• Development and Reproduction
• /
• v.12 no.2
• /
• pp.159-168
• /
• 2008

Nanog is a newly identified member of the homeobox family of DNA binding transcription factors that functions to maintain the undifferentiated state of stem cells. However, molecular mechanisms underlying the function of Nanog remain largely unknown. To elucidate the regulatory roles of Nanog involved in maintenance of P19 embryonal carcinoma (EC) stem cells, we transfected three small interfering RNA (siRNA) duplexes targeted against different regions of the Nanog gene into P19 cells. The Nanog siRNA-100 duplexes effectively decreased the expression of Nanog up to 30.7% compared to other two Nanog siRNAs, the Nanog siRNA-400 (67.9 %) and -793 (53.0%). When examined by RT-PCR and real-time PCR, the expression of markers for pluripotency such as Fgf4, Oct3/4, Rex1, Sox1 and Yes was downregulated at 48 h after transfection with Nanog siRNA-100. Furthermore, expression of the ectodermal markers, Fgf5 and Isl1 was reduced by Nanog knockdown. By contrast, the expression of other markers for pluripotency such as Cripto, Sox2 and Zfp57 was not affected by Nanog knockdown at this time. On the other hand, the expression of Lif/Stat3 pathway molecules and of the endoderm markers including Dab2, Gata4, Gata6 and the germ cell nuclear factor was not changed by Nanog knockdown. The results of this study demonstrated that the knockdown of Nanog expression by RNA interference in P19 cells was sufficient to modulate the expression of pluripotent markers involved in the self-renewal of EC stem cells. These results provide the valuable information on potential downstream targets of Nanog and add to our understanding of the function of Nanog in P19 EC stem cells.

• Korean Journal of Optics and Photonics
• /
• v.7 no.3
• /
• pp.227-231
• /
• 1996

The reflection spectrum of a $2H-PbI_2$ single crystal grown by vapour phase method were measured at 10 K near the fundamental absorption edge. The n= 1,2,3 Wannier exciton series and $A_{EP}$ reflection line were obtained from the reflection spectrum. Based on the 2nd phonon energy in the Raman spectrum, which is different from Nagamune's report, we suggest that $A_{EP}$ line is due to the bound state between the n=2 exciton and the 2nd phonon which surmise that this is LO phnon due to the second Raman process. The L-T splitting energy of n=1 exciton line was 6.56 meV and was consistent with the emission spectrum. The temperature dependence of the reflection spectrum showed that n=1 exciton peak was shifted to longer wavelength while, as the temperatre is raised, the sharpness of that with the increase of the L-T splitting energy decrease. From Wannier exiton series, the exciton binding energy and exciton radius was 30 meV and 14$\AA$, respectively.

• Journal of Korean Society for Atmospheric Environment
• /
• v.15 no.4
• /
• pp.385-392
• /
• 1999

This study was carried out to investigate the constituents of inorganic ions of precipitation in Mokpo and Yeochon area from Jan. 1996 to Dec. 1997. The volume-weighted mean pH of precipitation was 5.7(4.8~7.8) at Mokpo, and 5.6(5.1~7.4) at Yeochon area, respectively. The non-seasalt(nss) anion concentrations were found in order of $nss-SO^{2-}_4>NO^-_3>nss-Cl^-$ at two areas. The portion of $nss-SO^{2-}_4;and;NO^-_3$ was 71~84% out of anions. The the non-seasalt cation concentrations were found in order of $NH^+_4>nss-Ca^{2-}>nss-Mg^{2+}>nss-K^-$ at two areas. The portion of $NH^+_4;and; nss-Ca^{2+}$ was 85~92% out cations. Compared regionally the year concentraton of $nss-SO^{2-}_4$, the result of Yeochon was 3 times higher than that of Mokpo in 1996, while the results of two regions were almost similar in 1997. The reason was that Yeochon was restricted area of the use of 0.5% sulfur B-C oil, controlled air pollution emission area, controlled semitotal amounts of air pollution emission area and partial operating of factories in 1997. There were no ions having high correlation with $H^+,;but;nss-SO^{2-}_4,;NO^-_3,;NH^+_4;and;nss-Ca^{2+}$ showed high correlation coefficient each other. It seems that these ions have little correlation with $H^+$ because they are washed out on binding state. Factor analysis showed that the first factor was complicated factor containing anthropogenic and soil resource, the second factor was sea-salt resource and the third factor was independent behavior of hydrogen at Mokpo. While, the first factor was complicated factor containing anthropogenic and sea-salt resource, the second factor was $Ca(NO_3)_2$ salt and the third factor was $NH^+_4;and;SO^{2-}_4$ synergied by resource and combination at Yeochon.

