• Bulletin of the Korean Chemical Society
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• v.22 no.4
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• pp.409-412
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• 2001

Poly(p-tert-butyltrimethoxymonopropyloxycalix[4]arene-methylsiloxane) (TBCX-MS) has been prepared and used as a stationary phase in isothermal capillary gas chromatographic separation of some positional isomers. Retention factors (k) and separatio n factors $(\alpha)$ for the isomers were measured and compared with those on poly(p-tert-butyl-dimethoxydipropyloxycalix[4]arene-tetramethyldisiloxane) (TBCX-TMDS), poly(dimethoxydipropyloxycalix[4]arenetetramethyl-disiloxane) (CX-TMDS). Most of the isomers investigated are well resolved on TBCX-MS. Retention of all the compounds decreases on the three phases in the order, TBCX-TMDS ${\geq}$ TBCX-MS > CX-TMDS. Similar retention values on TBCX-TMDS and TBCX-MS seem to indicate that retention property of the two phases is not significantly affected by the spatial position of the calixarene moiety.

• Bulletin of the Korean Chemical Society
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• v.14 no.4
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• pp.457-461
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• 1993

Bioconcentration factors (BCF) in fish of organic nonelectrolytes are well correlated by a linear solvation energy relationship (LSER) of the form : log BCF= -0.95 + 4.74 $V_I/100 - 4.39{\beta} + 0.88{\alpha}$ where $V_I$ is the intrinsic solute molecular volume and ${\beta}$ and ${\alpha}$ are the solvatochromic parameters that measure hydrogen bond acceptor basicity and donor acidity of the compound. The LSER model can not only correlate the property with an accuracy comparable to molecular connectivity model but also provide a quantitative informationon on the nature and relative strength of solute-target system interactions affecting the property of interest. Such an information can hardly be obtained from molecular connectivity model.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.58 no.4
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• pp.347-352
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• 2013

Soybean sprout is a year-round traditional vegetable that is easily produced and relatively inexpensive in Korea. In addition, the sprout is known as a good source of protein, vitamins and minerals. The quality of the soybean sprout has been mainly evaluated only by its appearance like length, width, color, and the others without considering any odor or taste attributes. We studied the chemical factors affecting taste of soy sprouts cultivated with 5 recommended soybean cultivars through evaluation of chemical constituents in relation to their sensory characteristics. Correlation coefficient among the chemical constituents and sensory characteristics of soybean sprout showed that the linolenic acid and Ca contents were positively correlated with total acceptability of soybean sprout and histidine, aspartic acid, and serine showed a negative association with beany odor of soybean sprout. Multiple regression analysis was done to formulate selection criteria for good taste of soy sprout. The estimation of step-wise regression analysis conducted by 47 chemical components for major quality-related characteristics showed that linolenic acid and mineral contents were the main components increasing the acceptability of soybean sprout.

• Toxicological Research
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• v.6 no.2
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• pp.205-213
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• 1990

The regulation of neurotoxicants has usually been based upon setting reference doses by dividing a no observed adverse effect level (NOAEL) by uncertainty factors that theoretically account for interspecies and intraspecies extraploation of experimental results in animals to humans. Recently, we have proposed a four-step alternative procedure which provides quantitative estimates of risk as a function of dose. The first step is to establish a mathematical relationship between a biological effect or biomarker and the dose of chemical administered. The second step is to determine the distribution (variability) of individual measurements of biological effects or their biomarkers about the dose response curve. The third step is to define an adverse or abnormal level of a biological effect or biomarker in an untreated population. The fourth and final step is to combine the information from the first three steps to estimate the risk (proportion of individuals exceeding on adverse or abnormal level of a biological effect or biomarker) as a function of dose. The primary purpose of this report is to enhance the certainty of the first step of this procedure by improving our understanding of the relationship between a biomarker and dose of administered chemical. Several factors which need to be considered include: 1) the pharmacokinetics of the parent chemical, 2) the target tissue concentrations of the parent chemical or its bioactivated proximate toxicant, 3) the uptake kinetics of the parent chemical or metabolite into the target cell(s) and/or membrane interactions, and 4) the interaction of the chemical or metabolite with presumed receptor site(s). Because these theoretical factors each contain a saturable step due to definitive amounts of required enzyme, reuptake or receptor site(s), a nonlinear, saturable dose-response curve would be predicted. In order to exemplify this process, effects of the neurotoxicant, methlenedioxymethamphetamine (MDMA), were reviewed and analyzed. Our results and those of others indicate that: 1) peak concentrations of MDMA and metabolites are ochieved in rat brain by 30 min and are negligible by 24 hr, 2) a metabolite of MDMA is probably responsible for its neurotoxic effects, and 3) pretreatment with monoamine uptake blockers prevents MDMA neurotoxicity. When data generated from rats administerde MDMA were plotted as bilolgical effect (decreases in hippocampal serotonin concentrations) versus dose, a saturation curve best described the observed relationship. These results support the hypothesis that at least one saturable step is involved in MDMA neurotoxicity. We conclude that the mathematical relationship between biological effect and dose of MDMA, the first step of our quantitative neurotoxicity risk assessment procedure, should reflect this biological model information generated from the whole of the dose-response curve.

