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        검색결과 10

        6.
        2018.10 구독 인증기관·개인회원 무료
        Avermectin produced by Streptomyces avermitilis is an anti-nematodal agent against the pine wood nematode Bursaphelenchus xylophilus. However, its potential usage is limited by its poor water solubility. For this reason, continuous efforts are underway to produce new derivatives that are more water soluble. Glycosylation is generally used to enhance the aqueous solubility and biological activity of natural compounds. Uridine diphosphate (UDP)-glycosyltransferase (BLC) from Bacillus licheniformis is involved in the biosynthesis of the bioactive compound by transferring UDP-activated sugar moieties to acceptor molecules. Here, the enzymatic glycosylation of avermectin was catalyzed by uridine diphosphate (UDP) glycosyltransferase from Bacillus licheniformis with various UDP-sugars. As a result, the following four avermectin B1a glycosides were produced: avermectin B1a 4’’-β-D-glucoside, avermectin B1a 4’’-β-D-galactoside, avermectin B1a 4’’-β-L-fucoside and avermectin B1a 4’’-β-2-deoxy-D-glucoside. The avermectin B1a glycosides were structurally analyzed based on HR-ESIMS, 1D and 2D nuclear magnetic resonance (NMR) spectra. The solubility of avermectin B1a4’’-β-D-glucoside and avermectin B1a4’’-β-D-galactoside in water are 49 and 21 times higher than that of avermectin B1a. Consistent with the improved water solubility of avermectin glycosides, the anti-nematodal effect of avermectin B1a4’’-β-D-glucoside was found to exhibit the highest activity,which was approximately 32 times greater than that of avermectin B1a, followed by avermectin B1a 4’’-β-2-deoxy-D-glucoside, avermectin B1a 4’’-β-L-fucoside, and avermectin B1a 4’’-β-D-galactoside. These results show that glycosylation of avermectinB1a effectively enhances itsin vitro anti-nematodal activity and that avermectin glycosides can be further applied for treating infestations of the pine wood nematode B. xylophilus.
        7.
        2006.04 구독 인증기관·개인회원 무료
        Development of recycling method at cemented carbide scraps was researched. Some properties of recycled cemented carbides were investigated. Recycled WC fine powder suffered the surface oxidation. Therefore it was necessary to be done by reduction treatment at 1073K-3.6ks under hydrogen atmosphere. When sintering condition at 1673K-3.6ks was treated under vacuum condition, it gained the deflective strength of about 90%, and gained hardness and sintering density about same value compared with commercial alloys. As a result, it was able to recycle only by 7 processes.
        8.
        2023.05 KCI 등재 서비스 종료(열람 제한)
        Climate data were obtained over an eight-year period (July 2013 to June 2021) using an automatic weather observation system (AWS) installed at the foot of Mt. Geumo in Chilgok, Gyeongbuk. Using climate data, the statistical and meteorological characteristics of the local circulation between the Nakdong River and Mt. Geumo were analyzed. This study is based on automatic weather observation system data for Dongyeong, along with comparative climate data from the Korea Meteorological Administration (Chilgok) and the Gumi meteorological observatory. Over the eight- years, mountain and valley winds have occurred 48 times a year on average, with the highest occurring in May and the weakest winds in June and December. When mountain winds occurred, the temperature in the nearby lowland region more strongly decreased than when valley winds blew. However, the potential to use mountain winds to improve urban thermal environments is limited because mountain winds occur infrequently in summer when a drop in nighttime temperature is required.
        9.
        2008.10 KCI 등재 서비스 종료(열람 제한)
        Jatropha (Jatropha curcas L.) is a shrub or tree belonging the genus Euphorbiaceae and is cultivated in a tropical regions including South America, South-East Asia, India and Africa. Jatropha possibly is adapted to grow in a wide range of environments for producing non-edible oils. The objective of the study is to determine effect of salt and drought on plant growth characteristics. Treatments are thus followed, 100 and 200 mM NaCl and 5 and 10% PEG. Various physiological parameters such leaf length and width, stomatal conductance, chlorophyll fluorescence and gene expression were investigated. The results showed that from 2 days onwards, 100 and 200mM NaCl treatments were significantly suppressed leaf length, width, and stomatal conductance, but 5% and 10% PEG treatments showed a similar trend of control plants. Gene expression of JcACBP of the 100 mM NaCl was slightly decreased compred to those of other treatments. These results indicate that 100 and 200 mM NaCl treatments significantly showed negative response, but 5 and 10% PEG treatments improved plant growth and development of Jatropha.
        10.
        2006.04 KCI 등재 서비스 종료(열람 제한)
        The methanolic (MeOH) extract of A. fruticosa bark, which showed immune-regulatory activities, was separated to purify an active compared by means of a multi-stage column chromatography. This resulted in the isolation and characterization of an isoflavone glycoside named 4', 6-Dimethoxyisoflavone-7-O-β-D-glucopyranoside. Immuno-regulatory activities of the crude extract of Amorpha fruticosa LINNE bark were compared with that of an isoflavone glycoside (4', 6-dimethoxyisoflavone-7-O-β-D-glucopyranoside). The crude methanolic extract of A. fruticosa and purified single compound showed 16% of relatively low cytotoxicity at a maximum concentration of 1.0 g/L in cultivated normal human lung cell line (HEL299). Cell growth of human T cells was increased up to 15%, 0.5 g/L of the crude extract added group. This was higher than a single compound added one. On the other hand, specific production rates of IL-6 and TNF-α from T cell were higher in the purified compound treat group (0.82×10-4 pg/cell and 1.08×10-4 pg/cell, respectively), compared to 0.5 g/L of the crude extract added group (0.65×10-4 pg/cell and 0.84×10-4 pg/cell, respectively). In addition, the growth of NK-92MI cells incubated with the crude extract was higher up to 56% over the cells grown with a single compound (0.5 g/L). In overall, the crude extract showed relatively higher immuno-regulatory activities compared with a single compound, probably due to the synergic effect given by other substances existed in the crude extract. Even though the siolated compound stimulated higher secretion of cytokines from human T cells.