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Speciation of Arsenic from Soil Organic Matter in Abandoned Gold and Silver Mines, Korea
Ko, Il-Won,Kim, Kyoung-Woong,Hur, Hor-Gil The Korean Society for Applied Biological Chemistr 2008 Journal of Applied Biological Chemistry (J. Appl. Vol.51 No.1
Organic forms of arsenic (As) were determined through fractionation procedure of soil organic matter (SOM) in soil, sediments and mine tailing samples from the Myungbong, Dongil, and Okdong mining areas of southern Korea. An alkaline extraction method was applied to soil samples followed by the fractionation procedures of SOM by the DAX-8 and XAD-4 resin adsorption method. Major fraction of organic As species (42% to 98%) was found in acid-soluble fraction, whereas minor fraction (0.1 % to 67.8%) was present in the humic-associated As. In acid-soluble fractions, the transphillic- and hydrophilic-associated As were dominant in addition to As binding with humic and fulvic SOM. Arsenic binding was the strongest between pH 6 to 8 and reduced to about 70% at both low and high pH regions. The amount of both transphillic and hydrophillic associated As was less changed than humic and fulvic-associated As, in both low and high pH regions. This apparently indicates that As has stronger affinity towards hydrophillic rather than hydrophobic organics. From the experimental observation of As-binding SOM in natural soil, the ligand exchange model may be a feasible explanation of transphillic and hydrophillic affinity of As.
Ko, Hyeok-Jin,Lee, Eun-Woo,Bang, Won-Gi,Lee, Cheol-Koo,Kim, Kyoung-Heon,Choi, In-Geol Korean Society for Molecular and Cellular Biology 2010 Molecules and cells Vol.29 No.5
In seeking aryl acylamidase (EC 3.5.1.13) acting on an amide bond in p-acetaminophenol (Tylenol$^{TM}$), we identified a novel gene encoding 496 residues of a protein. The gene revealed a conserved amidase signature region with a canonical catalytic triad. The gene was expressed in E. coli and characterized for its biochemical properties. The optimum pH and temperature for the activity on p-acetaminophenol were 10 and 37$^{\circ}C$, respectively. The half-life of enzyme activity at 37$^{\circ}C$ was 192 h and 90% of its activity remained after 3 h incubation at 40$^{\circ}C$. Divalent metals was found to inhibit the activity of enzyme. The $K_m$ values for various aryl acylamides such as 4-nitroacetanilide, p-acetaminophenol, phenacetin, 4-chloroacetanilide and acetanilide were 0.10, 0.32, 0.83, 1.9 and 19 mM, respectively. The reverse reaction activity (amide synthesis) was also examined using various chain lengths ($C_1{\sim}C_4$ and $C_{10}$) of carboxylic donors and aniline as substrates. These kinetic parameters and substrate specificity in forward and reverse reaction indicated that the aryl acylamidase in this study has a preference for aryl substrate having polar functional groups and hydrophobic carboxylic donors.
Ko, Il-Won,Kim, Kyoung-Woong,Lee, Cheol-Hyo,Lee, Kwang-Pyo Korean Society for Biotechnology and Bioengineerin 2007 Biotechnology and Bioprocess Engineering Vol.12 No.5
The biodegradation rate of petroleum hydrocarbon-contaminated soil was evaluated by the effect of temperature variation through bioaugmentation and biostimulation. In this study, biokinetics of batch-, pilot-, and field-scale biodegradation were performed by the optimization of enhanced biodegradation, minimizing the inhibitory effects of seasonal variations such as the rainy and cold winter seasons. From the relationship between remedial timescale and initial concentration, the biokinetic isolines of the biodegradation were smaller in the winter than those in the other seasons. The scale-up of biodegradation process led to enhance its activation energy, and then the field-scale remedial action should be performed in the way to lower the activation energy from the chemical diffusion and microbial activation. Therefore, a remedial or field worker can obtain the remedial timescale from the given apparent data of biokinetics with respect to initial TPH concentration only after the simple remedial investigation.
