• 전기화학회지
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• 제7권1호
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• pp.26-31
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• 2004

The direct electrochemical studies of four laccases (plant and fungal laccases) have been investigated on a gold electrode functionalized with a new tether of 2.2'-dithiosalicylic aldehyde. Results from these studies indicate that the redox potential of the active site of plant laccase from Rhus vernificera is shifted to a more negative value(255 mV versus SCE) than that of fungal laccase from Pyricularia oryzae (480 mV versus SCE). Mechanistic studies indicate that the reduction of type-1 Cu precedes the reduction of type-2 and type-3 Cu ions when the electrode is poised initially at different potentials. Also a new tether, 2.2'-dithiosalicylic aldehyde, has been used to study the redox properties of two laccases (LCCI and Lccla) covalently attached to a gold electrode. An irreversible peak at 0.47V vs. SCE is observed in the cyclic voltammorams of LCCI. In contrast, the cyclic voltammograms of LCCIa contain a quasi-reversible peak at 0.18V vs. SCE and an irreversible peak at 0.50V vs. SCE. We find that the replacement of the eleven amino acids a the C-terminus with a single cysteine residue $(i.e., \;LCCI{\rightarrow}LCCIa)$ influences the rate of heterogeneous electron transfer between an electrode and the copper containing active sites $(K_{het}\;for\;LCCI=1.0\times10^{-2}\;s^{-1}\;and\;K_{het}\;for\;LCCI_a= 1.0\;times10^{-1}\;s^{-1}\'at\;0.18V\;versus\;SCE\;and\;4.0\times10^{-2}\;s^{-1}\;at\;0.50V\; versus\;SCE)$. These results show for the first time that the change of the primary structure of a protein via site-directed mutagenesis influences both the redox potentials of the copper ions in the active site and the rate of heterogeneous electron transfer.

• 한국동물학회지
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• 제26권4호
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• pp.225-233
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• 1983

哺乳動物의 排卵時 濾胞卵子의 成熟再開와 더불어 卵子를 緻密하게 둘러싸고 있는 卵子細胞들의 分散이 일어난다. 이 現象은 生殖巢刺戟호르몬의 促進을 받은 卵丘細胞들이 細胞間隔에 多量의 뮤코量을 分泌함으로써 이루어지는데 이 때 cAMP가 第二 傳達者로 作用을 한다고 알려져 있다. 본 實驗에서는 卵子-卵丘 複合體를 培養하면서 HCG (10 IU/ml)에 의해 誘導된 卵丘細胞의 分散에 puromycin과 actinomycin D가 미치는 영향을 調査한 바 다음과 같은 缺課를 얻었다. 1. Puromycin은 2 $\\mu$g/ml의 濃度에서 卵丘細胞의 分散을 현저히 抑制하였으며 이 效果는 可逆的이었다. 2. Puromycin의 分散抑制效果는 HCG의 刺戟기간 (3시간) 뿐 아니라 뮤코量의 合成時期 ($3\\sim18$시간)에서도 나타났다. 3. Actinomycin D는 0.025 $\\mu$g/ml의 濃度에서부터 卵丘細胞의 分散을 抑制하기 시작했다. 4. Actinomycin D의 分散抑制效果는 부분적인 可逆性을 나타내었으며 0.1 $\\mu$g/ml의 濃度에서는 非可逆的인 災害效果를 나타내었다. 위의 缺課로부터 HCG의 卵丘細胞 分散誘導過程에는 蛋白質 내지 RNA의 合成過程이 관여하는 것으로 測定되며 따라서 cAMP는 轉寫 내지 解讀水準에서 卵丘細胞의 分散을 調節하는 것 같다.

• 상하수도학회지
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• 제32권2호
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• pp.77-87
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• 2018

In this study, the effects of operating conditions on the formation of reversible and irreversible fouling were investigated in the filtration using ceramic membrane for water treatment process. The effect of coagulation pretreatment on fouling formation was also evaluated by comparing the performance of membrane filtration both with and without addition of coagulant. A resistance-in-series-model was applied for the analysis of membrane fouling. Total resistance (RT) and internal fouling resistance (Rf) increased in the membrane filtration process without coagulation as membrane flux and feed water concentrations increased. Internal fouling resistance, which was not recovered by physical cleaning, was more than 70% of the total resistance at the range of the membrane flux more than $5m^3/m^2{\cdot}day$. In the combined process with coagulation, the cake layer resistance (Rc) increased to about 30-80% of total resistance. As the cake layer formed by coagulation floc was easily removed by physical cleaning, the recovery rate by physical cleaning was 54~90%. It was confirmed from the results that the combined process was more efficient to recover the filtration performance by physical cleaning due to higher formation ratio of reversible fouling, resulted in the mitigation of the frequency of chemical cleaning.

