• BMB Reports
• /
• 제37권4호
• /
• pp.454-459
• /
• 2004

Experimental hyperoxia represents a suitable in vitro model to study some pathogenic mechanisms related to oxidative stress. Moreover, it allows the investigation of the molecular pathophysiology underlying oxygen therapy and toxicity. In this study, a modified experimental set up was adopted to accomplish a model of moderate hyperoxia (50% $O_2$, 96 h culture) to induce oxidative stress in the human leukemia cell line, U-937. Spectrophotometric measurements of mitochondrial respiratory enzyme activities, NMR spectroscopy of culture media, determination of antioxidant enzyme activities, and cell proliferation and differentiation assays were performed. The data showed that moderate hyperoxia in this myeloid cell line causes: i) intriguing alterations in the mitochondrial activities at the levels of succinate dehydrogenase and succinate-cytochrome c reductase; ii) induction of metabolic compensatory adaptations, with significant shift to glycolysis; iii) induction of different antioxidant enzyme activities; iv) significant cell growth inhibition and v) no significant apoptosis. This work will permit better characterization the mitochondrial damage induced by hyperoxia. In particular, the data showed a large increase in the succinate cytochrome c reductase activity, which could be a fundamental pathogenic mechanism at the basis of oxygen toxicity.

• 한국식품과학회지
• /
• 제35권6호
• /
• pp.1199-1203
• /
• 2003

한국산 녹차를 70% 에탄올로 추출한 후 Sephadex LH-20과 HPLC를 사용하여 polyphenol을 분리동정하였고 분리된 각 성분들의 angiotensin converting enzyme(ACE) 및 xanthine oxidase, tyrosinase의 저해효과를 확인하였다. 녹차로부터 HPLC로 polyphenol을 분리한 결과 epiafzelechin-$(4{\beta}{\rightarrow}8)$-epiafzelechin, procyanidin B-3-3-O-rhamnose, afzelechin-$(4{\alpha}{\rightarrow}8)$-catechin, prodelphinidin B-5-3,3'-di-O-digallate, (+)-taxifolin-3-O-D-xyloside 등 11종류를 분리하였다. ACE의 저해효과는 prodelphinidin-C-2-3,3'-di-O-gallate $100{\mu}M$에서 68.8%, procyanidin B-2-3,3'-digallate가 54.6%의 저해를 나타내었고, Xanthine oxidase는 prodelphinidin C-2-3,3'-di-O-gallate가 54.5%, procyanidin B-2-3,3'-digallate가 38.2%로 높은 저해효과를 보였다. Tyrosinase의 저해효과는 $100{\mu}M$ 농도에서 prodelphinidin C-2-3,3'-di-O-gallate가 42.1%, procyanidin B-2-3,3'-digallate와 procyanidin B-7이 각각 30.7%, 20.5%의 저해를 나타내었다. 따라서 녹차 추출물로부터 분리한 polyphenol이 혈압예방, 통풍 및 미백효과의 기능성 식품 신소재로서 이용이 가능하다는 것을 확인하였다.

• 대한화학회지
• /
• 제46권3호
• /
• pp.213-218
• /
• 2002

(${\eta}^5$-Cyclopentadienyl)(${\eta}^6$-1,2,3,4-tetramethyl-1,4-dibora-2,5-cyclohexadiene)Ni(5)는 cyclopentadienyl (carbonyl)-nickel dimer와 1,2,3,4-tetramethyl-1,4-dibora-2-cyclohexene (1)을 반응시켜서 주생성물로 얻었다. Di-allyl nickel과 2,3-diethyl-1,4-dimethyl-1,4-dibora-2-cyclohexene (2)을 -20$^{\circ}C$에서 반응시켜서 bis[${\eta}^6$-2,3-dimethyl-1,4-diethoxy-1,4-dibora-2,5-cyclohexadiene]nickel (6) 착화합물을 15% 수율로 생성하였다. 그리고 야-allyl nickel과 2,3-dimethyl-1,4-diethoxy-1,4-dibora-2-cyclohexene (3)을 역시 -20$^{\circ}C$에서 반응시켜서 22% 수율로 bis[${\eta}^6$-2,3-dimethyl-1,4-diethoxy-1,4-dibora-2,5-cyclohexadiene] nickel (7)을 생성하였다. 이들 double-decker 착화합물들은 불안정하여 분리하기 어려웠으며, NMR, MS, 원소분석 등으로 확인하였다.

• International Journal of Automotive Technology
• /
• 제8권4호
• /
• pp.413-419
• /
• 2007

Experimental study of additives on the ignition performance of a compression ignition natural gas engine is introduced, followed by results of a simulation of its working mechanism. From the experimental results, it is understood that engine ignition performance can be improved when a certain amount of Di-tertiary-butyl peroxide additive is added. If the mass fraction of Di-tertiary-butyl peroxide additive reaches as high as 14.2%, engine ignition can be realized at ambient temperatures with a glow plug temperature of about $750^{\circ}C$. From the simulation results, we verify that the Di-tertiary-butyl peroxide additive, by cracking its radicals at lower temperature, can accelerate reaction rate. Therefore, the additive is able to improve the ignition performance of natural gas significantly.

