Ah Reum Han

Ewha Womans University, Sŏul, Seoul, South Korea

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Publications (43)111.96 Total impact

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    ABSTRACT: Pinus densiflora Siebold et Zucc. and P. thunbergii Parl. are two representative pine species in the southern part of the Korean Peninsula that are often planted for reclamation purpose. In nature, P. thunbergii is distributed along the coastal areas, while P. densiflora is more inland. This study compared the growth and physiological performance of P. densiflora and P. thunbergii in different salinity levels. Seedling performance in root collar diameter growth, net photosynthetic rate and cation (Na, K, Ca and Mg) concentrations was examined at NaCl concentrations of 0, 50, 100, 150 and 200 mM for 95 days. Pinus densiflora showed significant decreases both in root collar diameter growth and net photosynthetic rate at a concentration of 50 mM NaCl (p < 0.001). On the otherhand, P. thunbergii maintained growth and photosynthesis at concentrations up to 100 mM NaCl treatment. Sodium and Mg concentrations in needles and stems of P. densiflora were more than twice the values of those in P. thunbergii in external salinity treatments (p < 0.05). However, the differences between the two species' root concentrations of Na and Mg were not statistically significant. The increased coverage of cuticular wax around stomata of P. densiflora needles with increasing external NaCl concentrations suggested the dehydration stress in the needles. Pinus densiflora needles at 200 mM NaCl had the plastoglobuli from thylakoid degradation and aging chloroplast. In saline conditions, P. densiflora uptakes and accumulates more ions such as sodium, in the aboveground organs than P. thunbergii, which contributes to the difference in their salinity tolerances, resulting in P. densiflora being salinity-sensitive and P. thunbergii being salinity-tolerant.
    No preview · Article · Jan 2016 · Asia life sciences
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    ABSTRACT: Anemone is a representative spring ephemeral in Korea, flushing immediately after the snow melts and flowering in early spring. This study investigated the spring flush, stem growth, flowering, and fruiting of three Anemone species (A. amurensis, A. raddeana and A. koraiensis) in a montane deciduous forest on Mt. Joongwang over two consecutive years (2014 and 2015). We sought to expand our understanding of the flowering phenology and environmental effects on growth of the species. The three species showed sequential flowering: A. amurensis flushed and bloomed first, followed by A. raddeana and A. koraiensis at 1-2 week intervals for about 37 days. The duration of flowering for each species was similar, and lasted about 24-25 days. High temperatures advanced plant emergence and the first-flowering time by 5-7 days in 2014 compared to 2015. The temperature at the time of first flowering for the three species was around 4.0°C. The mean environmental temperature during the flowering stage ranged from 5 to 10°C for all three species, indicating that they needed lower temperatures than common flowering cultivars in April. The plants grew to 13-18 cm for A. amurensis and A. raddeana, and 17-21 cm for A. koraiensis. The growth and flowering patterns of the three Anemone species indicate their potential for use as floriculture plants in cold seasons and early spring.
    No preview · Article · Dec 2015 · Horticulture, Environment and Biotechnology
  • AR Han · U Kang · YS Kil · EK Seo

    No preview · Article · Jun 2015 · Planta Medica
  • Yun‐Seo Kil · Ah‐Reum Han · Eun Kyoung Seo

    No preview · Article · Jan 2015 · ChemInform
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    ABSTRACT: Distinct seasons and diverse tree species characterize temperate deciduous forests in NE Asia, but large areas of deciduous forests have been converted to conifer plantations. This study was conducted to understand the effects of seasons and tree species on leaf litter decomposition in a temperate forest. Using the litterbag method, the decomposition rate and nitrogen, phosphorous, and carbon dynamics of Mongolian oak (Quercus mongolica), Korean pine (Pinus koraiensis), and their mixed leaf litter were compared for 24 months in a Mongolian oak stand, an adjacent Korean pine plantation, and a Mongolian oakKorean pine mixed stand. The decomposition rates of all the leaf litter types followed a pattern of distinct seasonal changes: most leaf litter decomposition occurred during the summer. Tree species was less influential on the leaf litter decomposition. The decomposition rates among different leaf litter types within the same stand were not significantly different, indicating no mixed litter effect. The immobilization of leaf litter N and P lasted for 14 months. Mongolian oak leaf litter and Korean pine leaf litter showed different N and P contents and dynamics during the decomposition, and soil P2O5 was highest in the Korean pine plantation, suggesting effects of plantation on soil nutrient budget.
    Preview · Article · Oct 2014 · Forests
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    Yun Seo Kil · Ah- Reum Han · Eun Kyoung Seo

