• IMMUNE NETWORK
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• v.2 no.2
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• pp.72-78
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• 2002

Background: The precise mechanism by which CTLA-4 regulates T cell immune responses is still not fully understood. Previously we proposed that CTLA-4 could downregulate T cell function by modulating a signaling cascade initiated from the T cell receptor complex. The evidence for this notion comes from our findings that CTLA-4 associated with the T cell receptor zeta (TCR zeta) chain, and hence regulated TCR zeta phosphorylation by co-associated SHP-2 tyrosine phosphatase (1). In this report, we investigated whether any other signaling molecules could be involved in the CTLA-4 signaling pathway. Methods: We have taken biochemical approaches, such as immunoprecipitation followed by autoradiography or immunoblotting, to identify the molecules associated with CTLA-4. To perform these assays, we used activated primary T cells and ectopically transfected 293 cells. Various truncation mutants of CTLA-4 were used to map the interaction site on CTLA-4. Results: We found that in addition to TCR zeta and SHP-2, a recently cloned small adaptor molecule, SAP (SLAM-associated protein), was also able to associate with CTLA-4. We identified the domain of SAP association in CTLA-4 being a motif involving GVYVKM. This motif has been previously found to bind SHP-2 through its phosphorylated tyrosine interaction with SH-2 domain of SHP-2. Indeed, co-expression of SAP and SHP-2 reduced their binding to CTLA-4 significantly, suggesting that SAP and SHP-2 compete for the common binding site, GVYVKM. Thus, by blocking SHP-2 recruitment SAP could function as a negative regulator of CTLA-4. Conclusion: Taken together, our data suggest the existence of complicate signaling cascade in regulating CTLA-4 function, and further provide evidence that SAP can act either as a positive or negative regulator depending on the nature of the associating receptors.

• Korean Journal of Environmental Agriculture
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• v.2 no.2
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• pp.59-64
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• 1983

A study was undertaken to investigate the persistence of 2,4-D and MCPP in two different Suweon soils under field conditions. MCPP was extracted from soil with aqueous calcium hydroxide solution and then derivatized to pentafluorobenzyl ester to enhance the electron capture sensitivity. Total recovery of MCPP from soil was 85.6% and the detection limit for 20g sample was 0.02 ppm. Ethyl ester of 2,4-D applied to soil was rapidly hydrolysed to 2,4-D with the half-life of less than 1 day. Half-life of total 2,4-D ethyl ester, including 2,4-D, incorporated into soils at a rate of 0.045 ㎏ a.i./10a was $4{\sim}7$ days and that of under laboratory conditions was $7{\sim}8$ days. Half-life of MCPP applied at a rate of 0.25㎏ a.i./10a under field conditions was $9{\sim}12$ days and that of under laboratory conditions was $12{\sim}23$ days.

• Journal of Microbiology and Biotechnology
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• v.27 no.7
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• pp.1281-1287
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• 2017

Bone morphogenetic protein-4 (BMP-4) is considered to have therapeutic potential for various diseases, including cancers; however, the high expression of biologically active recombinant human BMP-4 (rhBMP-4) needed for its manufacture for therapeutic purposes has yet to be established. In the current study, we established a recombinant Chinese hamster ovary (rCHO) cell line overexpressing rhBMP-4 as well as a production process using 7.5-l bioreactor (5 L working volume). The expression of the mature rhBMP-4 was significantly enhanced by recombinant furin expression. The combination of a chemically defined medium and a nutrient supplement solution for high expression of rhBMP-4 was selected and used for bioreactor cultures. The 11-day fed-batch cultures of the established rhBMP-4-expressing rCHO cells in the 7.5-L bioreactor produced approximately 32 mg/l of rhBMP-4. The mature rhBMP-4 was purified to homogeneity from the culture supernatant using a two-step chromatographic procedure, resulting in a recovery rate of approximately 55% and a protein purity greater than 95%. The N-terminal amino acid sequences and N-linked glycosylation of the purified rhBMP-4 were confirmed by N-terminal sequencing and de-N-glycosylation analysis, respectively. The mature purified rhBMP-4 has been proved to be functionally active, with an effective dose concentration of $EC_{50}$ of 2.93 ng/ml.

