• Steel and Composite Structures
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• 제35권6호
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• pp.799-813
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• 2020

Fatigue cracks of rib-to-deck (RD) joints have been frequently observed in the orthotropic steel decks (OSD) using conventional U-ribs (CU). Thickened edge U-rib (TEU) is proposed to enhance the fatigue strength of RD joints, and its effectiveness has been proved through fatigue tests. In-depth full-scale tests are further carried out to investigate both the fatigue strength and fractography of RD joints. Based on the test result, the mean fatigue strength of TEU specimens is 21% and 17% higher than that of CU specimens in terms of nominal and hot spot stress, respectively. Meanwhile, the development of fatigue cracks has been measured using the strain gauges installed along the welded joint. It is found that such the crack remains almost in semi-elliptical shape during the initiation and propagation. For the further application of TEUs, the design curve under the specific survival rate is required for the RD joints using TEUs. Since the fatigue strength of welded joints is highly scattered, the design curves derived by using the limited test data only are not reliable enough to be used as the reference. On this ground, an experiment-numerical hybrid approach is employed. Basing on the fatigue test, a probabilistic assessment model has been established to predict the fatigue strength of RD joints. In the model, the randomness in material properties, initial flaws and local geometries has been taken into consideration. The multiple-site initiation and coalescence of fatigue cracks are also considered to improve the accuracy. Validation of the model has been rigorously conducted using the test data. By extending the validated model, large-scale databases of fatigue life could be generated in a short period. Through the regression analysis on the generated database, design curves of the RD joint have been derived under the 95% survival rate. As the result, FAT 85 and FAT 110 curves with the power index m of 2.89 are recommended in the fatigue evaluation on the RD joint using TEUs in terms of nominal stress and hot spot stress respectively. Meanwhile, FAT 70 and FAT 90 curves with m of 2.92 are suggested in the evaluation on the RD joint using CUs in terms of nominal stress and hot spot stress, respectively.

• Journal of Applied Biological Chemistry
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• 제54권1호
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• pp.1-6
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• 2011

Poly-${\gamma}$-glutamic acid (${\gamma}$-PGA)는 청국장이 발효할 때 생성되는 점질성 물질의 하나로, monomer glutamic acid의 ${\alpha}$-아미노기와 ${\gamma}$-카르복실기 사이의 amide linkage에 의해 결합된 D(-)와 L(-) glutamic acid repeat units로 이루어진 homopolymer이다. 주로 Bacillus sp.에 의해 생산된다. ${\gamma}$-PGA는 수용성, 음이온성, 무독성, 생분해성, 생체적 합성, 식용 등의 다양한 특성을 가지고 있기 때문에 여러 분야에서 응용되고 있다. 본 실험에서 ${\gamma}$-PGA를 생산하는 균주를 우리나라의 전통발효식품인 청국장으로부터 분리하였다. 분리균주의 형태 및 배양학적, 생리학적 특성, API kit 및 16S rRNA 서열을 사용하여 동정한 결과, 분리균주 GS-2는 B. subtilis와 가장 유사하여 B. subtilis GS-2로 명명하였다. 분리 정제된 ${\gamma}$-PGA의 동정은 TLC, HPLC, FTIR 그리고 $^1H$-NMR spectroscopy를 통하여 확인하였다.

• 한국미생물·생명공학회지
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• 제30권2호
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• pp.142-150
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• 2002

