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급속 열처리시킨 n-GaAs에서 Photoreflectance 연구
김인수,배인호,최재두,김근형 嶺南大學校 基礎科學硏究所 1997 基礎科學硏究 Vol.17 No.-
The characteristics of rapid thermal annealed n-GaAs(100) is analyzed by the photoreflectance(PR) measurement. The Si highly doped n-GaAs was observed the FKO signals. The bandgap(E?) and surface electric field(E?) of as-grown sample were 1.423 eV and 2.65×10? V/cm, respectively. In the rapid thermal annealed samples, E? was increased and then decreased by increasing anealing temperature, and it was increased again at 800 ℃. These results could be explained by decreasing of the non-radiative recombination on samples. For the time dependence of the rapid thermal annealing, the amplitude of the PR signal was maximum at 20 sec, and E? was increased by 10.7 times than that of as-grown sample.
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Choi Geun-Hyoung,Lee Deuk-Yeong,Song A-Reum,Moon Bo-Yeon,Kim Jin-Hyo 한국응용생명화학회 2022 Applied Biological Chemistry (Appl Biol Chem) Vol.65 No.4
Perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) are persistent organic pollutants (POPs) that are prohibited from being produced and used. However, they remain in the agricultural environment and are transferred to crops. In addition, PFOA is classified as possibly carcinogenic to humans. To fully understand the exposure and risk of PFOA and PFOS for human in crops, a residue survey and estimation of dietary exposure assessment are needed. Therefore, we investigated the residues of PFOA and PFOS in upland soil and cultivated root crops. The average residues of PFOA and PFOS in the soil were < 0.054–0.541 μg kg– 1 and 0.024–0.111 μg kg– 1, and 0.067–0.193 μg kg– 1 and < 0.02 μg kg– 1 in the crops, respectively. The average PFOA residues were higher than PFOS in the soil and crops. The estimated daily intakes of PFOA and PFOS in the crops were 0.284 ng kgbw –1 day– 1 and 0.023 ng kgbw –1 day– 1, and the estimated hazard quotients were 0.355 and 0.013, respectively. In addition, the excess cancer risk of PFOA was calculated to be 1.99 × 10– 8. Thus, the non–carcinogenic and carcinogenic risks of PFOA and PFOS were not notable from the surveyed residues in the crops. However, the risks may be higher when the residues in other food crops are considered. Perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) are persistent organic pollutants (POPs) that are prohibited from being produced and used. However, they remain in the agricultural environment and are transferred to crops. In addition, PFOA is classified as possibly carcinogenic to humans. To fully understand the exposure and risk of PFOA and PFOS for human in crops, a residue survey and estimation of dietary exposure assessment are needed. Therefore, we investigated the residues of PFOA and PFOS in upland soil and cultivated root crops. The average residues of PFOA and PFOS in the soil were < 0.054–0.541 μg kg –1 and 0.024–0.111 μg kg –1 , and 0.067–0.193 μg kg –1 and < 0.02 μg kg –1 in the crops, respectively. The average PFOA residues were higher than PFOS in the soil and crops. The estimated daily intakes of PFOA and PFOS in the crops were 0.284 ng kg bw –1 day –1 and 0.023 ng kg bw –1 day –1 , and the estimated hazard quotients were 0.355 and 0.013, respectively. In addition, the excess cancer risk of PFOA was calculated to be 1.99 × 10 –8 . Thus, the non–carcinogenic and carcinogenic risks of PFOA and PFOS were not notable from the surveyed residues in the crops. However, the risks may be higher when the residues in other food crops are considered.
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Geun-Hyoung Choi,Dal-Soon Choi,Su-Myeong Hong,Oh-Kyoung Kwon,Hee Soo Eun,김정한,김진효 한국응용생명화학회 2012 Applied Biological Chemistry (Appl Biol Chem) Vol.55 No.3
Contamination levels of 17 polychlorinated dibenzop-dioxins (PCDDs)/polychlorinated dibenzofurans (PCDFs) and 12 dioxin-like polychlorinated biphenyls (DL-PCBs) were investigated on six major fruits consumed in Korea. Dioxin level was monitored on whole fruits. Average concentrations of PCDD/Fs were 0.042 pg/g fresh weight (f.w.) (apple), 0.0094 pg/g f.w. (grape), 0.1843 pg/g f.w. (mandarin orange), 0.2282 pg/g f.w. (peach), 0.1491 pg/g f.w. (pear), and 0.1330 pg/g f.w. (persimmon). For DL-PCBs, the average concentrations were 0.0932 pg/g f.w. (apple), 0.2649 pg/g f.w. (grape), 1.5437 pg/g f.w. (mandarin orange), 0.1942 pg/g f.w. (peach), 0.4591 pg/g f.w. (pear), and 0.4396 pg/g f.w. (persimmon). The major toxic equivalency (TEQ) contributors were identified as 1,2,3,7,8-pentachlorodibenzop-dioxin in PCDD and 2,3,4,7,8-pentachlorodibenzofuran in PCDFs. Most residual DL-PCBs showed no contribution to total TEQ values. The lowest TEQ level was recorded in peach (0.0161pg-TEQWHO/g f.w.), and the highest TEQ level was found in mandarin orange (0.0448 pg-TEQWHO/g f.w.). Total estimated daily intake (EDI) of dioxins from the six fruits was calculated at 3.8159 pg-TEQWHO/day, which is 1.59% of Korean tolerable daily intake based on 60 kg body weight.
