet energy transfer process is considered, and a prominent role of hydrogen bonds of the surrounding water network is suggested. Finally, the time evolutions of the TR-ESR signals have been analysed, and the corresponding decay parameters have been obtained at low temperatures. Our results provide insight on the role of water as a medium for the conductivity mechanism in Nafion membranes.

In this study, to obtain guanosine polycrystalline, novel crystallization method was performed on powder guanosine material. Effective crystallization conditions were achieved by adjustment of the concentration of the metal ions, chemical solutions, NaCl, KCl, glacial acetic acid, nitric oxide, perchloric acid, glutamic acid, and pH of buffer. Behaviors of the guanosine polycrystal samples exposed to high-energy values were investigated using ESR method. The polycrystal samples were exposed to gamma-rays for 48 and 72 h. ESR signals were not recorded from the non-irradiated sample and the sample irradiated for 48 h, but the polycrystalline sample irradiated for 72 h exhibited complex ESR spectra. ESR measurements were taken on the irradiated sample in temperature range from 300 to 450 K. On the basis of all these measurements dependence temperature, it can be said that the shape of the spectrum was to be dependent on temperature slightly. Hence, we assume that the radical structure occurred was resistance to high temperature. Two radicals were determined in the structure irradiated and these were called radical I and radical II. The g, hyperfine constants, and spin density were found to be ρ = 0.96, a N NH N = 2.7 mT , a N NH N = 1.155 mT , aN = 0.35 mT and g1 = 2.0093 for the radical I; aN = 4.7 mT and g2 = 2.0094 for the radical II.

Досліджено парамагнітні та фотокаталітичні властивості нанокаталізаторів TiO2, допованих C-S. Встановлено, що у вуглець-допованих каталізаторів з різним вмістом сірки наявні парамагнітні центри, що відносять до обірваних зв’язків у графітових структурах, інтенсивність їх ліній різко знижувалась після фотокаталітичної реакції. ЕПР сигнали Ti3 + центрів не було виявлено. Показано, що збудження світлом зразків ТіО2, незалежно від допування (типу і кількості), у смугу поглинання не призводить до появи люмінесценції, таким чином рекомбінація зарядів відбувається лише безвипромінювальним шляхом, частина якого проявляється у фотокаталізі, тоді як інша частина зарядів захоплюється/деактивується дефектами/пастками. Композитні зразки виявили підвищену фотокаталітичну активність в деструкції сафраніна T при УФ та видимому опроміненні порівняно з чистим TiO2. The paramagnetic and photocatalytic properties of C-S co-doped TiO2 nanocatalysts were investigated. It was established, that the carbon-doped catalysts with different sulfur content show the presence of paramagnetic centers, referred to the dangling bonds in graphitized structures, intensities of this lines were drastically lowered after photocatalytic reaction. The ESR signals from Ti3+ centers were not detected. It was showed, that the light excitation of samples, regardless of doping (type and quantity), in the absorption band did not lead to the appearance of luminescence, so the recombination of charges occurs only in a non-radiation way, part of which reveals in photocatalysis, while the other part of the charges is captured/deactivated by defects/traps. Composite samples showed enhancement of the photocatalytic activity in the destruction of safranine T under UV irradiation as compared to pure TiO2.

The mechanism of photodegradation of antenna system in cyanobacteria was investigated using spin trapping ESR spectroscopy, SDS-PAGE and HPLC-MS. Exposure of isolated intact phycobilisomes to illumination with strong white light (3500 μmol m − 2 s − 1 photosynthetically active radiation) gave rise to the formation of free radicals, which subsequently led to specific protein degradation as a consequence of reactive oxygen species-induced cleavage of the polypeptide backbone. The use of specific scavengers demonstrated an initial formation of both singlet oxygen ( 1 O 2 ) and superoxide (O 2 − ), most likely after direct reaction of molecular oxygen with the triplet state of phycobiliproteins, generated from intersystem crossing of the excited singlet state. In a second phase carbon-based radicals, detected through the appearance of DMPO-R adducts, were produced either via O 2 − or by direct 1 O 2 attack on amino acid moieties. Thus photo-induced degradation of intact phycobilisomes in cyanobacteria occurs through a complex process with two independent routes leading to protein damage: one involving superoxide and the other singlet oxygen. This is in contrast to the mechanism found in plants, where damage to the light-harvesting complex proteins has been shown to be mediated entirely by 1 O 2 generation.

