Kyung Tae Kim

Chungnam National University, Daiden, Daejeon, South Korea

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Publications (96)155.2 Total impact

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    ABSTRACT: Capillary electrochromatography was employed for enantioseparation of α-amino acids and their derivatives. (-)-18-Crown-6-2,3,11,12-tetracarboxylic acid bonded on the silica was used as the chiral stationary phase and methanol/Tris-citric acid (20 mM, pH 3.0-4.5) (20:80, v/v) was used as mobile phase. The enantioseparation performance was discussed and structure-chiral separation relationship were tried to be explained. The enantiomeric resolution was increased when the pH of the mobile phase decreased or hydrogen of amino acid was substituted with halogen. The resolution of 4-bromophenylalanine was 2.37 at pH 4.5, however, this value was increased to 3.35 at pH 3.0. Bromo- or chloro-substituted phenylalanine tended to show higher resolution than fluoro-substituted one. For fluoro-substituted phenylalanine the resolution was increased in order of 4-, 3- and 2-substituted one. α-Methyltryptamine did not show reasonable separation. As the thermodynamic study is a useful tool to understand the chiral recognition, the temperature effect on the enantioseparation was studied and the thermodynamic parameters were calculated. The most important mechanism of chiral recognition for the analytes tested could be barrier effects based on the thermodynamic calculations. The coefficient of determination between hydrophobicity and separation factor was found to be 0.87, indicating favorable separation with higher hydrophobicity of amino acids.
    Archives of Pharmacal Research 11/2014; · 1.54 Impact Factor
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    ABSTRACT: Reduced graphene oxide/alumina composite powders were prepared by mixing of graphene oxides and aluminum ions at the molecular-level. It was found that the composite consolidated from the powders showed that reduced graphene oxide were homogeneously dispersed and strongly bonded with the alumina matrix by oxygen atoms presenting at reduced graphene oxide/alumina interfaces. Both the hardness and the toughness of the composites were enhanced simultaneously by the addition of reduced graphene oxide, which act as bridges to restrain the propagation of cracks in the alumina matrix. It is clarified that graphenes can be utilized as promising reinforcements for enhancement in mechanical properties of ceramic materials when the molecular-level mixing process is applied.
    Carbon 11/2014; 78:212–219. · 6.16 Impact Factor
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    ABSTRACT: RNA interference (RNAi), mediated by small non-coding RNAs (e.g., miRNAs, siRNAs), influences diverse cellular functions. Highly complementary miRNA-target RNA (or siRNA-target RNA) duplexes are recognized by an Argonaute family protein (Ago2), and recent observations indicate that the concentration of Mg 2+ ions influences miRNA targeting of specific mRNAs, thereby modulating miRNA-mRNA networks. In the present report, we studied the thermodynamic effects of differential [Mg 2+ ] on slicing (RNA silencing cycle) through molecular dynamics simulation analysis, and its subsequent statistical analysis. Those analyses revealed different structural conformations of the RNA duplex in Ago2, depending on Mg 2+ concentration. We also demonstrate that cation effects on Ago2 structural flexibility are critical to its catalytic/functional activity, with low [Mg 2+ ] favoring greater Ago2 flexibility (e.g., greater entropy) and less miRNA/mRNA duplex stability, thus favoring slicing. The latter finding was supported by a negative correlation between expression of an Mg 2+ influx channel, TRPM7, and one miRNA's (miR-378) ability to downregulate its mRNA target, TMEM245. These results imply that thermodynamics could be applied to siRNA-based therapeutic strategies, using highly complementary binding targets, because Ago2 is also involved in RNAi slicing by exogenous siRNAs. However, the efficacy of a siRNA-based approach will differ, to some extent, based on the Mg 2+ concentration even within the same disease type; therefore, different siRNA-based approaches might be considered for patient-to-patient needs. Copyright: ß 2014 Nam et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability: The authors confirm that all data underlying the findings are fully available without restriction. All relevant data are within the paper and its Supporting Information files. Funding: The National Cancer Center, Korea [grant number NCC-1210460 to SN]; the Korean Research Institute of Bioscience and Biotechnology Research Initiative Program [to JL]; The Korean Ministry of Education, Science and Technology (MEST) [grant number 2012R1A1A2002676 to JL]; The Pioneer Research Center Program through the National Research Foundation of Korea funded by the Ministry of Science, ICT & Future Planning [grant number 2013M3C1A3064780 to JL]. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: CB is the Chair of Bioscience Advising, Indianapolis, IN, USA. This does not alter the authors' adherence to PLOS ONE policies on sharing data and materials. All other authors declare no potential competing interests.