Ko, Kyoung-Won,Choi, Bogyu,Park, Sunghyun,Arai, Yoshie,Choi, Won Chul,Lee, Joong-Myung,Bae, Hojae,Han, In-Bo,Lee, Soo-Hong MDPI 2017 INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES Vol.18 No.11
<P>Expansion of chondrocytes for repair of articular cartilage can lead to dedifferentiation, making it difficult to obtain a sufficient quantity of chondrocytes. Although previous studies have suggested that culture in a three-dimensional environment induces redifferentiation of dedifferentiated chondrocytes, its underlying mechanisms are still poorly understood in terms of metabolism compared with a two-dimensional environment. In this study, we demonstrate that attenuation of transglutaminase 2 (TG2), a multifunctional enzyme, stimulates redifferentiation of dedifferentiated chondrocytes. Fibroblast-like morphological changes increased as TG2 expression increased in passage-dependent manner. When dedifferentiated chondrocytes were cultured in a pellet culture system, TG2 expression was reduced and glycolytic enzyme expression up-regulated. Previous studies demonstrated that TG2 influences energy metabolism, and impaired glycolytic metabolism causes chondrocyte dedifferentiation. Interestingly, TG2 knockdown improved chondrogenic gene expression, glycolytic enzyme expression, and lactate production in a monolayer culture system. Taken together, down-regulation of TG2 is involved in redifferentiaton of dedifferentiated chondrocytes through enhancing glucose metabolism.</P>
Ko, Hyeok-Jin,Bang, Won-Gi,Kim, Kyoung Heon,Choi, In-Geol Kluwer Academic Publishers 2012 Biotechnology letters Vol.34 No.4
<P>Aryl acylamidase (EC 3.5.1.13, AAA) acts on the amide bond between aryl and acyl groups. Whole cells of Escherichia coli overexpressing a novel bacterial AAA synthesized p-acetaminophenol (p-AAP) from p-aminophenol (p-AP, aryl compound) and acetate (acyl donor). Optimum conditions were pH 5.5 and 35C with 100 mM p-AP and 600 mM sodium acetate in 100 mM sodium phosphate buffer including 1% (v/v) Triton X-100 for 60 h. 13.1 g p-AAP l(-1) was produced with a conversion yield of 87%.</P>
Ko You Keun,Lee Jong Kwon,Park Hye Kyung,Han Ae Kyung,Mun Sun Kyoung,Park Hye Jeong,Choung Hae Kyoung,Kim Se Mi,Choi Kwang Mo,Lee Nam Yong,Cho Duck,Kim Dae Won,강은숙 대한진단검사의학회 2023 Annals of Laboratory Medicine Vol.43 No.5
Background: Sterility and safety assurance of hematopoietic stem cell (HSC) products is critical in transplantation. Microbial contamination can lead to product disposal and increases the risk of unsuccessful clinical outcomes. Therefore, it is important to implement and maintain good practice guidelines and regulations for the HSC collection and processing unit in each hospital. We aimed to share our experiences and suggest strategies to improve the quality assurance of HSC processing. Methods: We retrospectively analyzed microbial culture results of 11,743 HSC products processed over a 25-year period (January 1996 to May 2021). Because of reorganization of the HSC management system in 2008, the 25-year period was divided into periods 1 (January 1996 to December 2007) and 2 (January 2008 to May 2021). We reviewed all culture results of the HSC products and stored aliquot samples and collected culture results for peripheral blood and catheter samples. Results: Of the 11,743 products in total, 35 (0.3%) were contaminated by microorganisms, including 19 (0.5%) of 3,861 products during period 1 and 16 (0.2%) of 7,882 products during period 2. Penicillium was the most commonly identified microorganism (15.8%) during period 1 and coagulase-negative Staphylococcus was the most commonly identified (31.3%) during period 2. HSC product contamination occurred most often during HSC collection and processing. Conclusions: The contamination rate decreased significantly during period 2, when the HSC management system was reorganized. Our results imply that handling HSC products by trained personnel and adopting established protocols, including quality assurance programs, aid in decreasing the contamination risk.