• Computers and Concrete
• /
• 제12권4호
• /
• pp.553-563
• /
• 2013

The present study aims to show how the problem of reproducing, as closely as possible, binders of historic mortars by mixing raw materials which are commercially available, can be formulated as a linear optimization problem. The study points out that by mixing five standard raw materials (end-members) it is possible to obtain mortar binders with the almost same chemical compositions of those determined on the historic and archaeological mortar samples studied in some recent scientific papers. An advanced function of the Microsoft Excel spreadsheet, the Solver add-in, was used for the calculation of the right amount of each raw material to be mixed for producing the new binders. This approach could be useful to provide an optimal solution in the process of restoration of ancient monuments, where it is necessary to replace the historic mortars with new highly compatible repair mortars.

• 한국독성학회:학술대회논문집
• /
• 한국독성학회 2002년도 Current Trends in Toxicological Sciences
• /
• pp.132-132
• /
• 2002

Effects of antioxidant vitamins were investigated in di(2-ethylhexyl) phthalate (DEHP)-induced endocrine disruption toxicity. After rats were treated with DEHP, and vitamin C and vitamin E were supplemented for 30 days.(omitted)

• Journal of Microbiology and Biotechnology
• /
• 제30권6호
• /
• pp.811-821
• /
• 2020

Mycobacterium tuberculosis produces mycolic acids which are relevant for persistence, recalcitrance to antibiotics and defiance to host immunity. c-di-GMP is a second messenger involved in transition from planktonic cells to biofilms, whose levels are controlled by diguanylate cyclases (DGC) and phosphodiesterases (PDE). The transcriptional regulator dosR, is involved in response to low oxygen, a condition likely happening to a subset of cells within biofilms. Here, we found that in M. bovis BCG, expression of both BCG1416c and BCG1419c genes, which code for a DGC and a PDE, respectively, decreased in both stationary phase and during biofilm production. The kasA, kasB, and fas genes, which are involved in mycolic acid biosynthesis, were induced in biofilm cultures, as was dosR, therefore suggesting an inverse correlation in their expression compared with that of genes involved in c-di-GMP metabolism. The relative abundance within trehalose dimycolate (TDM) of α-mycolates decreased during biofilm maturation, with methoxy mycolates increasing over time, and keto species remaining practically stable. Moreover, addition of synthetic c-di-GMP to mid-log phase BCG cultures reduced methoxy mycolates, increased keto species and practically did not affect α-mycolates, showing a differential effect of c-di-GMP on keto- and methoxy-mycolic acid metabolism.

• Journal of Photoscience
• /
• 제10권1호
• /
• pp.9-20
• /
• 2003

Recent studies on the photoreactivity of l,4-unsaturated systems have changed some ideas that were firmly established in this area of research for many years. Thus, we have described the first examples of 2-aza-di-$\pi$-methane (2-ADPM) rearrangements promoted by triplet-sensitization and by single electron transfer (SET) using electron-acceptor sensitizers. These reactions afford N-vinylaziridine and cyclopropylimine photoproducts in the first examples of di-$\pi$-methane processes that yield three-membered ring heterocycles. l-Aza-1,4-dienes also undergo SET-promoted l-aza-di-$\pi$-methane (l-ADPM) rearrangements via radical-cation intermediates using electron acceptor sensitizers. In some cases, alternative cyclizations yielding different carbocycles and heterocycles have been observed. The l-ADPM and di-$\pi$-methane (DPM) reactions also occur via radical-anion intermediates on irradiation using electron donor sensitizers. On the other hand, the photoreactivity reported for $\beta$,${\gamma}$-unsaturated aldehydes for many years was decarbonylation to the corresponding alkenes. However, our studies demonstrate that these compounds undergo the oxa-di-$\pi$-methane (ODPM) rearrangement with high chemical and quantum efficiency. A comparison of the photochemical reactivity of $\beta$,${\gamma}$-unsaturated aldehydes and corresponding methyl ketones has shown that the ketones do not undergo the ODPM rearrangement while the corresponding aldehydes are reactive by this pathway. Monosubstituted $\beta$,${\gamma}$-unsaturated aldehydes at C-2 undergo the ODPM rearrangement yielding the corresponding cyclopropane carbaldehydes diastereoselectively. Finally, we have described the first examples of reactions, similar to the well know Norrish Type I process, which take place in the triplet excited state of $\beta$,${\gamma}$-unsaturated carbonyl compounds by excitation of the C-C double bond instead of the carbonyl group.

• 대한수학회논문집
• /
• 제35권4호
• /
• pp.1075-1085
• /
• 2020

We investigate the relation between the notion of e-exactness, recently introduced by Akray and Zebary, and some functors naturally related to it, such as the functor P : Mod-R → Spec(Mod-R), where Spec(Mod-R) denotes the spectral category of Mod-R, and the localization functor with respect to the singular torsion theory.

• 대한화학회지
• /
• 제63권3호
• /
• pp.216-219
• /
• 2019