Cholesterol oxidase(EC 1.1.3.6)는 cholesterol을 산화 또는 이성화시키는 효소로, 혈중 cholesterol 측정 등의 임상진단용 시약에 이용되고 있으며, 여러 종류의 미생물에서 분리, 연구되어 왔다. 현재에는 농업 및 식품 등에도 응용이 기대되고 있는 매우 유용한 효소이다. 본 실험은 공시균인 Streptomyces polychromogenes IFO 13072의 효소 생산 조건과 cholesterol oxidase의 정제 및 효소학적 특성을 조사하였다. 효소 생산 조건을 검토한 결과, 탄소원으로 1% dextrin, 유기 질소원으로는 0.5% casamino acid, 무기 질소원으로는 0.5% sodium nitrate가 효소생산에 우수하였으며, 이들 탄소원, 질소원 이외 0.1% $KH_2$$PO_4$, 0.05% $MgSO_4$ㆍ$7H_2$O가 함유된 배지를 생산 최적 배지로 사용하였다. 본 효소의 정제는 30-80% 포화의 ($NH_4$)$_2$$SO_4$ 침전 및 cholesterol affinity column chromatography를 통하여 23.2%의 수율로 정제되었다. 정제된 효소는 SDS-PAGE에서 단일한 밴드를 보였으며, 분자량은 약 52,000 Da으로 추정되었다. 본 효소의 특성을 검토한 결과, 최적 온도와 최적 pH는 각각 $37^{\circ}C$, pH 7.0이었으며, 효소의 안정성은 온도 $25^{\circ}C$, pH 6.0~7.0의 범위까지 안정한 것으로 나타났다. 또한 본 효소는 금속이온으로 Hg와 Fe 이온의 존재시 크게 저해를 받았고, dithiothreitol과 mercaptoethanol, Isonicotinic acid와 같은 저해제에 의해서 상당히 실활 되었다. 본 cholesterol oxidase의 Michaelis 상수는 cholesterol을 기질로 하여 Lineweaver-Burk plot 분석에서 25 mM로 추산되었다

• Journal of Microbiology and Biotechnology
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• 제25권12호
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• pp.2125-2134
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• 2015

IrrE is a highly conserved global regulator in the Deinococcus genus and contributes to survival from high doses of UV radiation, ionizing radiation, and desiccation. Drad-IrrE and Dgob-IrrE from Deinococcus radiodurans and Deinococcus gobiensis I-0 each share 66% sequence identity. However, Dgob-IrrE showed a stronger protection phenotype against UV radiation than Drad-IrrE in the D. radiodurans irrE-deletion mutant (ΔirrE), which may be due to amino acid residues differences around the DNA-binding HTH domain. Site-directed mutagenesis was used to generate a Drad-IrrE A184S single mutant, which has been characterized and compared with the ΔirrE mutant complemented strain with Drad-irrE, designated ΔirrE-E. The effects of the A184S mutation following UV radiation and mitomycin C (MMC) shock were determined. The A184S mutant displayed significantly increased resistance to UV radiation and MMC shock. The corresponding A184 site in Dgob-IrrE was inversely mutated, generating the S131A mutant, which exhibited a loss of resistance against UV radiation, MMC shock, and desiccation. qPCR analysis revealed that critical genes in the DNA repair system, such as recA, pprA, uvrA, and ddrB, were remarkably induced after UV radiation and MMC shock in the ΔirrE-IE and A184S mutants. These data suggested that A184S improves the ability against UV radiation and MMC shock, providing new insights into the modification of IrrE. We speculated that the serine residue may determine the efficiency of DNA binding, leading to the increased expression of IrrE-dependent genes important for protection against DNA damage.

• 한국안광학회지
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• 제18권4호
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• pp.473-479
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• 2013

목적: 스마트폰 시청과 알코올 섭취에 따른 눈의 변화와 상관관계를 알아보고자 하였다. 방법: 안질환, 정신질환, 전신질환 그리고 알코올 대사에 관련된 약물복용의 병력이 없는 평소 건전한 음주습관을 가진 대상자 31명(남 18명, 여 13명)을 굴절검사, 각막곡률반경, 안압측정, 각막두께를 측정하고 분석하였다. 결과: 스마트폰 시청에 따른 호흡 중 혈중 알코올의 농도 변화는 15분, 30분, 45분, 60분 그리고 회복기에서 유의하게 감소하였다(p<0.01, p<0.001). 알코올 섭취 후 스마트폰 시청 전과 시청 후, 굴절검사 비교 결과 원주굴절력과 축에서 유의한 변화가 있었다(p=0.005, p=0.001). 알코올 섭취 후 스마트폰 시청에 따른 안압의 변화는 30분부터 유의하게 감소하였으며(p<0.001), 알코올을 섭취 한 상태에서 경과시간에 따른 스마트폰 시청은 각막두께에 유의한 변화를 주지 않았다. 결론: 스마트폰 시청과 알코올 섭취는 원주굴절력과 축 그리고 안압에 유의한 변화를 보인다. 시기능 피로를 초래할 수 있는 스마트폰 시청 및 알코올 섭취는 굴절검사 전 반드시 고려해야 할 요인이다.

