• Journal of Microbiology and Biotechnology
• /
• 제10권2호
• /
• pp.251-257
• /
• 2000

Chitin synthases are identified as key enzymes of chitin biosynthesis in most of the fungi. Among them, chitin synthase II has been reported to be and essential enzyme in chitin biosynthesis, and exists as a membrane-bound form. To search and screen new antifungal agents from natural resources to inhibit chitin synthase II, the assay conditions were established using the enzyme isolated from Saccharomyces cerevisiae ECY38-38A(pAS6) that overproduces only chitin synthase II. This enzyme was activated only by partial proteolysis with trypsin. Its actibity reached the maximum at $80{\;}\mu\textrm{g}/ml$ of trypsin and was strongly stimulated by 2.0 mM $Co^{2+}$, 1.0 nM UDP-[$^{14}C$]-GicNAc, and 32 mM free-GlcNAc. Under these assay conditions, the highest chitin synthase II activity was observed by incubation at $30^{\circ}C$ for 90 min. However, and extremely narrow range of organic solvents up to as much as 25% of DMSO and 25% of MeOH was useful for determining optimal assay conditions. After a search or potent inhibitors of chitin synthase II from natural resources, prodigiosin was isolated from Serratia marcescens and purified by solvent extration and silica gel column chromatographies. The structure of prodigiosin was determined by UV, IR, Mass spectral, and NMR spectral analyses. Its molecular weight and formula were found to be 323 and $C_{20}H_{25}N_{3}O$, respectively. Prodigiosin ingibited chitin synthase II by 50% at the concentration of $115{\;}\mu\textrm{g}/ml$.

• 한국해양학회지:바다
• /
• 제8권2호
• /
• pp.59-69
• /
• 2003

제주도 남부해역의 미세생물 먹이망 구조에 관한 연구의 일환으로써 부유성 유종섬모충(tintinnids)과 빈섬모충(aloricate oligotrichs)의 종 조성과 생물량의 계절 변화 특성에 대하여 중문주변해역의 6개 정점에서 1998년 7월부터 2000년 6월까지 매월 조사를 실시하였다. 조사기간 동안 출현한 유종섬모충은 총 39종으로 세포수 범위는 100~5,400 cells. 1$^{-1}$(평균 314 cells . 1$^{-1}$) 이었고 가을철과 겨울철에는 외양성 종류가 주로 우점하였으며 봄철과 여름철은 외양성 보다 연안성 종류가 우세하였다. 빈섬모충은 총 15종이 동정되었고 세포수 범위는 140~21,000 cells.1$^{-1}$(평균 2,356 cells.1$^{-1}$)로써 Strombidium속의 종들이 전 계절에 걸쳐 우점하였다. 계절에 따른 종 다양성과 생물량 변화는 유종섬모충의 경우 차이가 컸지만 빈섬모충은 큰 차이가 없었다. 유종섬모충의 계절별 수괴지표 특성은 연구 해역의 해양환경변화에 따라 영향을 받고 있었으나 빈섬모충은 특이한 수괴지표 특성을 보이지 않았다. 해역별로 보면 외해역 보다는 해안역에서 세포수가 높았고 종 다양성도 높았다 섬모충의 총 탄소량의 범위는 0.01~136.06 $\mu\textrm{g}$C.1$^{-1}$(평균 5.01 $\mu\textrm{g}$C.1$^{-1}$)로 탄소량과 세포수의 월별 변동이 반드시 일치하지는 않았다. 유종섬모충과 빈섬모충의 수심별세포수 분포는 모두 20 m층에서 가장 높았고 수직분포의 경향도 비슷하였으며, 엽록소 a 량의 수직분포와도 일치하고 있어 식물플랑크톤과 섬모충은 피식과 포식의 상관성을 보이고 있었다.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1992년도 춘계학술대회 논문집
• /
• pp.50-53
• /
• 1992

The GaP crystals are growth by Synthesis Solute Diffusion(SSD) method and its properties are investigated. Etch pits density along vertical direction of ingot is increased from 3.8${\times}$10$^4$cm$\^$-2/ of first freeze to 2.3${\times}$10$\^$5/cm$\^$-2/ of last freeze part. The carrier concentration and mobilities are measured to 197.49$\textrm{cm}^2$/V. sec and 6.75${\times}$10$\^$15/cm$\^$-3/ at room temperature. The temperature dependence of optical energy gap is empilically fitted to E$\_$g/(T)=2.3383-(6.082${\times}$10$\^$-4/T${\times}$/(373.096+T)[eV]. Photo-luminescence spectra measured at low temperature are consist with sharp line-spectra near band-gap energy and radiative recombination between shallow Si-donor to Zn-acceptor and its phonon reprica, and broad emission. The infrared absorption in GaP is cause to phonon coupling modes of TO, LO, LA, TA$_1$, TA$_2$and vibration modes of Ga$_2$O, Si-donor and Zn-acceptor, respectively.

