Electron Spin Resonance Spectrometer Research Articles

An integrated tunable isolator based on NiZn film fabricated by spin-spray plating

An innovative type of tunable isolator with a planar comb-like microstrip transmission line, which generate circular polarization magnetic field, has been realized with polycrystalline NiZn ferrite thick films fabricated by spin-spray plating (SSP) process with thickness of 10μm. The phase compositions, microstructure, magnetic hysteresis loop, and ferromagnetic resonance (FMR) linewidth of NiZn ferrite thick films have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM) and electron spin resonance (ESR) spectrometer, respectively. The NiZn ferrite thick films possess 4800Gauss saturation magnetization and 190Oe FMR linewidth measured at X-band. With an in-plane dc magnetic bias perpendicular to the comb-like microstrip transmission line, the transmission direction of left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP) were proved to be opposite. The non-reciprocal ferromagnetic resonance absorption leads to 11.6dB isolation and 5.78dB insertion loss at 17.57GHz with magnetic bias field of 3.5kOe. Furthermore, with external in-plane magnetic fields range from 0.5kOe to 3.5kOe, the central frequency was tuned from 5.63GHz to 17.57GHz. The state-of-the-art tunable isolator with a planar comb-like microstrip transmission line exhibit a great potential to be applied in different microwave components and radar system.

Fungicidal effect of combined nano TiO2 with erythrosine for mediated photodynamic therapy on Candida albicans: an in vitro study

Candida albicans is an opportunistic pathogen that can cause oral candidiasis. Antifungal drugs have been used for treatment, but resistance to these drugs has emerged in recent years. Photodynamic therapy is one of the alternative treatments. The purpose of this study was to evaluate the killing of C. albicans biofilms in photodynamic therapy in vitro by erythrosine (Ery) gel on its own or in combination with nano-titanium dioxide (TiO2) stimulated by blue light (BL). Four test groups were studied, namely, Ery gel at 220 and 440 μM, in the presence or absence of 1% TiO2 + BL, and the control group. After C. albicans biofilms were prepared, a photosensitizer was applied to them for 15 min. Test groups were then activated by BL with 15 J/cm2 energy for 1 min, and the number of CFU/mL in log10 was compared between the test and control groups. In addition, the generation of reactive oxygen species by the effective photosensitizer was tested by electron spin resonance spectrometer (ESR) using 2,2,6,6-tetramethyl-4-piperidone and 5,5-dimethyl-1-pyrroline N-oxide. C. albicans survival rates were different with statistical significance across all groups by the Kruskal-Wallis test (p < 0.001). The group of 440 μM Ery gel + 1% TiO2 + BL showed the highest efficacy (p = 0.05). Results of ESR showed that all Ery gel + BL groups generated significantly more singlet oxygen compared with control groups. None of the groups, however, generated detectable levels of hydroxyl radical and superoxide anion. Erythrosine with blue light is an effective photosensitizer that can kill C. albicans, and nano-titanium dioxide acts as a catalyst that enhances the effect of erythrosine.

Effect of body temperature on the pharmacokinetics of a triarylmethyl-type paramagnetic contrast agent used in EPR oximetry.

Pharmacokinetics of the tri[8-carboxy-2,2,6,6-tetrakis(2-hydroxymethyl)benzo[1,2-d:4,5-d']bis(1,3)dithio-4-yl]methyl radical (Oxo63) after a single bolus and/or continuous intravenous infusion was investigated in tumor-bearing C3H mice with or without body temperature control while under anesthesia. The in vivo time course of Oxo63 in blood was measured using X-band electron paramagnetic resonance spectroscopy. Distribution of Oxo63 in normal muscle and tumor tissues was obtained using a surface coil resonator and a 700-MHz electron paramagnetic resonance spectrometer. The whole-body distribution of Oxo63 was obtained by 300-MHz continuous-wave electron paramagnetic resonance imaging. The high-resolution 300-MHz time-domain electron paramagnetic resonance imaging was also carried out to probe the distribution of Oxo63. Urination of mice was retarded at low body temperature, causing the concentration of Oxo63 in blood to attain high levels. However, the concentration of Oxo63 in tumor tissue was lower with no control of body temperature than active body temperature control. The nonsystemized blood flow in the tumor tissues may pool Oxo63 at lower body temperature. Pharmacokinetics of the contrast agent were found to be significantly affected by body temperature of the experimental animal, and can influence the probe distribution and the image patterns. Magn Reson Med 79:1212-1218, 2018. © Published 2017. This article is a U.S. Government work and is in the public domain in the USA.

