• 대한화학회지
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• 제43권6호
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• pp.670-675
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• 1999

Methanopterin의 pteridine부분과 관련있는 구조를 가지는 6-[1-(4-ribityl-anilino)ethyl]-1,3,7-trimethyllumazine (2)를 합성하였다. 4-Ribitylaniline 유도체는 D-ribose와 N-benzoyl-4-bromoaniIine (7)을출발 물질로 하여 여러 단계를 거쳐 합성되었다. 6-Acetyl-1,3,7-trimethyllumazine (4)는 Timmis 반응을 이용하여 4-amino-1,3-dimethyl-5-nitrosouracil (3)과 2,4-pentanedione을 반응시켜 얻을 수 있었다. 화합물 4는 $NaBH_4$에 의한 환원반응과 뒤이은 $SOCl_2$에 의한 염소화반응으로 6-(1-chloroethyl)-1,3,7-trimethyllumazine (6)으로 변환되었다. 화합물 6과 4-(2,3:4,5-di-O-isopropylidene-D-ribityl)aniline (13)의 친핵성 치환반응으로 6-[1-{4-(2,3:4,5-di-O-isopropylidene-D-ribityl)anilino}ethyl]-1,3,7-trimethyllumazine (14)가 합성되었다 목표 화합물 2는 산 촉매하에서 화합물 14를 가수분해하여 얻어졌다.

• BMB Reports
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• 제28권1호
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• pp.72-78
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• 1995

Time-dependent inactivation of E. coli GTP cyclohydrolase I with a 2',3'-dialdehyde derivative of GTP (oGTP) was directed to the active site of the enzyme, and was dependent on the concentration of oGTP. The kinetics of inactivation were biphasic with a rapid reaction occurring immediately upon exposure of the enzyme to oGTP followed by a slow rate of inactivation. The $K_i$ value of oGTP for the enzyme was 0.25 mM. Inactivation was prevented by preincubation of the enzyme with GTP, the substrate of the enzyme. At 100% inactivation, 2.3 mol of [8.5'-$^3H$]oGTP were bound per each enzyme subunit, which consists of two identical polypeptides. The active site residue which reacted with the affinity label was lysine. oGTP interacted selectively with the ${\varepsilon}$-amino group of lysine in the GTP-binding site to form a morpholine-like structure which was stable without sodium borohydride treatment. However, triphosphate group was eliminated during the hydrolysis step. To identify the active site of the enzyme, [8.5'-$^3H$]oGTP-labeled enzyme was cleaved by endoproteinase Lys-C, and the $^3H$-labeled peptide was purified by HPLC. The amino acid sequence of the active site peptide was Pro-Ser-Leu-Ser-Lys, which corresponds to the aminoterminal sequence of the enzyme.

• 공업화학
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• 제8권4호
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• pp.610-616
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• 1997

낙동강에서 채취한 남조류 Microcystis로부터 간독성물질이자 protein phosphatase 1과 2A의 강력한 억제제인 microcystin-LR과 microcystin-RR을 분리하였다. 이들 물질의 독성과 구조와의 관계들을 알아보기 위하여 몇가지 유도체들을 합성하여 독성실험을 하였다. Glu와 MeAsp의 카르복실기를 에스테르화할 경우 독성을 잃어버리는 것을 알 수 있었다. 반면에 Mdha 잔기의 이중결합을 $NaBH_4$로 환원하여 Ala잔기로 전환한 경우에는 독성을 그대로 유지하였고 또한 microcystin-LR의 Arg잔기의 guanidyl기를 dimethylpyrimidyl기로 변환한 경우에도 독성에는 크게 영향을 주지 않는 것을 알 수 있었다. 따라서 2개의 카르복실기는 microcystin이 독성을 나타내는데 아주 중요한 역할을 하는 반면에, Mdha 및 Arg잔기의 존재는 큰 역할을 하지 않는 것으로 여겨진다.

