Hak Sung Lee

Catholic University of Korea, Sŏul, Seoul, South Korea

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Publications (40)46.23 Total impact

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    ABSTRACT: In this study, mesoporous titanosilicate (MTS)/reduced graphene oxide (RGO) composite materials were prepared as a function of the RGO content and used as novel adsorbents for a mixed-solute solution of methylene blue and rhodamine B (RhB). Adsorption capacities of the composite materials were higher than those of MTS or RGO by themselves, demonstrating that adsorptive performances of the composite materials are better than the inorganic or organic materials alone. Composite material containing 20 wt% RGO (20MTSG) showed the best adsorption capacity for both contaminants where its adsorptive behavior in the mixed-solute solution can be ascribed to the unique morphology of the large layered structure of MTS and RGO, as well as many aggregates of small-sized plates. Compared to the other composite materials, 20MTSG contained an abundant edge structure of RGO, resulting in a relatively higher RhB adsorption capacity. RhB preferred the adsorption sites on RGO to the adsorption sites on MTS due to steric hindrance inside the mesopores of MTS.
    Environmental Engineering Science 03/2014; 31(3):148-155.. · 1.15 Impact Factor
  • Hak Sung Lee, Jung Ho Suh
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    ABSTRACT: Continuous biosorption process for removal of lead and copper by laboratory scale fixed-bed reactor was carried out using Ca-loadedLaminaria japonica. All biosorption processes were observed as cation exchange such as Pb2+ vs. Ca2+, Cu2+ vs. Ca2+, and Pb2+ vs. Cu2+. The affinity of lead ions towardsL. japonica was stronger than that of copper ions because the initial amount of desorbed Cu2+ in Cu-Pb system was higher than that of eluted Pb2+ in Pb-Cu system.
    Korean Journal of Chemical Engineering 04/2012; 17(4):477-479. · 1.06 Impact Factor
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    ABSTRACT: Many natural compounds have been investigated as drug candidates to prevent human immunodeficiency virus (HIV) with low cytotoxicity. We tested whether ingenol from Euphorbia ingens exerts anti-HIV effects in human T cell lines. Ingenol effectively maintained high cell viability (CD50, >1 mM) in H9 and MT4 T cells. The efficacy of ingenol to inhibit HIV-1 infection was dose dependent. ED50 for 100 and 200 TCID50 of HIV-1 was 5.06 and 16.87 μM, respectively. Gag p24 antigen production in ingenol-treated MT4 cells was reduced by 24.5% on day 6 post-infection. While p24 antigen was reduced in ingenol-treated cells, levels of cytokines such as TNF-α and IL-6 and chemokines such as RANTES and MCP-1 were increased. dUTP level related to late apoptotic events was increased on day 2 post-infection of HIV by ingenol treatment, whereas expression of annexin V was unchanged. Reduced levels of iNOS and ZAP-70 after HIV infection were recovered by ingenol treatment. Ingenol helps T cells to survive longer against viremia after HIV-1 infection, without exerting cytotoxic effects. Ingenol can be considered a safe and efficacious candidate for immune-boosting therapy for AIDS patients.
    Osong public health and research perspectives. 09/2011; 2(2):109-14.
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    ABSTRACT: We prepared La-impregnated mesoporous silicates to investigate the adsorption of tetracycline in aqueous solution. Nitrogen adsorption-desorption isotherm tests confirmed the mesoporosity of the prepared materials, resulting in a decline in surface area and pore volume along with La loading amount. In adsorption tests, however, La impregnation improved the adsorption capacity of materials for tetracycline even though the surface area and the pore volumes were lower after La impregnation. Adsorption capacities for tetracycline showed a maximum value with La loading amounts. The highest adsorption capacity for tetracycline was 303.3 mg g(-1), which was acquired from the fitting of isotherm data of 10 wt% La-impregnated mesoporous silicates to the Langmuir model. Changes in FTIR patterns of tetracycline adsorbed on La-impregnated mesoporous silicates implied that the negatively charged oxygen of the tricarbonylamide group of tetracycline chemically interacted with La hydroxide species in materials in the neutral condition.
    Environmental Technology 03/2010; 31(3):233-41. · 1.61 Impact Factor
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    ABSTRACT: Histone deacetylase plays an important role in HIV latency. Novel histone deacetylase inhibitors, CG05 and CG06, were evaluated for their roles in HIV latency using ACH2 cells. Both inhibitors were highly efficient in reactivation of provirus and exerted lesser toxicity compared with other known histone deacetylase inhibitors. Histone acetylation increased when proviruses were reactivated by the compounds. These new inhibitors may contribute to the reduction of the HIV reservoir when used in conjunction with highly active antiretroviral therapy.
