• Journal of Life Science
• /
• v.16 no.3 s.76
• /
• pp.375-381
• /
• 2006

Aldehyde reductase was purified to electrophoretic homogeneity from Saccharomyces cerevisiae, and then enzymatic reduction of substituted carbonyl compounds was carried out by using the purified aldehyde reductase as a biocatalyst. Under preparative scale reaction renditions, the enzymatic reduction proceeded in high chemical yield with excellent chemoselectivity. The enzymatic reduction product was identified by TLC, GC, Mass, NMR and FT-IR. Benzoic acid, an inhibitor of aldehyde reductase, also potently inhibited the reduction of substituded carbonyl compounds. This enzyme exhibited a broad substrate specificity , and can utilize both NADH and NADPH as cofactors. The enzyme was strongly inhibited by benzoic acid and quercetin. The apparent Km for 4-cyanobenzaldehyde and 3-nitrobenzamide were 4.894 mM and 0.305 mM, respectively.

• The Microorganisms and Industry
• /
• v.17 no.2
• /
• pp.18-21
• /
• 1991

생물은 자기 복제를 통한 생장이나 생명유지를 위해 에너지를 필요로 한다. 화학영양생물은 화학에너지를 발효 혹은 호흡을 통해 생물학적 에너지로 전환시키며, 광영양생물은 광합성 작용을 통해 광에너지를 이용한다. 발효, 호흡, 광합성은 모두 산화-환원 반응을 통해 이루어진다. 생물의 모든 에너지 전환반응은 산화-환원 반응, 즉 전자의 흐름으로 이루어지며 생명현상이 에너지를 필요로 하기 때문에 생명현상은 전자의 흐름으로 이루어진다고 할 수 있다. 모든 생물이 에너지 전환 반응에 산화-환원 반응을 이용한다는 말은 생물이 많은 종류의 산화-환원 효소를 보유하고 있다는 뜻이며, 실제 많은 종류의 산화-환원 효소가 발견되고 연구되었다.

• Journal of the Korean Vacuum Society
• /
• v.1 no.2
• /
• pp.277-285
• /
• 1992

플라즈마 화학기상증착법과 저압 화학기상증착법을 사용하여 실리콘 기판 위에 텅 스텐 박막을 증착하였다. 반응기체로 WF6를 사용하였으며 환원기체로는 SiH4를 사용하였다. 플라즈마 증착법에 의한 텅스텐 박막의 성장은 환원기체의 유무에 상관없이 주로 기상 반응 에 의한 텅스텐 덩어리들의 증착에 의하여 이루어졌으며 비교적 균일도가 낮은 박막표면을 이루었다. 저압 화학증착법의 경우 환원기체를 사용하지 않았을 때에는 실리콘 기판에 의한 제한된 환원반응에 의해 텅스텐이 증착되었으나, 환원기체를 사용했을 때에는 초기의 실리 콘 기판에 의한 환원반응과 이어 일어나는 SiH4 기체와의 불균일계 환원반응의 두 단계반응 에 의하여 텅스텐 박막 증착이 이루어졌다. 저압 화학증착법의 경우 텅스텐 박막의 특성은 플라즈마 증착법에서 보다 우수하였으며 박막 성장은 island by island 양식을 따르는 것으 로 추정되었다. 박막은 $\alpha$-W의 체심입방 구조로 이루어졌으며 박막이 성장함에 따라 단결정 구조가 증가하였다.

• Proceedings of the Korean Radioactive Waste Society Conference
• /
• 2009.06a
• /
• pp.291-291
• /
• 2009

