Formation Of Stable Free Radicals Research Articles

Analysis of the Osseointegration Process of Dental Implants by Electron Paramagnetic Resonance: An In Vivo Study.

This research work presents an analysis of the process of an implant’s osseointegration to the jawbone tissue. The purpose of this work was to describe the processes of assimilation and the biochemical dynamics which occur during dental implantation using implants with different macro-microstructure surfaces at the level of stable free radicals using the electron paramagnetic resonance (EPR) method. The experimental investigation was conducted on seven Vietnamese minipigs over twelve months old and weighing up to 30 kg using implants with various macro-microstructure surfaces (SLA, RBM, and HSTTM) and implantation systems, namely the Adin, Sunran, Biomed, and Osstem systems. The integration of the implant into the bone triggered biochemical processes with the formation of stable free radicals. The EPR method was used to identify the formed paramagnetic species and to study the dynamics of the interaction between the surface of the implant and the bone after one and two months. The concentration of carbonate surface centers increased with the time that the implant was connected to the hard tissue. The “Sunran” and “HSTTM” were established as the most suitable implantation system and surface type, respectively, thanks to the highest rate of osseointegration (assimilation) with the bone (hard) tissue. Thus, the EPR method provides the opportunity to study implantation processes.

Antioxidant Activity and Stable Free Radicals in Robusta Green Coffee Genotypes/ Atividade antioxidante e Radicais Estáveis Livres em Genótipos de Café Verde Robusta

This study reports on physicochemical properties (total soluble solids, titratable acidity plus caffeine, trigonelline, 5-CQA, and total phenols contents) of five genotypes of Robusta coffee beans; Bamburral, Beira Rio, Clementino, Coringa, and Pirata. Green bean of Clementino presents the highest concentration of total soluble solids in dry basis (18.0%) and the lowest titratable acidity (154.0 mL-NaOH). Moreover, green beans of Clementino and Pirata show intermediate values of caffeine and trigonelline contents while presenting the highest yield index ofstable free radical formation after roasting, respectively equal to 26 and 23 (electron paramagnetic resonance-EPR data), and the highest content of 5-CQA (around 42 mg/g). Green beans of Bamburral, Beira Rio and Coringa show the highest concentration of total phenols (53 - 56 mg/g), meaning the highest antioxidant activities (IC50 test) but reduced yield index of formation of stable free radicals after roasting, respectively equal to 13.0, 5.9, and 13.0 (EPR data).

Study of L-Glutamic Acid in Solid State for its Possible Use as a Gamma Dosimeter at Different Temperatures (77, 195 and 295 K)

The experimental response of the dosimeter as a function of the irradiation temperature plays an important role, and this effect has consequences in the practical applications of dosimetry. In this work, L-glutamic acid (2-aminopentanedioic acid) is proposed to be a good response, easy to handle, and a cheap gamma dosimeter. For this purpose, polycrystalline samples were irradiated with gamma rays at 77, 195, and 295 K and doses in the kiloGray range (43–230 kGy). The potential use of the glutamic acid system as a chemical dosimeter is based on the formation of stable free radicals when the amino acid is exposed to ionizing radiation. The observed species in these experiments were attributed to deamination and decarboxylation reactions that were studied using electron spin resonance (ESR). The results indicate that the analysis generates a linear response as the irradiation dose increases in a reliable range for industrial and research purposes at three different temperatures.

Study of l-aspartic acid for its possible use as a dosimeter in the interval of 3.4–20kGy at different irradiation temperatures

Abstract Certain commercial applications of radiation processing increase the efficiency of chemical reactions at low temperatures to decrease the free radicals in the bulk material and avoid the synergistic effects of heat. Such applications have motivated the search for a reliable, low-temperature dosimeter for use under the conditions of the irradiation process. For this purpose, polycrystalline samples of l -aspartic acid (2-aminobutanedioic acid) were irradiated with gamma rays at low temperatures and doses in the kiloGray range (3.4–64 kGy). The potential use of the aspartic acid system as a chemical dosimeter is based on the formation of stable free radicals when the amino acid is exposed to ionizing radiation. These radicals can be studied and quantified using electron spin resonance (ESR). The response curves at different temperatures show that the intensity of the ESR spectra (the five characteristic lines) depends on the dose received. The response of the dosimeter increases with increasing temperature, and this relationship is linear up to 20 kGy at 298 K. The decay characteristics show that the change in the ESR signal over time is low and reproducible. In addition, the l -aspartic acid dosimeter is easy to handle and has low cost.

