• Korean Journal of Food Science and Technology
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• v.34 no.1
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• pp.18-23
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• 2002

The detection characteristics of gamma-irradiated $(0{\sim}4\;kGy)$ soybeans produced in Korea and China were investigated by thermoluminescene (TL), electron spin resonance (ESR), and DNA comet assay. The TL glow curves were shown at around $200^{\circ}C$ for irradiated soybeans, while that at $280^{\circ}C$ for the non-irradiated one. The normalization with a re-irradiation step at 1 kGy could verify the above detection results. The Korean soybean showed higher glow curves than Chinese did. The ESR spectroscopy for husks of irradiated soybeans revealed specific signals (g = 2.02374, 1.98715) derived from cellulose radical, which intensities were proportional to irradiation does, with the higher peaks in Chinese sample than Korean one. The DNA comet for the non-irradiated sample showed no or little tails, while those for irradiated samples above 0.5 kGy were remarkably changed in their length, size, and concentration, thus resulting in distinguishing non-irradiated from irradiated samples. As a result, TL, ESR, and DNA comet determinations were found suitable for the detection of irradiated soybean at 0.5 kGy or more, and negligible differences were observed between Korean and Chinese origins in their detection characteristics.

• Journal of the Korean Society of Food Science and Nutrition
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• v.32 no.1
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• pp.8-14
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• 2003

Multistep detection was peformed to identify irradiated dried anchovy. In thermoluminescence (TL) analysis, non-irradiated samples represented a lower peak at about 28$0^{\circ}C$, but irradiated samples showed a higher peak at around 20$0^{\circ}C$. The normalization with a re-irradiation step at 1 kGy could verify the identification results. Electron spin resonance (ESR) spectroscopy for bones separated from irradiated anchovy revealed specific signals (g=2.002,1.998) derived from a hydroxyapatite radical, which intensities were in proportion to the irradiation doses and still detectable even after 6 months of storage at -2$0^{\circ}C$. Six kinds of hydrocarbons (HC) were observed in dried anchovy samples and 1,7-hexadecadiene and 1-hexadecene were only detected in irradiated anchovy at 1 kGy or more. Also among 3 kinds of radiation-induced 2-alkylcyclobutanones (2-ACB) observed, 2-dodecylcy-clobutanone and 2-tetradecylcyclobutanone were unique in irradiated anchovy. As a result, the concentration of radiation-induced HCs and 2-ACBs were dependent on the irradiation dose and detectable after 6 months of storage. However, TL and ESR analyses were found simpler than the other methods for identification of irradiated boiled-dried anchovy.

• Nuclear Engineering and Technology
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• v.52 no.10
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• pp.2379-2386
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• 2020

This paper presents the results of the first intercomparison exercise performed by the Korea retrospective dosimetry (KREDOS) working group using electron paramagnetic resonance (EPR) spectroscopy. The intercomparison employed the alanine dosimeter, which is commonly used as the standard dosimeter in EPR methods. Four laboratories participated in the dose assessment of blind samples, and one laboratory carried out irradiation of blind samples. Two types of alanine dosimeters (Bruker and Magnettech) with different geometries were used. Both dosimeters were blindly irradiated at three dose levels (0.60, 2.70, and 8.00 Gy) and four samples per dose were distributed to the participating laboratories. Assessments of blind doses by the laboratories were performed using their own measurement protocols. One laboratory did not participate in the measurements of Magnettech alanine dosimeter samples. Intercomparison results were analyzed by calculating the relative bias, E_n value, and z-score. The results reported by participating laboratories were overall satisfactory for doses of 2.70 and 8.00 Gy but were considerably overestimated with a relative bias range of 10-95% for 0.60 Gy, which is lower than the minimum detectable dose (MDD) of the alanine dosimeter. After the first intercomparison, participating laboratories are working to improve their alanine-EPR dosimetry systems through continuous meetings and are preparing a second intercomparison exercise for other materials.