• 한국실천공학교육학회논문지
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• 제2권1호
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• pp.35-41
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• 2010

효소촉매반응은 통상적으로 반응속도가 매우 빠르고 동시에 높은 선택성을 보여 주는 특정이 있다. 단순 효소촉매 반응속도식을 보통 Michaelis-Menten식이라고 부른다. 효소의 활성을 간섭하는 화학물질을 저해제라고 하는데, 효소활성의 저해에는 가역적저해와 비가역적저해의 두 가지 형태로 나타난다. 만일 저해제가 수소결합과 같은 약한 결합으로 효소에 붙게 되면 이런 경우 효소저해는 가역적인 저해로 나타난다. 많은 효소 반응들은 그 반응으로부터 생성되는 생성물 자체에 의해서도 가역적 저해를 받게 된다. 생성물의 생성속도와 더불어 기질의 감소속도식은 비선형 미분방정식으로 나타 낼 수가 있다. 본 연구는 공학 분야의 학부교육을 목적으로 단순 효소반응속도식과 보다 더 복잡한 저해 효소반응속도식에 대한 수치해석의 결과를 보고 하고자 한다.

• 한국세라믹학회지
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• 제40권11호
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• pp.1085-1089
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• 2003

본 연구에서는 리튬이차전지의 음극재료로서 사용되고 있는 Mesocarbon Microbeads (MCMB) 카본 분말에 제2상 첨가물로서 소량의 주석산화물 (SnO$_2$) 을 균일하게 분산 첨가시킴으로써 카본전극 표면을 개질시켰으며, 이에 따른 전극의 전기화학적 특성 변화에 관하여 고찰하였다. 주석산화물 첨가 방법는 전하적정법을 사용하여 Sn 을 MCMB 분말에 삽입시키고, 다시 삽입된 Sn이 산화되도록 대기 중에서 25$0^{\circ}C$로 l 시간동안 후열처리를 하였다. 주석산화물이 첨가된 MCMB 카본분말로 Li/MCMB 전지 cell을 만들어 충방전시험을 수행한 결과, raw MCMB로 만든 전극보다 더 우수한 충방전 용량과 싸이클 특성을 나타내었다. 즉, 주석산화물 삽입에 의해 표면개질된 MCMB 카본 분말은 기존의 MCMB에 비해 높은 초기 방전용량과 충전용량을 나타내었고, 또한 높은 가역특성과 좋은 cycleability를 보였다. 삽입된 SnO$_2$의 양이 증가할수록 높은 가역용량을 나타내었고 비가역용량 역시 높은 값을 나타내었다.

• 대한화학회지
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• 제63권1호
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• pp.37-44
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• 2019

N,N'-bis(ethyldihydrogen phosphate)-1,4,5,8-naphthalene bis(dicarboximide) (EPNI) and N,N'-bis(ethyldihydrogen phosphate)-3,4,9,10-perylene bis(dicarboximide) (EPPI) and their zirconium bisphosphate multilayers (Zr-EPNI and Zr-EPPI), that had been briefly reported by us, were further investigated in terms of their electrochemical properties. EPNI in aqueous solution showed typical two reversible reductions at ITO electrode but the reductions were strongly dependent on solution pH while EPPI showed only an irreversible reduction. The single and mixed multilayers of Zr-EPNI and Zr-EPPI were well constructed on ITO electrode by the alternate adsorptions of zirconium ion and the bisimides. While Zr-EPNI multilayer on ITO electrode showed single broad reversible reduction with $E_{1/2}=-0.68V$, Zr-EPPI gave two separated reductions at $E_{1/2}=-0.54$ and -0.81 V vs SCE, quite differently from the solution properties. The average layer densities of the multilayers were estimated as $1.5{\times}10^{-10}$ and $2.3{\times}10^{-10}mol/cm^2$ for Zr-EPNI and Zr-EPPI, respectively. Both the monolayers of Zr-EPNI and Zr-EPPI could not completely block the electron transfer between $Fe(CN){_6}^{3-}$ in solution and ITO electrode but 3-5 layers of Zr-EPNI and Zr-EPPI could block it completely and mediated the one-way electron transfer at the potential shifted to their reduction potentials. When the monolayer of zirconium 1,10-decanediylbisphosphonate (Zr-DBP) was used as a sublayer of Zr-EPNI and Zr-EPPI layers, the mediated electron transfer became prominent without any direct electron transfer.