International audience; Silica obtained by annealing in air of gels produced from the controlled hydrolysis and condensation of methacryloxypropyltrimethoxysilane (MAPTES) exhibit lorentzian and gaussian EPR signals centered at g=2.0037 similar to those found in coals. The number and widths of lorentzian lines depend on the annealing temperature, and are attributed to graphitic clusters of different sizes showing spin exchange. These results agree with the estimated average dimensions of the clusters at the different annealing temperatures, obtained by correlating the carbon content with the number of spins. Inhomogeneous components have been identified by using the echo-detected EPR method and are attributed to smaller isolated clusters. These latter analyzed by ESEEM and HYSCORE show strong signals at the free nuclear frequencies of 13C and 1H nuclei only, and hyperfine interactions of 5 MHz with a 13C nucleus.

International audience; The generation of free radicals (Fenton chemistry) from various iron citrate complexes has been studied. Spin trapping methods have been used. The results can question concerning the innocence of added citric acid in foods and cold drinks. We concluded that in absence of pathological situation citric acid is probably not dangerous but it may become dangerous in situation of oxidative stress and/or iron overload.

Methods based on the electron spin resonance (ESR) phenomenon are used to study paramagnetic systems at temperatures that ranges from 1000 to below 1 K. Commercially available spectrometers achieve spin sensitivities in the order of 10^(10) spins/¿Hz at room temperature on sample with volumes in the order of few µl. This results can be improved by cooling the system at cryogenic temperatures, where the larger magnetization of paramagnetic samples cause the detected signal to increase. Furthermore operation at high field (frequency) turns as well in an improved spin sensitivity. For what it concern the spin sensitivity operation at cryogenic temperature and high frequency are thus beneficial. In 2008 the group of Dr. G. Boero proposed a novel detection method based on the integration of all the element responsible for the sensitivity on a single silicon chip. The methodology allowed to study sample with nanoliter scale volume with spin sensitivity that were at least 2 orders of magnitude better than the best commercial spectrometer. The proposed method has performance that are comparable with the one obtained on similar scales with micro-resonator based spectroscopy tool. During this thesis I have investigated the possibility of extending the use of the detection method from frequency that goes from 20 to 200 GHz and temperatures that range from 77 to 4 K. In this frame several domains were touched. First of all the design of CMOS silicon oscillators operating at frequency which are closed to the most modern technology frequency limit. The lack of model valid for the target frequencies and the needs of limiting the power consumption for matching the limited cooling power of cryogenic systems, made the subject a challenging and interesting research topic itself. The study produces a remarkable result of a system operating at about 170 GHz with a power consumption of about 3 mW at room temperature and about 1.5 mW at 4 K. With the realized devices the first measurements of integrated silicon CMOS LC oscillators at temperature below 77 K were performed. From this measurements we could confirm the presence of expected effect, such as minimum power consumption reduction and oscillator frequency increase. In addition to that, by measuring the frequency-bias characteristic, it's been noticed a succession of smooth region and sharp transitions. This jumps are tentatively attributed to the random telegraph signal (RTS) effect that is supposed to be the main responsible for the flicker noise in sub-micrometer MOS devices. Since the impact of RTS on the performance of highly scaled transistor performance is expected to grow with the technology scale down, measurement methods based on LC oscillator, that shows better sensitivity if compared with nowadays employed methods, might allow to better understand the mechanism governing the effect and to develop technological strategy for lowering the impact on the future CMOS technology node. The realized devices have finally demonstrated ESR performances that are comparable with the most recent publication done with miniaturized resonators on mass-limited samples. In fact sensitivity of about 10^(7) spins/¿Hz at 50 GHz and 300 K and of about 10^(6) spins/¿Hz at 28 GHz and 4 K, at least 3 orders of magnitude better then commercially available state of the art devices, have been proven.