• Korean Journal of Weed Science
• /
• v.4 no.1
• /
• pp.96-106
• /
• 1984

Changes in weed floras and development of plant resistance to herbicides seemed to be closely related with increased and repeated use of herbicides. Herbicide use increased from 5% of the total consumption of pesticide in 1950 to 45% in 1976 in world basis. About 200 herbicides have been introduced to agriculture so as to control about 206 weed species which have been recorded important to human beings. In Korea, there was about 351 times in increased use of herbicides from 1966 to 1982. Interspecific selection by herbicide is mainly responsible for changes in weed floras and resulted in varying tolerance or susceptibility to herbicides, together with the changes of agricultural practices. The present trend toward continuous cereal cultivation throughout world will lead to type of changes in weed floras favorable to therophyte which can survive under unfavorable conditions as seeds rather than the types of geophyte which can survive unfavorable seasons as buds placed below soil surface. However, geophyte such as Sagitaria pygmaea, and Scirpus jurtcoides, and Cyperus rotundus and Cynodon dactylon in temperate warm climate become severe paddy weeds, presumably because of the removal of annual weeds by herbicides. Since differential tolerance to 2,4-D was firstly reported in Agrostis stolofera, about 30 species of weeds in 18 genera are presently known to have developed resistance to triazine herbicides. Resistance of weed biotypes to triazine herbicide is not mainly due to limited absorption and translocation or to the difference in metabolism, but is the result of biochemical changes at the site of metabolic activity, such as a loss of herbicide affinity for triazine binding site in the photosystem II complex of the chloroplast membrane. Genetical study showed that plastid resistance to triazine was wholly inherited through cytoplasmic DNA in the case of Brassica campestris. Plant tissue culture method can be utilized as an alternate mean of herbicide screening and development of resistance variants to herbicides as suggested by Chaleff and Parsons. In this purpose, one should be certain that the primary target process is operational in cell culture. Further, there are a variety of obstacles in doing this type of research, particularly development of resistance source and it's regeneration because cultured cells and whole plants represent different developmental state.

• The Korean Journal of Nuclear Medicine
• /
• v.22 no.1
• /
• pp.21-26
• /
• 1988

Serum TBII measured by radioreceptor assay using $^{125}I-bovine$ TSH and porcine thyroid well membrane was checked before, 6 months and 12 months after initiation of thionamide regimens in 63 Graves' disease patients and was related with their remission state. 1) A significant difference (p < 0.01) in pre-treatment TBII was noted between the remitted [N = 45, TBII $40.9{\pm}18.2%$ $(mean{\pm}S.D)$] and the unremitted (N = 18, TBII $64.1{\pm}15.3%$) groups. 2) After 6 months of therapy, TBII were significantly decreased in both groups (to $20.2{\pm}10.3%$ and to $45.2{\pm}16.3%$, p<0.05 for each group) 3) At 12th month, TBII activities were not significantly decreased compared to the 6th month levels in both groups. 4) 3 of the 58 patients who were initially TBII positive (over 15%) converted negative. All the 3 belonged to the remitted group. 5) No significant differences were seen in initial and posttreatment TBII levels between propylthiouracil treated (N = 36) and methimazole treated (N = 27) cases. with above mentioned results, we observed that the TBII decreased significantly with 6 months of thionamide therapy and concluded that the pretreatment measurement of serum TBII may be clinically useful in predicting the response to thionamide regimen in the treatment of Graves' disease.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.200-200
• /
• 2013