    Full-text · Article · Jun 2014 · Bulletin of the Korean Chemical Society
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    ABSTRACT: isolation and structure elucidation
    No preview · Article · Feb 2014 · ChemInform
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    ABSTRACT: The main function of methionine sulfoxide reductases (Msr) in many organisms is to protect cells against oxidative stress caused by the catalyzed reduction of oxidized methionine to normal methionine. In a few micro-organisms, the existence of Msr as a fusion protein on a single polypeptide, MsrAB, was reported. However, Msr generally exists as separate enzymes MsrA and MsrB. Here, MsrAB from Helicobacter pylori (HpMsrAB) was overexpressed in Escherichia coli, purified, and crystallized to determine its structure. HpMsrAB X-ray diffraction data were collected to the resolution of 3.3 Å, and the crystals were found to belong to the tetragonal space group P41212, with the unit cell parameters a =100.91, b =100.91, and c =160.08 Å. The crystals corresponded to 5.38 Å3 Da−1 of Matthews coefficient and 77.2% solvent content from the molecular replacement suggest that there is a single molecule in an asymmetric unit. Due to their unusually high solvent content, diffraction of these crystals only reach a resolution of 3.3 Å. A preliminary solution was determined by molecular replacement. Further refinement of the structure is in progress.
    No preview · Article · Feb 2014 · Journal of the Korean Society for Applied Biological Chemistry
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    ABSTRACT: Abstract Glycerol-3-phosphate acyltransferase (GPAT) catalyzes the first committed step in triacylglycerol (TAG) and phospholipid biosynthesis, and has been considered as one of the drug targets for treating hepatic steatosis, insulin resistance, and other metabolic disorders. The aim of this study was to investigate the GPAT inhibitors from natural products and to evaluate their effects. The methanol extract of Aralia cordata roots showed a strong inhibitory effect on the human GPAT1 activity. A further bioactivity-guided approach led to the isolation of ent-pimara-8(14),15-dien-19-oic acid, (PA), one of the major compounds of A. cordata, which suppressed the GPAT1 activity with IC50 value of 60.5 μM. PA markedly reduced de novo lysophosphatidic acid synthesis through inhibition of GPAT activity and therefore significantly decreased synthesis of TAG in the HepG2 cells. These results suggest that PA as well as A. cordata root extract could be beneficial in controlling lipid metabolism.
    No preview · Article · Nov 2013 · Journal of medicinal food
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    ABSTRACT: Expression plasmids carrying different deoxysugar biosynthetic gene cassettes and the gene encoding a substrate-flexible glycosyltransferase DesVII were constructed and introduced into Streptomyces venezuelae YJ003 mutant strain bearing a deletion of a desosamine biosynthetic (des) gene cluster. The resulting recombinants produced macrolide antibiotic YC-17 analogues possessing unnatural sugars replacing native D-desosamine. These metabolites were isolated and further purified using chromatographic techniques and their structures were determined as D-quinovosyl-10-deoxymethynolide, L-rhamnosyl-10-deoxymethynolide, L-olivosyl-10-deoxymethynolide, and D-boivinosyl-10-deoxymethynolide on the basis of 1D and 2D NMR and MS analyses and the stereochemistry of sugars was confirmed using coupling constant values and NOE correlations. Their antibacterial activities were evaluated in vitro against erythromycin-susceptible and -resistant Enterococcus faecium and Staphylococcus aureus. Substitution with L-rhamnose displayed better antibacterial activity than parent compound YC-17 containing native sugar D-desosamine. The present study on relationships between chemical structures and antibacterial activities could be useful in generation of novel advanced antibiotics utilizing combinatorial biosynthesis approach.
    Full-text · Article · Jun 2013 · Journal of Biotechnology
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    ABSTRACT: Tree growth in subalpine ecosystems is sensitive to wind due to their wide exposure to strong winds and sparsely wooded short surroundings. This study was conducted to understand the effects of wind and topographic wind barriers on the tree growth in a subalpine ecosystem. The annual shoot growth, bud mortality and needle moisture content of Jezo spruce (Picea jezoensis (Siebold et Zucc.) Carrière) were compared between a wind-exposed site and a wind-protected site. The wind-exposed site was located in a windward position and was exposed directly to the prevailing winds from W and WSW. The wind-protected site was located on leeward slopes with topographic barriers that blocked the prevailing winds. The wind-exposed site had higher air temperature, lower soil water content and shallower snow depth than the wind-protected site in late winter and spring. The annual mean shoot growth on the wind-exposed site was 4 cm – significantly lower than that of 6.1 cm on the wind-protected site (P < 0.01). The bud mortality was highest at 32.9% in the western sectors of the upper crowns in the wind-exposed site, which was the crown sector that was most exposed to the prevailing winds. The needle moisture content decreased by 8–60% from January 2009 to April 2009, and the decrease was significantly higher in the wind-exposed site than in the wind-protected site (P < 0.01), indicating the potential for drought stress in trees in the wind-exposed site. Topographic wind barriers play a decisive role on the tree growth in subalpine areas by changing temperature and moisture regimes, lowering needle moisture loss and bud mortality, and reducing the potential for drought stress.
    No preview · Article · Dec 2012 · Agricultural and Forest Meteorology
  • UJ Youn · YS Kil · U Kang · YJ Lee · HJ Shin · JW Nam · AR Han · SH Sung · J Kim · SM Lee · D Lee · JH Lee · EK Seo