216 - Multifunctional Supplement is that the Key to Modulate Redox Signaling in Metabolic Syndrome Volunteers: Cellular Metabolic Index

Scientists around the world concur that maintaining proper levels of redox signaling, which often will mistakenly interpret as oxidative and nitrosative stress. So, identifying the roots of such condition allowed us to design a strategy of nutritional intervention. Utilizing this approach, we performed a randomized, controlled, long-term study of the effect of a multifunctional nutritional supplement on redox signaling and health markers in 48 healthy and pre-metabolic syndrome volunteers. The measurement of extended cellular metabolic index based on cellular and mitochondrial dependent ROS formation and respiratory activity was performed using electron spin resonance spectrometer NOXYSCAN. Spin probe 1-hydroxy-3-methoxycarbonyl-2.2.5.5-tetramethylpyrrolidine (CMH) and oxygen label NOX-14.1 were used. Health parameters (blood pressure, heart rate, lipid and glucose profile, bioavailability of circulating NO was analyzed at control day, after 6 and 12 weeks of twice daily supplementation. Long-term supplementation resulted in significant inhibition of metabolic activity (20.7% cellular and 42.6% mitochondrial). We also observed significant inhibition of extracellular NADPH oxidase dependent generation of superoxide, nearly complete inhibition of extracellular H2O2 formation as well as a 2.5 times increase in bioavailable NO. Evaluated health parameters were improved on healthy people with even greater effects on those with metabolic syndrome: significant improvements in lipid profiles (TC, LDL, HDL, VLDL and TG), glucose metabolism (glucose, insulin, HbA1c, HOMA, postprandial hyperglycemia), inflammatory resistance as well as expression of redox sensitive proteins as NRF2, eNOS, SOD1, HO1 were shown. For the first time, we demonstrate the effects of a multifunctional nutritional supplement containing minerals, vitamins, antioxidant and anti-inflammatory phytonutrients on cellular redox signaling in pre-metabolic syndrome volunteers. We observed strong correlation of extended cellular metabolic index with the more than 25 markers and the indicators of “optimal health” as lipid-, glucose-, inflammatory profile, expression of redox sensitive proteins and other functional cardiovascular parameters.

Synthesis and characterization of imidazole substituted trityl radicals and its optical properties