한국원자력연구원의 파이로 실험 시설인 ACPF (ACP Facility)에는 공학규모 전해환원 반응기가 설치되어 공정 대용량화를 위한 연구가 수행되고 있다 본 연구에서는 전해환원 공정의 Scale-up을 위해 기존 반응기를 개선하여 전해환원 실험을 수행한 결과를 담고 있다. 장치의 대형화 빛 원격운전성 향상을 위해 기존의 전해환원 반응기의 상부 플랜지는 보다 간단하게 정리되었으며 염 이송에 의한 고온 조건 노출 시간을 줄임과 동시에 염 재사용을 목적으로 상부 플랜지는 이중으로 설계되었다. 따라서, 반응 종료후 전극이 설치된 상부 플랜지를 들어 올림으로서 반응기를 불활성 분위기로 유지하는 동시에 전해환원 금속전환체를 회수 할 수 있도록 반응기가 제작되었다. 또한, 새로운 반응기는 용융염 내의 강제 유동을 위해 아르곤 버블링이 가능하도록 설계 제작되었다. 새로 제작 설치된 전해환원 반응기를 사용하여 산화물 분말을 혼합하여 준비한 모의 사용후핵연료를 사용하여 전해환원 실험을 수행하였다. 그 결과, 산화물이 충진된 음극의 전영역에서 고루 96% 이상의 높은 금속전환율을 얻었으며 시간에 따라 선택된 FP들의 용융염 내 거동을 측정하였다. 실리더 형태의 음극에서 Cs, Sr 등의 원소들이 용융염으로 시간에 따라 용출되는 것을 확인하였으며 동시에 반응기 재질인 Fe 등도 일부 용융염에서 검출되었다. 아르곤 버블링에 의한 강제 유동은 전압 및 전류 거동에는 큰 영향을 미치지 못하였으나 염의 휘발량을 증가시켜 영조성올 변화시키는 것으로 측정되었다. ACPF의 전해환원 실험결과를 바탕으로 반응기를 상부 기체상과 하부 액체상으로 나누어 전산모사를 수행하였다 상부 기체상은 유입되는 아르곤 기체와 발생되는 산소기체의 흐름을 모사하는 결과를 얻었으며 온도 및 산소의 분압을 계산하였다. 하부 액체상에서는 전기장을 모사하여 전류 밀도 등을 3차원으로 모사하였다.

• Resources Recycling
• /
• v.26 no.4
• /
• pp.3-8
• /
• 2017

Oxidation-reduction reaction is one of the most important reactions occurring in the aqueous phase. Analysis of the equilibria related to these oxidation-reduction reactions is of great value in designing many unit operations in hydrometallurgy, such as leaching, separation and electrochemical reactions. The construction of Frost diagram was discussed in this work. The conditions at which disproportionation and proportionation reactions can occur were explained by analyzing Frost diagram together with Latimer table. The information which can be obtained from Frost diagram was discussed.

• Korean Journal of Food Science and Technology
• /
• v.54 no.1
• /
• pp.1-7
• /
• 2022

Riboflavin (Rb), in the presence of methionine (Met) under light, generates superoxide radicals that can reduce nitro blue tetrazolium (NBT) to its corresponding formazan. The Rb-Met/NBT system has been used to measure the superoxide dismutase (SOD)-like activities of various antioxidants. However, the reaction mechanisms have not been clearly defined, and the assay conditions are not consistent. In this study, the effects of different photosensitizers and amino acids on NBT reduction in different solvents were investigated. NBT reduction in the Rb-Met/NBT system was more pronounced in phosphate-buffered saline, compared to distilled water or Tris (pH 7.5); histidine (His) instead of Met also led to considerable Rb-induced NBT reduction. Among the photosensitizers, methylene blue with His caused potent NBT reduction in Tris. Rb-induced NBT reduction combined with Met or His was quantitatively inhibited by SOD or gallic acid, but did not affect MB-induced reduction sensitively.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.10 no.2
• /
• pp.97-104
• /
• 2012

A porous $TiO_2$ pellet was electrochemically converted to the metallic titanium by using a $CaCl_2$ molten salt system at $850^{\circ}C$. Ni-$TiO_2$ and graphite electrodes were used as cathode and anode, respectively. The electrochemical behaviour of $TiO_2$ pellet was determined by a constant voltage control electrolysis. Various reaction intermediates such as $CaTiO_3$, $Ti_2O$ and $Ti_6O$ were observed by XRD analysis during electrolysis of the pellet. Once $TiO_2$ pellet was converted to a porous metallic structure, the porous structure disappeared by sintering and shrinking with increasing the reaction time at high temperature.