SynopsisObjective Skin irritation in personal cleansing has been correlated with surfactant binding with stratum corneum proteins. Polar and non-polar oils are increasingly being used in cleansing formulations which contain high (10–15%) level of anionic and non-ionic surfactants. However, the effects of oils in modulating skin damage from a cleansing product have not been studied in any detail. The objectives of this study are to determine whether low-viscosity polar and non-polar oils differ in their ability to reduce surfactant-induced skin irritation and, if so, how it might be related to their interactions with proteins. Methods Surfactant-induced skin irritation was measured by a 14-day in vivo cumulative patch irritation test. The methodology was similar to the well-known soap chamber test. Surfactant interactions with the water-soluble protein, bovine serum albumin (BSA), in the presence of oils were measured by conductometric titration. The effects of low-viscosity polar and non-polar oils on stratum corneum protein dynamics in the sulfhydryl group region were studied by electron paramagnetic resonance (EPR) using the covalently bound spin-label 3-maleimido-proxyl (5-MSL). EPR measurements were performed with stratum corneums obtained from discarded skins of 3- to 4-week-old female pigs. Simulation of the complex spectra provided insights on the environment and mobility of the protein-bound spin label. Results Addition of 1% polar sunflower seed oil (viscosity 42 centipoise) reduced in vivo irritation of 1% sodium lauryl ether sulphate with two ethoxylate/cocamidopropyl betaine (SLES/CAPB) by 20%, whereas 1% non-polar mineral oil (viscosity 15 centipoise) had no effect. Polar oil glyceryl trioleate (a major component in sunflower seed oil) at 10% level reduced surfactant binding to BSA protein in water by 40%, whereas the non-polar oil dodecane (a major component of mineral oil) at a similar level did not have any effect. The mobility of the spin label in a dry corneum was very low and was increased significantly with the addition of water and glycerol trioleate but less so with mineral oil. Conclusion Sunflower seed oil reduces surfactant-induced in vivo skin irritation more than mineral oil. This is possibly due to stronger interaction of polar oil with proteins, thus protecting it from surfactant binding.

Copper(II) and nickel(II) complexes of the terminally protected nonapeptide Ac-SGAEGHHQK-NH 2 modeling the metal binding sites of the (8–16) domain of amyloid-β have been studied by potentiometric, UV–vis, CD and ESR spectroscopic methods. The studies on the mutants containing only one of the histidyl residues (Ac-SGAEGAHQK-NH 2 , Ac-SGAEGHAQK-NH 2 ) have also been performed. The formation of imidazole and amide coordinated mononuclear complexes is characteristic of all systems with a preference of nickel(II) binding to the His14 site, while the involvement of both histidines in metal binding is suggested in the corresponding copper(II) complexes. The formation of bis(ligand) and dinuclear complexes has also been observed in the copper(II)-Ac-SGAEGHHQK-NH 2 system. The results provide further support for the copper(II) binding ability of the (8–16) domain of amyloid-β and support the previous assumptions that via the bis(ligand) complex formation copper(II) ions may promote the formation of the oligomers of amyloid-β.

The involvement of protein denaturation and/or misfolding processes in the insurgence of several diseases raises the interest in structural dynamic studies of proteins. The use of nitroxide spin labels with electron paramagnetic resonance is a powerful tool for detecting structural changes in proteins. In the present study, we apply this strategy to soybean peroxidase (SBP), a protein characterised by high thermal and structural stability, and we propose a simple method to analyse the anisotropy changes of the protein system and to relate them with the structural changes induced by protein unfolding. We examined the effect of temperature, guanidine hydrochloride and dimethylsulfoxide on the stability of SBP and looked for correlations between the ESR results and the experimental findings obtained by other techniques, reported in the literature. The agreement between data obtained through different strategies supports the validity and reliability of the ESR approach to protein unfolding.