Recently organic luminescent radical materials have attracted much attention as a class of novel luminescent materials which can produce doublet emission. Here we report two modified organic luminescent radicals TTM-Imz2 and TTM-Imz3 derived from tris(2,4,6-trichlorophenyl)methyl radical (TTM) through introduction of imidazole. Various measuring methods have been carried out to characterize the structure and radical properties of the two products, such as gas chromatography-mass spectrometer (GC-MS), Fourier transform infrared spectroscopy (FT-IR) and electron paramagnetic resonance spectrometer (EPR). The existence of single electron on two products has been confirmed by the EPR spectra with g TTM-Imz2=2.0040 and g TTM-Imz3=2.0038, which were close to the free electron ( g =2.0023). Then, photo- physical properties have been characterized through ultraviolet-visible spectroscopy (UV-vis), steady state fluorescence spectroscopy, transient state fluorescence spectroscopy, and so on. Absorption spectra of TTM-Imz2 and TTM-Imz3 both have a strong absorption band at short wavelength and a week absorption band at long wavelength. For TTM-Imz2, its absorption peaks are λ =382 and 552 nm, and for TTM-Imz3, λ =390 and 558 nm. Emission spectra of TTM-Imz2 and TTM-Imz3 in various solvents do not show significant change. The emission peak of TTM-Imz2 is λ =581 nm in hexane, and for TTM-Imz3, λ =584 nm. Compared to the emission peak of TTM, they have bathochromic shift about 20 nm. Using rhodamine 6G in ethanol as a standard, the relative fluorescence quantum yields of TTM-Imz2 and TTM-Imz3 in chloroform have been determined under excitation with λ ex=380 nm, which are up to 5.9% and 10.5% respectively. The excited luminescence lifetime ( τ ) of TTM-Imz2 and TTM-Imz3 in chloroform were 12.8 and 16.1 ns respectively determined by transient fluorescence decay. Furthermore, theoretical calculations have been carried out to study the molecular orbitals, electron distribution and the effect of imidazole moiety of the radicals. The DFT calculations (UB3LYP/6-31G(d, p)) results show that both of the radicals have propeller type planner structure with sp2 hybridization central carbon atom. And the dihedral angle between imidazole moiety and its adjacent benzene ring is 33°–35°. The singly occupied molecular orbital (SOMO) is mainly distributed on the central carbon atom and partially delocalized onto the benzene rings and the imidazole rings. The energy gap between SOMO and the lowest unoccupied orbital of TTM-Imz2 and TTM-Imz3 are 2.22 and 2.19 eV, respectively, which are lower than that of TTM (2.32 eV). Thus, compared to TTM, both of the absorption peaks and the emission peaks of the products have bathochromic shift. Finally, TGA measurements were performed to test the thermostability of the radicals. The thermal-decomposing temperature of TTM-Imz2 and TTM-Imz3 are 129°C and 182°C respectively. Moreover, the fluorescence intensity decay of the radicals in toluene was recorded under excitation of a pulse laser with λ ex=355 nm. The fluorescence intensity of TTM decreased rapidly with a half-time of 27.9 s, by contrast, TTM-Imz2 and TTM-Imz3 are more stable with a half-time of 1156.1 and 661.4 s, which are up to TTM′s 41.4 and 21.9 times. Finally, OLEDs of TTM-Imz2 and TTM-Imz3 have been fabricated. Both of the devices realized orange light emission. The maximum luminance of TTM-Imz3 reaches 147 cd/m2, and the maximum EQE of TTM-Imz2 and TTM-Imz3 reaches 1.1% and 2.9% respectively. In conclusion, the introduction of imidazole moiety in TTM-Imz2 and TTM-Imz3 increase the fluorescence quantum yields and enhanced the stability of the TTM radicals effectively, and orange light emission has been realized both in solution and OLEDs.

Angle-dependent electron spin resonance of [formula omitted] measured with planar microwave resonators and in-situ rotation

We present a new experimental approach to investigate the magnetic properties of the anisotropic heavy-fermion system YbRh2Si2 as a function of crystallographic orientation. Angle-dependent electron spin resonance (ESR) measurements are performed at a low temperature of 1.6K and at an ESR frequency of 4.4GHz utilizing a superconducting planar microwave resonator in a 4He-cryostat in combination with in-situ sample rotation. The obtained ESR g-factor of YbRh2Si2 as a function of the crystallographic angle is consistent with results of previous measurements using conventional ESR spectrometers at higher frequencies and fields. Perspectives to implement this experimental approach into a dilution refrigerator and to reach the magnetically ordered phase of YbRh2Si2 are discussed.

An electron paramagnetic resonance mobile universal surface explorer

Many samples cannot be studied by electron paramagnetic resonance (EPR) spectroscopy because they are too large to fit into the spectrometer and too precious to be destructively sampled for study. An EPR mobile universal surface explorer (MOUSE), also known as a unilateral EPR spectrometer, was constructed for studying this class of sample. The EPR MOUSE can nondestructively record a low frequency EPR (LFEPR) spectrum of a small region of any size object by placing the MOUSE against the object. The capabilities of the EPR MOUSE are demonstrated on paramagnetic paint pigments on canvas, magnetic ink on paper, and a ceramic candlestick. The mobile nature of the MOUSE will allow the spectrometer to be brought to the sample, thus opening new applications of EPR spectroscopy.

