• BMB Reports
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• 제40권5호
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• pp.625-635
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• 2007

The enzyme squalene synthase (EC 2.5.1.21) catalyzes a reductive dimerization of two farnesyl diphosphate (FPP) molecules into squalene, a key precursor for the sterol and triterpene biosynthesis. A full-length cDNA encoding squalene synthase (designated as TcSqS) was isolated from Taxus cuspidata, a kind of important medicinal plants producing potent anti-cancer drug, taxol. The full-length cDNA of TcSqS was 1765 bp and contained a 1230 bp open reading frame (ORF) encoding a polypeptide of 409 amino acids. Bioinformatic analysis revealed that the deduced TcSqS protein had high similarity with other plant squalene synthases and a predicted crystal structure similar to other class I isoprenoid biosynthetic enzymes. Southern blot analysis revealed that there was one copy of TcSqS gene in the genome of T. cuspidata. Semi-quantitative RT-PCR analysis and northern blotting analysis showed that TcSqS expressed constitutively in all tested tissues, with the highest expression in roots. The promoter region of TcSqS was also isolated by genomic walking and analysis showed that several cis-acting elements were present in the promoter region. The results of treatment experiments by different signaling components including methyl-jasmonate, salicylic acid and gibberellin revealed that the TcSqS expression level of treated cells had a prominent diversity to that of control, which was consistent with the prediction results of TcSqS promoter region in the PlantCARE database.

• Applied Microscopy
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• 제16권2호
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• pp.1-13
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• 1986

The purpose of this study was to investigate the morphology and intercellular junctions of the odontoblast of dental pulp in the rat incisor by means of the freeze fracture electron microscopy. Twenty male Sprague-Dawley rats weighing $150{\sim}200g$ were used. After being anesthetized by an intraperitoneal injection of 0.5 ml sodium pentobarbital per kg in body weight(60 mg/ml) the animals were perfused with 2.5% glutaraldehyde-2% paraformaldehyde fixative in 0.1 M cacodylate buffer, pH 7.2 through the ascending aorta for one hour. The incisors were carefully extracted from the jaws and demineralized by suspending them in 0.1 M EDTA in 3% glutaraldehyde (pH 7.2) for two weeks. After demineralization, the specimens were obtained from the portion divided into five equal parts. For freeze-fracture replication, demineralized tissues were infiltrated for several hours with 10%, 25% glycerol in 0.1M cacodylate buffer as a cryoprotectant and then frozen in liquid Freon 22 and stored in liquid nitrogen. Fracturing and replication were done in Balzers BAF 400D high-vacuum freeze-fracture apparatus at $-120^{\circ}C$ under routine $5X10^{-7}$ Torr vacuum. The tissue was immediately replicated with platinum unidirectionally at $45^{\circ}$ angle and reinforced with carbon at $90^{\circ}$ angle unidirectionally or by using a rotary stage. The replication process was monitored by a quartz-crystal device. The replicas were immersed in 100% methanol overnight. The tissue was then digested from the replica by clorox (laundry bleach), placed into 5% EDTA, and washed repeatedly with distilled water. The replicas were picked up on 0.3% formvar-coated 75 mesh grids and examined in the JEOL 100B electron microscope. The results were as follows; 1. Both in thin sections and freeze-fracture replicas, three types of intercellular junctions were recognizable in the plasma membrane of odontoblast: gap junction, tight junction and desmosome-like junction. 2. The nuclear pores were evenly distributed over the nuclear envelope. The pore complex formed a ring about 70 nm in diameter. 3. Gap junctions were found between odontoblasts as well as odontoblasts and neighbouring pulp cells (fibroblast, subodontoblastic cell process, nerve-like fibre). Gap junctions, which were round, ellipsoid and pear-shaped and 600 nm in diameter, were observed in the odontoblast. 4. Numerous round and ellipsoid gap junctions could be frequently seen on the plasma membranes in cell body and apical part of the odontoblasts. On the P face, the junctions were recognized as a cluster of closely packed particles, measuring about 9 nm in diameter, and on the E face, the junctions were recognized as a shallow grooves.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.254-255
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• 2012

