상변화 메모리 기술

납본여부: 납본

(Ge1Sb2Te4)₁-x(Sn1Bi2Te4)x 칼코겐 합금의 결정화 기구 및 상변화 메모리 거동

학위논문(박사) --서울대학교 대학원 :재료공학부,2007.Docto

Bacillus subtillis의 섬유소 분해효소의 domain 구조와 proteolysis

학위논문(박사) - 한국과학기술원 : 생물공학과, 1993.8, [ xi, 122 p. ]The proteolysis of endo-$\beta$-1,4-glucanse (endoglucanase) in Bacillus megaterium and the study of cellulose binding domain were performed in this study. An endoglucanase gene of Bacillus subtilis was cloned previously from B. subtilis BSE616 in E. coli in our laboratory. Also, we have transferred this gene in B. megaterium ATCC 14945 which was cellulolytic negative strain. This intact endoglucanase (52kD) secreted into the culture medium was gradually cleaved to truncated form (33 kD) by extracellular protease. The intact endoglucanase, truncated endoglucanase and extracellular protease were purified to certify the proteolysis and domain structure. The extracellular protease was purified by Q-Sepharose, Sephadex and Hydroxyapatite chromatography. The molecular weight of the purified extracellular protease was 38 kD. The protease showed maximal activity at 55$^\circ$C and at pH 7.5. The protease that requires $Ca^{++}$ for its activity was metal protease. The intact endoglucanase was purified by affinity towards insoluble cellulose and Mono-Q Chromatography. The truncated endoglucanase was purified by gel filtration and chromatofocusing. The cleavage of the intact endoglucanase was investigated by using immunoblotting and reaction with purified extracellular protease. The secreted form of endoglucanase was 52 kD at early log phase, and this enzyme was further turther into the smallest form (33kd) by the extracellular protease.silmilar results were obtained with chymotrypsin and trypsin.from the N-terminal sequencing data, it was concluded that direction of cieavage is from C-terminus. The molecular activities of these enzymes towards the soluble substrayes were identical. However, the insolube substrate, Avicel, was hydrolyzed slowly by the intact endgoglucanase on the other hand the truncated endolucanase did not hydrolyze the Avicel. Isoelectric points (pI) of the intact and truncated endoglucanase were 6.2 and 5.6, respectively. Optimum pH and temperature ...한국과학기술원 : 생물공학과

Escherichia coli 에서의 bacillus subtilis 균의 cellulase 유전인자의 molecular cloning 과 발현

학위논문(석사) - 한국과학기술원 : 생물공학과, 1985.2, [ viii, 53 p. ]Cellulase gene of Bacillus subtilis was cloned in Escherchia coli as a primary step of cloning the same gene in cells of alcohol producing organisms such as Zymomonas strains to let them ferment cellulosic materials into ethanol. The chromosomal DNA isolated from B.subtilis was partially digested with Hind III and ligated to the plasmid pBR 325 which was digested with Hind III and dephosphorylated with BAP. The ligated DNA was transformed into competent E.coli JM 83 cells and selected transformants showing cellulase activity by Congo-Red tests. Around 38,000 colonies were appeared on the selection media having ampicillin and chloramphenicol indicating the colonies are transformants. These transformed colonies were tooth-picked and transferred on LB agar containing 0.5\% of carboxy methyl cellulose (CMC) followed by Congo-Red tests. Among the 38,000 transformants tested only one colony, the 7324thly picked colony, showed clear halo indicating the transformant contains cellulase gene (CMCase gene). The new hybrid plasmid containing CMCase gene was designated as pDH 73. The plasmid pDH73 maintained stably in E.coli and expressed well for the production of CMCase of both intra- and extra-cellular types constitutively. The ratio of the two types was 9 to 1 with advantage to the intra-cellular CMCase. Although the CMCase activity of extra-cellular type was only one tenth of the total activity it may be concluded that the pDH73 contains DNA sequences which code for the secretion of CMCase out of the cell. It is of interest that the pDH 73 can not be digested by restriction endonucleases even with Hind III which was used to transfer CMCase gene on it. Several other resriction endonucleases were tried without success. Further studies to clarify this phenomenon should be followed.한국과학기술원 : 생물공학과