Six Decades of Progress in Magnetic Resonance: The Contributions of James S. Hyde

The development of electron paramagnetic resonance (EPR) and magnetic resonance imaging (MRI) over six decades is sketched with an emphasis on the contributions of James S. Hyde. For twenty years starting three years after the first commercial EPR spectrometer was shipped by Varian, he led commercial EPR developments, and then for more than forty years, he led development of instrumentation and biomedical applications of EPR at the Medical College of Wisconsin. It was there that he also made major contributions to MRI, and especially functional MRI.

Low-temperature Electronic Paramagnetic Resonance Measurements of TEMPO and 4-Hydroxy-TEMPO Benzoate for Purity Analyses by the Effective Magnetic-moment Method.

The purities of two high-purity organic compounds with a nitroxyl radical moiety were quantified based on their free-radical content using the effective magnetic-moment method. Magnetic moments were measured and X-band electron paramagnetic resonance (EPR) spectra were obtained using a superconducting quantum interference device and X-band EPR spectrometer, respectively, over a wide temperature range of near-room temperature to near-liquid-helium temperature. Concerning measurements of effective g-values using an EPR spectrometer, both the sweep direction and sweep speed were taken into account to obtain accurate g-values. The purities of 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) and 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl benzoate (4-hydroxy-TEMPO benzoate) were close to 1 kg kg-1 with relative uncertainties of 1%, which represented improved values compared to those obtained by us previously. These results show a possibility for both compounds to act as reference materials in providing reliable quantification of free radicals per unit mass using this analytical method.

The influence of radiotherapy on ceruloplasmin and transferrin in whole blood of breast cancer patients

Ceruloplasmin and transferrin are proteins which play a potential role in the process of breast cancer development. These molecules contain Cu2+ (ceruloplasmin) or Fe3+ ions (transferrin) and thus constitute paramagnetic centers, which can be studied using electron paramagnetic resonance method. The aim of the study was to determine how paramagnetic centers in whole blood of breast cancer patients change under the influence of radiation therapy. Samples of whole blood were taken from 17 women with breast cancer treated with radiotherapy. The measurements were carried out at 170 K using X-band electron paramagnetic resonance (EPR) spectrometer Bruker EMX-10. Two distinct EPR lines, derived from high-spin Fe3+ in transferrin and Cu2+ from ceruloplasmin, were revealed in all frozen samples. The amplitude and integrated intensity of the EPR signal from Cu2+ in ceruloplasmin significantly decreased in all patients after the delivery of the radiation fraction. When comparing the integral intensity of the signal from Fe3+ in transferrin, three different situations were identified which are patient specific: a significant increase, an insignificant change, or a significant decrease after the irradiation. A decreased level of Cu2+ from ceruloplasmin in patients after radiotherapy means a low level of ceruloplasmin in the plasma or an increased content of reduced Cu+ ions. Differences in the integrated intensity of the EPR signal from transferrin translate directly into the amount of bound iron. The observed changes could indicate how well the organism fights against cancer and how easily it adapts to the situation of biochemical stress.

Evaluation of a composite Gel-Alanine phantom on an end-to-end test to treat multiple brain metastases by a single isocenter VMAT technique.