Interest in nano-crystalline silicon (nc-Si) thin films has been growing because of their favorable processing conditions for certain electronic devices. In particular, there has been an increase in the use of nc-Si thin films in photovoltaics for large solar cell panels and in thin film transistors for large flat panel displays. One of the most important material properties for these device applications is the macroscopic charge-carrier mobility. Hydrogenated amorphous silicon (a-Si:H) or nc-Si is a basic material in thin film transistors (TFTs). However, a-Si:H based devices have low carrier mobility and bias instability due to their metastable properties. The large number of trap sites and incomplete hydrogen passivation of a-Si:H film produce limited carrier transport. The basic electrical properties, including the carrier mobility and stability, of nc-Si TFTs might be superior to those of a-Si:H thin film. However, typical nc-Si thin films tend to have mobilities similar to a-Si films, although changes in the processing conditions can enhance the mobility. In polycrystalline silicon (poly-Si) thin films, the performance of the devices is strongly influenced by the boundaries between neighboring crystalline grains. These grain boundaries limit the conductance of macroscopic regions comprised of multiple grains. In much of the work on poly-Si thin films, it was shown that the performance of TFTs was largely determined by the number and location of the grain boundaries within the channel. Hence, efforts were made to reduce the total number of grain boundaries by increasing the average grain size. However, even a small number of grain boundaries can significantly reduce the macroscopic charge carrier mobility. The nano-crystalline or polymorphous-Si development for TFT and solar cells have been employed to compensate for disadvantage inherent to a-Si and micro-crystalline silicon (${\mu}$-Si). Recently, a novel process for deposition of nano-crystralline silicon (nc-Si) thin films at room temperature was developed using neutral beam assisted chemical vapor deposition (NBaCVD) with a neutral particle beam (NPB) source, which controls the energy of incident neutral particles in the range of 1~300 eV in order to enhance the atomic activation and crystalline of thin films at room temperature. In previous our experiments, we verified favorable properties of nc-Si thin films for certain electronic devices. During the formation of the nc-Si thin films by the NBaCVD with various process conditions, NPB energy directly controlled by the reflector bias and effectively increased crystal fraction (~80%) by uniformly distributed nc grains with 3~10 nm size. The more resent work on nc-Si thin film transistors (TFT) was done. We identified the performance of nc-Si TFT active channeal layers. The dependence of the performance of nc-Si TFT on the primary process parameters is explored. Raman, FT-IR and transmission electron microscope (TEM) were used to study the microstructures and the crystalline volume fraction of nc-Si films. The electric properties were investigated on Cr/SiO2/nc-Si metal-oxide-semiconductor (MOS) capacitors.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.75.2-75.2
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• 2010

We studied the fabrication of polycrystalline silicon (pc-Si) films as seed layers for application of pc-Si thin film solar cells, in which amorphous silicon (a-Si) films in a structure of glass/Al/$Al_2O_3$/a-Si are crystallized by the aluminum-induced layer exchange (ALILE) process. The properties of pc-Si films formed by the ALILE process are strongly determined by the oxide layer as well as the various process parameters like annealing temperature, time, etc. In this study, the effects of the oxide film thickness on the crystallization of a-Si in the ALILE process, where the thickness of $Al_2O_3$ layer was varied from 4 to 50 nm. For preparation of the experimental film structure, aluminum (~300 nm thickness) and a-Si (~300 nm thickness) layers were deposited using DC sputtering and PECVD method, respectively, and $Al_2O_3$ layer with the various thicknesses by RF sputtering. The crystallization of a-Si was then carried out by the thermal annealing process using a furnace with the in-situ microscope. The characteristics of the produced pc-Si films were analyzed by optical microscope (OM), scanning electron microscope (SEM), Raman spectrometer, and X-ray diffractometer (XRD). As results, the crystallinity was exponentially decayed with the increase of $Al_2O_3$ thickness and the grain size showed the similar tendency. The maximum pc-Si grain size fabricated by ALILE process was about $45{\mu}m$ at the $Al_2O_3$ layer thickness of 4 nm. The preferential crystal orientation was <111> and more dominant with the thinner $Al_2O_3$ layer. In summary, we obtained a pc-Si film not only with ${\sim}45{\mu}m$ grain size but also with the crystallinity of about 75% at 4 nm $Al_2O_3$ layer thickness by ALILE process with the structure of a glass/Al/$Al_2O_3$/a-Si.