    AIDS (London, England) 02/2010; 24(4):609-11. · 4.91 Impact Factor
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    ABSTRACT: HIV-1 specific cytotoxic T lymphocytes (CTLs) have an important role as antiviral effector cells for controlling HIV-1 infection. To investigate CTL response during the early stage of HIV infection, we measured immunity-related factors including CD4+ T cell counts, CD8+ T cell counts, HIV-1 RNA viral loads and IFN-γ secretion according to CTL response in 78 selected primary HIV-1-infected Koreans. The CTL response was strongly induced by HIV-1 specific Gag and Nef peptides (p = 0.016) compared with induction by Tat or Env peptides. These results suggest that the major antiviral factors inducing strong HIV-specific CTL responses are associated with the Gag and Nef viral regions in primary HIV-1 infected Koreans. The relationship between viral load and CTL response showed varying correlations with time following HIV infection. CTL response was inversely correlated with viral loads at preseroconversion stage I (r = -0.224 to -0.33) and changed to a positive correlation at the preseroconversion stage II (r = 0.132 to 0.854). Finally, it changed to an inverse correlation again after seroconversion until a viral set point was established on serological profiling (r = -0.195 to -0.407). These findings demonstrate a dynamic correlation between viral load and subsequent CTL responses during early HIV infection.
    Virology Journal 01/2010; 7:239. · 2.09 Impact Factor
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    ABSTRACT: We prepared Fe-impregnated mesoporous silicates to investigate the adsorption of tetracycline in aqueous solution. Mesoporous silicates with different Fe content (5, 10, 30, 50 wt%) were prepared by an incipient wetness method. Adsorption kinetics for tetracycline showed that Fe-impregnation improved the adsorption ability for tetracycline. By fitting the adsorption kinetic data to a pseudo second-order model, we obtained a maximum adsorption amount of tetracycline with Fe30SBA-15 (30 wt% Fe-impregnated mesoporous silicates) at 41.7 mg/g. The pH dependency of tetracycline adsorption exhibited a volcano curve where the maximum adsorption onto the Fe30SBA-15 sample occurred in the neutral pH region. The introduction of Fe species into the SBA-15 revived the adsorption ability for tetracycline, whereas there was no interaction between tetracycline and SBA-15, a mesoporous silicate. These results suggest that impregnated Fe species produce an effective interaction with tetracycline in an aqueous system.
    Korean Journal of Chemical Engineering 01/2010; 27(1):116-120. · 1.06 Impact Factor
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    ABSTRACT: Helicobacter pylori causes diseases ranging from gastritis to peptic ulcer disease to gastric cancer. Geographically, areas with high incidences of H. pylori infection often overlap with areas with high incidences of gastric cancer, which remains one of the leading causes of cancer-related deaths worldwide. Strains of H. pylori that carry the virulence factor cytotoxin-associated gene A (cagA) are much more likely to be associated with the development of gastric cancer. Moreover, particular C-terminal polymorphisms in CagA vary by geography and have been suggested to influence disease development. We conducted a large-scale molecular epidemiologic analysis of South Korean strains and herein report a statistical link between the East Asian CagA EPIYA-ABD genotype and the development of gastric cancer. Characterization of a subset of the Korean isolates showed that all strains from cancer patients expressed and delivered phosphorylatable CagA to host cells, whereas the presence of the cagA gene did not strictly correlate to expression and delivery of CagA in all noncancer strains.
    Journal of clinical microbiology 02/2009; 47(4):959-68. · 4.16 Impact Factor
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    ABSTRACT: Resistance to metronidazole (MTZ) in Helicobacter pylori is associated with mutations in rdxA, encoding an oxygen-insensitive NADPH nitroreductase, and mutations in frxA, encoding a NAD(P)H-flavin oxidoreductase. Despite this association, the strict correlation of MTZ resistance with mutations in rdxA or frxA is still controversial. In this study, rdxA allelic replacement was used to distinguish resistance-associated nucleotide mutations from the natural genetic diversity of H. pylori. Replacement with truncated rdxA resulted in MTZ resistance, whereas replacement with missense-mutated rdxA from resistant clinical isolates failed to yield MTZ resistance. Thus, although truncation of rdxA confers MTZ resistance in G27 H. pylori, MTZ resistance found in other clinical isolates is not due to the identified amino-acid substitutions. Three of our MTZ-resistant clinical isolates expressed functional rdxA and two of these also encoded full-length frxA. Therefore, MTZ resistance can arise in H. pylori possessing functional rdxA, suggesting that other factors are involved in MTZ resistance.