• Bulletin of the Korean Chemical Society
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• v.24 no.12
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• pp.1737-1741
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• 2003

Azo-functionalized calix[4]arenes as ionophores for chloride-selective electrode, 5,11,17,23-Tetra-tert-butyl-25,27-bis[(N,N-dimethyl-aniline-azo-phenylthioureido)ethyl]oxy-26,28-dihydroxycalix[4]arene (4a) and 5,11,17,23-Tetra-tert-butyl-25,27-bis[(N,N-dimethyl-aniline-azo-phenylthioureido)ethyl]oxy-26,28-dimethoxycalix[4]arene (4b) were synthesized. The PVC membrane electrode based on azo-functionalized calix[4]arene 4a with o-NPOE exhibits a linear stable response over a wide concentration range ($1.5{\times}10^{-4}-1.0{\times}10^{-1}$) with a slope of -52.0 mV/decade and a detection limit of log[$Cl^-$] = -4.02. This ionophore-based membrane exhibited improved selectivity for chloride anion compared with classical Hofmeister series.

• Animal cells and systems
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• v.9 no.4
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• pp.239-244
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• 2005

A cDNA clone for a wound- and pathogen-induced gene in Chinese cabbage (Brassica rapa subsp. pekinensis) was isolated and characterized. The cabbage gene, designated BrPR4, encodes a pathogenesis-related protein 4 (PR4) of 140 amino acids. The BrPR4 protein shows high similarity with wound-inducible antifungal proteins of tobacco, potato, barley, and wheat. The BrPR4 gene is locally induced by a nonhost pathogen, Pseudomonas syringae pv. tomato, that elicits a hypersensitive response in Chinese cabbage. Treatment of the cabbage leaves with benzothiadiazole (BTH), methyl jasmonate or ethephon showed that the BrPR4 gene expression is strongly induced by ethylene, but not by methyl jasmonate or BTH. The BrPR4 gene is also activated by wounding. Interestingly, however, the wound-inducible BrPR4 gene expression is repressed by salicylic acid or BTH, suggesting that there is cross-talk between salicylate-dependent and -independent signaling pathways.

• Korean Journal of Materials Research
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• v.18 no.1
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• pp.26-31
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• 2008

The dc resistivity and thermoelectric power of bilayered perovskite $La_{1.4}(Sr_{0.2}Ca_{1.4})Mn_2O_7$ were measured as a function of the temperature. In the ferromagnetic phase, ${\rho}(T)$ was accurately predicted by $a_0+a_2T^2+a_{4.5}T^{4.5}$ with and without an applied field. At high temperatures, a significant difference between the activation energy deduced from the electrical resistivity and thermoelectric power, a characteristic of small polarons, was observed. All of the experimental data can be feasibly explained on the basis of the small polaron.

• Korean Journal of Plant Taxonomy
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• v.49 no.2
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• pp.127-139
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• 2019