An ESR investigation of the interaction of spin-labelled penetratin with heparin, heparansulfates and several phospholipid vesicle formulations is reported. Penetratin is a 16-aa peptide corresponding to the third helix of the Antennapedia homeodomain and belonging to the cell-penetrating peptide family. The present study shows that ESR spectroscopy can provide specific and reliable information about the mechanism of interaction of penetratin with polysaccharides and lipids, at a molecular level. The study showed that: (i) heparin and heparansulfates specifically interact with spin-labelled penetratin and promote peptide aggregation and concentration on their molecular surface; (ii) penetratin does not interact with neutral lipids, whereas it enters negatively charged lipid bilayers; (iii) cholesterol plays a negative effect on the insertion of penetratin into the lipid membrane; (iv) the interaction of penetratin with lipid vesicles is strongly dependent on lipid concentration. In a low lipid regime, penetratin associates with the polar heads of phospholipids and aggregates on the membrane surface; once the lipid concentration attains a threshold, the peptide enters the lipid bilayer. This step is characterized by reduced peptide mobility and partial disaggregation.It has been shown that ESR spectroscopy is a valuable investigation tool in studies related to the still unclear mechanism of the internalization process.

International audience; Reactive oxygen species (ROS), including superoxide anion and hydrogen peroxide (H2O2), have a diverse array of physiological and pathological effects within living cells depending on the extent, timing, and location of their production. For measuring ROS production in cells, the ESR spin trapping technique using cyclic nitrones distinguishes itself from other methods by its specificity for superoxide and hydroxyl radical. However, several drawbacks, such as the low spin trapping rate and the spontaneous and cell-enhanced decomposition of the spin adducts to ESR-silent products, limit the application of this method to biological systems. Recently, new cyclic nitrones bearing a triphenylphosphonium (Mito-DIPPMPO) or a permethylated β-cyclodextrin moiety (CD-DIPPMPO) have been synthesized and their spin adducts demonstrated increased stability in buffer. In this study, a comparison of the spin trapping efficiency of these new compounds with commonly used cyclic nitrone spin traps, i.e., 5,5-dimethyl-1-pyrroline N-oxide (DMPO), and analogs BMPO, DEPMPO, and DIPPMPO, was performed on RAW 264.7 macrophages stimulated with phorbol 12-myristate 13-acetate. Our results show that Mito-DIPPMPO and CD-DIPPMPO enable a higher detection of superoxide adduct, with a low (if any) amount of hydroxyl adduct. CD-DIPPMPO, especially, appears to be a superior spin trap for extracellular superoxide detection in living macrophages, allowing measurement of superoxide production in unstimulated cells for the first time. The main rationale put forward for this extreme sensitivity is that the extracellular localization of the spin trap prevents the reduction of the spin adducts by ascorbic acid and glutathione within cells.

International audience; Reactive oxygen species are by-products of aerobic metabolism involved in the onset and evolution of various pathological conditions. Among them, the superoxide radical is of special interest as the origin of several damaging species such as H2O2, hydroxyl radical, or peroxynitrite (ONOO−). Spin trapping coupled with ESR is a method of choice to characterize these species in chemical and biological systems and the metabolic stability of the spin adducts derived from reaction of superoxide and hydroxyl radicals with nitrones is the main limit to the in vivo application of the method. Recently, new cyclic nitrones bearing a triphenylphosphonium or permethylated β-cyclodextrin moiety have been synthesized and their spin adducts demonstrated increased stability in buffer. In this article, we studied the stability of the superoxide adducts of four new cyclic nitrones in the presence of liver subcellular fractions and biologically relevant reductants using an original setup combining a stopped-flow device and an ESR spectrometer. The kinetics of disappearance of the spin adducts were analyzed using an appropriate simulation program. Our results highlight the interest of the new spin trapping agents CD-DEPMPO and CD-DIPPMPO for specific detection of superoxide with high stability of the superoxide adducts in the presence of liver microsomes.

We have studied the time-dependent behavior of the director following the step-rotation of a nematic sample subject to a static magnetic field. The director orientation has been monitored using ESR spectroscopy, and we have developed a model-independent analysis of the spectra to yield the distribution function for the director with respect to the magnetic field. This reveals that immediately following the step-rotation the director is uniformly aligned parallel to the field and then adopts a range of orientations before returning to a state of uniform alignment with the director at the step-rotation angle to the field. This unusual behavior of the director is compared with the predictions of nematodynamic theory by employing an exact treatment of the Leslie-Ericksen equations to calculate the time and space dependence of the director orientation.