• 상하수도학회지
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• 제21권6호
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• pp.679-687
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• 2007

Nanoscale zero valent ion (nZVI) technology is emerging as an innovative method to treat contaminated groundwater. The activity of nZVI is very high due to their high specific surface area, and supporting this material can help to preserve its chemical nature by inhibiting oxidation. In this study, nZVI particles were attached to granular ion-exchange resin through borohydride reduction of ferrous ions, and chemical reduction of nitrate by this material was investigated as a potential technology to remove nitrate from groundwater. The pore structure and physical characteristics were measured and the change by the adsorption of nZVI was discussed. Batch tests were conducted to characterize the activity of the supported nZVI and the results indicated that the degradation of nitrate appeared to be a pseudo first-order reaction with the observed reaction rate constant of $0.425h^{-1}$ without pH control. The reduction process continued but at a much lower rate with a rate constant of $0.044h^{-1}$, which is likely limited by mass transfer. To assess the effects of other ions commonly found in groundwater, the same experiments were conducted in simulated groundwater with the same level of nitrate. In simulated groundwater, the rate constant was $0.078h^{-1}$ and it also reduced to $0.0021h^{-1}$ in later phase. The major limitation in application of ZVI for nitrate reduction is ammonium production. By using a support material with ion exchange capacity, the problem of ammonium release can be solved. The ammonium was not detected in the batch test, even when other competitive ions such as calcium and potassium existed.

• Membrane and Water Treatment
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• 제8권1호
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• pp.51-71
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• 2017

Antimicrobial polyethersulfone ultrafiltration membranes containing zerovalent iron ($Fe^0$) and magnetite ($Fe_3O_4$) nanoparticles were synthesized via phase inversion method using polyethersulfone (PES) as membrane material and nano-iron as nanoparticle materials. Zerovalent iron nanoparticles (nZVI) were prepared by the reduction of iron ions with borohydride applying an inert atmosphere by using $N_2$ gases. The magnetite nanoparticles (nMag) were prepared via co-precipitation method by adding a base to an aqueous mixture of $Fe^{3+}$ and $Fe^{2+}$ salts. The synthesized nanoparticles were characterized by scanning electron microscopy, X-ray powder diffraction, and dynamic light scattering analysis. Moreover, the properties of the synthesized membranes were characterized by scanning electron microscopy energy dispersive X-ray spectroscopy and atomic force microscopy. The PES membranes containing the nZVI or nMag were examined for antimicrobial characteristics. Moreover, amount of iron run away from the PES composite membranes during the dead-end filtration were tested. The results showed that the permeation flux of the composite membranes was higher than the pristine PES membrane. The membranes containing nano-iron showed good antibacterial activity against gram-negative bacteria (Escherichia coli). The composite membranes can be successfully used for the domestic wastewater filtration to reduce membrane biofouling.

• 대한화학회지
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• 제27권6호
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• pp.434-440
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• 1983

테트라히드로프란 용액에서 수소화붕소나트륨과 붕산트리페닐을 사용해서 카르복시산, 카르복시산염, 3차아미드 및 술폭시드를 환원하는 새로운 방법을 개발하였다. 즉 카르복시산은 실온에서 6~12시간에 정량적으로 환원될 수 있으며, 지방족 카르복시산염은 실온에서 6시간에 정량적으로 환원되나 방향족 산염은 $65^{\circ}C$에서 24시간이 소요되었다. 3차 아미드는 실온에서 3~6시간에 88∼100%의 좋은 수율로 환원되었으며, 조사한 대부분의 술폭시드는 실온에서 1~6시간에 98∼100%의 수율로 환원되었으나, 디페닐술폭시드는 보다 격렬한 조건에서 48시간에 환원할 수 있었다.

• 대한핵의학회지
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• 제28권2호
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• pp.227-233
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• 1994