• 한국식품위생안전성학회지
• /
• 제18권2호
• /
• pp.43-50
• /
• 2003

A liquid chromatographic method, using matrix solid-phase dispersion (MSPD) is developed for the extraction of residual furazolidone in chicken eggs. Blank or fortified egg samples (0.5 g) were blended with Octadecylsilyl (Bulk $C_{18}$, 40${\mu}{\textrm}{m}$, 18%. load, endcapped. 2 g) derivatized silica. After homogenization, $C_{18}$/egg and Na$_2$S $O_4$matrix were transferred to a column made of 10 ml glass syringe and filter paper and compressed 4.0∼4.5 ml volume. The column was washed with 8 ml of hexane and dried under $N_2$ gas. Furazolidone was eluted with acetonitrile (8 ml) under gravity. The eluate containing furazolidone was free from interfering compounds when analyzed by HPLC with UV detection (365 nm, photodiode array). Calibration curves were linear (r = 0.99985) and inter- (1.47%) and intra-assay (5.29%) variabilities for the concentration range examined (7.8∼497 ng/g of eggs, 20 ${mu}ell$ injection volume) were indicative of an acceptable methodology for the analysis of furazolidone. Average recovery of furazolidone added to egg was 96.2%. The limit of detection for the proposed method was 1 ng/g for furazolidone. The method using MSPD is proposed as an alternative assay to the classical method which involves the use of large volumes of a harmful solvent and requires a long tedious separation and clean-up processes prior to its determination.

• Journal of Microbiology
• /
• 제35권1호
• /
• pp.1-9
• /
• 1997

Distribution of airborne microorganisms was determined with two different types of air samplers, the Anderson cascade sampler and the Aerobioscope sampler, in the vicinity of Taejon. The size distribution of particles carrying bacteria and fungi was concurrently measured. The concentration of detected viable airborne particles was greatly varied. It was observed that the number of microbial particles increased in April and October. The most isze o particles carrying bacteria was larger than 4.7 .mu.m in mean aerodiameter, which made up 69.8% of the total particle fraction. About 63.2% of fungi-carrying particles were smaller than 4.7 .mu.m in aerodiameter. The distribution of particles on Yellow Sand Phenomena days was also analyzed. The number of fine particles having mass median aero-diameter from 1.0 to 10.mu.m increased on Yellow Sand Phenomena days to about 6 times that on normal days and the n umber of colony forming unit (CFU/$\textrm{m}^3$) of airborne bacteria also increased by 4.3 times in April. The reuslts from the Anderson sampler showed that the concentration of bacteria increased greatly on the fraction of fine particles ranging from 0.6 $\mu$m to 4.7 $\mu$m in diameter. Unlike the increase in bacterial floraon Yellow Sand Phenomena days, the fungal concentration slightly decreased and showed a normal size distribution parttern. This study suggests that a long-range transmission of bacteria results form bacteria adsorbing onto the fine particles during the Yellow Sand Phenomena.