We studied in the temperature range 4–300 K the dynamics and the electron spin echo decay of the radical 4-oxo-2,2,6,6,-tetramethyl-1-piperidinyloxyl (tempone) doping substitutionally a single crystal of the diketone 2,2,4,4-tetramethyl-cyclobutan-1,3-dione. Electron nuclear double resonance (ENDOR) and high field electron paramagnetic resonance (EPR) spectra (110 GHz) displayed three types of motion: interconversion between twisted-crossover conformations, rotation of the methyl groups and libration of the radical in the crystal matrix. At room temperature all the motions are fast, and they reach the slow motion re′gime each at a different temperature, being all slow below 80 K. An approximate value of 9 kJ mol-1 for the energy barrier hindering the rotation of the tempone methyl groups is estimated. At low temperature their motion is too slow to give any contribution to the echo decay. The echo decays as a linear exponential in the range 100–300 K, due to the radical motions. At T

Samples of two fullerene derivatives, namely, C{sub 60}C{sub 2}H{sub 4}N(CH{sub 3}) and C{sub 60}C{sub 2}H{sub 4}N(Ph{sub 2}C{sub 6}H{sub 4}-4-OCH{sub 3}) in poly(methyl methacrylate) (PMMA), were prepared either by solvent evaporation from CHCl{sub 3} solutions or by thermal polymerization of methyl methacrylate monomers containing the fulleropyrrolidines. In the first case PMMA behaves as a neutral polymeric matrix, while in the second the material swells by absorption of the solvent and its glass transition temperature is shifted up by 8{degree}C with respect to undoped material. Both pieces of evidence are typical of cross-linking between the polymer chains that involves fulleropyrrolidines. EPR and ODMR spectroscopies are applied to the study of the cross-linked species. It is found its excited triplet state is characterized by unusually large electron dipolar splitting ({vert_bar}D{vert_bar} = 248x10{sup -4} cm{sup -1}). Calculations of D have been carried out using a model that considers {sup 3}C{sub 60} and the fullerene derivatives as a collection of fully localized double bonds. The experimental negative sign of D has been reproduced for {sup 3}C{sub 60}, and a positive sign of D is expected for cross-linked fulleropyrrolidine affected by cross-links in the equatorial region. Such a sign reversal can explain the different spin polarizationmore » patterns exhibited by their EPR spectra. 38 refs., 5 figs., 1 tab.« less

Low molecular weight, soluble and characterizable saccharide complexes of iron(III) were synthesised from MeOH using stoichiometric quantities of saccharides and sodium metal. Monosaccharides such as d -glucose, l -sorbose, d -fructose, d -mannose and d -galactose, and disaccharides such as lactose, maltose and sucrose were used for complexation. The final iron(III)-saccharide complexes were isolated, purified and characterised by various analytical, spectroscopic methods including Mossbauer, magnetic susceptibility and electrochemical methods. While half of these complexes were found to be mononuclear, the rest exhibited characteristics close to hydroxo-bridged dinuclear species. The inherent stability and hydrolytically robust nature of these complexes over a wide range of pH was demonstrated. The reductive release of iron from these complexes was shown to be better than that of the iron-dextran complex reported in the literature. Based on their demonstrated properties these may be considered as potentially important in the oral nutritional supplementation of iron.

The mechanism underlying the ionophoric activity of CyPLOS (cyclic phosphate-linked oligosaccharide, 2), a carbohydrate-based synthetic ion transporter decorated with four tetraethylene glycol (TEG) chains, has been investigated by an integrated electron spin resonance (ESR) approach. The mode of interaction of the ionophore with lipid bilayers has been studied by quantitatively analyzing the perturbations in the ESR spectrum of an ad hoc synthesized spin-labeled CyPLOS analog (6), and, in parallel, in the spectra of spin-labeled lipids mixed with 2. The results point to a positioning of the cyclic saccharide backbone close to the lipid headgroups, largely exposed to the aqueous medium. The TEG chains, carrying a terminal benzyl group, are deeply inserted among the lipid acyl chains, showing good mobility and flexibility. As a consequence, the order of the acyl chain packing is significantly reduced, and water penetration in the bilayer is enhanced. The resulting asymmetric perturbation of the bilayer leads to its local destabilization, thus facilitating, through a non-specific mechanism, the ion transport through the membrane.

