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Kwack, Kyu-Bum 생화학분자생물학회 2000 Journal of biochemistry and molecular biology Vol.33 No.2
Recombinant protein G has been utilized in the purification of antibodies from various mammalian species based on the interaction of antibodies with protein G. The interaction between immunoglobulin and protein G may not be restricted to the Fc protion of antibodies, as many different $F(ab)_2$ or Fab fragments can also bind to protein G. I found both FAb $F(ab)_2$ of 145-2C11, a hamster anti-mouse $CD3{\varepsilon}$ antibody, bound to the protein G-sepharose. Interestingly, Fab and $F(ab)_2$ of 145-2C11 did not bind to the protein A-sepharose. The binding of Fab and $F(ab)_2$ of 145-2C11 to protein G provided a useful method to remove proteases, chopped fragments of the Fc region, and other contaminating proteins. The remaining intact antibody in the protease reaction mixture can be removed by using a protein A-sepharose, because the Fab and $F(ab)_2$ portions of 145-2C11 did not bind to protein A-sepharose. The specific binding of Fab and $F(ab)_2$ portions of 145-sC11 to a protein G-sepharose (though not to a protein A-sepharose) and binding of intact 145-2C11 to both protein A- and G-sepharose will be useful in developing an effective purification protocol for Fab and $F(ab)_2$ portions of 145-2C11.
In-Situ Heat Cooling using Thick Graphene and Temperature Monitoring with Single Mask Process
( Kyu Hyun Kwack ),( Kuk Jin Chun ) 한국센서학회 2015 센서학회지 Vol.24 No.3
In this paper, in-situ heat cooling with temperature monitoring is reported to solve thermal issues in electric vehicle (EV) batteries. The device consists of a thick graphene cooler on top of the substrate and a platinum-based resistive temperature sensor with an embedded heater above the graphene. The graphene layer is synthesized by using chemical vapor deposition directly on the Ni layer above the Si substrate. The proposed thick graphene heat cooler does not use transfer technology, which involves many process steps and does not provide a high yield. This method also reduces the mechanical damage of the graphene and uses only one photomask. Using this structure, temperature detection and cooling are conducted simultaneously using one device. The temperature coefficient of resistance (TCR) of a 1×1mm(2) temperature sensor on 1-im-thick graphene is 1.573×103 ppm/°C. The heat source cools down 7.3°C from 54.4°C to 47.1°C.
(Kyu Bum Kwack) 생화학분자생물학회 2000 BMB Reports Vol.33 No.2
Recombinant protein G has been utilized in the purification of antibodies from various mammalian species based on the interaction of antibodies with protein G. The interaction between immunoglobulin and protein G may not be restricted to the Fc portion of antibodies, as many different F(ab`)₂ or Fab fragments can also bind to protein G. I found both Fab and F(ab`)₂ of 145-2C11, a hamster anti-mouse CD3ε antibody, bound to the protein G-sepharose. Interestingly, Fab and F(ab`)₂ of 145-2C11 did not bind to the protein A-sepharose. The binding of Fab and F(ab`)₂ of 145-2C11 to protein G provided a useful method to remove proteases, chopped fragments of the Fc region, and other contaminating proteins. The remaining intact antibody in the protease reaction mixture can be removed by using a protein A-sepharose, because the Fab and F(ab`)₂ portions of 145-2C11 did not bind to protein A-sepharose. The specific binding of Fab and F(ab`)₂ portions of 145-2C11 to a protein G-sepharose (though not to a protein A-sepharose) and binding of intact 145-2C11 to both protein A- and Gsepharose will be useful in developing an effective purification protocol for Fab and F(ab`)₂ portions of 1452C11.
Kwack Kyu Hwan,Lee Jae-Hyung,Moon Ji-Hoi 한국미생물학회 2022 The journal of microbiology Vol.60 No.2
“Antibiotic tolerance” promotes the rapid subsequent evolution of “antibiotic resistance,” however, it is often overlooked because it is difficult to distinguish between tolerant and susceptible organisms. A commensal bacterium S. anginosus subsp. anginosus strain KHUD_S1, isolated from dental biofilm was found to exhibit a high MBC/MIC ratio of 32 against vancomycin. We observed KHUD_S1 cells exposed to vancomycin did not grow but maintained viability. Transmission electron microscope showed KHUD_S1 cells possessed a dense, thick capsule and maintained the cell wall integrity upon vancomycin exposure. To infer the underlying mechanisms of the vancomycin tolerance in KHUD_S1, we performed whole genome sequencing and RNA sequencing. The KHUD_S1 genome carried three genes encoding branching enzymes that can affect peptidoglycan structure through interpeptide bridge formation. Global gene expression profiling revealed that the vancomycin-induced downregulation of carbohydrate and inorganic ion transport/metabolism as well as translation is less prominent in KHUD_S1 than in the vancomycin susceptible strain KHUD_S3. Based on the transcriptional levels of genes related to peptidoglycan synthesis, KHUD_S1 was determined to have a 3D peptidoglycan architecture distinct from KHUD_S3. It was found that, under vancomycin exposure, the peptidoglycan was remodeled through changes in the interpeptide bridge and transpeptidation reactions. Collectively, these features of S. anginosus KHUD_S1, including a dense capsule and differential gene expression in peptidoglycan synthesis, may contribute to vancomycin tolerance. Our results showing the occurrence of vancomycin tolerance amongst oral commensal bacteria highlight the need for considering future strategies for screening of antibiotic tolerance as an effort to reduce antibiotic resistance.