    The Journal of Antibiotics 02/2009; 62(1):43-50. · 2.19 Impact Factor
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    ABSTRACT: Electric power equipment must be operated in the state of high reliability with its responsibility in the seamless power supply. Therefore, persistent maintenance is very important. There are many maintenance methods well known in industrial business. Among them, the reliability-centered maintenance (RCM) is a state of the art maintenance technique. This paper shows a RCM method for electric power equipments. This reliability-centered maintenance (RCM) has been applied in the fields of aerospace, nuclear power plants and rail system, etc. In this paper, we design the FMEA flow for power transformer and evaluate the importance level based on the fault information. The importance level is applied to the inspection period, fault detection method and operator selection. The results of the system are provided as a worksheet containing the information that needs to be maintained.
    Condition Monitoring and Diagnosis, 2008. CMD 2008. International Conference on; 05/2008
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    ABSTRACT: As the recent trend of the monitoring and diagnosis technique for high-voltage GIS, many power industrial companies are researching and developing on-line preventive and diagnosis system of PD (partial discharge) for GIS. In succession of high-voltage class, the demand in transmission and distribution class is increasing and the scope of its application is spreading. Thus, we developed on-line iPDM (intelligent partial discharge monitoring) system for 25.8 kV cubicle-GIS (C-GIS). We are briefly introduced the configuration of on-line iPDM system using UHF methods for effectively diagnosing the insulation condition of C-GIS. For the internal UHF sensor, we designed the novel model with high sensitivity and checked experiment results as antenna performance factor. Comparing of ERA method and UHF method, the relationship between pC-dBm is described based on experimental results. The measured data is converted to frequency domain data and we can search the frequency with peak value except external noise. And then input data of ANN (artificial neural network) model is made from normalized zero span data. Finally, our expert system can judge the risk level from PD magnitude and its cause. In this paper, we will describe the development results and the actual experience of the on-line iPDM system for C-GIS in KOREA.
    Condition Monitoring and Diagnosis, 2008. CMD 2008. International Conference on; 05/2008
  • Antiviral Research. 05/2008; 78(2):A40–A41.
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    ABSTRACT: Source samples were collected to construct source profiles for 9 different source types, including soil, road dust, gasoline/diesel-powered vehicles, a municipal incinerator, industrial sources, agricultural/biomass burning, marine aerosol, and a coal-fired power plant. Seasonal profiles for ‘Chinese aerosol’, aerosols derived from the urban area of China, were reconstructed from seasonal PM2.5 compositions reported in Beijing, China. Ambient PM2.5 at a receptor site was also measured during each of the four seasons, from April 2001 to February 2002, in Seoul. The Chemical Mass Balance receptor model was applied to quantify source contributions during the study period using the estimated source profiles. Consequently, motor vehicle exhaust (33.0%), in particular 23.9% for diesel-powered vehicles, was the largest contributor affecting the PM2.5 levels in Seoul, followed by agricultural/biomass burning (21.5%) and ‘Chinese aerosol’ (13.1%), indicating contributions from long-range transport. The largest contributors by season were: for spring, ‘Chinese aerosol’ (31.7%); for summer, motor vehicle exhaust (66.9%); and for fall and winter, agricultural/biomass burning (31.1% and 40.1%, respectively). These results show different seasonal patterns and sources affecting the PM2.5 level in Seoul, than those previously reported for other cities in the world.
    Journal of Korean Society for Atmospheric Environment. 01/2008; 24(E1):32-43.
  • Antiviral Research - ANTIVIR RES. 01/2008; 78(2).
  • Olga Snisarenko, Hak Sung Lee
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    ABSTRACT: The present study was carried out in a batch system using Ca-loaded brown algae Laminaria Japonica for its sorption and desorption capacity of chromium. The mono-component Langmuir isotherm model was used to present gathered results. Laminaria Japonica biomass reveals large suiface area and a high chromium sorption capacity - almost 48% (38.44 mg/g) of its dry weight at pH 4.5. Elution treatments such as 0.1 N HNO3, 1 N NaOH, EDTA, Aqua Regia (3HCl+HNO3), 0.5 M H2SO4 and 700degC treatment were used for the desorption performance of chromium ion sorbed. The binary form of Langmuir isotherm was used to present the results of two-metal sorption experiments. Cr ion reveals higher affinity to binding sites of biomass.