    PLoS ONE 10/2014; · 3.53 Impact Factor
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    ABSTRACT: Piwi-interacting RNAs (piRNAs) are 26-31 nt small noncoding RNAs that are processed from their longer precursor transcripts by Piwi proteins. Localization of Piwi and piRNA has been reported mostly in nucleus and cytoplasm of higher eukaryotes germ-line cells, where it is believed that known piRNA sequences are located in repeat regions of nuclear genome in germ-line cells. However, localization of PIWI and piRNA in mammalian somatic cell mitochondria yet remains largely unknown. We identified 29 piRNA sequence alignments from various regions of the human mitochondrial genome. Twelve out 29 piRNA sequences matched stem-loop fragment sequences of 7 distinct tRNAs. We observed their actual expression in mitochondria subcellular fractions by inspecting mitochondrial-specific small RNA-Seq datasets. Of interest, the majority of the 29 piRNAs overlapped with multiple longer transcripts (expressed sequence tags) that are unique to the human mitochondrial genome. The presence of mature piRNAs in mitochondria was detected by qRT-PCR of mitochondrial subcellular RNAs. Further validation showed detection of Piwi by colocalization using anti-Piwil1 and mitochondria organelle-specific protein antibodies.
    Biochemical and Biophysical Research Communications 01/2014; · 2.28 Impact Factor
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    ABSTRACT: Marine-derived natural products from invertebrates comprise an extremely diverse and promising source of the compounds from a wide variety of structural classes. This study describes the discovery of five marine natural products with activity against Trypanosoma species by natural product library screening using whole cell in vitro assays. We investigated the anti-trypanosomal activity of the extracts from the soft corals and echinoderms living in Vietnamese seas. Of the samples screened, the methanolic extracts of several marine organisms exhibited potent activities against cultures of Trypanosoma brucei and T. cruzi (EC50 < 5.0 μg/mL). Among the compounds isolated from these extracts, laevigatol B (1) from Lobophytum crassum and L. laevigatum, (24S)-ergost-4-ene-3-one (2) from Sinularia dissecta, astropectenol A (3) from Astropecten polyacanthus, and cholest-8-ene-3β,5α,6β,7α-tetraol (4) from Diadema savignyi showed inhibitory activity against T. brucei with EC50 values ranging from 1.57 ± 0.14 to 14.6 ± 1.36 μM, relative to the positive control, pentamidine (EC50 = 0.015 ± 0.003 μM). Laevigatol B (1) and 5α-cholest-8(14)-ene-3β,7α-diol (5) exhibited also significant inhibitory effects on T. cruzi. The cytotoxic activity of the pure compounds on mammalian cells was also assessed and found to be insignificant in all cases. This is the first report on the inhibitory effects of marine organisms collected in Vietnamese seas against Trypanosoma species responsible for neglected tropical diseases.
    Molecules (Basel, Switzerland). 01/2014; 19(6):7869-80.
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    ABSTRACT: With IPTV, channel zapping time is one of the significant problems. It occurs when the user wants to change the channel but needs to wait until the target channel is available. Various schemes reducing the time have been suggested, which download the candidate channels of the future use in advance. In this paper we propose a new method which further reduces the channel zapping time by pre-downloading the candidate channels during the time latency between two successive push operations of the buttons of remote controller made by the user. Computer simulation verifies its effectiveness in various operational conditions. More importantly, it can be employed together with other scheme of reducing channel zapping time without any additional overhead.
