Electron Spin Resonance Spectroscopy Methods Research Articles

The Effect of a Magnetic Field on the Transport of Functionalized Magnetite Nanoparticles into Yeast Cells

Magnetic nanoparticles are of great interest to scientists as potential drug carriers. Therefore, it is essential to analyze the processes these nanoparticles undergo at the cellular level. The present paper demonstrates the effect of a constant and rotating magnetic field on penetration of TEMPOL-functionalized magnetite nanoparticles into yeast cells. The interactions between nanoparticles and yeast cells without and with a magnetic field were studied using electron spin resonance spectroscopy (ESR). The results showed that the ESR method can monitor the effect of a magnetic field on the magnetite nanoparticle penetration rate into the cells.

Volatiles and Tendency of Radical Formation of Cold‐Pressed Brazil Nut Oil During Ambient Storage

AbstractCold‐pressed Brazil nut oil (BNO) is a value‐added nontimber forest coproduct of market interest, despite the lack of knowledge about its ambient storage stability. The objective of the present study was to investigate oxidative changes in BNO stored in clear and brown glass bottles under retail conditions with a focus on monitoring for the first time the formation of volatile aroma compounds (VAC), the depletion of tocopherol analogs, and the tendency of radical formation. VAC, whose formation continuously increased and correlated with storage time, were detected using headspace‐solid‐phase microextraction‐gas chromatography–mass spectrometry. Depletion of tocopherols was more pronounced for the oil stored in clear glass bottles and the content loss was higher for alpha‐tocopherol than for gamma‐tocopherol. Furthermore, the tendency of radical formation was detected using a spin‐trapping electron spin resonance spectroscopy method, which was demonstrated to be a simpler, faster, and less sample‐demanding tool to monitor the oxidative status of BNO stored under retail conditions and its results significantly correlated with those obtained using traditional methods for the determination of primary oxidation products. However, the simultaneous measurement of key off‐flavor volatiles is recommended for samples with unknown history.

ESR Study on Scavenging Effect of Squalene on Free Radicals in Mainstream Cigarette Smoke

Radicals in mainstream cigarette smoke (MCS) have been proposed to contribute to the harm caused by cigarette smoking. In the present study, we used natural antioxidant, squalene, to treat cigarette filters and tobacco for scavenging gas- and particulate-phase free radicals in MCS. The scavenging activities of cigarette filter and tobacco containing squalene against gas and particulate-phase free radicals were detected and quantified using spin-trapping or directly electron spin resonance spectroscopy method. The results revealed that squalene could significantly scavenge gas- and particulate-phase free radicals in MCS in a dose-dependent manner. The radical-scavenging activity of cigarette filter treatment was higher than that of tobacco treatment, irrespective of either gas-phase free radicals, or particulate-phase free radicals in MCS. Among them, 3 mg squalene/filter treatment showed that the highest scavenging effects against gas- and particulate-phase free radicals were 35.9 and 35.4%, respectively. The use of squalene as potential scavenger for reducing free radicals in cigarette smoke is discussed.

Development and Correlation between the Organic Radical Concentration in Different Malt Types and Oxidative Beer Stability

An optimized version of the patented electron spin resonance spectroscopy method, using a novel internal standard (52Cr: MgO), was used to monitor the development of organic radicals during the malting process and the radical content in different commercial specialty malts. The temperature during the withering and kilning steps in malt production had a direct influence on the generation of stable organic radicals in the finished malt, whereby higher temperatures resulted in greater radical concentrations. The majority of organic radicals in pilsner malt were bound in the husk and, therefore, did not significantly transfer into the wort and subsequent beer. In roasted malts, the organic radicals were distributed more uniformly throughout the kernel. Furthermore, depending on the organic radical content and Maillard reaction products present in the endosperm of crystal and roasted malts, more oxidation reactions took place during the mashing, and there was higher radical formation during the wort boiling process. Consequently, the endogenous antioxidant potential value and sulfur dioxide content in the final beer were reduced. These results indicate that there is a direct link between organic radicals in the endosperm generated by the kilning temperature during the malting process and color as an indicator of Maillard reaction products and the oxidative stability of the resultant beer.

Structural characterization of CVD diamond films using Raman and ESR spectroscopy methods

Defects in diamond thin films synthesized by the Hot Filament Chemical Vapor Deposition (HF CVD) method were investigated by Electron Spin Resonance (ESR) and Raman spectroscopy. A series of diamond films of different quality have been synthesized from a mixture of hydrogen and acetylene at different total gas pressure in the range of 20–120 mbar. It was observed that the film morphology changed with increasing deposition pressures from the so-called “ball-like” structure via (1 1 1) and (1 0 0) type texture to the morphology having a mixed character. A comparative study on the ESR and Raman spectra of these films is performed.

Recognition of malignant processes with neural nets from ESR spectra of serum albumin

Cancer diseases are the focus of intense research due to their frequent occurrence. It is known from the literature that serum proteins are changed in the case of malignant processes. Changes of albumin conformation, transport efficiency, and binding characteristics can be determined by electron spin resonance spectroscopy (ESR).The present study analysed the binding/dissociation function of albumin with an ESR method using 16-doxyl stearate spin probe as reporter molecule and ethanol as modifier of hydrophobic interactions. Native and frozen plasma of healthy donors (608 samples), patients with malignant diseases (423 samples), and patients with benign conditions (221 samples) were analysed. The global specificity was 91% and the sensitivity 96%. In look-back samples of 27 donors, a malignant process could be detected up to 30 months before clinical diagnosis.To recognise different entities of malignant diseases from the ESR spectra, Artificial neural networks were implemented. For 48 female donors with breast cancer, the recognition specificity was 85%. Other carcinoma entities (22 colon, 18 prostate, 12 stomach) were recognised with specificities between 75% and 84%. Should these specificity values be reproduced in larger studies, the described method could be used as a new specific tumour marker for the early detection of malignant processes. Since transmission of cancer via blood transfusion cannot be excluded as yet, the described ESR method could also be used as a quality test for plasma products.