This work aims to evaluate the application of a cylindrical phantom made of dosimetric gel containing alanine pellets distributed inside the gel volume during an end-to-end test of a single isocenter VMAT for simultaneous treatment of multiple brain metastases. The evaluation is based on the comparison of the results obtained with the composite phantom with the treatment planning system (TPS) dose distribution validated by using the clinical conventional quality control with point and planar dose measurements. A cylindrical MAGIC-f gel phantom containing alanine dosimeters (composite phantom) was used to design the VMAT plan in the treatment planning system (TPS). The alanine dosimeters were pellets with radius of 2.5 mm and height of 3 mm, and played the role of brain metastasis inside the gel cylinder, which simulated the cerebral tissue. Five of the alanine dosimeters were selected to simulate five lesions; five planning target volumes (PTVs) were created including the dosimeters and irradiated with different doses. Conventional quality assurance (QA) was performed on the TPS plan and on the composite phantom; a phantom containing only gel (Gel 1 phantom) was also irradiated. One day after irradiation, magnetic resonance images were acquired for both phantoms on a 3T scanner. An electron spin resonance spectrometer was used to evaluate alanine doses. Calibration curves were constructed for the alanine and the gel dosimeters. All the gel only measurement was repeated (Gel 2 phantom) in order to confirm the previous gel measurement. The VMAT treatment plan was approved by the conventional QA. The doses measured by alanine dosimeters on the composite gel phantom agreed to the TPS on average within 3.3%. The alanine dose for each lesion was used to calibrate the gel dosimeter measurements of the concerned PTV. Both gel dose volume histograms (DVH) achieved for each PTV were in agreement with the expected TPS DVH, except for a small discrepancy observed for the Gel 2 curve of PTV1 and the Gel 1 curve of PTV5. In a 3D gamma analyses performed for each PTV volume independently, comparing both the gels' measurements to the TPS and using 3%/3 mm, 5%/2 mm, and 7%/2 mm, more than 90% of the points were approved for all the PTVs, except for the PTV5 comparison in the Gel 1 measurement and for the PTV2 comparison in the Gel 2 measurement. A 3D gamma analysis was also applied for each PTV independently, to compare both gel measurements in order to evaluate the consistence of repeated gel measurements of the same plan, and more than 94.5% of the points were approved. The composite Gel-Alanine phantom can be used for the end-to-end test of a single isocenter VMAT for simultaneous treatment of multiple brain metastases. The use of the alanine as the lesion cores for the treatment planning provided the precise dose measurements inside each lesion and allowed the conversion of the gel R2 values based on an accurate dose measurement inside the target.

14 GHz longitudinally detected electron spin resonance using microHall sensors

In this work we developed a home-made LOngitudinally Detected Electron Spin Resonance (LODESR) spectrometer based on a microsize Hall sensor. A coplanar waveguide (CPW)-resonator is used to induce microwave-excitation on the sample at 14GHz. We used InSb cross-shaped Hall devices with active areas of (10μm×10μm) and (5μm×5μm). Signal intensities of the longitudinal magnetization component of DPPH and YIG samples of volumes about (10μm)3 and (5μm)3, are measured under amplitude and frequency modulated microwave magnetic field generated by the CPW-resonator. At room temperature, 109spins/G√Hz sensitivity is achieved for 0.2mT linewidth, a result which is still better than most of inductive detected LODESR sensitivities.

Development of the Implantable Resonator System for Clinical EPR Oximetry.

Hypoxic tumors are more resistant to radiotherapy and chemotherapy, which decreases the efficacy of these common forms of treatment. We have been developing implantable paramagnetic particulates to measure oxygen in vivo using electron paramagnetic resonance. Once implanted, oxygen can be measured repeatedly and non-invasively in superficial tissues (<3 cm deep), using an electron paramagnetic resonance spectrometer and an external surface-loop resonator. To significantly extend the clinical applications of electron paramagnetic resonance oximetry, we developed an implantable resonator system to obtain measurements at deeper sites. This system has been used to successfully obtain oxygen measurements in animal studies for several years. We report here on recent developments needed to meet the regulatory requirements to make this technology available for clinical use. radio frequency heating is discussed and magnetic resonance compatibility testing of the device has been carried out by a Good Laboratory Practice-certified laboratory. The geometry of the implantable resonator has been modified to meet our focused goal of verifying safety and efficacy for the proposed use of intracranial measurements and also for future use in tissue sites other than the brain. We have encapsulated the device within a smooth cylindrical-shaped silicone elastomer to prevent tissues from adhering to the device and to limit perturbation of tissue during implantation and removal. We have modified the configuration for simultaneously measuring oxygen at multiple sites by developing a linear array of oxygen sensing probes, which each provide independent measurements. If positive results are obtained in additional studies which evaluate biocompatibility and chemical characterization, we believe the implantable resonator will be at a suitable stage for initial testing in human subjects.