    2014 IEEE 11th Consumer Communications and Networking Conference (CCNC); 01/2014
  • Kyung Tae Kim, Jong Won Lee, Won Ho Jo
    Macromolecular Chemistry and Physics 12/2013; 214(23). · 2.39 Impact Factor
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    ABSTRACT: Wireless sensor network has been used for many years, and a great number of schemes and applications have been developed based on it. Object tracking is one of key tasks which are required in a number of applications of WSN. In this paper we propose an efficient prediction-based object tracking scheme employing the face network topology. The proposed scheme uses the trajectory of the object and enhanced least square method to predict the path. Computer simulation reveals that the proposed scheme improves the tracking accuracy and energy efficiency compared to the existing prediction-based scheme. The improvement gets more significant as the moving speed of the object becomes higher.
    2013 IEEE International Conference on High Performance Computing and Communications (HPCC) & 2013 IEEE International Conference on Embedded and Ubiquitous Computing (EUC); 11/2013
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    ABSTRACT: Aging-dependent physiological conditions are attributed to parenchymal structural changes to cellular functions in aged organisms. To understand these aging-dependent processes, we compared the glucose formation capacity of primary hepatocytes from young (4-month-old) and old (24-month-old) Fisher 344 rats. The primary hepatocytes from old rats showed a higher glucose output and a higher expression of the key gluconeogenesis-regulating enzyme, phosphoenol pyruvate carboxykinase (PEPCK), compared with those from the young animals. The in situ hybridization study showed increased PEPCK mRNA expression in the aged liver tissues. The livers from old rats showed loosened hexagonal hepatic lobular structures, increased collagen accumulation, and high expression of the hypoxia marker hypoxia-inducible factor 1α (HIF1α). Hypoxia increased the PEPCK mRNA and protein expression levels in accordance with the HIF1α expression. PEPCK promoter luciferase reporter assay showed that hypoxia increased PEPCK through transcriptional activation. Furthermore, the Hepatocyte nuclear factor α (HNF4α) protein, but not the HNF4α mRNA level, increased in parallel with the PEPCK mRNA expression under hypoxic conditions. The glucose production increased in hypoxic condition, but this increment diminished by HNF4α siRNA in young hepatocytes. Moreover, increased glucose production from old rat hepatocytes was reversed by the down-regulation of HNF4α through a specific siRNA. This study suggests that the mild hypoxic conditions in response to aging-dependent hepatic structural changes may contribute to the induction of the gluconeogenic enzyme PEPCK through HNF4α protein stabilization.
    Experimental gerontology 10/2013; · 3.34 Impact Factor
  • Sung Jin Choi, Kyung Tae Kim, Hee Yong Youn
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    ABSTRACT: Currently, sensor networks are widely used in various fields. Here secure operations are required for critical applications since the damages are significant if the network is compromised or disrupted. For the security of wireless sensor network, the earlier schemes typically employ asymmetric cryptography. These schemes are, however, often unsuitable for wireless sensor network due to the limited computational power and energy of the sensor nodes. To address this issue, various approaches have been developed, and the random key predistribution approach has been recognized as an effective approach. One shortcoming, however, is that a common key is not guaranteed to be found between any two nodes wanting to communicate. This paper proposes a new robust key predistribution scheme solving this problem, with which the security is not compromised even though the data exchanged between the nodes are tapped by an adversary. This is achieved by using the keys assigned based on the notion of eigenvalue and eigenvector of a square matrix of a pool of keys. Mathematical analysis and computer simulation reveal that the proposed scheme significantly reduces the overhead required for secure connectivity and energy consumption of sensor nodes compared to the existing approaches.
