• Journal of Plant Biology
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• v.31 no.3
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• pp.227-237
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• 1988

Effects of putrescine on senescence in detached leaves of Chinese cabbage (Brassica campestris L.) in the light were investigated. The putrescine as a potent antisenescence substane markedly inhibited chlorophyll and protein loss at the 10mM concentraton in the detached leaves during the dark incubation. In the light, however, putrescine showed the opposite effects to dark incubation. The chlorphyll loss by putrescine in the light was stopped with darktransfer, and inhibited competitively by a divalent cation Ca2+. In the light, putrescine reduced the protease activity. Putrescine, in the light, increased H2O2 content and reduced the activities of enzymes -superoxide dismutase (EC 1.15.1.1), peroxidase (EC 1.11.1.7), catalase (EC 1.11.1.6-involved in inhibiting the accumulation of free radicals. These results suggest that the effects of puterscine on chlorophyll and protein loss in detached leaves of Chinese cabbage in the light are related to the cationic nature of putrescine and the accumulation of free radicals.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.4
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• pp.1064-1071
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• 1994

There are three active radicals which become to the scale of flame diagnostics at the flame front. They are OH, CH and $C_2$ radical. For this, optical measurement system which could monitor simultaneously the luminous waves of three radicals, was constructed. These were analyzed statistically into the cross correlation, coherence and phase. Through such an statistical treatment, combustion characteristics was investigated at the primary zone of gas turbine combustor. The local equivalence ratio was predicted with the ratio of luminuous intensity between CH and $C_2$ radical. This result was matched up to the equivalence ratio calculated from gas composition within 5% error. In general, equivalence ratio was said to be 1.0 at flame front, but it could be increased up to about 1.2 depending on the degree of swirl intensity in case of changing properly the air amount of primary zone.

• Korean Journal of Pharmacognosy
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• v.34 no.4 s.135
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• pp.324-326
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• 2003

The methanol (MeOH) extract and ist fractions of Taraxacum mongolicum (Compositae) were examined for their scavenging effects on 1,1-diphenyl-2- phenylhydrazyl (DPPH) and superoxide radicals, and hepatoprotective effects on tacrine-induced cytotoxicity in human hepatoma cell line, Hep G2 cells. Both methylene chloride $(CH_2Cl_2)$ and butanol (n-BuOH) soluble fractions of the MeOH extract showed the free radicals scavenging and hepatoprotective effects. From these results, it is suggested that hepatoprotective effect of these fractions partly relies on their free radical scavenging activity.

• Journal of the Korean Chemical Society
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• v.56 no.4
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• pp.464-467
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• 2012

A novel chitosan derivative with double quaternary ammonium salt-2-pyridine-acetyl-N-trimethyl chitosan chloride (PATMCS) was synthesized and the antioxidant activity of PATMCS against hydroxyl radicals was assessed. The results indicated that PATMCS had potent hydroxyl scavenging activity. The $IC_{50}$ of PATMCS was 0.13 mg/mL. PATMCS showed 100% scavenging effect at a dose of 0.8 mg/mL which markedly better than that of N-trimethyl chitosan chloride (TMCS). It was confirmed that quaternary chitosan derivatives showed potent antioxidant activity. PATMCS has double quaternary ammonium salt structure in the molecules. Therefore, the antioxidant activity of PATMCS was better than TMCS. The above results are theoretically fundamental for further development and making use of chitosan resources to prepare new antioxidants.

• Bulletin of the Korean Chemical Society
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• v.31 no.9
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• pp.2479-2482
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• 2010

Using a pinhole-type glass nozzle equipped for a corona-excited supersonic expansion (CESE), precursor 2,6-dichlorotoluene seeded in a large amount of inert carrier gas helium was discharged to produce jet-cooled but electronically excited benzyl-type radicals. The visible vibronic emission spectrum was recorded with a long-path monochromator to observe vibronic bands in the $D_1{\rightarrow}D_0$ electronic transition of benzyl-type radicals. The spectral analysis revealed the generation of not only the 2,6-dichlorobenzyl radical as a typical product, but also the o-chlorobenzyl radical as an unexpected species, which indicates the possible molecular rearrangement in eliminating a chlorine atom from the benzene ring. A possible mechanism is proposed for the formation of the o-chlorobenzyl radical from the precurs or in the gas phase.