기존 메모리 반도체에 비교해 빠른 재생속도와 높은 집적도, 비휘발성 등의 특성을 가지는 MRAM (Magnetic Random Access Memory)은 DRAM, flash memory 등을 대체할 수 있는 차세대 기억 소자로서 CoFeB/MgO/CoFeB로 구성된 한 개의 MTJ (Magnetic Tunnel Junction)를 단위 메모리로 사용한다. 이 MTJ 물질들은 고밀도 플라즈마를 이용한 건식 식각공정시 Cl2, BCl3 등과 같은 chlorine 을 포함한 가스를 이용하여 왔으나 식각 후 sidewall에서 발생하는 부식과 식각 선택비 확보의 어려움 등으로 마스크 물질에 제약을 받고 소자 특성이 감소하게 되는 등의 문제가 있다. 따라서 이러한 식각 문제점을 해결하기 위한 대안으로 noncorrosive 가스인 CO/NH3, CH3OH, CH4 등을 이용한 MTJ 식각 연구가 진행되어 오고 있으며 이중 CO/NH3 혼합가스는 부식성이 없고 hard mask와의 높은 선택비를 가지는 기체로 CO gas에 NH3 gas를 첨가하게 되면 etch rate이 증가하는 특성을 보인다. 또한 rf pulse-biased power를 이용하여 이온의 입사를 시간에 따라 제어함으로써 pulse off time 때 etch gas와 MTJ 물질간의 chemical reaction을 향상시킬 수 있다. 따라서 본 연구에서는 CO/NH3 혼합가스를 이용하여 다양한 rf pulse-biased power 조건에서 MTJ 물질인 CoFeB, MgO와 hard mask 물질인 W을 식각 한 뒤 식각특성을 분석하였으며 MTJ surface의 chemical binding state, surface roughness 측정을 진행하였다. 식각 샘플의 측정은 Alpha step profiler, XPS (X-ray Photoelectron Spectroscopy), AFM (Atomic Force Microscopy)를 통해 진행되었다. Time-averaged pulse bias에서는 duty ratio가 감소할수록 etch rate의 큰 감소 없이 CoFeB/W, MgO/W 물질의 etch selectivity가 향상됨을 확인할 수 있었으며 pulse off time 구간에서의 chemical reaction 향상으로 인해 식각부산물의 재증착이 감소하고 CoFeB의 surface roughness가 감소하는 것을 확인하였다.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.398-398
• /
• 2013

The electronic properties and the local structure of tantalum oxide thin film with variation of oxygen flow rate ranging from 9.5 to 16 sccm (standard cubic centimeters per minute) have been investigated by X-ray photoelectron spectroscopy (XPS), Reflection Electron Energy Loss Spectroscopy (REELS), and X-ray absorption spectroscopy (XAS). The XPS results show that the Ta4f spectrum for all films consist of the strong spin-orbit doublet $Ta4f_{7/2}$ and $Ta4f_{5/2}$ with splitting of 1.9 eV. The oxygen flow rate of the film results in the appearance of new features in the Ta4f at binding energies of 23.2 eV, 24.4 eV, 25.8, and 27.3 eV, these peaks attribute to $Ta^{1+}$, $Ta^{2+}$, $Ta^{4+}$/$Ta^{2+}$, and $Ta^{5+}$, respectively. Thus, the presence of non-stoichiometric state from tantalum oxide ($TaO_x$) thin films could be generated by the oxygen vacancies. The REELS spectra suggest the decrease of band gap for tantalum oxide thin films with increasing the oxygen flow rate. The absorption coefficient ${\mu}$ and its fine structure were extracted from the fluorescence mode of extended X-ray absorption fine structure (EXAFS) spectra. In addition, bond distances (r), coordination numbers (N) and Debye-Waller factors (${\sigma}^2$) each film were determined by a detailed of EXAFS data analysis. EXAFS spectrapresent both the increase of coordination number of the first Ta-O shell and a considerable reduction of the Ta-O bond distance with the increase of oxygen flow rate.