    International Journal of Distributed Sensor Networks 06/2013; 2013. · 0.92 Impact Factor
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    ABSTRACT: OBJECTIVE: To assess the relationship between mycoplasma infection and human infertility, we determined the concordance of Ureaplasma urealyticum (UU) and Mycoplasma hominis (MH) detection in infertile and fertile couples, and assessed semen parameters in both groups. METHODS: Fifty infertile couples without a female factor attending a fertility clinic and 48 fertile couples were randomly screened for UU and MH. The concordance between partners was compared between the fertile and infertile groups. Semen and endocervical specimens were evaluated using the commercially available Mycofast Evolution2 test. RESULTS: UU was detected in 24 semen specimens (48%) from the infertile men, in 12 specimens from fertile men (25%), in 20 endocervical specimens from infertile women (40%), and 11 from fertile women (22.9%). UU was detected higher in infertile men than in fertile men (P = .022). The concordance of UU was higher in infertile couples (32%) than in fertile couples (12.5%, P = .022). The concordance of MH between male and female partners in the 2 groups did not differ significantly. The mean values of total motility, progressive motility, normal morphology, vitality, and total motile sperm count were significantly lower in sperm from infertile men than from fertile men. Progressive motility and vitality were significantly lower in UU-positive men than in men without UU, and low total motility and total motile sperm count were significantly related to the presence of MH. CONCLUSION: Clinicians should consider the roles of UU and MH in infertility and routinely screen infertile couples for the presence of these mycoplasma species.
    Urology 04/2013; · 2.42 Impact Factor
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    ABSTRACT: A quantitative method for determining levels of three bioactive compounds based on pattern recognition was developed and fully validated for the quality control of Alismatis Rhizoma (AR) by HPLC. Separation conditions were optimised using an Optimapak C18 column (250 mm × 4.6 mm, 5 μm) with a mobile phase of acetonitrile and 0.1% aqueous phosphoric acid and detection wavelengths of 205 and 245 nm. Method validation yielded acceptable linearity (r2 > 0.9998) and percent recovery (98.06%-101.71%). Limits of detection ranged from 0.08 to 0.15 μg/mL. Levels of the three bioactive compounds, alisol C acetate, alisol B, and alisol B acetate, in AR were 0.07-0.45, 0.38-10.32, and 1.13-8.59 mg/g dried weight, respectively. Pattern analyses based on these three compounds were able to differentiate Chinese and Korean samples accurately. The results demonstrate that alisol B and its acetate may be used as marker compounds for AR quality and can be regulated to no less than 0.36 and 1.29 mg/g of dried sample, respectively. The method described here is suitable for quantitative analyses and quality control of multiple components in AR.
    Bulletin- Korean Chemical Society 04/2013; 34(7):2081. · 0.84 Impact Factor
  • Kyung Tae Kim, Won Ho Jo
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    ABSTRACT: Although graphene itself is a zero-bandgap semimetal, graphene nanoribbon (GNR) with a width smaller than 10 nm exhibits semiconducting behavior that renders them suitable for active materials of electronic devices. Several methods have been reported to produce GNRs, such as lithography, unzipping of CNTs, mechanical exfoliation and CVD. However, the uncontrollable character of these methods or in some case the harsh conditions restrict severely the quality of the resulting graphenes and consequently limit their applications. In this study, we synthesized GNRs with various widths from the corresponding polymer precursors and investigated their TFT properties. For synthesis of GNRs, we first synthesized polymers with phenylene, naphthalene and anthracene units by the Suzuki coupling reaction between dibromine monomer and diboronic ester monomer. The polymers were then converted into the corresponding GNRs through intramolecular cyclodehydrogenation reaction. The cyclodehydrogenation were identified quantitatively by NMR analysis. All GNR-based TFTs showed ambipolar transport behavior. The anthracene-based GNR exhibits the best TFT performance among three GNRs due to longer conjugated length, larger width and stronger π-stacking as compared to phenylene- and naphthalene-based GNRs.