    01/2007;
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    ABSTRACT: Ambient measurements were made using two sets of annular denuder system during the four seasons (April 2001 to February 2002) and were then compared with the results during the period of 1996-1997 to estimate the trends and seasonal variations in concentrations of gaseous and fine particulate matter (PM2.5) principal species. Annual averages of gaseous HNO3 and NH3 increased by 11% and 6%, respectively, compared with those of the previous study, whereas HONO and SO2 decreased by 11% and 136%, respectively. The PM2.5 concentration decreased by -17%, 35% for SO4(2-), and 29% for NH4+, whereas NO3- increased by 21%. Organic carbon (OC) and elemental carbon (EC) were 12.8 and 5.98 microg/m(-3), accounting for -26 and 12% of PM2.5 concentration, respectively. The species studied accounted for 84% of PM2.5 concentration, ranging from 76% in winter to 97% in summer. Potential source contribution function (PSCF) analysis was used to identify possible source areas affecting air pollution levels at a receptor site in Seoul. High possible source areas in concentrations of PM2.5, NO3-, SO4(2-), NH4+, and K+ were coastal cities of Liaoning province (possibly emissions from oil-fired boilers on ocean liners and fishing vessels and industrial emissions), inland areas of Heibei/Shandong provinces (the highest density areas of agricultural production and population) in China, and typical port cities (Mokpo, Yeosu, and Busan) of South Korea. In the PSCF map for OC, high possible source areas were also coastal cities of Liaoning province and inland areas of Heibei/Shandong provinces in China. In contrast, high possible source areas of EC were highlighted in the south of the Yellow Sea, indicating possible emissions from oil-fired boilers on large ships between South Korea and Southeast Asia. In summary, the PSCF results may suggest that air pollution levels in Seoul are affected considerably by long-range transport from external areas, such as the coastal zone in China and other cities in South Korea, as well as Seoul itself.
    Journal of the Air & Waste Management Association (1995) 08/2006; 56(7):911-21. · 1.20 Impact Factor
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    Hak Sung Lee, Seung Yi Kang, Cha-Gyun Shin
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    ABSTRACT: Retroviral integrases insert viral DNA into target DNA. In this process they recognize their own DNA specifically via functional domains. In order to analyze these functional domains, we constructed six chimeric integrases by swapping domains between HIV-1 and HFV integrases, and two point mutants of HFV integrase. Chimeric integrases with the central domain of HIV-1 integrase had strand transfer and disintegration activities, in agreement with the idea that the central domain determines viral DNA specificity and has catalytic activity. On the other hand, chimeric integrases with the central domain of HFV integrase did not have any enzymatic activity apart from FFH that had weak disintegration activity, suggesting that the central domain of HFV integrase was defective catalytically or structurally. However, these inactive chimeras were efficiently complemented by the point mutants (D164A and E200A) of HFV integrase, indicating that the central domain of HFV integrase possesses potential enzymatic activity but is not able to recognize viral or target DNA without the help of its homologous N-terminal and C-terminal domains.
    Molecules and Cells 05/2005; 19(2):246-55. · 2.21 Impact Factor
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    ABSTRACT: Advanced oxidation involving O<sub>3</sub>/catalyst was used to eliminate 1,4-dioxane and to compare the degradability of dioxane-contaminated water with O<sub>3</sub> only and O<sub>3</sub>/H<sub>2</sub>O<sub>2</sub>. Oxidation experiments were carried out in a bubble column reactor under different oxidation sources such as O<sub>3</sub> only, O<sub>3</sub>/ H<sub>2</sub>O<sub>2</sub>, and O<sub>3</sub>/catalyst. The O<sub>3</sub>/H<sub>2</sub>O<sub>2</sub> and O<sub>3</sub>/catalyst process effectively converted dioxane to more biodegradable intermediates. On the economic aspect, O<sub>3</sub>/catalyst process could be reduce the treatment cost of 1,4-dioxane instead of O<sub>3</sub>/H<sub>2</sub>O<sub>2</sub> process which have high cost of H<sub>2</sub>O<sub>2</sub>.
