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화학적 , 대사적 산화반응중 생성되는 S - oxide 를 이용한 O - ethyl S - methyl ethylphosphonothioate (1) 의 독성 기작에 관한 연구
허장현,한대성 ( J . H . Hur,T . R . Fukuto,D . S . Han ) 한국환경농학회 1991 한국환경농학회지 Vol.10 No.2
O-ethyl S-methyl ethylphosphonothioate [LD_(50) (rat, oral) 4.6㎎/㎏ : K_i(bovine erythrocyte acetylcholinesterase) 303 M^(-1min-1)] was selected as a model compound to study the mode of action of O, S-dialkyl alkylphosphonothioates which have been hypothesized to be toxic via a bioactivation process. Two chemical oxidants, meta-chloroperoxybenzoic acid and monoperoxyphthalic acid, and rat liver microsomal oxidases were used to mimic the action of mixed function oxidases on the model compound. The formation of S-oxide, a very unstable active intermediate, was proposed based on the identification of metabolic products. Furthermore, a trapping experiment with ethanol showed that the unstable intermediate S-oxide had the ability to phosphorylate acetylcholinesterase which is an important enzyme in nerve systems. The S-oxide intermediates are presumed to be responsible for the toxicity of O,S-dialkyl alkylphosphonothioates.
허장현,한대성 ( Jang Hyun Hur,Dae Sung Han ) 한국환경농학회 1993 한국환경농학회지 Vol.12 No.2
O-Ethyl S-methyl ethylphosphonothioate was studied for chemical and metabolic oxidation using ^(31)P-NMR analyses. The chemical shifts of O-ethyl ethylphosphonic acid (2) which is one of major metabolites were changed with the variation of oxidation systems. ^(31)P-NMR chemical shifts of 2 were observed at 40.15ppm from oxidaton by MCPBA, 30.98 ppm by MMPP, 29.31 ppm from in vitro rat liver microsomal oxidation, and 29.10 ppm from in vivo metabolism in houseflies. ^(31)P-NMR chemical shift of 2 in two different solvents such as deutero-chloroform and deuterium oxide were observed at 30.70 ppm and 40.15 ppm, respectively. And those of the metabolites were also observed at around 30 ppm under the conditions of pH 3, 5.6 and 14 and 47.91 ppm under pH 1 which is a strong acidic condition. It could be explained that the ionized form of 2 should have greater shielding effect on phosphorus atom and hence shows upfield chemical shift in polar solvents and alkaline conditions. On the other hand, a protonated form under organic solvents and the strong acidic condition should have less shielding effect than its ionized form, shifting the peak downfield.
RBF interpolation을 이용한 효율적인 혼합형 격자 변형 기법
허장현,박수형 한국전산유체공학회 2022 한국전산유체공학회지 Vol.27 No.2
In the present study, radial basis function(RBF) interpolation based hybrid methods are developed for Multi-block structured grid deformation. The algorithm is combined with transfinite interpolation(TFI) and spring analogy(SPR). Each method uses RBF, TFI and SPR respectively for deformation of interior mesh points while block interface is deformed by RBF equally. The main objective of the paper is to compare the performance of hybrid schemes. Characteristics of RBF interpolation for different radial basis functions are also investigated. Two wind tunnel test cases are selected to validate the algorithm:NACA0012 airfoil in pitching oscillation and NACA0015 wing oscillation. The algorithm is validated by comparing the numerical results from grid deformation methods and the result from rigidly rotating grid. Finally, RBF-TFI hybrid scheme with high order radial basis function is suggested for efficient unsteady simulation on Multi-block structured grid.