The purported four hybrid origins of Asplenium in Korea were tested based on morphological, cytological and DNA sequence data. Asplenium castaneo-viride, A. ${\times}$ uiryeongse, A. ${\times}$ montanus, and A. ${\times}$ kitazawae share several morphological characteristics with the Asian walking fern A. ruprechtii and related taxa as parents and show a sympatric distribution with the putative parents, raising the possibility of hybrid origins: A. castaneo-viride (A. ruprechtii and A. incisum), A. ${\times}$ uiryeongse (A. ruprechtii and A. pekinense), A. ${\times}$ montanus (A. ruprechtii, A. trichomanes, and A. incisum), and A. ${\times}$ kitazawae (A. ruprechtii and A. sarelii). We investigated flow cytometry and chloroplast DNA sequence data (rbcL, rps4-trnS, and rps4-trnS intergenic spacer) to clarify the hybridization and origin of each hybrid. In the flow cytometry analyses, A. ruprechtii shows diploid (2x) only, whereas A. castaneo-viride (3x, 4x), A. ${\times}$ uiryeongse (3x), A. ${\times}$ montanus (3x, 4x), and A. ${\times}$ kitazawae (2x, 4x) exhibit polyploidy, suggesting hybrid events along speciation. The rbcL and rps4-trnS and rps4-trnS intergenic spacer data suggest that A. ruprechtii is one the maternal ancestors of all four hybrids. In addition, the rps4-trnS and rps4-trnS intergenic spacer data indicate that A. incisum is also the maternal ancestor of A. ${\times}$ kitazawae and A. ${\times}$ montanus, proposing multiple hybridization events for these two hybrids. In A. ${\times}$ montanus, morphological features such as the leaf forms and sympatric distributions of the species also support the multimaternal hypothesis, but the morphological features of A. ${\times}$ kitazawae must be examined with consideration of hybrid events. To clarify the complex hybrid evolutionary lineages of the four Asplenium hybrids, further research with taxon sampling and molecular markers should be conducted.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.12
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• pp.1806-1814
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• 1993

Efficient speech coders using tree coding combined with harmonic scaling are designed at the rate of 4.8 kilobitts/sec (kbps). A time domain harmonic scaling algorithm (TDHS) is used to compress input speech by a factor of two. This process allows the tree coder have 1.5 bits/sample for 4.8 kbps in the case of a 6.4 kHz sampling rate. In the backward adaptive tree coder, there are three components of the code generator, including a hybrid adaptive quantizer, a short-term predictor and a pitch predictor. The robustness of the tree coder is achieved by carefully choosing the input of the short term predictor adaptation. Also, inclusion of a smoother in the pitch predictor improves the error performance of tree coder in the noisy channel. Subjectively, tree coding combined with TDHS provides good quality speech at 4.8 kbps.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.4
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• pp.395-404
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• 2016

A 6-bit 3.4 GS/s flash ADC in a 65 nm CMOS process is reported along with the proposed 4x time-domain interpolation technique which allows the reduction of the number of comparators from the conventional $2^N-1$ to $2^{N-2}$ in a N-bit flash ADC. The proposed scheme effectively achieves a 4x interpolation factor with simple SR-latches without extra clocking and calibration hardware overhead in the interpolated stage where only offset between the $2^{N-2}$ comparators needs to be calibrated. The offset in SR-latches is within ${\pm}0.5$ LSB in the reported ADC under a wide range of process, voltage supply, and temperature (PVT). The design considerations of the proposed technique are detailed in this paper. The prototype achieves 3.4 GS/s with 5.4-bit ENOB at Nyquist and consumes 12.6 mW power at 1 V supply, yielding a Walden FoM of 89 fJ/conversion-step.

• Archives of Metallurgy and Materials
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• v.65 no.4
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• pp.1297-1301
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• 2020

The purpose of this study was to investigate the mechanical properties of beta type aged Ti-4Mo-4Cr-X (X = V, Sn, Zr) quaternary alloy for use as a cardiovascular stent. Titanium (Ti) alloys were fabricated using a vacuum arc remelting furnace process. To homogenize the specimens of each composition and remove the micro segregation, all cast specimens were subjected to homogenization at 850℃ for 4 h, which was 100℃ higher than the β-transus temperature of 750℃. The tensile strength and elongation of the aged Ti-4Mo-4Cr-X (X = V, Sn, Zr) alloys were increased as compared to the homogenized alloys. In addition, many α/β interface boundaries formed after aging treatment at 450℃, which acted as inhibitors of strain and caused an increase in tensile strength. The elongation of Ti-4Mo-4Cr-X alloys consisting of α + β phases after aging treatment was improved by greater than 30%. Results of a potentiodynamic polarization test showed that the lowest current density of Ti-4Mo-4Cr-4Sn with 1.05 × 10^-8 A/cm² was obtained. The present Ti-4Mo-4Cr-X alloys showed better corrosion characteristics as compared to the 316L stainless steel and L605 (Co-Cr alloy) cardiovascular stent alloys.