Broadband W-band Rapid Frequency Sweep Considerations for Fourier Transform EPR.

A multi-arm W-band (94 GHz) electron paramagnetic resonance spectrometer that incorporates a loop-gap resonator with high bandwidth is described. A goal of the instrumental development is detection of free induction decay following rapid sweep of the microwave frequency across the spectrum of a nitroxide radical at physiological temperature, which is expected to lead to a capability for Fourier transform electron paramagnetic resonance. Progress toward this goal is a theme of the paper. Because of the low Q-value of the loop-gap resonator, it was found necessary to develop a new type of automatic frequency control, which is described in an appendix. Path-length equalization, which is accomplished at the intermediate frequency of 59 GHz, is analyzed. A directional coupler is favored for separation of incident and reflected power between the bridge and the loop-gap resonator. Microwave leakage of this coupler is analyzed. An oversize waveguide with hyperbolic-cosine tapers couples the bridge to the loop-gap resonator, which results in reduced microwave power and signal loss. Benchmark sensitivity data are provided. The most extensive application of the instrument to date has been the measurement of T1 values using pulse saturation recovery. An overview of that work is provided.

Contrasting characteristics of aqueous reactive species induced by cross-field and linear-field plasma jets

A comparative study on aqueous reactive species in deionized water treated by two types of plasma jets is presented. Classified by the direction of the electric field in the jet device, a linear-field jet and cross-field jet have been set up. Concentrations of several aqueous reactive species are measured quantitatively by chemical fluorescent assays and electron spin resonance spectrometer. Results show that these two-type plasma jets would generate approximately the same gaseous reactive species under the same discharge power, but the linear-field plasma jet is much more efficient at delivering those species to the remote deionized water. This leads to a much more aqueous short-lived species including OH and produced in water, which are mainly correlated to the solvation of gaseous short-lived species such as ions and electrons. Regarding the long-lived species of aqueous H2O2, the concentration grows faster when treated by the linear-field plasma jet in the initial stage, but after 10 min it is similar to that treated by the cross-field counterpart due to the vapor–liquid equilibrium. The aqueous peroxynitrite is also predicted to be produced as a result of the air inclusion in the feeding gas.

Microwave Spin Frequency Comb Memory Protocol Controlled by Gradient Magnetic Pulses

We have demonstrated a combination of frequency comb spin-echo protocol in a conventional microwave pulsed electron spin resonance spectrometer with gradient pulses of the external magnetic field applied for on-demand retrieval of signal microwave pulses at the required moments of time. A natural high-finesse periodic structure was used as a carrier of stored information. The structure is made out of hyperfine lines of electron spin resonance of tetracyanoethylene anion radicals in toluene at room temperature. Herein, we have also observed that using the pulses of gradient magnetic field can increase the memory capacity. The experimental results demonstrated promising opportunities for controlling electron nuclear spin coherence, which could be useful for implementation of broadband microwave or optical-microwave noise free quantum memory protocols.

Remote microwave monitoring of magnetization switching in CoFeB/Ta/CoFeB spin logic device

Stable magnetic states of the MgO/CoFeB/Ta/CoFeB/MgO/Ta spin valve as well as transitions between the states were detected by microwave magnetoresistance (MMR) measured in the cavity of an electron spin resonance spectrometer. Advantages of this experimental technique are the possibility to study the orientation dependence of the MMR, the absence of the additional contact/sample interfaces, the wireless control of the spin valves, and the compatibility of the MMR measurements with ferromagnetic resonance experiments. The magnetic field dependence of the first derivation of the microwave absorption allows one to judge about the negative magnetoresistance of the layers and positive interlayer giant magnetoresistance. The obtained experimental results could be used for engineering of the microwave high sensitive sensors available for remote identification of the stable magnetic and logic states of the spin valves needful in medical spintronics to detect biological objects labeled with nanoparticles.