In Vivo ESR Studies on Subcutaneously Injected Multilamellar Liposomes in Living Mice

An innovative, noninvasive, low-frequency electron spin resonance (ESR) spectroscopy method was applied and adapted to investigate the integrity of multilamellar liposomes from hydrogenated phospholipids after subcutaneous injection in living mice. Moreover, the fate of the injected liposomal preparations was examined, as well as the possibility to achieve a depot effect. Highly concentrated solutions of the spin probe 2,2,6,6-tetramethyl-4-trimethylammoniumpiperidine-1-oxyl-iodide (CAT-1; 138 mM) were encapsulated in liposomes. They were characterized by laser diffraction, and the liberation of spin probe was investigated by ESR spectroscopy. Line shape changes allowed the differentiation between encapsulated and released CAT-1 after subcutaneous injection of liposomes. Multilamellar liposomes form a local depot at the site of injection. A sustained release of the spin probe from the depot was monitored by means of ESR. Whereas 40% of the spin probe was released within the first 96 h after administration, 60% remained in intact liposomes under the skin. No depot formation could be observed after injection of CAT-1 solutions, but a fast signal decrease due to systemic distribution and bioreduction of the nitroxide spin probe. Noninvasive analysis of liposomal integrity in living animals was successfully accomplished using a new L-Band ESR spectroscopy method. The liberation of CAT-1 from liposomes in vitro and in vivo was monitored by changes in the lineshape of ESR spectra and Heisenberg spin exchange. The significance of liposomal integrity for the formation of a localized drug depot effect was proved.

Evaluation of oxidative stability of vegetable oils by monitoring the tendency to radical formation. A comparison of electron spin resonance spectroscopy with the Rancimat method and differential scanning calorimetry

Electron spin resonance spectroscopy (ESR), based upon the spin trapping technique, was applied at 60 °C for evaluating the oxidative stability of 11 vegetable oil samples, including sunflower oil, rapeseed oil and their mixtures. The ESR results were compared with the oxidative stability values provided by the Rancimat method and differential scanning calorimetry (DSC) at 100 °C. High linear correlations were found between ESR and Rancimat ( r=0.963), and between ESR and DSC ( r=0.979), suggesting that ESR can predict the oxidative stabilities provided by the Rancimat method, as well as by DSC, within a wide range of stability values. In order to examine the capability of each method to evaluate antioxidant activity, different concentrations of α-tocopherol were tested in purified sunflower oil and purified rapeseed oil. Minor differences among the three methods were found when low concentrations of α-tocopherol were used, whereas similar responses were obtained at the highest antioxidant concentration assayed. In comparison with the Rancimat method and DSC, the ESR method is concluded to be useful as a method employing milder conditions and shorter time, and which can be applied for the evaluation of oxidative stability of oils containing volatile antioxidants and other lipid systems containing water.

Albumin transport analysis of different collected and processed plasma products by electron spin resonance spectroscopy

Background: Changes of albumin conformation flexibility and binding characteristics in plasma products can be determined by electron spin resonance spectroscopy (ESR) with spin probes as reporter molecules. Methods: Quality of albumin transport was analyzed in different processed plasma units using a new ESR method which provides estimation of albumin properties by examination of albumin molecular structure changes. Results: In serum of healthy donors could not be obtained any abnormalities. Transport function of albumin in plasma products can be influenced by various methods of plasma collection, preparation, and filtration. Evident are changes in capacity of fatty acid binding sites and ordering changes of bound substrates. Transport respiratory detoxification efficiency is decreased between 30% and 70% in all FFP compared to control values. Conclusions: ESR spectroscopy can be used as a quality test for plasma. The ESR technique has a big potential for determination of conformation changes of macromolecules and as a global tumor marker test for donor screening.

Studies of the Electrolytic Reduction Mechanism of Anthracene, Benzophenone and Anthraquinone by the Use of Polarography and Electron Spin Resonance Spectroscopy

Abstract The electrochemical reduction mechanism of anthracene, benzophenone and anthraquinone was studied in N,N′-dimethylformamide (DMF) and/or its water mixture by means of polarography and electron spin resonance spectroscopy (ESR). The polarograms of these compounds consisted of two well-defined waves in anhydrous DMF: the first wave corresponds to the formation of the anion radical and the second wave to the reduction of the anion radical to the dinegative anion. When water was added, the limiting current of the first wave increased at the expense of the second wave. In order to elucidate the reduction mechanism of these molecules in DMF-water mixture, the kinetic behavior of the anion radical was studied by the ESR method. It has been found that the reduction of anthracene is understood by the protonation mechanism, but that of anthraquinone is not explained by the protonation mechanism at all; the disproportionation of the anion radical must be considered. For the reduction of benzophenone both the protonation and the disproportionation mechanism must be taken into consideration.