• Korean Chemical Engineering Research
• /
• v.44 no.4
• /
• pp.356-362
• /
• 2006

The $SO_2$ reduction using CO and $H_2$ over Sn-Zr based catalysts was performed in this study. Sn-Zr based catalysts with Sn/Zr molar ratio (0/1, 1/4, 1/1, 2/1, 3/1, 1/0) were prepared by the precipitation and co-precipitation method. The effect of the temperature on the reaction characteristics of the $SO_2$ reduction with a reducing agent such as $H_2$ and CO was investigated under the conditions of space velocity of $10,000ml/g_{-cat.}h$, $([CO(or\;H_2)]/[SO_2])$ of 2.0. As a result, the activity of Sn-Zr based catalysts were higher than $SnO_2$ and $ZrO_2$. The reactivity for the $SO_2$ reduction with CO was higher than that with $H_2$, and sulfur yield in the $SO_2$ reduction by $H_2$ was higher than that by CO. The reactivity for the $SO_2$ reduction with $H_2$ was increased with the reaction temperature regardless of Sn-Zr based catalyst with a Sn/Zr molar ratio. $SnO_2-ZrO_2$ (Sn/Zr=1/4) had highest activity at $550^{\circ}C$, in the $SO_2$ reduction with $H_2$ and $SO_2$ conversion of 94.4％ and sulfur yield of 66.4％ were obtained at $550^{\circ}C$. On the other hand, in the $SO_2$ reduction by CO, the reactivity was decreased with the increase over $325^{\circ}C$. At the optimal temperature of $325^{\circ}C$, $SO_2$ conversion and sulfur yield were about 100％ and 99.5％, respectively, in the $SO_2$ reduction over $SnO_2-ZrO_2$ (Sn/Zr=3/1). Also, the $SO_2$ reduction using syngas with $CO/H_2$ ratio over $SnO_2-ZrO_2$ (Sn/Zr=2/1) was performed in order to investigate the application possibility of the simulated coal gas as the reductant in DSRP. As a result, the reactivity of the $SO_2$ reduction using syngas with $CO/H_2$ ratio was increased with increasing the CO content of syngas. Therefore, it could be known that DSRP using the simulated coal gas over Sn-Zr based catalyst is possible to be realized in IGCC system

• Applied Chemistry for Engineering
• /
• v.3 no.2
• /
• pp.305-311
• /
• 1992

The experimental study on the reduction of $In_2O_3$ was performed by using thermogravimetric analyzer. The reduction of $In_2O_3$ was occurred at above $300^{\circ}C$. The reduction rates were rapidly increased with the reaction temperature, whilehardly affectedby the flow rate of hydrogen gas. It was found that the unreacted core model could be applied for the analysis of the reduction data and the rate control step was the chemical reaction of $In_2O_3$ with hydrogen on the surface of unreacted $In_2O_3$. The apparent activation energy for this reaction was 20kcal/g-mol $H_2$ and the rate equation of $In_2O_3$ reduction with hydrogen could be expressed in the following equation. ${\frac{dX}{dt}}=1.6{\times}10^5e^{-20000/RT}(1-X)^{2/3}$

• Journal of the Korean Chemical Society
• /
• v.17 no.4
• /
• pp.275-285
• /
• 1973

The addition of one mole of aluminum chloride to three moles of sodium borohydride in tetrahydrofuran gives a turbid solution with enormously more powerful reducing properties than those of sodium borohydride itself. The reducing properties of this reagent were tested with 49 organic compounds which have representative functional groups. Alcohols liberated hydrogen immediately but showed no sign of hydrogenolysis of alkoxy group. Aldehydes and ketones were reduced rapidly within one hr. Acyl derivatives were reduced moderately, however, carboxylic acids were reduced much more slowly. Esters, lactones and epoxides were reduced readily than sodium borohydride or borane. Tertiary amide was reduced slowly, however, primary amide consumed one hydride for hydrogen evolution but reduction was sluggish. Aromatic nitrile was reduced much more readily than aliphatic nitrile. Nitro compounds were inert to this reagent but azo and azoxy groups were slowly attacked. Oxime was reduced slowly but isocyanate was only partially reduced. Disulfide and sulfoxide were attacked slowly but sulfide and sulfone were inert. Olefin was hydroborated rapidly.