• Journal of the Korean Wood Science and Technology
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• 제29권1호
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• pp.60-67
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• 2001

소나무(Pinus densiflora)재의 1차조직과 2차조직의 조직구조, 미세구조 및 머서화(mercerization)에 의한 셀룰로오스의 결정구조 변화를 검토하였다. 그 결과, 1차조직의 세포는 원형에 가깝고 내강이 크며 배열이 무질서한 데 비하여, 2차조직의 세포는 장방형이고 비교적 규칙적인 배열을 갖고 있다. 섬유장은 1차조직 $200{\sim}250{\mu}m$, 2차조직 $1,500{\sim}1,600{\mu}m$였으며, 내강경은 1차조직 $40{\sim}50{\mu}m$, 2차조직 $10{\sim}20{\mu}m$였다. 그리고 1차조직과 1차방사조직은 2차조직의 세포에 비해 미목화된 세포가 많았다. 1차조직과 2차조직에서 셀룰로오스 결정의 면간격과 미결정 폭의 차이는 없었으나 상대결정화도는 각각 23%와 35%로 다소 차이가 있었다. 배향성에 있어서 1차조직의 미결정은 무배향을 나타냈으나 2차조직의 미결정은 섬유축에 $20{\sim}30^{\circ}$의 배향성을 나타냈다. 머서화 과정 동안에 1차조직 셀룰로오스 결정은 셀룰로오스 II로 변화되었지만 2차조직의 셀룰로오스 결정은 거의 변화되지 않았다. 따라서 양 조직간의 결정변태의 차이는 목화 정도의 차이에 의한 리그닌의 영향으로 생각되었다.

• Asian Pacific Journal of Cancer Prevention
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• 제15권23호
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• pp.10413-10420
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• 2015

Side effects are an unavoidable consequence of chemotherapy drugs, during which liver injury often takes place. The current study was designed to investigate the protective effect of Astragalus polysaccharides (APS) against the hepatotoxicity induced by frequently-used chemical therapy agents, cyclophosphamide (CTX), docetaxel (DTX) and epirubicin (EPI)) in mice. Mice were divided into five groups, controls, low or high dose groups ($DTX_L$, $CTX_L$, $EPI_L$ or $DTX_H$, $CTX_H$, $EPI_H$), and low or high dose chemotherapeutics+APS groups ($DTX_L$+APS, $CTX_L$+APS, $EPI_L$+APS or $DTX_H$+APS, $CTX_H$+APS, $EPI_H$+APS). Controls were treated with equivalent normal saline for 28 days every other day; low or high dose group were intraperitoneal (i.p) injected with low or high doses of CTX, DTX and EPI for 28 days every other day; low or high dose chemotherapeutics+APS group were separately intraperitoneal (i.p) injected with chemotherapeutics for 28 days every other day and i.p with APS (100 mg/kg) for 7 days continually from the 22th to the 28th days. The body weight, serum levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST), histopathological features, and ultrastructure morphological change of liver tissues, protein expression level of caspase-3 were estimated at different time points. With high dose treatment of DTX, CTX and EPI, weight gain was inhibited and serum levels of ALT and AST were significantly increased. Sections of liver tissue showed massive hepatotoxicity in $CTX_H$ group compared to the control group, including hepatic lobule disorder, granular and vacuolar degeneration and necrosis in hepatic cells. These changes were confirmed at ultrastructural level, including obvious pyknosis, heterochromatin aggregation, nuclear membrane resolution, and chondrosome crystal decrease. Western blotting revealed that the protein levels of caspase-3 increased in $CTX_H$ group. The low dose groups exhibited trivial hepatotoxicity. More interestingly, after 100 mg/kg APS, liver injury was redecued not only regarding serum transaminase activities (low or high dose chemotherapeutics+APS group), but also from pathological and ultrastructural changes and the protein levels of caspase-3 ($CTX_H$+APS group). In conclusion, DTX, CTX and EPI induce liver damage in a dose dependent manner, whereas APS exerted protective effects.