Electron Magnetic Resonance and Density Functional Theory Study of Room Temperature X-Irradiated β-d-Fructose Single Crystals

Stable free radical formation in fructose single crystals X-irradiated at room temperature was investigated using Q-band electron paramagnetic resonance (EPR), electron nuclear double resonance (ENDOR), and ENDOR induced EPR (EIE) techniques. ENDOR angular variations in the three main crystallographic planes allowed an unambiguous determination of 12 proton HFC tensors. From the EIE studies, these hyperfine interactions were assigned to six different radical species, labeled F1-F6. Two of the radicals (F1 and F2) were studied previously by Vanhaelewyn et al. [Vanhaelewyn, G. C. A. M.; Pauwels, E.; Callens, F. J.; Waroquier, M.; Sagstuen, E.; Matthys, P. J. Phys. Chem. A 2006, 110, 2147.] and Tarpan et al. [Tarpan, M. A.; Vrielinck, H.; De Cooman, H.; Callens, F. J. J. Phys. Chem. A 2009, 113, 7994.]. The other four radicals are reported here for the first time and periodic density functional theory (DFT) calculations were used to aid their structural identification. For the radical F3 a C3 carbon centered radical with a carbonyl group at the C4 position is proposed. The close similarity in HFC tensors suggests that F4 and F5 originate from the same type of radical stabilized in two slightly different conformations. For these radicals a C2 carbon centered radical model with a carbonyl group situated at the C3 position is proposed. A rather exotic C2 centered radical model is proposed for F6.

Stable free radicals and peroxyl radical trapping capacity in red wines.

Thirty-two experimental red wines, obtained from eight cultivars and aged in bottles for 2 and 7 years, were examined for the presence of stable free radicals (SFR), for the peroxyl radical trapping capacity (PRTC), and for the concentrations of some important polyphenol families. Aging significantly increases SFR, polyphenol polymers with n > or = 5 (HMWP), and PRTC and is accompanied by a strong decrease of free anthocyanins. Multivariate regression analyses show that HMWP and SFR are independently associated with PRTC while HMWP and anthocyanins are independently associated with the formation of SFR. These results indicate that polymeric polyphenols generated from anthocyanins and proanthocyanidins during wine aging are able to convert highly reactive free radicals into nonreactive radicals through electron delocalization. The strict correlation between SFR and antioxidant activity that we found suggests that these characteristics are related to the functional properties of food.

Magnetic Resonance Studies of Thermally Modified Wood

Summary Thermal modification of wood produces a wood material with many interesting properties, such as enhanced dimensional stability, lower equilibrium moisture content and increased biological durability. Changes in the chemical structure of pine (Pinus sylvestris) caused by thermal treatment were investigated by studying various components of wood using 13C CPMAS NMR spectroscopy. Electron spin resonance (ESR) spectroscopy on the same set of samples was used to study the formation and stability of free radicals formed during the treatment. The most remarkable changes revealed by solid state NMR were the increase in relative crystallinity of cellulose and destruction and deacetylation of hemicelluloses. Changes in the lignin fraction were mostly registered as diminishment in the methoxyl content, although the intensity of the aromatic region increased relative to the carbohydrate fraction during the treatment. Increase in the intensities of the ESR signals from thermally treated wood samples proves the formation of stable free radicals. In addition, radical formation is believed to take part in condensation reactions leading to crosslinks within the lignin and possibly between lignin and other wood components. Both of the methods used indicate that the changes are most remarkable when the treatment temperature is over 200°C.

Degradation in polytetrafluoro ethylene by 62 mev protons

The aim of our study is to describe the dose dependent proton induced modifications in Polytetrafluoro ethylene (PTFE) by using Fourier Transform Infra-red spectroscopy (FTIR), Thermogravimetric analysis (TGA), Differential Scanning Calorimetry (DSC) and X-ray diffraction analysis (XRD). The shifting of the main peak along with a decrease in its intensity, the decrease in thermal stability and melting point and the formation of stable free radicals were observed in the polymer by proton irradiation.