농산물 중 잔류농약 시험법의 매질보정 검량법의 대표시료 탐색 연구
허장현 ( Jang-hyun Hur ),조영주 ( Yeong-ju Jo ),최정윤 ( Jeong-yoon Choi ),함헌주 ( Hun-ju Ham ),최재웅 ( Jae-woong Choi ),허경진 ( Kyung-jin Hur ) 한국환경농학회 2022 한국환경농학회 학술대회집 Vol.2022 No.-
최근 간편하고 신속한 QuEChERS 추출법과 질량분석기를 이용하는 분석법이 보편화됨에 따라 잔류농약 분석 시 비의도적 간섭물질로 인해 유발되는 농산물의 매질효과(matrix effect)에 관한 관심이 증가하고 있다. 매질효과(matrix effect)는 주로 질량분석기로 분석하는 과정에서 시그널 억제(suppression) 또는 시그널 증가(enhancement)와 같은 현상으로 나타난다. 이러한 현상은 매질별로 상이하게 나타나고 분석성분의 감도 변화에도 큰 영향을 미쳐 정량분석 업무에 어려움을 준다. 일선 분석 현장에서는 시료별 매질효과(matrix effect)를 최소화하고자 동일한 시료를 활용하는 매질보정(matrix matched) 방법을 활용하고 있으나 모든 농산물 시료마다 모든 바탕시료(matched matrix)를 준비하기에는 한계가 있다. 본 연구는 다소비 농산물을 선정하여 식약처 ‘다성분 시험법-제2법’ 분석 시 매질효과 특성을 살펴보고 이를 바탕으로 대표매질 선정을 위한 탐색 가능성을 모색하기 위하여 도출되었다. 우선 식물성 원료 7종 중 곡류(6품목), 서류(3품목), 두류(4품목), 견과 종실류(5품목), 과일류(11품목), 채소류(17품목), 버섯류(4품목)의 다소비 식품 50품목을 선정하여 현행 분석법으로 정량 가능한 460여 종 다성분 잔류농약에 대한 농산물별 매질효과를 산출하였다. 분석대상 농산물은 시중에서 구매한 후 사전 실험을 통해 식약처 ‘다성분 시험법-제2법’ 분석에서 잔류농약이 검출되지 않는 농산물을 사용하였다. 매질효과 평가를 위한 실험은 잔류농약 510종 중 정량 가능한 460여 종을 LC와 GC-MS/MS를 사용하여 정량하여 용매표준용액의 검량선과 매질표준 용액의 검량선을 비교하여 매질효과(%)를 산출하였다. 산출된 matrix effect 범위는 soft (≤±20%), medium (±20%< ME≤±50%), strong ( >±50%) range로 구분하였으며, soft range는 정량성을 확보할 수 있는 국제적 기준으로 판단하였다. 현재까지 결과는 LC-MS/MS 분석은 45품목, GC-MS/MS 분석은 32품목이 완료되어 일부 시료에 대한 매질효과를 평가하였다. 평가 결과 매질효과(%)는 ±20% 이내 soft range 매질효과를 보이는 성분 수가 LC-MS/MS는 245성분 중 곡류, 서류, 두류, 견과종실류, 버섯류에서 204∼245성분(83.3∼100.0%), 과일류와 채소류는 115∼241성분(46.9∼98.4%)이었다. GC-MS/MS는 261성분 중 곡류, 서류, 두류, 견과종실류, 버섯류에서 211∼247성분(80.8∼94.6%), 과일류와 채소류는 192∼238성분(73.6∼91.2%)이었다. 특히 과일류와 채소류 농산물 중 LC-MS/MS 분석에서 딸기, 마늘, 양파, GC-MS/MS 분석에서 커피원두, 수박, 배추, 시금치, 마늘에서 상대적으로 높은 수준의 매질효과가 관찰되었다. 본 연구 결과를 바탕으로 그룹별, 성분별 매질효과를 상호 비교하여, 향후 대체 또는 대표매질 선정 가능성을 평가하고자 한다.
Cytomegalovirus Retinitis after Intravitreal Bevacizumab Injection in an Immunocompetent Patient
배소현,김태완,정흠,허장원 대한안과학회 2013 Korean Journal of Ophthalmology Vol.27 No.1
We report a case of cytomegalovirus (CMV) retinitis after intravitreal bevacizumab injection. A 61-year-old woman with diabetic macular edema developed dense vitritis and necrotizing retinitis 3 weeks after intravitreal bevacizumab injection. A diagnostic vitrectomy was performed. The undiluted vitreous sample acquired by vitrectomy was analyzed by polymerase chain reaction and culture. Polymerase chain reaction of the vitreous was positive for CMV DNA. Other laboratory results did not show evidence of other infectious retinitis and systemic immune dysfunction. Human immunodeficiency virus antibodies were also negative. After systemic administration of ganciclovir, retinitis has resolved and there has been no recurrence of retinitis during the follow-up period of 12 months. Ophthalmologists should be aware of potential risk for CMV retinitis after intravitreal bevacizumab injection.
유기인계 살충제 Phosalone 원제 중의 불순물 동정 및 독성효과
임금춘,허장현,한대성 ( Geum Choon Lim,Jang Hyun Hur,Dae Sung Han ) 한국환경농학회 1995 한국환경농학회지 Vol.14 No.2
The purpose of this study was to investigate the identification and the toxicological effects of some impurities present in the technical grade phosalone (94.4%). In instrumental analyses of the technical phosalone, the five impurities such as phosalone oxon, 6-chloro-3-methylthio-2-oxobenzoxazole, 6-chloro-2-oxobenzoxazole, O,O,S-triethyl phosphorodithioate (OOSTEPDT) and dichlorophosalone were identified. The bimolecular inhibition rate constants (k_i) indicated that the technical phosalone inhibited both AChE and BuChE about ten times faster than the purified phosalone did. From in vivo studies the technical phosalone showed greater inhibition for mouse brain AChE, rat blood ChE`s and mouse cytosolic non-specific esterases. It was presumed that some impurities present in the technical phosalone such as phosalone oxon cause such inhibition patterns of the technical phosalone observed in this study.