• Journal of Microbiology and Biotechnology
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• 제22권11호
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• pp.1532-1539
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• 2012

The ${\alpha}$-galactosidase-coding gene agaAJB13 was cloned from Sphingomonas sp. JB13 showing 16S rDNA (1,343 bp) identities of ${\leq}97.2%$ with other identified Sphingomonas strains. agaAJB13 (2,217 bp; 64.9% GC content) encodes a 738-residue polypeptide (AgaAJB13) with a calculated mass of 82.3 kDa. AgaAJB13 showed the highest identity of 61.4% with the putative glycosyl hydrolase family 36 ${\alpha}$-galactosidase from Granulicella mallensis MP5ACTX8 (EFI56085). AgaAJB13 also showed <37% identities with reported protease-resistant or Sphingomonas ${\alpha}$-galactosidases. A sequence analysis revealed different catalytic motifs between reported Sphingomonas ${\alpha}$-galactosidases (KXD and RXXXD) and AgaAJB13 (KWD and SDXXDXXXR). Recombinant AgaAJB13 (rAgaAJB13) was expressed in Escherichia coli BL21 (DE3). The purified rAgaAJB13 was characterized using p-nitrophenyl-${\alpha}$-D-galactopyranoside as the substrate and showed an apparent optimum at pH 5.0 and $60^{\circ}C$ and strong resistance to trypsin and proteinase K digestion. Compared with reported proteaseresistant ${\alpha}$-galactosidases showing thermolability at $50^{\circ}C$ or $60^{\circ}C$ and specific activities of <71 U/mg with or without protease treatments, rAgaAJB13 exhibited a better thermal stability (half-life of >60 min at $60^{\circ}C$) and higher specific activities (225.0-256.5 U/mg). These sequence and enzymatic properties suggest AgaAJB13 is the first identified and characterized Sphingomonas ${\alpha}$-galactosidase, and shows novel protease resistance with a potential value for basic research and industrial applications.

• Journal of Microbiology and Biotechnology
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• 제23권11호
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• pp.1500-1508
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• 2013

Ebosin, a novel exopolysaccharide produced by Streptomyces sp. 139, has obvious antirheumatic arthritis activity in vivo, and its biosynthesis gene cluster (ste), consisting of 27 open reading frames, has been identified. This paper reports our study of the gene functionality of ste8, the predicted protein product of which is homologous to some bacterial chain length determinant Wzz proteins. For characterization of Ste8, ste8 was cloned and expressed in the mutant strain E. coli 086:H2 (${\Delta}wzz$). The functional complementation of wzz by ste8 was demonstrated by the restoration of wild-type lipopolysaccharide biosynthesis and increased levels of serum resistance of E. coli 086:H2 (${\Delta}wzz$) (pET30a-ste8). To examine the function of ste8 in ebosin biosynthesis, the gene was knocked out with a double crossover via homologous recombination. The molecular weight of the ebosin derivative EPS-8m produced by the mutant Streptomyces sp. 139 ($ste8^-$) was much lower than that of ebosin, and the binding activity of EPS-8m for IL-1R decreased significantly compared with ebosin. These results demonstrate that ste8 encodes a chain length determinant (Wzz) that functions in ebosin biosynthesis.

• 한국약용작물학회지
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• 제15권5호
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• pp.339-345
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• 2007

Field performance and morphological characterization was conducted on seven transgenic lines of Codonopsis lanceolata expressing ${\gamma}-TMT$ gene. The shoots were obtained from leaf explants after co-cultivation with Agrobacterium tume-faciens strain LBA 4404 harboring a binary vector pYBI 121 that carried genes encoding ${\gamma}-Tocopherol$ methyltransferase gene (${\gamma}-TMT$) and a neomycin phosphotransferase II gene (npt II) for kanamycin resistance. The transgenic plants were transferred to a green house for acclimation. Integration of T-DNA into the $T_0\;and\;T_1$ generation of transgenic Codonopsis lanceolata genome was confirmed by the polymerase chain reaction and southern blot analysis. The progenies of transgenic plants showed phenotypic differences within the different lines and with relative to control plants. When grown in field, the transgenic plants in general exhibited increased fertility, significant improvement in the shoot weight, root weight, shoot height and rachis length with relation to the control plants. However, all seven independently derived transgenic lines produced normal flower with respect to its shape, size, color and seeds number at its maturity. Indicating that the addition of a selectable marker gene in the plant genome does not effect on seed germination and agronomic performance of transgenic Codonopsis lanceolata. $T_1$ progenies of these plants were obtained and evaluated together with control plant in a field experiment. Overall, the agronomic performance of $T_1$ progenies of transgenic Codonopsis lanceolata showed superior to that of the seed derived non-transgenic plant. In this study, we report on the morphological variation and agronomic performance of transgenic Codonopsis lanceolata developed by Agrobacterium transformation.