Melanin, melanin "ghosts," and melanin composition in Cryptococcus neoformans

Melanin synthesis is associated with virulence for the pathogenic fungus Cryptococcus neoformans. Exposure of nonmelanized C. neoformans 4067 cells to 4 M guanidinium isothiocyanate followed by 6 M HCl at 100 degrees C resulted in complete solubilization of cellular structures. However, exposure of melanized C. neoformans 24067 to the same conditions produced a suspension of black particles. Analysis of black particles with transmission and scanning electron microscopy revealed cell "ghosts" with electron-dense walls. Electron spin resonance (ESR) spectroscopy of suspensions of black particles revealed a signal indicative of a stable free radical population. The magnitude of the ESR signal was increased by illumination, Zn2+ ions, and basic pH. Boiling the black particles produced only a small reduction in the magnitude of the ESR signal. These ESR changes are characteristic of melanin. Exposure of melanized black cells to 0.1 or 0.5% NaOCl bleached the cells white and abolished the ESR signal, consistent with melanin disruption. ESR spectroscopy was used to study the rate of stable free radical formation, taken as an index of melanization, of C. neoformans 24067 cells growing in medium with 1.0 mM L-dopa at 30 and 37 degrees C over the course of 14 days. Melanization was slower at 37 degrees C. but by day 14, cells grown at 30 and 37 degrees C. had comparable levels or melanin. ESR spectroscopy of seven melanized C. neoformans strains revealed that some strains differed by up to eightfold in melanin content. The ESR spectra of C. neoformans 24067 grown in minimal medium containing either 1.0 mM catechol, dopamine, or L-dopa revealed large differences in signal amplitude. The relative melanin contents were 0.05, 0.45, and 1.0 for C. neoformans grown in media with catechol, dopamine. and L-dopa, respectively. Quantitative analysis revealed that melanin comprised 15.4% of the dry mass of the cell after 10 days of growth in medium containing 1.0 mM L-dopa. The results suggest (i) a useful protocol for isolating C. neoformans melanin, (ii) a role for melanin in maintaining cell wall integrity, (iii) disruption of melanin by NaOCl, (iv) strain differences in melanin content after growth in L-dopa, and (v) quantitative and/or qualitative differences in the melanin produced after growth in various substrates.

Studies on photofading and stable free radical formation in reactive dyed cellulosic systems under their exposure to light

In light exposed systems of cotton and C.I. Reactive Red 3, C.I. Reactive Black 5 and C.I. Direct Blue 78 azo dyes, respectively, generated stable free radicals could be detected. The observed hyperfine splitting of ESR spectra suggest the free radical are formed in the chromophore. Based upon the calculated g-values the location of the generated unpaired electron could be assumed on one of the C atoms of the dye molecule.

Electron spin resonance investigations of gamma-irradiated shrimp shell

Gamma-irradiation of shrimp shell induces the formation of stable free radicals, which can be monitored by electron spin resonance (ESR) spectroscopy. The ESR spectrum of the free radicals is more complex than was originally reported, and was found to be species-dependent. The results presented include the effects of the following parameters on the ESR spectrum: different types of pre- and post-irradiation processing, absorbed dose, storage time, and species variations. The effects of these parameters on the ESR spectra are used to explain discrepancies between previously reported spectra for irradiated shrimp shell. Finally, the possible application of ESR spectroscopy as a tool for post-irradiation monitoring of shrimp is assessed.

Identification by epr spectroscopy of carvacrol and thymol as the major sources of free radicals in the oxidation of plant essential oils

AbstractThe formation of stable free radicals upon reaction of the essential oils of 10 plant species with ultraviolet radiation and the superoxide radical anion, O2−, has been investigated by electron paramagnetic resonance (EPR) spectroscopy. Only the oils from oregano, summer savory and thyme produced EPR spectra and the results can be accounted for in terms of free radicals produced by the closely related phenolics, carvacrol and thymol. These observations are interpreted in terms of the known antioxidant properties of these molecules.

