• Journal of the Korea Institute of Information Security & Cryptology
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• v.31 no.1
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• pp.83-97
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• 2021

Wireless sensors that make up the Wireless Sensor Network generally have extremely limited power and resources. The wireless sensor enters the sleep state at a certain interval to conserve power. The Sleep deflation attack is a deadly attack that consumes power by preventing wireless sensors from entering the sleep state, but there is no clear countermeasure. Thus, in this paper, using clustering-based binary search tree structure, the Sleep deprivation attack detection model is proposed. The model proposed in this paper utilizes one of the characteristics of both attack sensor nodes and normal sensor nodes which were classified using machine learning. The characteristics used for detection were determined using Long Short-Term Memory, Decision Tree, Support Vector Machine, and K-Nearest Neighbor. Thresholds for judging attack sensor nodes were then learned by applying the SVM. The determined features were used in the proposed algorithm to calculate the values for attack detection, and the threshold for determining the calculated values was derived by applying SVM.Through experiments, the detection model proposed showed a detection rate of 94% when 35% of the total sensor nodes were attack sensor nodes and improvement of up to 26% in power retention.

• 한국생물공학회:학술대회논문집
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• 2005.04a
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• pp.37-37
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• 2005

Human chorionic gonadotropin (hCG) is a heterodimeric glycoprotein hormone consisting of non-covalently linked two subunits, the ${\alpha}$ and ${\beta}$ subunit. It has been used as a infertility drug for ovulation to mimic luteinizing hormone $(LH).^{1)}$ A stable cell line was established by transfection of Rc/CMV-i-dhfr-hCG, expression vector containing hCG ${\alpha}-$ and ${\beta}-genes$, into dihydrofolate reductase-deficient CHO cells and subesquent methotrexate-mediated gene amplification. Anchorage-dependent CHO cells were adapted into a serum-free and/or animal component-free suspension medium through gradual serum weaning for the hCG production. The established cell line showed typical morphological characteristics and growth profile of CHO cells, and could produce FSH with passage-to-passage consistency. The high density perfusion culture of the CHO cells was carried out in Celligen Plus bioreactor equipped with a spin-filter as a internal cell retention device. The cell density reached up to $>1x10^{7}$ cells/ml in less than 7 days and a perfusion-control strategy based on cellular consumption rates of glucose was $established.^{2)}$ Biologically active recombinant hCG was purified by a series of chromatographic steps including anion exchange chromatography and hydrophobic interaction chromatography to homogeneity. The highly purified recombinant hCG was characterized for physicochemical, immunological and biological properties.

• International Journal of Industrial Entomology and Biomaterials
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• v.7 no.2
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• pp.127-131
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• 2003

Protein disulfide isomerase (PDI) found in the endoplasmic reticulum (ER) catalyzes disulfide bond exchange and assists in protein folding of newly synthesized proteins. PDI also functions as a molecular chaperone and has been found to be associated with proteins in the ER. In addition, PDI functions as a subunit of two more complex enzyme systems: the prolyl-4-hydroxylase and the triacylglycerol transfer proteins. A cDNA that encodes protein disulfide isomerase was previously isolated from Bombyx mori (bPDI), in which open reading frame of 494 amino acids contained two PDI-typical thioredoxin active site of WCGHCK and an ER retention signal of the KDEL motif at its C-terminal, and we report its functional characterization here. This putative bPDI cDNA is expressed in insect Sf9 cells as a recombinant proteins using baculovirus expression vector system. The bPDI recombinant proteins are successfully recognized by antirat PDI antibody, and shown to be biologically active in vitro by mediating the oxidative refolding of reduced and scrambled RNase. This suggests that bPDI may play an important role in protein folding mechanism of insects.

• Journal of Microbiology and Biotechnology
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• v.11 no.6
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• pp.915-921
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• 2001

Phytase improves the bioavailability of phytate phosphorus in plant foods to humans and animals, and reduces the phosphorus pollution of animal waste. In order to express a high level of fungal phytase in Saccharomyces cerevisiae, various expression vectors were constructed with different combinations of promoters, translation enhancers, signal peptides, and terminator. Three different promoters fused to the phytase gene (phyA) from Aspergillus niger were tested: a galactokinase (GAL1) promoter, glyceraldehyde-3-phosphate dehydrogenase (GPD) promoter, and yeast hybrid ADH2-GPD promoter consisting of alcohol dehydrogenase II (ADH2) and a GPD promoter. The signal peptides of phytase, glucose oxidase (GO), and rice amylase 1A(RAmy1A) were included. Plus, the translation enhancers of the ${\Omega}$ sequence and UTR70 from the tobacco mosaic virus (TMV) and spinach, respectively, were also tested. Among the recombinant vectors, pGphyA06 containing the GPD promoter, the ${\Omega}$ sequence, RAmy1A, and GAL7 terminator expressed the highest phytase activity in a culture filtrate, which was estimated at 20 IU/ml. An intracellular localization of the expressed phytase activity in a culture filtrate, which was estimated at 20 IU/ml. An intracellular localization of the expressed phytase was also performed by inserting an endoplasmic reticulum (ER) retention signal, KDEL sequence, into the C-terminus of the phytase within the vector pHphyA-6. It appeared that the KDEL sequence directed most of the early expression of phytase into the intracellular compartment yet more than $60\%$ of the total phytase activity was still retained within the cell even after the prolonged (>3 days) incubation of the transformant. However, the intracellular enzyme activity of the transformant without a KDEL sequence was as high as that of the extracellular one, thereby strongly suggesting that the secretion of phytase in S. cerevisiae appeared to be the rate-limiting step for the expression of a large amount of extracellular recombinant phytase, when compared with other yeasts.

• Journal of Life Science
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• v.17 no.8 s.88
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• pp.1129-1134
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• 2007

In the previous our study, a cDNA that encodes protein disulfide isomerase from Bombyx mori (bPDI)was isolated and characterized. bPDI has an open reading frame of 494 amino acids contained two PDI-typical thioredoxin active site of WCGHCK and ER (endoplasmic reticulum) retention signal of the KDEL motif at its C-terminal. Recent studies have demonstrated that misfolded proteins are accumulated in many diseases including Alzheimer’s, goiter, emphysema, and prion infections. bPDI was over-expressed or knock-downed in Sf9 cells to study the relationship between bPDI expression and protections against protein misfolding. bPDI gene was cloned in insect expression vector pIZT/V5-His for over-expression and bPDI double-stranded RNA (dsRNA) was generated for knock-down. Over-expression of bPDI significantly improved survival rate, but bPDI dsRNA transfection significantly reduced survival rate after 48 hours exposure. In mock-transfected or wild-type cells had no significant effect. The results support the view that bPDI is one of the important intracellular components for cell protect mechanism, especially, against ER stress such as protein misfolding.