• 한국재료학회지
• /
• 제13권6호
• /
• pp.347-351
• /
• 2003

II-Ⅵ ZnO compound semiconductor thin films were grown on $\alpha$-Al$_2$O$_3$(0001) single crystal substrate by radical beam assisted molecular beam epitaxy and the optical properties were investigated. Zn(6N) was evaporated using Knudsen cell and O radical was assisted at the partial pressure of 1$\times$10$^{4}$ Torr and radical beam source of 250-450 W RF power. In $\theta$-2$\theta$ x-ray diffraction analysis, ZnO thin film with 500 nm thickness showed only ZnO(0002)and ZnO(0004) peaks is believed to be well grown along c-axis orientation. Photoluminescence (PL) measurement using He-Cd ($\lambda$=325 nm) laser is obtained in the temperature range of 9 K-300 K. At 9 K and 300 K, only near band edge (NBE) is observed and the FWHM's of PL peak of the ZnO deposited at 450 RF power are 45 meV and 145 meV respectively. From no observation of any weak deep level peak even at room temperature PL, the ZnO grains are regarded to contain very low defect density and impurity to cause the deep-level defects. The peak position of free exciton showed slightly red-shift as temperature was increased, and from this result the binding energy of free exciton can be experimentally determined as much as $58\pm$0.5 meV, which is very closed to that of ZnO bulk. By van der Pauw 4-point probe measurement, the grown ZnO is proved to be n-type with the electron concentration($n_{e}$ ) $1.69$\times$10^{18}$$cm^3$, mobility($\mu$) $-12.3\textrm{cm}^2$/Vㆍs, and resistivity($\rho$) 0.30 $\Omega$$\cdot$cm.

• 대한화장품학회지
• /
• 제24권3호
• /
• pp.89-95
• /
• 1998

The aim of this study is to elucidate the anti-microbial activity and anti-oxidative activity of water-soluble chitosan with a molecular weight of 5,000-200,000. Water-soluble chitosans have demonstrated a regular anti-microbial activity on the tested strians by the paper disk method. In the MIC (Minimum Inhibitory Concentration) test, CC-01 (MW=5,000) with the lower MW showed the higher MIC value than the higher MW chitosan. The MW of chitosan increase, the MIC decreases. MICs of 4 chitosans(CC-02∼CC-05) against S. aureusTCC 65389, E coli ATCC 8739, p. aeruginosa, ATCC 9027 and C. albicans ,ATCC 10231 were 7.0-39.O$\mu\textrm{m}$, whereas MICs of chitosans against A. niger were over 2.OmM. Formula containing chitosan showed higher anti-microbial activities than the formula made with the chemical preservatives(Methylparaben 0.2％ and Imidazolidinyl Urea 0.3％). Among 5 water-soluble chitosans, CC-03(MW=92,163) showed the most potent anti-oxidative activity (IC$\sub$50/ : 0.2mM). In conclusion, the water-soluble low molecular weight chitosan could be served as natural preservatives and antioxidant in cosmetics.

• 환경위생공학
• /
• 제5권2호
• /
• pp.45-52
• /
• 1990

This study is to discuss limiting factors influenced on the removal efficiency of organic materials investigated using the polypropyrene biofilter which appropriate to attach micro-organism in order to apply the contact oxidation proce,:5. The results obtained in the experiment were as follows : 1. In the range o: pH 4.0~ 12.0 was obtained the removal efficiency of COD higher than 85% It was proved that variation of pH(4.0 ~ 12.0) was nothing to do with the removal efficiency of substrate in continuous reactor. 2. Temperature to obtain removal efficiency of COD higher than 85% was $10^{\circ}$ ~$40^{\circ}$. Removal efficiency of COD was no less than those at high temperature if MLVSS concentration was maintained 8,000~ 15,000 m/1. 3. In the continuous reactor, the volumetric loading of COD for removal efficiency higher than 95% had to be 0.5~1.5 kg COD/.d below. And then the HRT was Bhrs. 4. In comparison with the conventional activate sludge process, the contact oxidation process was excellent in removal efficiency, sludge production rate and maintenance.

• 대한한의학회지
• /
• 제24권3호
• /
• pp.72-83
• /
• 2003

Objective : The goal of the present study was to investigate the protective effect of Gamiheechum-tang (Jiaweixiqian-tang; GHCT) on brain tissue damage from chemical or ischemic insults. Methods : Levels of cultured cortical neuron death caused by toxic chemicals were measured by LDH release assay. Neuroprotective effects of GHCT on brain tissues were examined in vivo by ischemic model of middle cerebral artery (MCA) occlusion. Results : Animal groups treated with GBCT showed significantly decreased hypertension, and reduced levels of aldosterone, dopamine, and epinephrine in the plasma. GHCT treatments ($l0-200\mu\textrm{g}/ml$) significantly decreased cultured cortical neuron death mediated by AMPA, kainate, BSO, or Fe2+ when measured by LDH release assay. Yet, cell death mediated by NMDA was effectively protected by GHCT at the highest concentration examined ($200\mu\textrm{g}/ml$). In the in vivo experiment examining brain damage by MCA occlusion, affected brain areas by ischemic damage and edema were significantly less in animal groups administered with GHCT compared to the non-treated control group. Neurological examinations of forelimbs and hindlimbs showed that GHCT treatment improved animals' recovery from ischemic injury. Moreover, the extent of injury in cortical and hippocampal pyramidal neurons in ischemic rats was much reduced by GHCT, whose morphological features were similarly observed in non-ischemic animals. Conclusion : The present data suggest that GBCT may play an important role in protecting brain tissues from chemical or ischemic injuries.