• Journal of Environmental Health Sciences
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• v.48 no.6
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• pp.315-323
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• 2022

Background: Socioeconomical disadvantaged communities are more vulnerable to environmental chemical exposure and associated health effects. However, there is limited information on chemical exposure among vulnerable populations in Korea. Objectives: This study investigated chemical exposure among underprivileged populations. We measured urinary metabolites of phthalates in urban disadvantaged communities and investigated their correlations with residential environment factors and relative socioeconomic vulnerability. Methods: Urine samples were collected from 64 residents in a disadvantaged community in Seoul. A total of eight phthalate metabolites were analyzed by liquid chromatography-mass spectroscopy. Analytical method used by the Korean National Environmental Health Survey (KoNEHS) was employed. Covariate variance analysis and general linear regression adjusted with age, sex and smoking were performed. Results: Several phthalate metabolites, namely monomethyl phthalate (MMP), monoethyl phthalate (MEP), mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), and mono-n-butyl phthalate (MnBP) had higher levels than those reported in the adults of 4th KoNEHS. Notably, the MnBP level was higher in the lower socioeconomic group (geometric mean [GM]=47.3 ㎍/g creatinine) compared to non-recipients (GM=31.9 ㎍/g creatinine) and the national reference level (GM=22.0, 28.2 and 32.2 ㎍/g creatinine for adults, 60's and 70's, respectively.). When age, sex and smoking were adjusted, MEP and MnBP were significantly increased the lower socioeconomic group than non-recipients (p=0.014, p=0.023). The lower socioeconomic group's age of flooring were higher than non-recipients, not statistically significant. Conclusions: These results suggest that a relatively low income and aged flooring could be considered as risk factors for increased levels of phthalate metabolites in socioeconomic vulnerable populations.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.238-238
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• 2006

Through ultra-violet photoemission spectroscopy in-situ experiment, 0.67 eV energy barrier between 1-hexadecanethiol (HDT)-modified gold and pentacene was observed, which was 0.03 eV smaller than the energy barrier between bare gold and pentacene despite HDT modified gold had 0.8 eV lower work function than that of bare gold. This result is opposed to the idea that increasing the work function a metal decreases the energy barrier. This can be explained by two factors. One is the absence of interface dipole, which is observed in pentacene deposited on gold. The other is reduced ionization energy which can be explained through polarization energy or electronic splitting of molecular orbital with more crystalline structure observed through X-ray diffraction patterns.

• Polymer(Korea)
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• v.31 no.2
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• pp.105-110
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• 2007

We investigated resin, thinner, painting, and injection for analyzing the chemical effect of polymer, and made the optimum solution with the best performance of ABS (acrylonitrile butadiene styrene) resin. The effect depended on chemical material especially its chemical and physical properties instead of mechanical transformation. When we looked over ABS resin, injection, chemical material and painting, we found out thinner was the main factor for painting problem. Throughout this test, we could solve the problem, secure the system for control process and drop many factors for changing quality.

• Biotechnology and Bioprocess Engineering:BBE
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• v.10 no.4
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• pp.329-333
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• 2005

This study was designed to investigate the stability of a lipase fused with a cellulose­binding domain (CBD) to cellulase. The fusion protein was derived from a gene cluster of a CBD fragment of a cellulase gene in Trichoderma hazianum and a lipase gene in Bacillus stearother­mophilus L1. Due to the CBD, this lipase can be immobilized to a cellulose material. Factors affecting the lipase stability were divided into the reaction-independent factors (RIF), and the re­action-dependent factors (RDF). RIF includes the reaction conditions such as pH and tempera­ture, whereas substrate limitation and product inhibition are examples of RDF. As pH 10 and $50^{\circ}C$ were found to be optimum reaction conditions for oil hydrolysis by this lipase, the stability of the free and the immobilized lipase was studied under these conditions. Avicel (microcrystal­line cellulose) was used as a support for lipase immobilization. The effects of both RIF and RDF on the enzyme activity were less for the immobilized lipase than for the free lipase. Due to the irreversible binding of CBD to Avicel and the high stability of the immobilized lipase, the enzyme activity after five times of use was over $70\%$ of the initial activity.

• Journal of Microbiology and Biotechnology
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• v.17 no.7
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• pp.1113-1119
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• 2007

Human bone marrow-derived mesenchymal stem cells (hBMMSCs) must differentiate into osteogenic cells to allow for successful bone regeneration. In this study, we investigated the effects of different combinations of three soluble osteogenic differentiation-inducing factors [L-ascorbic acid (AC), ${\beta}$-glycerophosphate (${\beta}G$), and bone morphogenic protein-2 (BMP-2)] and the presence of a hydroxyapatite (HA) substrate on hBMMSC osteogenic differentiation in vitro. hBMMSCs were cultured in medium containing various combinations of the soluble factors on culture plates with or without HA coating. After 7 days of culture, alkaline phosphatase (ALP) activity, calcium deposition, and osteoprotegerin (OPG) and osteopontin (OPN) expression were measured. The effects of individual and combined factors were evaluated using a factorial analysis method. BMP-2 predominantly affected expression of early markers of osteogenic differentiation (ALP and OPG). HA had the highest positive effect on OPN expression and calcium deposition. The interaction between AC, ${\beta}G$, and HA had the second highest positive effect on ALP activity.

• Journal of Hydrogen and New Energy
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• v.17 no.3
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• pp.286-292
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• 2006

Chlamydomonas reinhardtii is a green algae that can use light energy and water to produce hydrogen under anaerobic condition. This work reports the effect of limiting factors on hydrogen production in sulfur deprived anaerobic C. reinhardtii culture. In order to confirm the relationship between hydrogen production and limiting factors such as residual PSII activity and endogenic substrate degradation, the increase in chlorophyll concentration and the decrease in starch concentration was investigated during sulfur deprivation. The overall hydrogen production increased depending on cell density in range of $0.4{\sim}0.96\;g$ DCW/l. At this time, the increase in chlorophyll concentration during 24 h after sulfur deprivation increased in proportion to hydrogen production, however, the decrease in starch concentration was not proportional to that. Therefore, hydrogen production under sulfur deprivation using green alga was closely associated with the residual PSII activity than the endogenic substrate degradation.