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Geun-hee Choi,Yeong Byeon,Hyoung Yool Lee,Kyoungwhan Back 한국육종학회 2015 한국육종학회 심포지엄 Vol.2015 No.07
Caffeic acid O-methyltransferase (COMT) methylates N-acetylserotonin into melatonin; that is, it has N-acetylserotonin O-methyltransferase (ASMT) activity. The ASMT activity of COMT was first detected in Arabidopsis thaliana COMT (AtCOMT). To confirm the ASMT activity of COMT in other plant species, we evaluated the ASMT activity of a COMT from rice (Oryza sativa) (OsCOMT). Purified recombinant OsCOMT protein from Escherichia coli was used to validate the high ASMT activity of OsCOMT, similar to that of AtCOMT. The Km and Vmax values for the ASMT activity of OsCOMT were 243 μm and 2,400 pmol/min/mg protein, which were similar to those of AtCOMT. Similar to AtCOMT, OsCOMT was localized in the cytoplasm. In vitro ASMT activity was significantly inhibited by either caffeic acid or quercetin in a dose-dependent manner. Analogously, in vivo production of melatonin was significantly inhibited by quercetin in 4-week-old detached rice leaves, suggestive of a positive role of COMT in melatonin biosynthesis in plants.
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Benzaldehyde as a new class plant growth regulator on Brassica campestris
( Geun Hyoung Choi ),( Jin Ho Ro ),( Byoung Jun Park ),( Deuk Yeong Lee ),( Mi Sun Cheong ),( Dong Yeol Lee ),( Woo Duck Seo ),( Jin Hyo Kim ) 한국응용생명화학회 2016 Journal of Applied Biological Chemistry (J. Appl. Vol.59 No.2
Plant growth regulator is an essential pesticide to date while the available active ingredient is not well understood unlike fungicide, insecticide and herbicide. This study was aimed to evaluate a new chemical class of plant growth regulator, and the total of 92 benzene derivatives were screened for their germination and early stage of the root growth regulation on Brassica campestris. Thirty benzaldehydes, nine acids, one amide, and one ester showed potent root growth inhibitory activity (>70 % inhibition) while only salicylaldehyde showed potent germination inhibition (IC50 = 81.2 mg/L) suggesting that benzaldehyde was a key module candidate for the growth inhibition. Benzaldehydes were further evaluated for root growth inhibition. 2,3-Dihydroxybenzaldehyde and salicylaldehyde showed IC50 values of 8.0 and 83.9 mg/L, respectively. On the other hand, salicylaldehyde, and 2,4,5- trihydroxybenzaldehyde were found to have root growth promotion effects less than 10 mg/L. This result suggests that the benzaldehyde is a new class candidate for plant growth regulator.
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( Geun Hyoung Choi ),( Leesun Kim ),( Deuk Yeong Lee ),( Cho Long Jin ),( Sung Jin Lim ),( Byung Jun Park ),( Nam Jun Cho ),( Jin Hyo Kim ) 한국응용생명화학회 2016 Journal of Applied Biological Chemistry (J. Appl. Vol.59 No.2
The quantitative analytical method for the bioactive substance, 3-cyano-4-methoxy-N-methyl-2-pyridone (ricinine) and an index compound, ricinoleic acid in castor plant (Ricinus communis) extract or oil was developed. For the determination of a pyridone alkaloid compound, ricinine, successive cartridge cleanup method combined with ultra-performance liquid chromatography was set up with ENVI-CarbTM (0.5 g) and C18 SPE cartridges. Accuracy and precision were evaluated through fortification studies of one biopesticide (PE) at 10 and 100 mg kg.1. Mean recoveries of ricinine were 98.7 and 96.0 % associated with less than 10 % RSD, respectively. For the determination of ricinoleic acid in castor extract and oil, saponification and methylation were optimized using gas chromatography-time of flight mass spectrometry. Recovery was more than 84.8 % associated with 6.2 % RSD after derivatization procedure. Both methodologies developed were applied to analyze real samples including three castor oil products and six commercially available biopesticides containing R. communis, collected at Korean market. The contents of ricinine and ricinoleic acid in most commercial biopesticides were less than the oil or extract contents indicated by label.