• 한국콘텐츠학회논문지
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• 제9권10호
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• pp.451-463
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• 2009

본 연구의 목적은 태양전지의 변환효율을 높이기 위한 박막형 소재 물질 개발과 전지의 조립과정을 개선 발달시키기 위한 것이다. 이 연구에 사용된 이산화티타니움은 물과 알콕사이드 몰비, 용액 pH의 변화, 분말의 묵힘조건 등 반응조건을 조절한 솔-겔 방법에 의하여 조제되었다. 준비된 이산화티타니움은 $300{\sim}750^{\circ}C$의 열처리조건 범위에서 소결하였다. $600^{\circ}C$의 열조건에서 만들어진 이산화티타니움은 XRD 패턴에서 강한 세기의 아나타제형이 나타났고, $750^{\circ}C$에서 소결되었을 때에는 아나타제형와 루틸형의 혼합물이 나타났다. 또한 소결온도와 묵힘시간 등에 따라 합성된 이산화티타니움의 특성은 묵힘시간이 증가함에 따라 아나타제형 결정으로 변환되는 것을 확인할 수 있었다. 한편 전류밀도는 묵힘시간과 온도에 따라 증가하였고, 변환효율은 전류밀도의 증가로 역시 증가함을 알 수 있었다. 산소분위기하에서 산소와 카드뮴텔루라이드의 화학결합이 생성됨을 관찰할 수 있었고, 카드뮴텔루라이드의 박막위의 산소가 크롬메이트와 하이드라진 처리에 의하여 감소되는 것을 알수 있었다. 결론적으로 공기분위기하에서 $550^{\circ}C$의 급속 소결조건에서 만들어진 카드뮴텔루라이드의 에너지변환효율은 $0.07cm^2$, $1.0cm^2$의 면적에 대해 각각 12.0%, 6.0%로 나타내었다.

• Journal of Chest Surgery
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• 제36권4호
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• pp.219-228
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• 2003

배경: 액체질소에 의한 냉동방법은 생물학과 의학에서 세포와 조직의 장기보존으로는 성공적인 방법이다. 잘 조절된 냉동속도와 해동의 방법과 함께 글라이세롤이나 디메칠설폭사이드 같은 냉동보존제의 사용으로 얼음결정이 생기는 것을 방지하여 구조의 유지와 생존율을 모두 향상시킬 수 있으며 반영구적으로 보존할 수 있다. 여러 조직의 초저온냉동에는 조직에 맞는 냉동속도가 있다. 대상 및 방법: 가장 적합한 냉동곡선과 이를 위한 냉동챔버온도를 찾기 위해서 우리들은 조직의 열역학적 계산을 두 가지 방법으로 하였다. 하나는 직접계산방법으로 모든 냉동 대상물의 열물리학적 특성, 잠재용융열, 면적, 농도와 체적을 알아야 계산할 수 있다. 이러한 방법은 매우 복잡하고 어떠한 경우에는 실제 값을 알 수 없다. 다른 방법은 간접계산방법으로 우선 기존의 냉동곡선으로 조직을 냉동시켜 조직의 실제 냉동곡선을 얻은 다음 시간상수로 냉동곡선을 분석한 다음 온도반응을 계산하고 적합한 x차방정식을 대입시켜 냉동 시 온도상승을 막고 이것을 거꾸로 냉동챔버온도를 산출하는 방식이다. 결과: 이 냉동 프로그램을 중배엽줄기세포, 연골세포와 골아세포에 적용시켜 검사하였다. 조직의 온도는 온도상승과정 없이 이상적인 냉동곡선을 따라 감소하였다. 그러나 세포의 양과 수용액의 양이 적어 냉동곡선간의 생존력이 통계학적으로 차이가 있지는 않았다. 만약 더욱 부피가 큰 조직을 냉동시키거나 프로그램을 순차적으로 계속한다면 이상곡선에 더욱 근접하게 되어 차이가 있을 것으로 판단된다. 결론： 이 프로그램은 이상적인 냉동곡선으로 조직을 냉동시키기 위한 냉동챔버온도를 쉽게 찾을 수 있도록 도움이 될 것이다.