    No preview · Article · Jul 2012 · Planta Medica
  • Y.J. Lee · E. Lee · A.-R. Han · J.-I. Song · Y. Kwon · E.-K. Seo
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    ABSTRACT: Marine organism extracts were prepared from 26 species of Korean indigenous marine organisms, including 25 species belonging in class Anthozoa of phylum Cnidaria and a species belonging to subphylum Urochordata of phylum Chordata, and screened their inhibitory effects against μ-calpain. As a result, the thirteen extracts were found to be active in the criteria of IC50 << 100 μg/mL. Among them, the MeOH extracts of Plexauroides praelonga and Alveopora japonica showed remarkable μ-calpain inhibitory activity with IC50 values of 4.62 ± 0.22 and 4.82 ± 0.07 μg/mL, respectively. In addition, chemical investigation of A. japonica led to the isolation of an active compound, hexadecyl tetradecanoate, as a selective cathepsin B inhibitor (IC5o = 9.05 ± 2.45 μM). This compound was isolated as constituent of A. japonica for the first time in the present study.
    No preview · Article · Jun 2012 · Natural Product Sciences
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    ABSTRACT: A multiplex PCR and DNA array for quick detection of Bacillus cereus, Staphylococcus aureus, Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella spp. was developed using specific genetic markers derived from virulence-related genes. The genetic markers of cytK, sei, prfA, rfB, and hilA gene specifically amplified DNA fragments of 320 bp, 500 bp, 700 bp, 1.0 kb and 1.2 kb from B. cereus, S. aureus, L. monocytogenes, E. coli O157:H7, and Salmonella spp., respectively. These markers are specific for the detection of the corresponding target pathogens. The sensitivity of the genetic markers was down to ∼0.5 fg genomic DNA and ∼101 CFU/ml (one bacterial cell per reaction) of bacterial culture. The combination of mPCR and DNA macroarray hybridization sensitively and specifically detected B. cereus, S. aureus, L. monocytogenes, E. coli O157:H7, and Salmonella spp., in complex mixed cultures and food matrices. Thus, this mPCR and macroarray-based approach serves as rapid and reliable diagnostic tool for the detection of these five pathogens.
    No preview · Article · Jun 2012 · Annals of Microbiology
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    ABSTRACT: Methionine sulfoxide reductase (Msr) is a repair enzyme that reduces oxidized methionine to methionine. The Msr enzyme is divided into MsrA and MsrB, which reduce the S and R configurations of the substrate, respectively. In some pathogenic bacteria MsrA and MsrB exist in a fusion-protein form, MsrAB. In this study, the recombinant MsrA part of MsrAB from Haemophilus influenzae (HIMsrA) was overexpressed, purified and crystallized using the hanging-drop vapour-diffusion method. A diffraction data set was collected to 1.6 Å resolution. The crystal of HIMsrA was found to belong to space group P4(1)2(1)2, with unit-cell parameters a = b = 57.29, c = 186.28 Å, a calculated Matthews coefficient of 1.82 Å(3) Da(-1) and two molecules per asymmetric unit. A preliminary solution was determined by molecular replacement. Refinement of the structure is currently in progress.
    No preview · Article · May 2012 · Acta Crystallographica Section F Structural Biology and Crystallization Communications
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    ABSTRACT: Three new flavonoids, 5,6,7,8,3′,4′-hexamethoxyhomoflavone (1), 5,6,7,8,4′-pentamethoxyhomoflavone (2) and 3,6,7,8,2′,5′-hexamethoxyflavone (3) were isolated from the peels of mature fruits of Citrus unshiuMarcow (Rutaceae), together with the three known compounds 6,7,8,4′-tetramethoxyflavone (=6,7,8-trimethoxy-2-(4-methoxyphenyl)-4H-1-benzopyran-4-one), 3,5,7,8,2′,5′-hexamethoxyflavone (=2-(2,5-dimethoxyphenyl)-3,5,7,8-tetramethoxy-4H-1-benzopyran-4-one), and scopoletin (=7-hydroxy-6-methoxy-2H-1-benzopyran-2-one) of which the former two have never been isolated from natural resources, although they have been reported as synthetic compounds. The structures of 1–3 were elucidated on the basis of spectroscopic evidence, including 1D- and 2D-NMR analysis.
    No preview · Article · Feb 2012 · Helvetica Chimica Acta