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Choi, Geun-Hyoung,Lee, Deuk-Young,Jeong, Dong-Kyu,Kuppusamy, Saranya,Lee, Yong Bok,Park, Byung-Jun,Kim, Jin-Hyo Elsevier 2017 Journal of integrative agriculture Vol.16 No.8
<P>Research on the occurrence of perfluorochemicals (PFCs) such as perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) in the agricultural environment is lacking, in spite of their potential risk via food chain transfer from aquatic and soil-plant systems to animals and/or humans. In the present study, for the first time, soil and water samples collected from 243 different agricultural sites adjacent to waste water treatment plants (WWTPs) belonging to 81 cities and 5 provinces with different levels of industrialization in South Korea were monitored for concentrations of PFOS and PFOA by use of solid phase extraction and liquid chromatography-tandem mass spectroscopy (LC-MS/MS). Significant mean concentrations of PFOA (0.001-0.007 mu g L-1 water and <0.05-1.573 mu g kg(-1) soil) and PFOS (0.001-0.22 mu g L-1 water and <0.05-0.741 mu g kg(-1) soil) were found in all samples. Concentrations of PFCs in soils were high, highlighting that soil is an important sink for PFCs in the agricultural environment. Samples from near WWTPs in Gyeongsang Province contained the highest concentrations of PFOS and PFOA, reflecting the concentration of heavy industry in the province. The concentrations of PFCs in agricultural water (most samples <0.05 mu g L-1) and soils (most samples <1 mu g kg(-1)) from South Korea were less than acceptable guideline values, indicating that South Korea is not a hotspot of PFOS and PFOA contamination and that there is negligible risk to human and ecological health from these chemicals. However, further studies investigating the seasonal variation in PFOA, PFOS and other perfluorochemical concentrations in the agricultural environment are needed.</P>
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Choi, Ihn-Geun,Son, Hyun-Gyun,Yang, Byung-Hwan,Kim, Seok Hyeon,Lee, Jun-Suk,Chai, Young-Gyu,Son, Bong Ki,Kee, Baik Seok,Park, Byung Lae,Kim, Lyoung Hyo,Choi, Yoo Hyun,Shin, Hyoung Doo Wiley Subscription Services, Inc., A Wiley Company 2005 Human mutation Vol.26 No.3
<P>Alcoholism is a multifactorial and polygenic disorder involving complex gene-to-gene and gene-to-environment interactions. Alcohol metabolism is one of the biological determinants that could significantly be influenced by genetic polymorphisms in alcohol-metabolism genes. These genetic polymorphisms are believed to influence drinking behavior and development of alcoholism. Direct DNA sequencing of whole ADH1B and ADH1C genes revealed 36 sequence variants, including six nonsynonymous and 14 novel polymorphisms. Seventeen polymorphisms among them were selected for genotyping in a larger study (n=352) based on linkage disequilibria (LDs) among SNPs, locations, and frequencies. Hardy-Weinberg equilibrium (HWE) analyses of polymorphisms revealed severe deviations only in alcoholics, which strongly suggest that a selection bias (or pressure) may be involved. The analyses of genotype distribution in alcoholics (n=106) and normal controls (n=246) showed dramatic associations with the risk of alcoholism. Fourteen polymorphisms in ADH1C and ADH1B showed a series of different strengths of association and magnitudes of risk. Based on referent and subgroup analysis, it was strongly suggested that the genetic effects come from the ADH1B*47Arg/*47Arg genotype, and that the positive signals from other sites are just tracking the genetic effect of ADH1B His47Arg. In this article we present summaries of previous studies and of the present study, to give an overview of the worldwide effects of ADH1B His47Arg on the risk of alcoholism. The information derived from this study could be valuable for understanding the genetic factors involved in the risk of alcoholism and facilitate further investigation in other ethnic groups. Hum Mutat 26(3), 224–234, 2005. © 2005 Wiley-Liss, Inc.</P>
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Endosulfan Plant Uptake Suppression Effect on Char Amendment in Oriental Radish
Choi, Geun-Hyoung,Lee, Deuk-Yeong,Seo, Dong-Cheol,Kim, Leesun,Lim, Sung-Jin,Ryu, Song-Hee,Park, Byung-Jun,Kim, Jeong-Han,Kim, Jin Hyo Springer Netherlands 2018 Water, Air and Soil Pollution Vol.229 No.1
<P>Persistent organic pollutants (POPs) immobilization in farm land is an important issue to solve the residue in crop, and char has been considered for the remediation. In here, three commercially available chars like powdered oak char (POC), granulated oak char (GOC), and rice husk char (RHC) including powdered activated carbon (PAC) were investigated for their potential to adsorb and immobilize endosulfan in the soil. The maximum adsorption capacities (mg g(-1)) of the applied chars as POC, GOC, and RHC were 714.8, 322.6, and 181.8, respectively, and the capacity of POC was similar with PAC (713.8). In addition, the pore volume (0.138 cm(3) g(-1)) and the surface area (270.3 m(2) g(-1)) of POC were over 3-fold higher than GOC and RHC. The bioconcentration factor (BCF) reducing effect of alpha-, beta-endosulfan, and endosulfan sulfate in oriental radish (Raphanus sativus var. sativus) was investigated by amendment of three commercially available chars to the contaminated soils. The BCF of total endosulfan was 0.025 in the radish root. POC treatments effectively suppressed the endosulfan uptake (BCF 0.002). However, GOC and RHC showed little BCF reducing effect of endosulfan in radish.</P>
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