Kwack, Seung Jun,Kim, Kyu Bong,Kim, Hyung Sik,Lee, Byung Mu Informa UK (TaylorFrancis) 2009 Journal of toxicology and environmental health. Pa Vol.72 No.21
<P>In order to comparatively assess the systemic toxicity and sperm parameters, nine phthalate diesters, including di(2-ethylhexyl) phthalate (DEHP), di(n-butyl) phthalate (DBP), di-n-octyl phthalate (DnOP), diethyl phthalate (DEP), butylbenzyl phthalate (BBP), dimethyl phthalate (DMP), di-isodecyl phthalate (DIDP), diundecyl phthalate (DUP), and di-isononyl phthalate (DINP), and five phthalate monoesters, including mono(2-ethylhexyl) phthalate (MEHP), monobutyl phthalate (MBuP), monobenzyl phthalate (MBeP), monoethyl phthalate (MEP), monomethyl phthalate (MMP), and phthalic acid (PA) were administered orally to Sprague-Dawley male rats at 250 (phthalate monoesters and PA) or 500 mg/kg body weight (bw)/d (phthalate diesters) for 4 wk. Liver weights were significantly increased in g roups treated with DEHP, DBP, BBP, DIDP, DINP, MEHP, and MBuP compared to the control. Testes weights were significantly reduced only in DEHP, DBP, and MEHP-treated groups compared to the control. Significant decreases in red blood cell (RBC) and hematocrit (Ht) levels were observed in DEHP-treated rats, whereas significant increases in mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), and platelet (PLT) levels were found in the DEHP-treated group. Hemoglobin (Hb) level was reduced only in the DMP group. Similar to effects on testis and epididymal weights, DEHP and MEHP significantly reduced sperm numbers and motility. In particular, DnOP, DBP, BBP, MEP, MBuP, DUP, DINP, and MBeP significantly lowered the sperm counts and sperm motility of epididymal sperm, detected by a change in the sperm motion parameters. The strongest to the weakest adverse effects for sperm motility were as follows: DEHP > DBP > DnOP > DUP > DIDP > BBP among diesters and MBuP > MEP > MEHP among monoesters, respectively. These results suggest that the adverse effects of phthalate esters (PEs) on sperm parameters in male rats are greater with phthalate diesters than monoesters, which may be useful for the risk assessment of phthalates.</P>
Risk Assessment of Soybean-Based Phytoestrogens
Kwack, Seung Jun,Kim, Kyu-Bong,Kim, Hyung Sik,Yoon, Kyung Sil,Lee, Byung Mu Informa UK (TaylorFrancis) 2009 Journal of toxicology and environmental health. Pa Vol.72 No.21
<P>Koreans generally consume high quantities of soybean-based foods that contain a variety of phytoestrogens, such as, daidzein, zenistein, and biochalin A. However, phytoestrogens are considered to be potential endocrine-disrupting chemicals (EDC), which interfere with the normal function of the hormonal and reproductive systems. Therefore, dietary exposure to soybean-based phytoestrogens is of concern for Koreans, and comparative dietary risk assessments are required between Japanese (high consumers) versus Americans (low consumers). In this study, a relative risk assessment was conducted based upon daily intake levels of soybean-based foods and phytoestrogens in a Korean cohort, and the risks of photoestrogens were compared with those posed by estradiol and other EDC. Koreans approximately 30-49 yr of age consume on average a total of 135.2 g/d of soy-based foods including soybean, soybean sauce, soybean paste, and soybean oil, and 0.51 mg/kg body weight (bw)/d of phytoestrogens such as daidzein and genistein. Using estimated daily intakes (EDI) and estrogenic potencies (EP), margins of safety (MOS) were calculated where 0.05 is for estradiol (MOS value <1, considered to exert a positive estrogenic effect); thus, MOS values of 1.89 for Japanese, 1.96 for Koreans, and 5.55 for Americans indicate that consumption of soybean-based foods exerted no apparent estrogenic effects, as all MOS values were all higher than 1. For other synthetic EDC used as reference values, MOS values were dieldrin 27, nonylphenol 250, butyl benzyl phthalate 321, bisphenol A 1000, biochanin A 2203, and coumesterol 2898. These results suggest that dietary exposure to phytoestrogens, such as daidzein and genistein, poses a relatively higher health risk for humans than synthetic EDC, although MOS values were all greater than 1.</P>