• Archives of Pharmacal Research
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• v.27 no.9
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• pp.947-953
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• 2004

The antioxidative and hepatoprotective potentials of two anthraquinones, alaternin (2-hydroxy-emodin) and emodin, to scavenge and/or inhibit hydroxyl radicals generated by the Fenton reaction and to protect tacrine-induced cytotoxicity in human liver derived HepG2 cells were evaluated, respectively. The inhibitory activity on hydroxyl radical generated in a cell-free chemical system (FeSO$_4$/$H_2O$$_2$) was investigated by a fluorescence spectrophotometer using a highly fluorescent probe, 2$^1$,7$^1$-dichlorofluorescein. The hydroxyl radical scavenging activity was determined by electron spin resonance spectroscopy using 5,5-dimethy-1-pyrroline-N-oxide as hydroxyl radicals trapping agents. Tacrine-induced HepG2 cell toxicity was determined by a 3-［4,5-dimethylthiazole-2yl］-2,5-diphenyltertrazolium bromide assay. Although the scavenging activity of alaternin on hydroxyl radical was similar to that of emodin in dose-dependent pat-terns, the inhibitory activity exhibited by the former on hydroxyl radical generation was stron-ger than that of the latter, with $IC_{50}$/ values of 3.05$\pm$0.26 $\mu$M and 13.29$\pm$3.20 $\mu$M, respectively. In addition, the two anthraquinones, alaternin and emodin showed their hepatoprotective activ-ities on tacrine-induced cytotoxicity, and the EC$_{50}$ values were 4.02 11M and 2.37 $\mu$M, respec-tively. Silymarin, an antihepatotoxic agent used as a positive control exhibited the EC$_{50}$ value of 2.00 $\mu$M. These results demonstrated that both alaternin and emodin had the simultaneous antioxidant and hepatoprotective activities.ies.

• Preventive Nutrition and Food Science
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• v.7 no.1
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• pp.57-61
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• 2002

Electron spin resonance (ESR) spectroscopy was used to investigate the effect of irradiation dose and storage time on the free radical concentrations in gamma-irradiated dried seasoning powder. Seasoning powders of dried squid flavor, shrimp flavors, kimchi flavor, spicy beef soup flavor and soy sauce flavor were irradiated with doses of 0, 1, 3, 5, 7 and 9 kGy at room temperature using a Co-60 irradiator. Characteristic signals of free radicals were observed in all the irradiated samples of this experimental while these signals were not detected in non-irradiated samples. Since the free radical concentrations linearly increased with the applied doses (1~9 kGy), highly positive correlation coefficients ($R^2$ = 0.9285~0.9965) were obtained between irradiation doses and free radical concentrations during all the storage times. Free radical concentrations of the irradiated flavored seasoning powder did not change even at 16 weeks of storage at room temperature, while those of dried squid, shrimp and spicy beef soup flavors decreased until 2 weeks of storage after irradiation with 5 kGy or over, and these of soy cause flavors slowly decreased until 8 weeks of storage after irradiation with 3 kGy or over. Although the free radical concentrations decreased with storage times, the characteristic signals of the irradiated seasoning powders of dried squid, shrimp, spicy beef and soy sauce flavors were observed even after 16 weeks of storage at room temperature.

• Journal of Marine Bioscience and Biotechnology
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• v.1 no.2
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• pp.126-135
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• 2006

Phlorotannins which is oligomeric polyphenol of phloroglucinol unit were isolated from solvent fractions of methanolic extract of the brown alga, Ecklonia cava (EC). The inhibitory effects of phlorotannins from EC solvent fractions on oxidative stress were examined in human dermal fibroblasts (HDFs) related to wrinkle formation. Among the solvent fractions, phlorotannins from ethyl acetate fraction exerted the highest scavenging effect on DPPH radical, hydroxyl radical and alkyl radical analyzed by electron spin resonance (ESR) spectroscopy. The levels of intracellular reactive oxygen species (ROS) and lipid peroxidation were measured using 2',7'-dichlorofluorescin diacetate (DCFH-DA) and diphenyl-1-pyrenylphosphine (DPPP), respectively. Their levels were significantly decreased in the presence of phlorotannins from ethyl acetate fraction, compared with other fractions obtained from EC extract (P < 0.01). Furthermore, intracellular glutathione (GSH) level was significantly increased in a time dependent manner by the phlorotannins. Therefore, these results suggest that phlorotannins from EC extract could have a therapeutic potential for prevention and treatment of several diseases such as wrinkle formation related to oxidative stress.

• Journal of the Korean Chemical Society
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• v.39 no.4
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• pp.237-243
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• 1995