• Molecules and Cells
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• 제38권5호
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• pp.409-415
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• 2015

Low-barrier hydrogen bonds (LBHBs) have been proposed to have important influences on the enormous reaction rate increases achieved by many enzymes. ${\Delta}^5$-3-ketosteroi isomerase (KSI) catalyzes the allylic isomerization of ${\Delta}^5$-3-ketosteroid to its conjugated ${\Delta}^4$-isomers at a rate that approache the diffusion limit. Tyr14, a catalytic residue of KSI, has been hypothesized to form an LBHB with the oxyanion of a dienolate steroid intermediate generated during the catalysis. The unusual chemical shift of a proton at 16.8 ppm in the nuclear magnetic resonance spectrum has been attributed to an LBHB between Tyr14 $O{\eta}$ and C3-O of equilenin an intermediate analogue, in the active site of D38N KSI. This shift in the spectrum was not observed in Y30F/Y55F/D38N and Y30F/Y55F/Y115F/D38N mutant KSIs when each mutant was complexed with equilenin, suggesting that Tyr14 could not form LBHB with the intermediate analogue in these mutant KSIs. The crystal structure of Y30F/Y55F/Y115F/D38N-equilenin complex revealed that the distance between Tyr14 $O{\eta}$ and C3-O of the bound steroi was within a direct hydrogen bond. The conversion of LBHB to an ordinary hydrogen bond in the mutant KSI reduced the binding affinity for the steroid inhibitors by a factor of 8.1-11. In addition, the absence of LBHB reduced the catalytic activity by only a factor of 1.7-2. These results suggest that the amount of stabilization energy of the reaction intermediate provided by LBHB is small compared with that provided by an ordinary hydrogen bond in KSI.

• 한국토양비료학회지
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• 제41권3호
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• pp.164-169
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• 2008

토양에 과잉으로 집적된 염류에 대한 작물의 양분과잉 흡수 피해 기작을 밝히고 그 피해를 경감할 수 있는 기술을 개발하고자 토마토 유묘에 염 스트레스를 유발하고 이때 식물체 생장반응 비교와 잎 중 질소와 당의 변화를 구명하고자 본 시험을 수행한 결과는 다음과 같다. 가. 염 스트레스에 의한 식물체의 생장특성은 생체중과 건물중의 감소와 엽면적이 작고, 지상부와 지하부의 건물중 비가 낮아져 지상부의 생장 저해가 뿌리보다 큰 것으로 보인다. 나. 염 스트레스를 받은 토마토 잎은 잎의 기공이 닫혀 있어 광합성능이 감소하였다. 다. EC $6dS\;m^{-1}$ 정도의 염 농도에서는 어린 토마토 잎 중 수용성당과 전분함량이 현저하게 감소하였다. 라. 염 스트레스를 받으면 토마토 잎 중 총 질소함량이 크게 낮아졌으며, $NO_3^-$ 농도는 낮아지는 반면 $NH_4^+$ 농도는 높아졌다.