Irradiation of 20mg of natural $Dy(NO_3)_3$ in a neutron flux of $2{\times}10^{13}n/cm^2$ sec for 4 hours gave 5.76 Ci of $^{165}Dy$(specific activity, 610mCi/mg Dy) with high radionuclidic purity (>99.9 %). $^{165}Dy-MA$ was prepared in a quantitative yield by reacting the aqueous solution of $^{165}Dy(NO_3)_3$ with sodium borohydride solution in 0.2N NaOH. Coulter particle analyzer exhibited mean particle size of $2.6{\mu}m$ (range $1{\sim}6{\mu}m$), Even though the $^{165}Dy-MA$ suspension in saline was stored at $37^{\circ}C$ for 24 hours or autoclaved at $121^{\circ}C$ for 30minutes, there was no significant change in particle size and leakage problem indicating the prepared $^{165}Dy-MA$ is sufficiently stable. In-vivo retention studies were carried out by administering $^{165}Dy-MA$ into the knee joint space of normal rabbits. Gamma camera analysis showed high retention in joint space of normal rabbits. Gamma camera analysis showed high retention in joint space even at 24 hours after administration (> 99.9%). The ease with which the $^{165}Dy-MA$ can be made in the narrow size range and their high invitro and vivo stability make them attractive agents for radiation synovectomy.

• 한국식품과학회지
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• 제20권3호
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• pp.453-458
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• 1988

식품의 가공, 저장 및 조리중 있어서 Maillard 반응으로 용이 하게 생성되는 Maillard 반응생성물과 비투석성 melanoidin의 아질산염 소거작용에 관하여 검토하였는데 그 결과를 요약하면 다음과 같다. 1. Maillard 반응생성물과 비투석성 melanoidin의 아질산염 소거능은 우수한 것으로 나타났다. 2. 반응용액의 pH변화에 따른 아질산염 소거능은 pH1.2에서 가장 켰으며 pH가 증가 할수록 아질산염 소거능은 감소하였다. 3. 환원능을 소실시키고 난 후의 아질산염 소거능은 pH1.2에서 1/2이하로 감소하였다. 4. Maillard반응생성물이 나타내는 아질산염 소거작용에는 melanoidin이 크게 관여하는 것으로 나타났다.

• 한국식품과학회지
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• 제5권4호
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• pp.240-248
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• 1973

1. myo-inositol의 산화(酸化) 생성물(生成物)인 inosose를 환원(還元)하여 ax.- 및 eq.-alcohol에 도달(到達)시켰다. 2. 2-O-(p-hydroxybenzoyl)-myo-inositol [IX], 4-O-(p-hydroxybenzoyl)-myo-inositol [X], O-(p-hydroxybenzoyl)-scyllo-inositol [XX], 그리고 2-O-(p-hydroxybenzoyl)-epi-inositol [XXVI] 등(等) 신화합물(新化合物) 4종(種)을 합성(合成)하였고 이것을 얻기 위하여 합성(合成)한 [V], [VI], [VII], [VIII], [XVIII], [XIX], [XXIV], [XXV] 등(等) 8종(種) 화합물(化合物)도 아직까지의 문헌(文獻)에 기재(記載)가 없는 화합물(化合物)들이다. 3. 여기서 합성(合成)한 ester [IX] [X], [XX], [XXVI] 4종(種)은 모두 항균력(抗菌力)이 나타나며 epi-inositol ester [XXVI] 의 Aspergillus oryzae에 대(對)한 항균력(抗菌力)이 가장 강력(强力)하게 나타난다. 이와 같이 항균력(抗菌力)은 화합물(化合物)의 입체구조(立體構造)와 관련(關聯)되는 것 같다.

• 분석과학
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• 제13권5호
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• pp.636-645
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• 2000

본 연구에서는 GC/MS를 이용하여 수질시료로부터 7종의 유기주석화합물을 분석하는 방법을 연구하였다. Hydrogenation과 ethylation의 반응시의 pH, 반응시간, 반응시약의 농도 등을 변화시켜 최적 반응조건을 조사하였다. n-Hexane을 용매로 사용한 액체-액체 추출 후 hydrogenation에 의한 유기주석염화물의 추출 회수율은 61-112% 범위로 나타났다. 물시료에서 ethylation한 후 n-hexane으로 추출한 경우의 추출 회수율이 74-113% 범위로 나타나 hydrogenation의 경우보다 높은 추출율을 보였다. 또한 ethylation후 styrene-divinylbenzene (SDB) 재질의 disk형의 고체상을 사용하고 추출 용매로 methylene chloride를 사용한 경우 61-97% 범위의 회수율을 나타냈다. Hydrogenation과 ethylation에 의한 검출한계는 각각 0.05-0.5 ng/ml와 0.02-0.05 ng/ml로 나타났다.