The measurments of neutral semiquinone radicals, which were formed from the laser flash photolysis of anthraquinone (AQ) in the mixed solvents were carried out by the time resolved electron spin resonance (trESR) spectroscopy. The chemically induced dynamic electron polarization (CIDEP) spectra of the neutral semiquinone radical (AQH${\cdot}$) and semiquinone radical anion (AQ${\cdot}$-) were successively detected in the laser flash photolysis of AQ in the mixtures of 2-propanol (PrOH) and triethylamine (TEA). The neutral semiquinone radical was short-lived with the half-life of 0.8 ${\mu}sec$, whereas the semiquinone radical anion was relatively stable and then its cwESR could be observed. The rate constant of the spin-depolarization of semiquinone radical anion was $2.6{\times}10^5 sec^{-1}$ and the decay of the radical anion was the first order reaction with the rate constant of $3.0{\times}10^2\; sec^{-1}$. No CIDEP of semiquinone radical anion was observed in the mixture of PrOH and the lower concentration of TEA than 2 percent. The CIDEP spectrum of the neutral semiquinone radical was detected in the mixture of benzene and TEA with the half-life of 3.0 ${\mu}sec$. The neutral semiquinone radical could not be detected by cwESR. Neither CIDEP nor ESR absorption could be observed in PrOH, TEA or benzene only.

• Korean Journal of Food Science and Technology
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• v.31 no.3
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• pp.606-611
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• 1999

To identify irradiated foods, studies have been carried out with electron spin resonance (ESR) spectroscopy on bone containing foods, such as chicken, pork, and beef. Bones cleaned, pieced and dried were irradiated with doses of 0, 1, 3, 5 kGys using a $Co^{60}$ irradiator. The bones were placed in a resonant quartz tube with an internal diameter of about 4.0 mm within the Bruker Win-ESR spectrometer, and the intensity of the ESR signal could be quantified by double integration of the first derivative spectrum. The irradiated bone presented an asymmetric absorption in shape, different from that of an unirradiated one. It could be possible to detect at doses lower than 1 kGy below the dose employed commercially (3 kGy) in the case of irradiated chicken bone. The signal intensity was greatest in the beef bone, intermediate in the pork bone and lowest in the chicken bone; it was normally lower for smaller animals than for larger species, and small variations were observed between samples of the same species. The intensity of the signal induced in bones increased linearly with irradiation doses in the range of 1.0 kGy to 5.0 kGy, and it was possible to distinguish between samples given low and high doses of irradiation. The signal stability for 6 weeks made them ideal for the quick and easy identification of irradiated meats.

• Korean Journal of Food Science and Technology
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• v.34 no.3
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• pp.396-399
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• 2002

Electron spin resonance (ESR) spectroscopy was used to investigate the effect of irradiation dose and storage time on the free radical concentrations in gamma-irradiated sesame (Korean and Sudan) and perilla seeds (Korea). The samples were sealed with packed pyrex tube (50 g respectively) and then irradiated with doses of 0, 1, 5 and 10 kGy at room temperature using a Co-60 irradiator. Each sample in ESR quartz tube were calculated with ESR signals by Bruker-EPR spectrometer for 4 weeks. Free radicals detected for irradiated and unirradiated samples were higher than those of unirradiated ones. Since the free radical concentrations linearly incresed with the applied doses $(1{\sim}10\;kGy)$, highly positive correlation coefficients $(R^2=0.9926{\sim}0.9994)$ were obtained between irradiation doses and free radical concentrations right after irradiation. Although the free radical concentrations decreased with storage time, the signals of free radical in irradiated samples were observed even after 4 weeks of storage at room temperature.

• Korean Journal of Materials Research
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• v.20 no.11
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• pp.606-610
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• 2010

Films consisting of a silicon quantum dot superlattice were fabricated by alternating deposition of silicon rich silicon nitride and $Si_3N_4$ layers using an rf magnetron co-sputtering system. In order to use the silicon quantum dot super lattice structure for third generation multi junction solar cell applications, it is important to control the dot size. Moreover, silicon quantum dots have to be in a regularly spaced array in the dielectric matrix material for in order to allow for effective carrier transport. In this study, therefore, we fabricated silicon quantum dot superlattice films under various conditions and investigated crystallization behavior of the silicon quantum dot super lattice structure. Fourier transform infrared spectroscopy (FTIR) spectra showed an increased intensity of the $840\;cm^{-1}$ peak with increasing annealing temperature due to the increase in the number of Si-N bonds. A more conspicuous characteristic of this process is the increased intensity of the $1100\;cm^{-1}$ peak. This peak was attributed to annealing induced reordering in the films that led to increased Si-$N_4$ bonding. X-ray photoelectron spectroscopy (XPS) analysis showed that peak position was shifted to higher bonding energy as silicon 2p bonding energy changed. This transition is related to the formation of silicon quantum dots. Transmission electron microscopy (TEM) and electron spin resonance (ESR) analysis also confirmed the formation of silicon quantum dots. This study revealed that post annealing at $1100^{\circ}C$ for at least one hour is necessary to precipitate the silicon quantum dots in the $SiN_x$ matrix.