• Journal of Biosystems Engineering
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• 제32권6호
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• pp.455-461
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• 2007

The electric current of a flow injection type enzyme-sensor was measured to confirm the stable operating conditions of the sensor. The current of the sensor was decreased as the buffer solution velocity increased. Under the limitation of the cycle time to be below 10 minutes, the effective ranges of the buffer solution velocity were suggested $0.10{\sim}0.26$, $0.12{\sim}0.24$, $0.1{\sim}0.25$ and $0.05{\sim}0.10\;cm/s$ of 1.0, 1.4, 2.4 and 3.4 mm of the electrode diameters, respectively. As the reaction time of the enzyme and the substrate was increased, the current was decreased because of the dilution between the sample and buffer solution. Therefore, it could be recommended that the reaction time was able to be selected as shortly as possible in consideration of the total cycle time. As the result of the experiments using a different volume ratio of the enzyme to substrate, it was concluded that the substrate had to be mixed with the same amount of the enzyme. The current have increased remarkably in proportion to the electrode diameter under 0.1 cm/s of the buffer solution velocity but there was no difference over 0.1 cm/s of the buffer solution velocity. The cross type arrangement of the electrode was highly suggested for application and machining of the sensor.

• 전기화학회지
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• 제7권1호
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• pp.44-48
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• 2004

The two-component type enzyme amplified amperometric DNA assay is described to use an ambient $O_2$ of the substrate of the DNA labeling enzyme. Although the assay detects DNA only at > 0.5M concentration, a concentration $\~10^6$ fold higher than the sandwich-type enzyme amplified amperometric DNA assay, it can be run with an always available substrate. The assay utilizes screen-printed carbon electrodes (SPEs) which were pre-coated by a co-electrodeposited film of an electron conducting redox hydrogel and a 37-base long single-stranded DNA sequence. The DNA in the electron conducting film hybridizes and captures, when present, the 37-base long detection-DNA, which is labeled with bilirubin oxidase (BOD), an enzyme catalyzing the four-electron reduction of $O_2$ to water. Because the redox hydrogel electrically connects the BOD reaction centers to the electrode, completion of the sandwich converts the film from non-electrocatalytic to electrocatalytic for the reduction of $O_2$ to water when the electrode is poised at 200 mV vs. Ag/hgCl. The advantage or the assay over the earlier reported sandwich type enzyme amplified amperometric DNA assay, in which the amplifying enzyme was horseradish peroxidase, is that it utilizes ambient $O_2$ instead of the less stable and naturally unavailable $H_2O_2$.

• 공업화학
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• 제25권1호
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• pp.107-112
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• 2014

흑연가루의 결합재로 클로로술폰화 폴리에틸렌 고무용액을, 매개체로 ferrocene을 사용하여 장미조직을 고정한 과산화수소 정량 바이오센서를 제작하였다. 실험 전극전위 영역에서 보여준 Hanes-Woolf 도시의 선형성은 기질의 환원이 장미 과산화효소의 촉매력에 의한 것임을 보여 주었다. 또 얻어진 10개 이상의 전기화학 파라미터들은 전극이 정량적으로 성능을 발휘하고 있음을 입증하였다. 이런 사실들은 효소전극의 실용화를 위하여 장미조직이 상업용 과산화효소를 대치하여 사용될 수 있음을 확신시켜 주는 것이었다.

• Bulletin of the Korean Chemical Society
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• 제18권11호
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• pp.1149-1152
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• 1997

An enzyme electrode for the amperometric measurement of urea was prepared by co-immobilizing L-glutamate dehydrogenase and urease onto an Immobilon-AV affinity membrane attached to a glassy carbon electrode. The reduced nicotinamide adenine dinucleotide(NADH) was used as the electroactive species. The electrochemical oxidation of NADH was monitored at +1.0 volt vs. Ag/AgCl. The enzyme-immobilized electrode was linear over the range of 2.0 × 10-5 to 2 × 10-4 M. The response time of the electrode was approximately 3 min. and the optimum pH of the enzyme immobilized membrane was pH 7.4-7.6 (Dulbcco's buffer solution). It was stable for at least two weeks or 50 assays. There was no interference from other physiological species, except from high levels of ascorbic acid.