• Natural Product Sciences
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• v.7 no.3
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• pp.72-75
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• 2001

The antioxidant activity of roasted defatted perilla (Perilla frutescens) seed was determined by measuring its radical scavenging effect on 1,1-diphenyl-2- picrylhydrazyl (DPPH) radicals, inhibitory activity on total reactive oxygen species generation in kidney homogenates using 2',7'-dichlorodihydro-fluorescein diacetate, and scavenging effect on authentic peroxynitrites. The methanolic extract of roasted defatted perilla seed showed strong scavenging activity in both DPPH and peroxynitrite radicals, and thus fractionated with several solvents. The antioxidant activity potential of the individual fraction was in the order of ethyl acetate>n-butanol>dichloromethane>water>n-hexane fraction. The ethyl acetate soluble fraction exhibiting strong antioxidant activity was further purified by repeated silica gel and Sephadex LH-20 column chromatography. Luteolin was isolated as one of the active principles from the ethyl acetate fraction, together with the inactive chrysoeriol and apigenin.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2003.11a
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• pp.315-316
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• 2003

대기중 광화학반응에서 생산되는 이차 생성물중의 하나인 $H_2O$$_2$(hydrogen peroxide)는 peroxy radicals간의 결합에 의해 생성된다. HO$_2$ + HO$_2$ $\longrightarrow$ $H_2O$$_2$+ $O_2$ 이렇게 생성된 $H_2O$$_2$는 대기중에서 주요 산화제로 작용하며, pH 4.5 이하 수용액 내에서 S(IV)를 S(VI)로 산화시켜 H$_2$SO$_4$(sulfuric acid)를 생성 한다. 또한 $H_2O$$_2$는 대기중에서 odd-hydrogen radicals(OH, HO$_2$, and RO$_2$)의 저장고 역할과 함께 odd-hydrogen radical의 생성과 소멸에 작용하여 대기의 산화력을 반영한다(Lee et al. 2000). (중략)

• Biomedical Science Letters
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• v.13 no.4
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• pp.313-317
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• 2007

Melanogenesis refers to the biosynthesis of melanin pigment in melanocytes. Melanogenesis is controlled by the intra- and extracellular environments. In the present study, to develop a new whitening agent, it was investigated the antioxidant activity and the inhibitory effect of Ailanthi Radicis Cortex extract on tyrosinase activity and on melanogenesis in the B16/F1 melanoma cells. The inhibition ratio of tyrosinase activity of ethylacetate fraction from Ailanthi Radicis Cortex was higher than that of arbutin. The ethylacetate fraction showed scavenging activities of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals and superoxide anion radicals in a dose dependent manner. The highest inhibitory activity of melanogenesis was also in ethylacetate fraction ($40.0{\pm}5%$ at the concentration of $400{\mu}g/ml$). This study demonstrates that the Ailanthi Radicis Cortex extract might be used to be a potential agent for skin whitening.

• Kyungpook Mathematical Journal
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• v.54 no.4
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• pp.595-606
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• 2014

In this paper three more right Jacobson-type radicals, $J^r_{g{\nu}}$, are introduced for near-rings which generalize the Jacobson radical of rings, ${\nu}{\in}\{0,1,2\}$. It is proved that $J^r_{g{\nu}}$ is a special radical in the class of all near-rings. Unlike the known right Jacobson semisimple near-rings, a $J^r_{g{\nu}}$-semisimple near-ring R with DCC on right ideals is a direct sum of minimal right ideals which are right R-groups of type-$g_{\nu}$, ${\nu}{\in}\{0,1,2\}$. Moreover, a finite right $g_2$-primitive near-ring R with eRe a non-ring is a near-ring of matrices over a near-field (which is isomorphic to eRe), where e is a right $g_2$-primitive idempotent in R.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.93-93
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• 2010

In this talk, I will introduce a reactive force field (ReaxFF) molecular dynamics (MD) simulation. In contrast to common MD simulations with empirical FFs, we can predict chemical reactions (bond breaking and formation) in large scale systems with the ReaxFF simulation where all of the ReaxFF parameters are from quantum mechanical calculations such as density functional theory to provide high accuracy. Accordingly, the ReaxFF simulation provides both accuracy of quantum mechanical calculations and description of large scale systems of atomistic simulations at the same time. Here, I will first discuss a theory in the ReaxFF including the differences from other empirical FFs, and then show several applications for studying chemical reactions of SiHx radicals on Si surfaces, which is an important issue in Si process.