    Carbon 03/2013; 63:1038-. · 6.16 Impact Factor
  • Min Soo Kang, Kyung Tae Kim, Jea Uk Lee, Won Ho Jo
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    ABSTRACT: A high-yielding dispersion of graphene at high concentration in solvent is critical for practical applications. Herein, we demonstrate the formation of a stable dispersion of pristine graphene in ethanol by exfoliating graphite flakes into individual graphene layers using a non-ionic polymer surfactant under bath-type sonication. Oligothiophene-terminated poly(ethylene glycol) was synthesized and used as a non-ionic and amphiphilic surfactant for exfoliating graphite into graphene. A high-quality graphene film was fabricated from the exfoliated graphene solution by the vacuum filtration method. TEM and SEM reveal that the size of exfoliated graphene flakes is larger than 1 μm. When the graphene film was treated with nitric acid and thionyl chloride after washing with solvent, the film showed high performance with a sheet resistance of 0.3 kΩ sq−1 and a transparency of 74% at 550 nm.
    J. Mater. Chem. C. 02/2013; 1(9):1870-1875.
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    Kyung Tae Kim, Injoon Son, Gook Hyun Ha
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    ABSTRACT: Carbon nanotube-dispersed bismuth telluride matrix (CNT/) nanopowders were synthesized by chemical routes followed by a ball-milling process. The microstructures of the synthesized CNT/ nanopowders showed the characteristic microstructure of CNTs dispersed among disc-shaped nanopowders with as an average size of 500 nm in-plane and a few tens of nm in thickness. The prepared nanopowders were sintered into composites with a homogeneous dispersion of CNTs in a matrix. The dimensionless figure-of-merit of the composite showed an enhanced value compared to that of pure at the room temperature due to the reduced thermal conductivity and increased electrical conductivity with the addition of CNTs.
    Journal of Korean Powder Metallurgy Institute. 01/2013; 20(5).
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    ABSTRACT: A new synthesis route for Pt nanoparticles by direct electrochemical reduction of a solid-state Pt ion precursor () is demonstrated. Solid -supported polyethyleneimine (PEI) coatings on the surface of glassy carbon electrode were prepared by simple mixing of solid into a 1.0% PEI solution. The potential cycling or a constant potential in a PBS (pH 7.4) medium were applied to reduce the solid precursor. The reduction of Pt(IV) began at around -0.2 V and the reduction potential was ca. -0.4 V. A steady state current was achieved after 10 potential cycling scans, indicating that continuous formation of Pt nanoparticles by electrochemical reduction occurred for up to 10 cycles. After applying the reduction potential of -0.6 V for 300 s, Pt nanoparticles with diameters ranging from were observed, with an even distribution over the entire glassy carbon electrode surface. Characteristics of the Pt nanoparticles, including their performance in electrochemical reduction of are examined. A distinct reduction peak observed at about -0.20 V was due to the electrocatalytic reduction of by Pt nanoparticles. From the calibration plot, the linear range for detection was 0.1-2.0 mM and the detection limit for was found to be 0.05 mM.
    Bulletin- Korean Chemical Society 01/2013; 34(12). · 0.84 Impact Factor
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    ABSTRACT: Logistics is a crucial ingredient in the operation of an organization. Here how to efficiently deliver the supplies to the consumers in the field under the given condition is the key issue. The general logistics system is usually too complex to be modeled mathematically, or the models are overly computation intensive to be applied in real-time environment. This paper proposes a new method for logistics based on multi-agent system using modified A* algorithm to find the best route between the agents. In addition, genetic algorithm and K-medoids algorithm are used for selecting and clustering the agents to maximize the throughput of logistics. Computer simulation verifies the efficiency of the proposed scheme for a complicated application domain of military logistics.