• 대한화학회지
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• 제59권6호
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• pp.554-559
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• 2015

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 춘계학술대회 논문집 전자세라믹스 센서 및 박막재료 반도체재료 일렉트렛트 및 응용기술
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• pp.100-103
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• 2000

In the case of immobilizing of glucose oxidase into polypyrrole (PPy) using electrosynthesis, the glucose oxidase (GOx) forms a coordinate bond with the polymers backbone. However, because of intrinsic insulation and net-chain of the enzyme, the charge transfer and mass transport are obstructed during the film growth. Therefore, the film growth is dull. We synthesized the enzyme electrode by electropolymerization added some organic solvent. A formative seeds of film growth is delayed by adding ethanol. The delay is induced by radical transfer between ethanol and pyrrole monomer. The radical transfer shares the contribution of dopant between electrolyte anion and GOx polyanion. This may lead to increase amount of immobilized the enzyme in PPy. For the UV absorption spectra of synthetic solution before synthesis and after, in the case of ethanol added, the optical density was slightly decreased for the GOx peaks. It suggests amount of GOx in the solution was decreased and amount of GOx in the film was increased. We established qualitatively that amount of immobilization can be improved by adding a little ethanol in the synthetic solution. It is due to radical transfer reaction. The radical transfer shares the contribution of dopant between small and fast electrolyte anion and big and slow GOx polyanion.

• 분석과학
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• 제20권1호
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• pp.49-54
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• 2007

For the practical use as a biosensor, a rubber electrode bound by polybutadiene was newly devised for the determination of hydrogen peroxide. Then its electrochemical behaviors were investigated. The signal could be obtained at low electrode potential between 0.0 ~ -0.5 V (vs. Ag/AgCl) with a detection limit of $1.4{\times}10^{-4}M$ and its potential dependence was linear in the experimental range. Especially its Lineweaver-Burk plot showed a very good linearity giving the evidence of a good enzyme immobilization on the surface of the electrode. And mechanical stability of the electrode resulted from using rubber binder presented a new possibility for the practical use of biosensor.

• Journal of Microbiology
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• 제43권5호
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• pp.451-455
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• 2005

In this study, whole cells and a crude enzyme of Candida peltata were applied to an electrochemical bioreactor, in order to induce an increment of the reduction of xylose to xylitol. Neutral red was utilized as an electron mediator in the whole cell reactor, and a graphite-Mn(IV) electrode was used as a catalyst in the enzyme reactor in order to induce the electrochemical reduction of $NAD^+$ to NADH. The efficiency with which xylose was converted to xylitol in the electrochemical bioreactor was five times higher than that in the conventional bioreactor, when whole cells were employed as a biocatalyst. Meanwhile, the xylose to xylitol reduction efficiency in the enzyme reactor using the graphite-Mn (IV) electrode and $NAD^+$ was twice as high as that observed in the conventional bioreactor which utilized NADH as a reducing power. In order to use the graphite-Mn(IV) electrode as a catalyst for the reduction of $NAD^+$ to NADH, a bioelectrocatalyst was engineered, namely, oxidoreductase (e.g. xylose reductase). $NAD^+$ can function in this biotransformation procedure without any electron mediator or a second oxidoreductase for $NAD^+/NADH$ recycling

• Preventive Nutrition and Food Science
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• 제3권1호
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• pp.36-42
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• 1998

Ion-selective eleltrodes(ISEs) are simple electrodechemical devices for the direct measurement of ions in the samples. A novel potentiometric biosensor for the determination of L-Malate or D-isocitrate has been developed by using CO2-3 -ISE-FIA system was composed of a pump, an injector, a malic enzyme or isocitric dehydrogenase enzyme reactor, a CO2-3 -ISE, a pH/mV meter, and an integrater. The various factors, such as buffer capacity types of plstericizer and polymer, were optimized for the CO2-3 selectivity. In this novel CO2-3 --ISE-FIA system, the potential difference due to the amount of CO2-3 produced from each enzyme reaction was proportional to the amount of L-malate or D-isocitrate.

• Korean Chemical Engineering Research
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• 제54권6호
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• pp.817-821
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• 2016

Levodopa or L-3,4-dihydroxyphenylalanine (L-DOPA) is the direct precursor of the neurotransmitter dopamine. L-DOPA is a well-known neuroprotective agent for the treatment of Parkinson's disease symptoms. L-DOPA was synthesized using the enzyme, tyrosinase, as a biocatalyst for the conversion of L-tyrosine to L-DOPA and an electrochemical method for reducing L-DOPAquinone, the product resulting from enzymatic synthesis, to L-DOPA. In this study, three electrode systems were used: A glassy carbon electrode (GCE) as working electrode, a platinum, and a Ag/AgCl electrode as auxiliary and reference electrodes, respectively. GCE has been modified using electropolymerization of pyrrole to facilitate the electron transfer process and immobilize tyrosinase. Optimum conditions for the electropolymerization modified electrode were a temperature of $30^{\circ}C$ and a pH of 7 producing L-DOPA concentration 0.315 mM. After 40 days, the relative activity of an enzyme for electropolymerization remained 38.6%, respectively.