Formation of stable free radicals from kampo medicines TJ-9, TJ-15, TJ-23, TJ-96, TJ-114 and their antioxidant effect on low density lipoproteins.

The Japanese herbal Kampo medicines TJ-9 (A), TJ-15 (B), TJ-23 (C), TJ-114 (D) and TJ-96 (E) were effective (2-5x less than alpha-tocopherol) in inhibiting a copper-induced peroxidation of low density lipoprotein. Kampo medicines dissolved in n-butanol formed stable free radical(s), detected by EPR spectroscopy as a single asymmetric line with g-value g = 2.005. The radical concentration increased in the order: C less than D approximately A approximately E less than B. When the Kampo medicines were oxidized in n-butanol by excess of PbO2 their radical concentration increased 7-15 fold and was in the order C less than D less than A approximately E much less than B. A relationship between the potency of the medicines to inhibit peroxidation of LDL and their ability to form stable free radicals upon oxidation was observed. The medicine which formed more radicals was more efficient in inhibiting peroxidation of LDL. In order to study whether Kampo medicines can reduce alpha-tocopherol radical, the alpha-tocopherol radical was generated by the reaction of alpha-tocopherol with UV irradiated di-tert-butylperoxide and by autooxidation of alpha-tocopherol in n-butanol (25 microliters ml-1) in air. In both systems vitamin-C greater than Kampo B decreased the concentration of the alpha-tocopherol radical and the EPR spectrum of Kampo B stable radical(s) appeared. The effect of other Kampo medicines was not clearly seen since their EPR spectra were superimposed with the spectrum of the alpha-tocopherol radical. The results indicate that Kampo medicines possess electron donor properties and ability to form stable radical(s). The results may contribute to understanding beneficial effects of Kampo medicines in diseases in which free radical damage is suggested.

Special Features of Stable Free Radical Formation on Plasma-irradiated α-d-Glucose Studied by ESR Spin-Trapping Technique

Abstract The structure of the stable free radicals produced in argon plasma-irradiated α-d-glucose was characterized by the ESR spectral measurements of the spin adducts obtained from the reactions with 2,4,6-tri-t-butylnitrosobenzene (BNB) with the aid of computer simulations.

Formation of stable free radicals in saccharides by heating or by UV irradiation.

Formation of stable free radicals in saccharides by heating or by UV irradiation.

Stable free radical formation in the binary powders of silicates and organic compounds.

Stable free radical formation was observed in the binary powders of silicates and general organic compounds by the use of ESR at room temperature in the air. A large amount of free radicals was formed, if an OH or COOH group containing organic molecule was used. Free radicals were stable not only in the air but also in the suspension of benzene. However, they disappeared immediately upon contact with proton donating liquid molecules. Increase in spectral intensities with time and variation of spectral shapes with moisture were observed.

Formation of Stable Free Radicals in Alkaline Solutions of Some Monosaccharides.

Formation of Stable Free Radicals in Alkaline Solutions of Some Monosaccharides.

The formation of stable free radicals in the hardening and thermal degradation of phenol-formaldehyde resins

The formation of stable free radicals in the hardening and thermal degradation of phenol-formaldehyde resins

A REVIEW OF EXPERIMENTAL WORK WITH DIQUAT AND RELATED COMPOUNDS

Summary. Published literature on diquat (9,10‐dihydro‐8a, 10a‐diazonia phenanthrene dibromide; 1,1′‐ethylene‐2,2′‐dipyridylium dibromide) and related dipyridyl herbicides is reviewed. Their activity is probably connected with the formation of stable free radicals on reduction and both photosynthetic and respiratory processes may be associated with free radical formation in the plants. These herbicides are rapid‐acting translocated desiccants and kill the aerial parts of most plants, but are safe as soon as they touch the ground, having no residual effect through the soil. Possible uses are as desiccants, in place of cultivation to clear fallows and seedbeds before sowing, in pre‐emergence weedkilling, for weeding round trees and bushes and, with directed spraying, for inter‐row weeding in row crops.Revue des essais effectués avec le Diquat et des composés apparentés