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최권영,남궁세윤,박현아 한국공업화학회 2017 한국공업화학회 연구논문 초록집 Vol.2017 No.1
In this report, we present structural modification of bioindigo by adopting nitroindole as a substrate. Interestingly, when nitroindole was used as a substrate, the final product synthesized, which was identified as 4,4’-dinitroindigo, showed completely different color of yellow. Considering the color of indigo was blue, color shift from blue to yellow seemed very interesting and versatile by simply introducing nitrogroups in indole. The synthesized yellow dye was verified by TLC separation and structurally identified by H-NMR and MALDI-TOF analysis. And the synthesized nitroindigo was well solubilized in water, whereas the original blue indigo dye was little soluble. In order to introducing one-pot nitration group into indole, we are now further studying P450 enzyme dependent nitration of indole and synthesis of nitroindigo from renewable biomass such as glucose.
Non-enzymatic PLP-dependent Oxidative Deamination of Amino Acids Induces Higher Alcohol Synthesis
최권영 한국생물공학회 2015 Biotechnology and Bioprocess Engineering Vol.20 No.6
Pyridoxal phosphate (PLP) is an organic cofactor found in all transaminase enzymes. In this study PLP was used to replace the enzymatic deamination step in the Ehrlich pathway, for the oxidative conversion of amino acids into 2-keto acids. PLP functions in an enzymeindependent manner. It was further used in the synthesis of higher alcohols through a sequential enzymatic reduction in vitro and in vivo. PLP-dependent oxidation was investigated against five representative amino acids: valine, leucine, isoleucine, norvaline, and phenylalanine. In vitro amino acid oxidation resulted in approximately 45 ~ 75% [mole/mole] of each 2-keto acid conversion and in vitro ammonia formation was less than 2-keto acid formation, with 20% of conversion yields. Whole cell E. coli expressing reduction enzymes KivD/ADH with both single amino acid and amino acid mixture (4% yeast extract) gave the highest yield (30 ~ 55%) in the presence of the PLP-Cu complex and following enzymatic reactions.
짧은 채널 길이의 다결정 실리콘 박막 트랜지스터의 전기적 스트레스에 대한 연구
최권영,김용상,한민구 대한전자공학회 1995 전자공학회논문지-A Vol.32 No.8
The electrical stress of short channel polycrystalline silicon (poly-Si) thin film transistor (TFT) has been investigated. The device characteristics of short channel poly-Si TFT with 5$\mu$m channel length has been observed to be significantly degraded such as a large shift in threshold voltage and asymmetric phenomena after the electrical stress. The dominant degradation mechanism in long channel poly-Si TFT's with 10$\mu$m and 20$\mu$m channel length respectively is charage trappling in gate oxide while that in short channel device with 5.mu.m channel length is defect creation in active poly-Si layer. We propose that the increased defect density within depletion region near drain junction due to high electric field which could be evidenced by kink effect, constitutes the important reason for this significant degradation in short channel poly-Si TFT. The proposed model is verified by comparing the amounts of the defect creation and the charge trapping from the strechout voltage.