• Environmental Engineering Research
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• 제24권2호
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• pp.298-308
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• 2019

This work deals with the membrane fouling mode and the unclogging in seawater ultrafiltration process. The identification of the fouling mechanism by modeling the experimental flux decline was performed using both the classical models of Hermia and the combined models of Bolton. The results show that Bolton models did not bring more precise information than the Hermia's and the flux decline can be described by one of the four Hermia's models since the backwash interval is ${\leq}60$ min. An experimental screening study has been then conducted to choose among 5 parameters (backwash interval, duration, pulses and the flow-rate or injected hypochlorite concentration) those that are the most influential on the fouling and the net water production. It has emerged that fouling is mainly affected by the backwash interval; its prolongation from 30 to 60 min engenders an increase in the reversible fouling and a decrease in the irreversible fouling. This later is also significantly reduced when the hypochlorite concentration increases from 4.5 to 10 ppm. Moreover, the net water production significantly increases with increasing the filtration duration up to 60 min and decreases with decreasing the backwash duration and backwash flow-rate from 10 to 40 s and from 15 to ${\geq}20L.min^{-1}$, respectively.

• Molecules and Cells
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• 제45권1호
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• pp.26-32
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• 2022

Living cells generate, sense, and respond to mechanical forces through their interaction with neighboring cells or extracellular matrix, thereby regulating diverse cellular processes such as growth, motility, differentiation, and immune responses. Dysregulation of mechanosensitive signaling pathways is found associated with the development and progression of various diseases such as cancer. Yet, little is known about the mechanisms behind mechano-regulation, largely due to the limited availability of tools to study it at the molecular level. The recent development of molecular tension probes allows measurement of cellular forces exerted by single ligand-receptor interaction, which has helped in revealing the hitherto unknown mechanistic details of various mechanosensitive processes in living cells. Here, we provide an introductory overview of two methods based on molecular tension probes, tension gauge tether (TGT), and molecular tension fluorescence microscopy (MTFM). TGT utilizes the irreversible rupture of double-stranded DNA tether upon application of force in the piconewton (pN) range, whereas MTFM utilizes the reversible extension of molecular springs such as polymer or single-stranded DNA hairpin under applied pN forces. Specifically, the underlying principle of how molecular tension probes measure cell-generated mechanical forces and their applications to mechanosensitive biological processes are described.

• 대한암한의학회지
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• 제12권1호
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• pp.83-89
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• 2007

Chemotherapy has many known side effects. Neuropathy is a common side effect when using cisplatin. The clinical course varies and depends on the agents used and their cumulative dose. Although symptoms can resolve completely, in most patients chemotherapy-induced peripheral neuropathy is either only partially reversible or completely irreversible. Current management for chemotherapy-induced peripheral neuropathy is symptomatic relief using membrane stabilizing medications and antidepressants. Dysaesthesia and pain involving the feet and hands are described in traditional korean medicine. In traditional korean medicine, the pathogenesis is related to the inability to direct Qi and Blood to the extremities, and is associated with Qi, Blood, Yang and Kidney deficiencies. We report a case of a 52 years old female patient treated with acupuncture and bleeding treatment for the goal of improving the symptoms of chemotherapy induced peripheral neuropathy. Further study and other medical method will be needed in order to improve the effect and determine the long-term effect of traditional korean medicine in treating Chemotherapy-induced Peripheral Neuropathy.

• 한국전기전자재료학회논문지
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• 제19권8호
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• pp.724-731
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• 2006

We investigated the electrochemical properties for Langmuir-Blodgett (LB) films mixed with 4-octyl-4'-(5-carboxylpentamethyleneoxy)azobenzene (denoted as 8A5H) and phospholipid(L-a-dimyristoylphosphatidylcholine, denoted as DMPC and L-a-dilauroylphosphayidylcholine, denoted as DLPC). The LB films of 8A5H, 8A5H-DMPC and 8A5H-DLPC mixture monolayers were deposited by using the LB method on the indium tin oxide(ITO) glass. The electrochemical properties measured by using cyclic voltammetry with a three-electrode system, an Ag/AgCl reference electrode, a platinum wire counter electrode and LB film-coated ITO working electrode at various concentrations(0.1, 0.5, and 1.0 mol/L) of $NaClO_4$ solution. A measuring range was reduced from initial potential to -1350 mV, continuously oxidized to 1650 mV and measured to the initial point. The scan rates were 50, 100, 150 and 200 mV/s, respectively. As a result, LB films of 8A5H and 8A5H-DLPC mixture monolayers appeared irreversible process caused by only the oxidation current from the cyclic voltammogram and LB films of 8A5H-DMPC monolayer mixture was found to be caused by a reversible oxidation-reduction process.