• 대한지하수환경학회지
• /
• 제7권3호
• /
• pp.103-115
• /
• 2000

갈색 침전물의 생성은 우리나라 지하수의 개발 및 공급에 있어 흔히 발생하는 문제 중의 하나인데, 이에 따라 색도, 맛, 탁도 및 용존 철 함량 등의 항목에 있어 먹는 물 수질 기준을 초과하게 되고, 물 공급 시스템에 스케일링의 문제를 야기하게 된다. 경기도 파주 지역 지하수의 경우에도 양수 후 몇 시간 내에 갈색 침전물이 형성되어 수질을 악화시키고 있다. 본 연구에서는 지하수의 탁도를 유발하는 원인과 지화학적 반응 경로를 이해하고자, 평형열역학 및 반응속도론적 접근을 통하여 갈색 침전물의 형성과정을 파악하였다. 본 연구결과는 침전물의 형성을 최소화하기 위한 적정 양수 기법은 물론 수질 향상을 위한 최적 수처리 기법을 설계하는데 있어 중요한 자료로 활용될 것이다. 파주 지역의 암반 지하수는 물/암석(편마암)반응에 의해 Ca-$HCO_3$형의 수질 특성을 보인다. SEM-EDS 및 XRD 분석 결과, 갈색 침전물은 비정질의 함철 산화물 또는 수산화물로 해석된다. 다양한 공극 크기(6, 4, 1, 0.45, 0.2 $\mu\textrm{m}$)를 갖는 여과지를 이용한 다단계 여과 결과, 이들 침전물은 크기에 있어 대부분 1 내지 0.45$\mu\textrm{m}$의 입도를 갖는 콜로이드 형태이지만, 질량 분포로 볼 때는 1 내지 6$\mu\textrm{m}$범위가 우세함(총 질량의 약 81%)을 알 수 있다. 다량의 용존 철(II)은 지하수 유동 중에 철 함량이 높은(최대 3wt.%) 단층 파쇄암 내의 녹니석(clinochore)의 용해로부터 기원하는 것으로 판단된다. PHREEQC 프로그램을 이용한 포화지수 계산 및 pH-Eh 관계도에 대한 검토 결과, 침전물은 함철 수산화물임이 확인되며, 환원 조건에 있던 심부 지하수가 양수에 의해 산소에 노출되면서 화학성 변화(특히, 산화)에 의하여 침전함을 알 수 있다. 양수 이후의 시간 경과와 더불어 양수된 지하수의 pH, DO, 알칼리도는 점차 감소하며. 탁도는 증가하다가 일정 시간 경과 후 감소하는 경향을 보인다. 양수 이후의 경과 시간에 따른 용존 철(II)의 농도 감소율(즉, 반응 속도)은 Fe(II)=10.l exp(-0.0009t)로 표현된다. 따라서 갈색 침전물의 생성 반응은 양수 및 양수 후 저장 과정 중에 산소의 유입에 따른 산화 반응에 기인하며, 그 반응은 시간, 산소분압 및 pH에 의존함을 알 수 있다. 탁도를 제거하여 음용 가능한 수질을 확보하기 위해서는, 충분한 시간 동안 충분한 크기를 갖는 탱크 내에서의 다단계 저장 및 폭기를 거친 이후에 응집된 침전물에 대한 여과가 제안된다. 이때, 비용 절감 차원에서 상이한 입도 조건에서의 다단계 여과가 효과적일 것으로 생각된다. 한편, 개발 관정 내에서의 스케일링을 최소화하기 위해서는 심부 지하수로 산소가 풍부한 천층 지하수가 유입되는 과정을 최소화할 필요가 있다. 이를 위해서는 적정 채수량 범위 내에서의 지속적인 양수가 효과적일 것이다. 아울러, 산소가 풍부한 천층 지하수의 채수를 위한 별도의 관정 설치도 고려할 수 있을 것이다.