• 대한화학회지
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• 제67권3호
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• pp.204-207
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• 2023

• Journal of Microbiology and Biotechnology
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• 제18권5호
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• pp.983-989
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• 2008

Human insulin is a hormone well-known to regulate the blood glucose level. Recombinant preproinsulin, a precursor of authentic insulin, is typically produced in E. coli as an inactive inclusion body, the solubilization of which needs the addition of reducing agents such as $\beta$-mercaptoethanol. To make authentic insulin, recombinant preproinsulin is modified enzymatically by trypsin and carboxypeptidase B. The effects of $\beta$-mercaptoethanol on the formation of human insulin derivatives were investigated in the enzymatic modification by using commercially available human proinsulin as a substrate. Addition of 1 mM $\beta$-mercaptoethanol induced the formation of various insulin derivatives. Among them, the second major one, impurity 3, was found to be identical to the insulin B chain fragment from $Phe_1$ to $Glu_{21}$. Minimization of the formation of insulin derivatives and concomitant improvement of the production yield of human insulin were achieved by the addition of hydrogen peroxide. Hydrogen peroxide bound with $\beta$-mercaptoethanol and thereby reduced the negative effects of $\beta$-mercaptoethanol considerably. Elimination of the impurity 3 and other derivatives by the addition of over 10 mM hydrogen peroxide in the presence of $\beta$-mercaptoethanolled to a 1.3-fold increase in the recovery efficiency of insulin, compared with those for the case without hydrogen peroxide. The positive effects of hydrogen peroxide were also confirmed with recombinant human preproinsulin expressed in recombinant E. coli as an inclusion body.

• Bulletin of the Korean Chemical Society
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• 제33권7호
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• pp.2207-2212
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• 2012

Dimethylaluminum isopropoxide (DMAI, $(CH_3)_2AlO^iPr$) as a single precursor, which contains one aluminum and one oxygen atom, has been adopted to deposit non-stoichiometric aluminum oxide ($AlO_x$) films by low pressure metal organic chemical vapor deposition without an additional oxygen source. The atomic concentration of Al and O in the deposited $AlO_x$ film was measured to be Al:O = ~1:1.1 and any serious interfacial oxide layer between the film and Si substrate was not observed. Gaseous by-products monitored by quadruple mass spectrometry show that ${\beta}$-hydrogen elimination mechanism is mainly contributed to the $AlO_x$ CVD process of DMAI precursor. The current-voltage characteristics of the $AlO_x$ film in Au/$AlO_x$/Ir metalinsulator-metal (MIM) capacitor structure show high ON/OFF ratio larger than ${\sim}10^6$ with SET and RESET voltages of 2.7 and 0.8 V, respectively. Impedance spectra indicate that the switching and memory phenomena are based on the bulk-based origins, presumably the formation and rupture of filaments.

• 대한화학회지
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• 제22권5호
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• pp.281-288
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• 1978

1-염화 및 2-염화나프탈렌술포닐과 아닐린과의 반응에서 그 반응의 유사 일차 반응속도상수($k_{obs}$)를 구하고 또한 2차 반응속도 상수 $k_2$및 3차반응 촉매속도상수 $k_3$도 $k_{obs}$로 부터 구하였다. 1-염화나프탈렌술포닐과의 반응에서는 Peri-hydrogen 효과가 관측되었다. 또한 Brensted 그림표에서는 큰 값의 ${\beta}$와 Hammett 그림표의 기울기로부터 크 음의 ${\rho}$값을 얻었다. 따라서 이 반응의 메카니즘은 매우 낮은 활성화파라미터의 값을 갖는 결과로$S_AN$반응메카니즘과 잘 일치되지만 associative$S_N2$메카니즘으로도 동일하게 잘 설명될 수 있었다.

• Molecular & Cellular Toxicology
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• 제4권4호
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• pp.307-310
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• 2008

AAD16034 is an alginate lyase from Pseudoalteromonas sp. IAM14594. A very close homologue with known 3D structure exists (marine bacterium Pseudoalteromonas sp. strain no. 272). A three-dimensional structure of AAD16034 was generated based on this template (PDB code: 1J1T) by comparative modeling. The modeled enzyme exhibited a jelly-roll like structure very similar to its template structure. Both enzymes possess the characteristic alginate sequence YFKhG+Y-Q. Since AAD16034 displays enzymatic activity for poly-M alginate, docking of a tri-mannuronate into the modeled structure was performed. Two separate and adjacent binding sites were found. The ligand was accommodated inside each binding site. By considering both binding sites, a plausible binding pose for the poly-M alginate polymer could be deduced. From the modeled docking pose (i.e., the most important factor that attracts alginate polymer into this lyase) the most likely interaction was electrostatic. In accordance with a previous report, the hydroxyl group of Y345 was positioned close to the ${\alpha}$-hydrogen of ${\beta}$-mannuronate, which was suitable to initiate a ${\beta}$-elimination reaction. K347 was also very near to the carboxylatemoiety of the ligand, which might stabilize the dianion intermediate during the ${\beta}$-elimination reaction. This implies that the characteristic alginate sequence is absolutely crucial for the catalysis. These results may be exploited in the design of novel enzymes with desired properties.

• 대한한방부인과학회지
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• 제20권1호
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• pp.32-49
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• 2007

Purpose: Breast cancer is the most common disease in Korean women. Despite remarkable improvements in treatment strategies against various cancer during the past 40 years, breast cancer still remains as one of the main causes of cancer mortality among women in the whole world. This study was carried out to investigate antioxidative and anti-proliferative effects on MCF-7 human breast cancer cells of Ikiyangyoung-Tang extract. Methods: We measured a content of polyphenol and flavonoid in the Ikiyangyoung-Tang extract, eliminative ability of DPPH radical, ABTS free radical and hydrogen peroxide, antioxidative effects of linoleic acid, cytotoxicity on MCF-7 human breast cancer cells. MCF-7 cells were cultured in Dulbecco's modified Eagle's medium/F12(DMEM/F12) supplemented with 10 % fetal bovine serum(FBS; Gibco) and antibiotics. Results : The extract of Ikiyangyoung-Tang contains polyphenol of 168.3${\pm}$12.8 ${\mu}$g/mg and flavonoid of 84.3${\pm}$3.4 ${\mu}$g/mg. Above results show profitable abilities of elimination of ${\alpha}$-${\alpha}$-Diphenyl-${\beta}$-picrylhydrazyl(DPPH) radical, ABTS free radical and hydrogen peroxide. Also, the extract of Ikiyangyoung-Tang strongly inhibits the proliferation of MCF-7 cells in a dose ependent manner. And. it has cytotoxicity on NIH3T3 cells. Conclusion : It can be concluded that Ikiyangyoung-Tang extract has an antioxidative effect and antiproliferative effect on MCF-7 human breast cancer cells.