    Information Networking (ICOIN), 2013 International Conference on; 01/2013
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    Bulletin- Korean Chemical Society 01/2013; 34(5). · 0.84 Impact Factor
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    ABSTRACT: Graphene oxide (GO) prepared in bulk quantities by oxidation of graphite with strong oxidants contains many hydrophilic groups, such as hydroxyl, epoxy, and carboxyl acid. We present a method to efficiently convert these hydrophilic groups into alkyl and alkyl ether groups by a one step reaction of bimolecular nucleophilic substitution with alkyl bromide. The functionalized graphene oxide (fGO) can be homogeneously dispersed as exfoliated monolayers in various organic solvents without degradation of size and shape of graphene oxide sheet. The degree of substitution reaction of each hydrophilic group in GO with alkyl bromide is quantitatively determined by comparing the deconvoluted O 1s X-ray photoelectron spectrum of GO with that of fGO. Addition of a small amount of fGO in poly(ethylene terephthalate) (PET) improves remarkably tensile and gas barrier properties of PET/fGO composite due to homogeneous dispersion of fGO sheets in PET matrix.
    ACS Applied Materials & Interfaces 07/2012; 4(8):4184-91. · 5.90 Impact Factor
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    ABSTRACT: We investigated the pharmacokinetic profile of (R)- and (S)-zaltoprofen (ZPF) in rats using rapid and selective liquid chromatography with solid-phase extraction (SPE). The ZPF enantiomers were extracted from a small volume of plasma (0.2mL) by means of SPE using cartridges and were analyzed on a Chiralcel OJ-H (4.6mm×150mm, 5μm) column with ultraviolet detection at 244nm. The lower limit of quantification of the ZPF enantiomers in plasma was 0.1μg/mL. The validated method was successfully applied to chiral pharmacokinetic studies of oral administration of racemic ZPF to rats. (S)-ZPF showed significantly higher AUC, T(max), and C(max) and a longer half-life than (R)-ZPF, indicating higher bioavailability of the (S)-isomer. A total of 8 samples (about 12% of the total number of samples) were selected for incurred sample reanalysis (ISR). The % difference between the re-assay concentrations and the original concentrations were all less than 15% of their mean values and met the acceptance criteria for ISR.
    Journal of pharmaceutical and biomedical analysis 05/2012; 70:567-73. · 2.45 Impact Factor

Publication Stats

480 Citations
155.20 Total Impact Points

Institutions

  • 2014
    • Chungnam National University
      • College of Pharmacy
      Daiden, Daejeon, South Korea
  • 2013–2014
    • National Cancer Center Korea
      • Molecular Epidemiology Branch
      Kōyō, Gyeonggi Province, South Korea
  • 2010–2014
    • Korea Institute of Materials Science
      Sŏngnam, Gyeonggi Province, South Korea
  • 2005–2013
    • Sungkyunkwan University
      • College of Information and Communication Engineering (SoICE)
      Sŏul, Seoul, South Korea
  • 2004–2013
    • Gachon University
      • Department of Electrical Engineering
      Sŏngnam, Gyeonggi Province, South Korea
  • 1998–2013
    • Seoul National University
      • • Department of Materials Science and Engineering
      • • Department of Food and Nutrition
      Sŏul, Seoul, South Korea
  • 2012
    • Vietnam Military Medical University
      Hà Nội, Ha Nội, Vietnam
  • 2008–2010
    • Konkuk University
      Sŏul, Seoul, South Korea
    • Hanyang University
      • Major in Obstetrics and Gynecology
      Sŏul, Seoul, South Korea
  • 2003–2008
    • Seoul National University Hospital
      Sŏul, Seoul, South Korea
  • 2007
    • Myongji University
      • Department of Mathematics
      Seoul, Seoul, South Korea
  • 2006
    • Korea Institute of Machinery and Materials
      Sŏul, Seoul, South Korea
    • Korea Advanced Institute of Science and Technology
      • Department of Materials Science and Engineering
      Sŏul, Seoul, South Korea