Es wurden zahlreiche halogenierte Aromaten mit sehr starken Oxidationsmitteln (Dioxygenylsalzen, Peroxodisulfuryldifluorid) zu den entsprechenden Radikalkationen oxidiert. Es wurden erstmals die Kristallstrukturen der Radikalkationen des Pentafluorbenzols, 1,2,4,5-Tetrafluorbenzols, Octafluortoluols, p-Decafluorxylols, Decafluorbiphenyls, Hexabrombenzols und des Hexaiodbenzols durch Einkristallstrukturanalyse bestimmt. Zusätzlich wurden alle Radikalkationen ESR-spektroskopisch untersucht. Die bemerkenswerteste Veränderung im Pentafluorbenzolradikalkation, 1,2,4,5- Tetrafluorbenzolradikalkation, Octafluortoluolradikalkation und p-Decafluorxylolradikalkation, ist eine deutliche Bindungsverlängerung zweier C–C-Bindungen am Kohlenstoffgerüst um 0,05–0,07 Å. Das Decafluorbiphenylradikalkation planarisiert sich um etwa 20° gegenüber dem neutralen Decafluorbiphenyl und zeigt eine einzigartige Bindungsverkürzung an der zentralen C–C-Bindung. Beim Hexabrombenzolradikalkation sind vier C–C-Bindungen, anstelle von nur zweien, elongiert. Das Hexaiodbenzolradikalkation zeigt keine Änderungen am Kohlenstoffgerüst gegenüber der neutralen Spezies. Es gibt bemerkenswerte Kationen· · ·Anionen- Kontakte an den Iodatomen. In allen Fällen verkürzen sich die C–Halogen- Bindungen in den Radikalkationen. Alle Befunde wurden durch quantenchemische Berechnungen (B3LYP/6–311++G(d,p) bzw. SDB-aug-cc-pVTZ/MDF46ECP für Iod) überprüft und bestätigt. Durch die Oxidation werden bestimmte Bindungen geschwächt, so dass es zur Bindungselongation kommt. Nur im Falle des Hexaiodbenzols wird an den Iodatomen oxidiert, so dass der strukturelle Einfluß auf das Kohlenstoffgerüst gering ist., Many halogenated aromatic molecules have been converted into the corresponding radical cations by very strong oxidizers (dioxygenyl salts, peroxodisulfuryldifluoride). For the first time the crystal structures of the radical cations of pentafluorobenzene, 1,2,4,5-tetrafluorobenzene, octafluorotoluene, p-decafluoroxylene, decafluorobiphenyl, hexabromobenzene and hexaiodobenzene have been determined by single crystal determination. Additionally these radical cations have been investigated by ESR spectroscopy. The most remarkable feature is the elongation of two C–C bonds by 0.05–0.07 Å in the pentafluorobenzene radical cation, the 1,2,4,5-tetrafluorobenzene radical cation, the octafluorotoluene radical cation and the p-decafluoroxylene radical cation. The decafluorobiphenyl radical cation is flattened by approximately 20° compared to the parent molecule. Furthermore it shows the central C–C bond to be shortened which is a unique feature. Usually oxidation elongates C–C bonds. Four C–C bonds of the hexabromobenzene radical cation are elongated, whereas in the hexaiodobenzene radical cation no changes in the C–C bond lengths are found. There are remarkable cation· · ·anion contacts for the iodine atoms. For all the radical cations the carbon–halogen bond is shortened. The observed structures for the radical cations are confirmed by quantum chemical calculations (B3LYP/6–311++G(d,p) or SDB-aug-cc- pVTZ/MDF46ECP for iodine). The oxidation weakens certain C–C bonds which results in increase of their length. The hexaiodobenzene radical cation is an exception, here the iodine atoms are oxidized which hardly affects the carbon skeleton.