A wide‐line low frequency electron paramagnetic resonance spectrometer

AbstractA continuous wave, homodyne, low frequency electron paramagnetic resonance spectrometer is described which can accommodate 15 cm diameter objects. The spectrometer can utilize small volume and surface coil probes operating between 100 and 500 MHz. The magnetic field can be scanned between 0 and 35 mT and is thus suitable for g &lt; 2 spins and wide absorption lines. The spectrometer can record conventional field swept, field cycled, and spatially resolved spectra. Details of the instrument design and representative spectra from six different samples are presented. This design has applications to study objects with cultural heritage significance.

Comparison of protective effect of ascorbic acid on redox and endocannabinoid systems interactions in in vitro cultured human skin fibroblasts exposed to UV radiation and hydrogen peroxide

The mechanisms of biological activity of commonly used natural compounds are constantly examined. Therefore, the aim of this study was to compare ascorbic acid efficacy in counteracting the consequences of UV and hydrogen peroxide treatment on lipid mediators and their regulative action on antioxidant abilities. Skin fibroblasts exposed to UVA and UVB irradiation, treated with hydrogen peroxide and ascorbic acid. The redox system was estimated through reactive oxygen species (ROS) generation (electron spin resonance spectrometer) and antioxidants level/activity (HPLC/spectrometry) which activity was evaluated by the level of phospholipid metabolites: 4-hydroxynonenal, malondialdehyde, 8-isoprostanes and endocannabinoids (GC/LC-MS) in the human skin fibroblasts. Protein and DNA oxidative modifications were also determined (LC). The expression of nuclear factor erythroid 2-related factor 2 (Nrf2), its activators and inhibitors as well as pro/anti-apoptotic proteins and endocannabinoid receptors was examined (Western blot) and collagen metabolism was evaluated by collagen biosynthesis and prolidase activity (spectrometry). UVA and UVB irradiation and hydrogen peroxide treatment enhanced activity of xanthine and NADPH oxidases resulting in ROS generation as well as diminution of antioxidant phospholipid protection (glutathione peroxidase-glutathione-vitamin E), what led to increased lipid peroxidation and decreased endocannabinoids level. Dysregulation of cannabinoid receptors expression and environment of transcription factor Nrf2 caused apoptosis induction. Ascorbic acid partially prevented ROS generation, antioxidant capacity diminution and endocannabinoid systems disturbances but only slightly protected macromolecules such as phospholipid, protein and DNA against oxidative modifications. However, ascorbic acid significantly prevented decrease in collagen type I biosynthesis. Ascorbic acid in similar degree prevents UV (UVA and UVB) and hydrogen peroxide-dependent redox imbalance. However, this antioxidant cannot efficiently protect cellular macromolecules and avert metabolic dysregulation leading to apoptosis.

Electron spin resonance studies on deuterated nitroxyl spin probes used in Overhauser-enhanced magnetic resonance imaging.

The electron spin resonance studies were carried out for 2mm concentration of 14 N-labeled and 15 N-labeled 3-carbamoyl-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl, 3-carboxy-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl, 3-methoxycarbonyl-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl and their deuterated nitroxyl radicals using X-band electron spin resonance spectrometer. The electron spin resonance line shape analysis was carried out. The electron spin resonance parameters such as linewidth, Lorentzian component, signal intensity ratio, rotational correlation time, hyperfine coupling constant and g-factor were estimated. The deuterated nitroxyl radicals have narrow linewidth and an increase in Lorentzian component, compared with undeuterated nitroxyl radicals. The dynamic nuclear polarization factor was observed for all nitroxyl radicals. Upon 2 H labeling, about 70% and 40% increase in dynamic nuclear polarization factor were observed for 14 N-labeled and 15 N-labeled nitroxyl radicals, respectively. The signal intensity ratio and g-value indicate the isotropic nature of the nitroxyl radicals in pure water. Therefore, the deuterated nitroxyl radicals are suitable spin probes for in vivo/in vitro electron spin resonance and Overhauser-enhanced magnetic resonance imaging modalities. Copyright © 2017 John Wiley & Sons, Ltd.