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세균의 Methienyl-tRNA Synthetase를 저해하는 새로운 항생물질의 스크리닝
곽진환(Jin Hwan Kwak),조영준(Young Jun Cho),송난규(Nan Kyu Song) 대한약학회 2001 약학회지 Vol.45 No.3
Aminoacyl Trna synthetase of bacteria are known as potential targets for new anti- microbial agents. To isolate new inhibitors of bacterial methionyl-Trna synthetases from natural sources, a new target-oriented screening system using whole cells which are over-expressing a target enryme was developed. Approximately 8,000 culture broths of microorganisms from soils were teated by this screening system. Among them, ten culture broths was found to contain inhibitory activity against methionyl-Trna synthetases of Escherichia coli. For the validation of the screening system, this new method was compared with in vitro enzymatic method. Seven out of 10 culture broths showed inhibitory activity against methionyl-Trna synthetases of E. coli This result showed that the new screening system was comparable to the enzyme assay. Thus we believe that our screening system as a new method can be applied for the soreening of new antibiotics inhibiting bacterial methionyl-tRNA synthetases from natural products.
곽진환(Jin Hwan Kwak),신성희(Sunghee Shin),임희대(Hee-Dae Lim) 한국전지학회 2021 한국전지학회지 Vol.1 No.1
마그네슘 이차전지는 금속 표면에서 이온부동피막이 쉽게 형성되기 때문에 에테르계열의 유기 전해질의 사용이 제한적이었다. 본 연구에서는 마그네슘 금속 표면에 이온 전도성 막을 형성하는 연구로써, 60℃의 온화한 온도에서 승화된 아이오딘과 마그네슘을 직접 반응시켜 MgI₂ 막을 형성하였다. 표면 분석을 통해 마그네슘과 아이오딘 사이의 화학 결합을 증명하였으며, 그 결과 에테르 기반 전해질에서 낮은 계면 저항 및 우수한 전기화학 특성을 보였다. Rechargeable Mg metal batteries have been limitedly developed because Mg surface is prone to form ion-insulating layers in contacting with ether-based electrolytes. In this study, artificial MgI₂ layer could be form on the surface by directly reacting Mg metal and iodine at a mild temperature of 60℃. Formation of MgI₂ on the surface was clearly demonstrated by various analysis. As a result, significantly reduced interfacial resistance was observed in contacting with Mg(TFSI)₂-DEGDME electrolyte, which results in the improved electrochemical performances.
토양균의 α-amylase 저해제 검색 및 분리에 관한 연구(제1보) : Streptomyces DMC -225 균주의 저해 성분의 분리 및 작용
곽진환(Jin Hwan Kwak),서병석(Byung Suk Su),최응칠(Eung Chil Choi),김병각(Byong Kak Kim) 한국생약학회 1985 생약학회지 Vol.16 No.1
To find amylase inhibitors produced by microorganisms from soils, a strain which had a strong inhibitory activity against bacterial α-amylase was isolated from the soil sample collected in Seoul. The morphological and physiological characteristics of this strain on several media and its utilization of carban sources showed that it was one of Streptomyces species according to the International Streptomyces Project method. The amylase inhibitor of this strain was purified by means of acetone precipitation, adsorption on Amberlite XAD-2, and column chromatography on Amberlite CG-50 and SP-sephadex C-25. The inhibitor was stable at the pH range of 1-10 and at 100℃ for half an hour, and had inhibitory activities against other amylases such as salivary α-amylase, pancreatic α-amylase, fungal α-amylase and glucoamylase.The kinetic studies of the inhibitor showed that its inhibitory effect on starch hydrolysis by α-amylase was non-competitive.
새로운 Fluoronaphthyridinone계 항균제 DW286의 그람 양성세균에 대한 항균 활성
곽진환(Jin-Hwan Kwak),박희수(Hee Soo Park),정성지(Sung Ji Jung),정지웅(Ji-Woong Jeong),김요셉(Joseph Kim),최동락(Dong-Rack Choi),최응칠(Eung-Chil Choi) 대한약학회 2012 약학회지 Vol.56 No.5
In vitro antibacterial activity of DW286 was tested against recently collected clinical isolates of Gram-positive strains by the two fold agar dilution method. In vivo activity of DW286 was also determined against systemic infections in mice caused by Staphylococcus aureus. DW286 showed 16~64-fold more potent in vitro activities than ciprofloxacin against Gram-positive bacteria. Against systemic infection model caused by two S. aureus strains, one being methicillin-susceptible and the other methicillin-resistant, DW286 (ED50s, 0.16 mg/kg and 4.36 mg/kg, respectively) was more potent than gemifloxacin (1.37 mg/kg, 26.58 mg/kg, respectively).
곽진환(Jin Hwan Kwak),김일혁(Il Hyuk Kim) 한국생약학회 1974 생약학회지 Vol.5 No.3
Experiments were carried out to evaluate the anti-inflammatory activity of Caragana chamlagu LAMARCK roots, which was known to be effective as antineuralgic, antirheumatic and antiarthritic, etc. in the folk cures of this country. The ether extract of the root has shown significant effects against the rat paw edema induced by 1% carrageenin and its potency was comparable with acetylsalicylic acid, a anti-inflammatory drug, when given orally in 5% acacia gum suspension. The ethanol and hexane extracts, on the other hand, stimulated the formation of rat paw edema under the same experimentation.
세균의 지방산 생합성 효소 (Enoyl-Acyl Carrier Protein Reductase, Fabl)를 저해하는 새로운 항균물질의 스크리닝
곽진환(Jin Hwan Kwak) 大韓藥學會 2002 약학회지 Vol.46 No.1
Enoyl-Acyl Carrier Protein Reductase (Fabl) of bacteria is known as an important target for new antibacterial drugs and plays a determinant role in completing cycles of elongation in type-ll tatty acid synthase system. In this study; a fabI gene from Staphylococcus aureus 6538p was cloned in Pet-l4b vector and Fabl protein was over-produced in Escherichia coli BL2l (DE3). NH2-terminal His-tagged Fabl protein was purified by nickel-nitrilotriacetic acid (Ni-NTA) metal- affinity chromatography. Purified 6xHis-tagged Fabl showed a catalytic activity on trans-2-octenoyl-N-acetylcysteamine by utilizing NADPH as a cofactor. For the discovery of new Fabl inhibitors from chemical libraries, a target-oriented screening system using a 96-well plate was developed. About 10,000 chemical libraries from Korea Chemical Bank were tested in this screening system, and 26 chemicals (0.25%) among them showed an inhibitory activity against Fabl enzyme. This result showed that a new screening system can be used for the discovery of new Fabl inhibitors.
Bacillus licheniformis EMR-1에서의 MLS 유도내성 기전 -erm K의 크로닝-
최응칠,곽진환,B.와이스브럼,Choi, Eung-Chil,Kwak, Jin-Hwan,Weisblum, Bernard 대한약학회 1988 약학회지 Vol.32 No.4
Inducible MLS resistance gene of Bacillus licheniformis specified by erm K was subcloned in Bacillus subtilis and the DNA sequence corresponding to its control region was determined. The determinant erm K was in Pvu II=Hind III fragment, which was 1.3 kb. The leader region is capable of forming a complex series of inverted complementary repeat sequences (ICRS) centering on at least six axes of symmetry, some of them mutually exclusive, in a way that resulted ultimately in post-transcriptional unmasking of the ribosome loading site for methylase synthesis.