    Science and Technology, 2005. KORUS 2005. Proceedings. The 9th Russian-Korean International Symposium on; 01/2005
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    ABSTRACT: Fine particles (PM2.5) were collected during all four seasons, from April 2001 to February 2002, in Seoul, South Korea, using an annular denuder system. Elemental compositions of ambient PM2.5 were analyzed using the proton-induced X-ray emission method. The greatest contributors (> or = 2%) to the PM2.5 mass were sulfur (S), silicon (Si), chlorine (Cl), aluminum (Al), and iron (Fe) in the spring; S in the summer; and S and Cl in the fall. S, Cl, and Si were the major elements in the winter. S was the most abundant species among the elements, ranging from 5.3 to 7.9%, followed by Si and Cl. From analysis of variance, PM2.5 mass, Al, Si, potassium, calcium, and Fe showed significant seasonal differences during the four seasons (p < 0.001). Enrichment factor (EF) analysis was carried out to identify the sources affecting the aerosol in the Seoul area. On the basis of the mean EF values, elemental S, copper, zinc, and lead may be emitted from anthropogenic sources (EF > 50). Elemental Al, Si, titanium, and Fe may be emitted from crustal sources (EF < 3). Additionally, a correlation analysis was carried out for source identification. The results of the correlation analysis were confirmed by the results of the EF analysis.
    Journal of the Air & Waste Management Association (1995) 05/2004; 54(4):432-9. · 1.20 Impact Factor
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    ABSTRACT: DA-125, a novel derivative of adriamycin, is known for its anti-cancer activity. In this study, the inhibitory mechanism of DA-125 on topoisomerase was investigated in the simian virus 40 (SV40) replicating CV-1 cell by studying the SV40 DNA replication intermediates and DNA-topoisomerase complexes. DNA-protein complexes that were formed in the drug-treated cells were quantitated by using a glass filter assay. SV40 DNA replication intermediates that were accumulated in the drug-treated CV-1 cell were analyzed in a high resolution gel. DA-125 did not accumulate B-dimers of SV40 DNA replication intermediates which were found in the adriamycin-treated CV-1 cells. DA-125 induced a dose-dependent formation of the DNA-protein complexes, while adriamycin did not. When adriamycin and etoposide (VP16) were added to the SV40-infected cells at the same time, adriamycin blocked the formation of the DNA-protein complexes induced by VP16 in a dose-dependent manner. However, DA-125 blocked the formation of the DNA-protein complexes induced by VP16 up to the maximum level of the DNA-protein complexes that were induced by DA-125 alone. Adriamycin and DA-125 did not inhibit the formation of the DNA-protein complexes that were caused by camptothecin, a known topoisomerase I poison. DA-125 is bifunctional in inhibiting topoisomerase II because it simultaneously has the properties of the topoisomerase II poison and the DNA intercalator. As a topoisomerase II poison, DA-125 alone induced dose-dependent formation of the DNA-protein complexes. However, as a DNA intercalator, it quantitatively inhibited the formation of the DNA-protein complexes induced by a strong topoisomerase II poison VP16. Furthermore considering that the levels of the DNA-protein complex induced by VP16 were decreased by DA-125 in terms of the topoisomerase II poison, we suggest that DA-125 has a higher affinity to the drug-binding sites of DNA than VP16 has.
    Archives of Pharmacal Research 02/2004; 27(1):77-82. · 1.54 Impact Factor

Publication Stats

292 Citations
46.23 Total Impact Points

Institutions

  • 2009
    • Catholic University of Korea
      • Department of Internal Medicine
      Sŏul, Seoul, South Korea
  • 2006
    • Harvard University
      • Harvard School of Public Health
      Cambridge, MA, United States
  • 2005
    • Chung-Ang University
      • Department of Systems Biotechnology
      Seoul, Seoul, South Korea
  • 1997–2005
    • University of Ulsan
      • • School of Chemical Engineering and Bioengineering
      • • Department of Chemical Engineering
      Urusan, Ulsan, South Korea
    • Kyungsung University
      Tsau-liang-hai, Busan, South Korea
    • McGill University
      Montréal, Quebec, Canada
  • 2001–2004
    • Ulsan College
      Urusan, Ulsan, South Korea
  • 1999–2002
    • Seowon University
      Seishō-gun, North Gyeongsang, South Korea
  • 1989
    • Pusan National University
      • Department of Polymer Science and Engineering
      Tsau-liang-hai, Busan, South Korea