Thermotropic liquid crystal trans-4- heptylcyclohexanecarboxylic acid (HCCA) doped with 4-oxo-2, 2, 6, 6, -tetramethyl-1-piperidinyloxy spin probe (Tempone) is investigated by electron spin resonance (ESR) spectroscopy in the presence of chiral bisoxalamide gelator 1 during both cooling and heating cycles.

The electron paramagnetic resonance (EPR) spectroscopy is widely applied for retrospective dosimetric purposes by means of quantitative detection of radicals in tooth enamel and bone samples. In this work we report a study by cw and pulsed EPR on two samples of human tooth enamel respectively irradiated by UV (254 nm) and γ-exposed. The continuous wave (cw) EPR spectra have shown the usual presence in both samples of two types of CO 2 − radicals, with axial and orthorombic g tensors. We have obtained the electron spin echo detected EPR (ED-EPR) spectra at 80 K of the two samples, and we have shown that they are suitable to mark the difference between the effects produced by the different irradiations. At low temperature the contribution to the ED-EPR spectrum of the mobile radical with the axial g tensor is still present in the UV irradiated sample, but not in the γ-irradiated one, where its dynamics is too slow to average the g tensor. We have moreover studied the two-pulse electron spin echo decay on varying the microwave power, a well established method for measuring the Instantaneous Diffusion. We have found that the spectral diffusion parameter is almost the same for both radiation types, whereas the Instantaneous Diffusion is significantly larger for γ-exposed samples than for UV irradiated ones. This difference is due to a higher local microscopic concentration of free radicals for samples irradiated with γ photons.

In this study, to obtain guanosine polycrystalline, novel crystallization method was performed on powder guanosine material. Effective crystallization conditions were achieved by adjustment of the concentration of the metal ions, chemical solutions, NaCl, KCl, glacial acetic acid, nitric oxide, perchloric acid, glutamic acid, and pH of buffer. Behaviors of the guanosine polycrystal samples exposed to high-energy values were investigated using ESR method. The polycrystal samples were exposed to gamma-rays for 48 and 72 h. ESR signals were not recorded from the non-irradiated sample and the sample irradiated for 48 h, but the polycrystalline sample irradiated for 72 h exhibited complex ESR spectra. ESR measurements were taken on the irradiated sample in temperature range from 300 to 450 K. On the basis of all these measurements dependence temperature, it can be said that the shape of the spectrum was to be dependent on temperature slightly. Hence, we assume that the radical structure occurred was resistance to high temperature. Two radicals were determined in the structure irradiated and these were called radical I and radical II. The g, hyperfine constants, and spin density were found to be rho = 0.96, a(NNH)(N) = 2.7 mT, a(NNH)(N) = 1.155 mT, a(N) = 0.35 ml and g(1) = 2.0093 for the radical 1; a(N) = 4.7 ml and g(2) = 2.0094 for the radical II. (C) 2011 Elsevier B.V. All rights reserved.

Combustion-derived soot is a polydispersion of carbon-based molecules/particles ranging from a molecular scale length to a particle scale length (1-100 nm). It is considered responsible of respiratory and heart disease (Kumfer et al., 2009), and its mechanisms of action is related to the composition and structure, in turn mainly depending on the fuel and temperature environment in which soot is generated. Soot particles present a structural variability at a mesoscopic scale (size, geometry, nanostructure, primary particle diameter) that can be responsible of a different lung deposition degree and particle translocation behaviour. The toxic effects of inhaled dusts are believed to be mainly driven by oxidative stress which is the result of reactive oxygen species (ROS) (i.e. hydrogen peroxide, superoxide anion, hydroxyl radical) either generated directly by the particles/molecules or by cells in response to the particle exposure (Donaldson et al., 2005). This work aims to gain insights about the radical activity measured by electron spin resonance of soot generated from different fuels, namely benzene and ethylene, in relation to the specific local chemistry and nanostructural features as inferred by FT-IR and Raman spectroscopy. This study was performed on soot washed by solvent in order to eliminate light PAH (< 300u) adsorbed on soot surface with the aim to study the specific soot activity independently from the well known role of PAH. Copyright © 2010 AIDIC servizi S.r.l.