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    ABSTRACT: We compared soil seed banks between a secondary natural forest and an adjacent big leaf mahogany (Swietenia macrophylla King) plantation in the Mt. Makiling Forest Reserve, Philippines to understand seed bank dynamics, the relationship between soil seed bank and aboveground vegetation and effects of canopy gaps on soil seed banks in a tropical rain forest. Stand inventorying was conducted and soil seed bank composition and density were examined in February and August 2008. Seeds were germinated to identify the species. Aboveground species composition and small canopy gaps little influenced soil seed bank composition and density. Only three species in the secondary natural forest and six species in the big leaf mahogany plantation were commonly found in both soil seed banks and aboveground vegetation. Most species in soil seed banks were pioneer or mid seral species which came from the outside of the stands. The dominant species in soil seed banks were mid seral species in the secondary natural forest and pioneer species in the big leaf mahogany plantation. Differences in soil seed bank composition and density were greater between stands than between gap closure levels, implying little effects of small canopy gaps on soil seed bank composition and density in the study sites. The low soil seed bank density of late seral species suggests that soil seed bank may not be the major source of late seral species regeneration while high soil seed bank density of pioneer and mid seral species implies that soil seed bank can be critical in the regeneration of pioneer and mid seral species in tropical rain forests.
    No preview · Article · Jan 2012 · Journal of Environmental Science and Management
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    ABSTRACT: The adult and the early stages of Cydia piceicola, sp. nov., are described and illustrated from Korea. Larvae of the new species feed on Picea jezoensis (Siebold et Zucc.) Carrière, The life history and larval feeding habits are briefly discussed.
    Full-text · Article · Nov 2011 · Entomological Research
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    ABSTRACT: Metabolic engineering of plant-specific phenylpropanoid biosynthesis has attracted an increasing amount of attention recently, owing to the vast potential of flavonoids as nutraceuticals and pharmaceuticals. Recently, we have developed a recombinant Streptomyces venezuelae as a heterologous host for the production of flavonoids. In this study, we successfully improved flavonoid production by expressing two sets of genes predicted to be involved in malonate assimilation. The introduction of matB and matC encoding for malonyl-CoA synthetase and the putative dicarboxylate carrier protein, respectively, from Streptomyces coelicolor into the recombinant S. venezuelae strains expressing flavanone and flavone biosynthetic genes resulted in enhanced production of both flavonoids.
    No preview · Article · Nov 2011 · Journal of Microbiology and Biotechnology
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    ABSTRACT: Kanamycin is one of the most widely used antibiotics, yet its biosynthetic pathway remains unclear. Current proposals suggest that the kanamycin biosynthetic products are linearly related via single enzymatic transformations. To explore this system, we have reconstructed the entire biosynthetic pathway through the heterologous expression of combinations of putative biosynthetic genes from Streptomyces kanamyceticus in the non-aminoglycoside-producing Streptomyces venezuelae. Unexpectedly, we discovered that the biosynthetic pathway contains an early branch point, governed by the substrate promiscuity of a glycosyltransferase, that leads to the formation of two parallel pathways in which early intermediates are further modified. Glycosyltransferase exchange can alter flux through these two parallel pathways, and the addition of other biosynthetic enzymes can be used to synthesize known and new highly active antibiotics. These results complete our understanding of kanamycin biosynthesis and demonstrate the potential of pathway engineering for direct in vivo production of clinically useful antibiotics and more robust aminoglycosides.
    Full-text · Article · Nov 2011 · Nature Chemical Biology

Publication Stats

314 Citations
111.96 Total Impact Points

Institutions

  • 2007-2015
    • Ewha Womans University
      • • College of Pharmacy
      • • Department of Chemistry Nano Science
      • • Center for Cell Signaling and Drug Discovery Research
      Sŏul, Seoul, South Korea
  • 2014
    • Korea University
      Sŏul, Seoul, South Korea
  • 2006-2014
    • Seoul National University
      • • Department of Forest Sciences
      • • School of Chemical and Biological Engineering
      Sŏul, Seoul, South Korea
  • 2013
    • Korea Research Institute of Bioscience and Biotechnology KRIBB
      • Targeted Medicine Research Center
      Anzan, Gyeonggi-do, South Korea
  • 2012
    • Kangwon National University
      • Department of Biological Environment
      Shunsen, Gangwon-do, South Korea