• Korean Journal of Food Science and Technology
• /
• v.10 no.2
• /
• pp.157-161
• /
• 1978

Physicochemical properties of rice starches from Paldal(japonica type) and Tongil(indica type) were investigated. There were no significant differences in water-binding capacity, blue value and amylose content between the two starches. Paldal starch showed a higher value for-swelling power than Tongil starch. Amylograph data showed that both Paldal and Tongil starches had similar paste viscosities except setback in which Tongil starch showed a higher value. No significant differences were observed for intrinsic viscosity and glucose units per segment between Paldal and Tongil amylopectin fractions. However, the intrinsic viscosity for Tongil amylose was considerably higher than Paldal amylose. The rate of retrogradation of Tongil starch gels at $21^{\circ}C$ was faster than Paldal starch gels.

• Asian Journal of Turfgrass Science
• /
• v.25 no.1
• /
• pp.69-72
• /
• 2011

Soil aggregate is a vigorous procedure including soil physical, chemical, and biological processes. Pore space created by binding these particles together improves retention and exchange of air and water. Various researches have reported that the benefits of organic polymers that may increase aggregate stability. The purpose of the study was to determine if a liquid organic polymer mixture has any influence on perennial ryegrass quality or soil aggregation. $Turf2Max^{(R)}$ was applied to two soils as a source of liquid organic polymer. Fine-loamy soil from local Iowa topsoil with 4.0% organic matter was screened and dried. Commercial baseball infield clay, $QuickDry^{(R)}$, was used as the second soil There were three rates of liquid organic polymer (0, 2, and 4%). there was no visual improvement in turf grass color, quality, or growth by using organic polymer. It is possible that aggregate stability increases with use of organic polymer. The aggregate stability study needs to be repeated in the greenhouse and then substantiated under field conditions for these preliminary observations.

• Journal of Microbiology and Biotechnology
• /
• v.27 no.5
• /
• pp.956-964
• /
• 2017

Compactin and pravastatin are competitive cholesterol biosynthesis inhibitors of 3-hydroxy-3-methylglutaryl-CoA reductase and belong to the statin drugs; however, the latter shows superior pharmacokinetic characteristics. Previously, we reported that the bacterial P450, CYP105D7, from Streptomyces avermitilis can catalyze the hydroxylation of 1-deoxypentalenic acid, diclofenac, and naringenin. Here, we demonstrate that CYP105D7 could also catalyze compactin hydroxylation in vitro. In the presence of both bacterial and cyanobacterial redox partner systems with an NADPH regeneration system, the reaction produced two hydroxylated products, including pravastatin (hydroxylated at the C6 position). The steady-state kinetic parameters were measured using the redox partners of putidaredoxin and its reductase. The $k_m$ and $k_{cat}$ values for compactin were $39.1{\pm}8.8{\mu}M$ and $1.12{\pm}0.09min^{-1}$, respectively. The $k_{cat}/K_m$ value for compactin ($0.029min^{-1}{\cdot}{\mu}M^{-1}$) was lower than that for diclofenac ($0.114min^{-1}{\cdot}{\mu}M^{-1}$). Spectroscopic analysis showed that CYP105D7 binds to compactin with a $K_d$ value of $17.5{\pm}3.6{\mu}M$. Molecular docking analysis was performed to build a possible binding model of compactin. Comparisons of different substrates with CYP105D7 were conclusively illustrated for the first time.