• 미생물학회지
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• 제41권2호
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• pp.152-156
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• 2005

신생아의 분변에서 분리한 Pediococcus acidilacti GMB7330은 내산성(pH 2-3) 및 내담즙성$(1.0\%)$을 가지며 Helicobacter pylori에 대해 항균 활성을 나타내었다. P. acidilactici GMB7330의 H. pylori에 대한 저해 특성을 H. Pylori의 균수와 urease 활성 변화, 그리고 전자현미경을 이용한 세포구조 파괴를 관찰하므로써 조사하였다. P. acidilactici GMB 7330의 배양여액(pH 4.5)은 배양 24시간만에 H. pylori의 중식을 약 4 log 감소시켰다. 이때 P. acidilactici GMB7330의 배양여액의 pH를 중성으로 조절하였을 경우에는 pH 4.5의 경우보다 항균력이 다소 감소하기는 하였으나 완전히 소실되지는 않았다. 뿐만 아니라, P. acidilactici GMB7330과 유사한 농도의 젖산을 생성하는 유산균주 Lactobacillus sp. GM7311의 경우 H. pylori에 대해서 항균력을 나타내지 않는 것으로 미루어 P. acidilactici GMB7330의 항균 활성에는 배양 중 생성된 젖산 이외의 물질이 관여하는 것으로 관찰되었다. 또한 P. acidilactici GMB7330은 pH값에 관계없이 H. pylori의 urease 활성을 $50\%$이상 감소시켰으며, P. acidilactici GMB7330의 배양여액을 처리한 H. pylori 균주는 세포벽 구조의 파괴로 인한 세포 내부물질의 유출이 관찰되었다.

• Asian Pacific Journal of Cancer Prevention
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• 제16권18호
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• pp.8281-8285
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• 2016

Background: Helicobacter pylori is a cause of chronic gastritis, peptic ulcer disease, and gastric malignancy, infection being a serious health problem in Thailand. Recently, clarithromycin resistant H. pylori strains represent the main cause of treatment failure. Therefore this study aimed to determine the prevalence and pattern of H. pylori resistance to clarithromycin in Suranaree University of Technology Hospital, Suranree University of Technology, Nakhon Ratchasima, Northeastern Thailand, Nakhon Ratchasima province, northeast of Thailand. Materials and Methods: This hospital-based cross-sectional study was carried out between June 2014 and February 2015 with 300 infected patients interviewed and from whom gastric mucosa specimens were collected and proven positive by histology. The gastric mucosa specimens were tested for H. pylori and clarithromycin resistance by 23S ribosomal RNA point mutations analysis using real-time polymerase chain reactions. Correlation of eradication rates with patterns of mutation were analyzed by chi-square test. Results: Of 300 infected patients, the majority were aged between 47-61 years (31.6%), female (52.3%), with monthly income between 10,000-15,000 Baht (57%), and had a history of alcohol drinking (59.3%). Patient symptoms were abdominal pain (48.6%), followed by iron deficiency anemia (35.3%). Papaya salad consumption (40.3%) was a possible risk factor for H. pylori infection. The prevalence of H. pylori strains resistant to clarithromycin was 76.2%. Among clarithromycin-resistant strains tested, all were due to the A2144G point mutation in the 23S rRNA gene. Among mutations group, wild type genotype, mutant strain mixed wild type and mutant genotype were 23.8%, 35.7% and 40.5% respectively. With the clarithromycin-based triple therapy regimen, the efficacy decreased by 70% for H. pylori eradication (P<0.01). Conclusions: Recent results indicate a high rate of H. pylori resistance to clarithromycin. Mixed of wild type and mutant genotype is the most common mutant genotype in Nakhon Ratchasima province, therefore the use of clarithromycin-based triple therapy an not advisable as an empiric first-line regimen for H. pylori eradication in northeast region of Thailand.