• BMB Reports
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• v.39 no.4
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• pp.452-456
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• 2006

To elaborate the peroxidase activity of cytochrome c in the generation of free radicals from $H_2O_2$, the mechanism of DNA cleavage mediated by the cytochrome c/$H_2O_2$ system was investigated. When plasmid DNA was incubated with cytochrome c and $H_2O_2$, the cleavage of DNA was proportional to the cytochrome c and $H_2O_2$ concentrations. Radical scavengers, such as azide, mannitol, and ethanol, significantly inhibited the cytochrome c/$H_2O_2$ system-mediated DNA cleavage. These results indicated that free radicals might participate in the DNA cleavage by the cytochrome c and $H_2O_2$ system. Incubation of cytochrome c with $H_2O_2$ resulted in a time-dependent release of iron ions from the cytochrome c molecule. During the incubation of deoxyribose with cytochrome c and $H_2O_2$, the damage to deoxyribose increased in a time-dependent manner, suggesting that the released iron ions may participate in a Fenton-like reaction to produce $\cdot$OH radicals that may cause the DNA cleavage. Evidence that the iron-specific chelator, desferoxamine (DFX), prevented the DNA cleavage induced by the cytochrome c/$H_2O_2$ system supports this mechanism. Thus we suggest that DNA cleavage is mediated via the generation of $\cdot$OH by a combination of the peroxidase reaction of cytochrome c and the Fenton-like reaction of free iron ions released from oxidatively damaged cytochrome c in the cytochrome c/$H_2O_2$ system.

• Journal of the Korean Chemical Society
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• v.24 no.3
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• pp.250-258
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• 1980

Various radicals may add to isonitriles to give imidoyl radcals RN=CR'. This may be also generated via abstraction of imidoyl hydrogen from imine in the following manner: RN=CR' ＋ R"${\cdot}{\rightarrow}$ RN=CR' ＋ R"-H Imidoyl radicals would be stabilized via two pathways, ${\beta}$-cleavage and atom transfer reactions. ${\beta}$-Cleavage may occur in two directions depending upon structure of the radicals. Cyanide transfer and the "so-called" normal ${\beta}$-cleavage are the two modes of ${\beta}$-cleavage. Addition of t-butoxy radical to t-butyl isocyanide 7 generates an imidoyl radical t-Bu-N=C-O-Bu-t, which undergoes ${\beta}$-cleavage to give t-butyl isocyanate and t-butyl radical. Addition of phenyl radical to 7 forms the intermediate radical t-Bu-N=$C-C_6H_5$, which decomposes to give benzonitrile and t-butyl radical. The t-butyl radical generated from the ${\beta}$-cleavage adds to 7 giving the radical t-Bu-N=C-Bu-t, which cleaves only to pivalonitrile and t-butyl radical, inducing radical chain isomerization. Trimethylsilyl radical adds to 7 to give the intermediate t-Bu-N=$C-Si(CH_3)_3$, which collapses to $(CH_3)_3$SiCN and a t-butyl radical.

• Journal of Embryo Transfer
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• v.12 no.2
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• pp.161-169
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• 1997

This study was conducted to compare the insemination time of bovine oocytes and determine the effects of glucose(1.5 mM) on the development of bovine embryos at early cleavage stage. Oocytes were matured for 24 h, followed by exposure to sperm and cultured in modified Tyrode's media drops or with bovine oviduct epithelial cell monolayer prepared in TCM199(BOECM). Insemination time and culture system were varied in each experiment. In experiment 1, to investigate the developmental capacity of bovine embryos after different time of exposure to sperm, bovine ova and sperm were co-incubated for 18, 30 or 54 h, respectively. The development to blastocysts of 30 and 54 h insemination groups were significantly higher(P<0.05) than 18 h group, and in case of blastocysts of cleaved embryos, 30 h group were significantly higher(P<0.05) than other groups. In experiment 2, we investigated the effect of glucose on early bovine embryos. After 18 h insemination, in vitro fertilized oocytes were separated following 3 groups ; G+0, C+24 and C+48. Oocytes of G+0 group were cultured in glucose added Tyrode's medium after fertilization, oocytes in C+24 and C+48 groups were cultured in glucose free Tyrode's medium after fertilization. After 24 h culture, G+24 group was moved to glucose added medium. All oocytes of 3 groups were moved to BOECM after 48 h culture. The rates of cleavage and development to blastocysts in G+0 group were significantly lower than other groups. In experiment 3, we determined the effects of glucose exposure from 8 to 20 h after insemination on the cleavage and development of oocytes. The oocytes in glucose added group had high capacity of cleavage and further development. This study shows that in bovine oocytes, the optimal exposure to sperm is 30 h and glucose exposure to bovine one-cell embryos is detrimental to their first cleavage and further development in vitro but there has no evidence of detrimental effect of glucose(1.5 mM) exposure to bovine embryos over the two-cell stage in vitro.

• Applied Biological Chemistry
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• v.37 no.6
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• pp.447-450
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• 1994

Rate of hydrolysis ethylene phosphate, dimethylphosphate and hydroxyethylmethylphosphate in neutral water have been measured. Hydrolysis of ethylene phosphate proceeds with P-0 bond cleavage $(k_{obs}=3{\times}10^{-7}s^{-1}\;at\;100^{\circ}C,\;{\Delta}H{\neq}=24\;kcal,\;{\Delta}S{\neq}=25.5\;eu)$. In constrast, hydrolysis of dimethylphosphate proceeds with C-O bond cleavage $(k_{obs}=3{\times}10^{-7}s^{-1}\;at\;150^{\circ}C)$. The rate constant for P-O bond cleavage of dimethylphosphate is estimated at $1{\times}10^{-11}s^{-1}\;at\;150^{\circ}C,\;({\Delta}H{\neq}=36\;kcal,\;{\Delta}S{\neq}=25.5\;eu)$. A phosphodiesterase catalyzed hydrolysis of dimethylphosphate is $10^{17}$ times faster than the simple water rate. The observed rate of hydrolysis of hydroxyethylmethylphosphate is comparable to that of dimethylphosphate indicating C-O bond cleavage $(k_{obs}=6{\times}10^{-7}s^{-1}\;at\;150^{\circ}C)$.

• Journal of Animal Science and Technology
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• v.57 no.8
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• pp.27.1-27.6
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• 2015

This study was designed to investigate the effects of ${\alpha}$-tocopherol and granulosa cells monolayer on nuclear maturation and cleavage rates of ovine cumulus-oocyte complexes (COCs). The COCs (n = 2814) were matured in maturation medium supplemented with various concentration of ${\alpha}$-tocopherol (0, 5, 10, $15{\mu}g/ml$), oocytes were incubated at $39^{\circ}C$ with 5 % $CO_2$ for 24 h in three culture systems: (a) maturation medium (MM; n = 884), (b) co-cultured with granulosa cells (CG; n = 982) and (c) co-cultured with granulosa cells and cells were further cultured in MM for 12 h (CG + 12hMM; n = 948). Our results showed that ${\alpha}$-tocopherol had no effect on GVBD and MII as compared to control group, but when ${\alpha}$-tocopherol added to maturation medium the rate of cleavage decreased. This indicates interaction of above mentioned factors in any of the treatments showed no significant differences on the rate of maturation and cleavage stages (MII, GVBD and cleavage) (p > 0.05). The oocytes co-cultured with granulosa cells for 24 h had beneficial effects on cleavage rate. The maximum MII and cleavage rates were achieved when oocytes had extra 12 h culture in the maturation medium without granulosa cells. Results also showed our modified co-culture system (CG + 12hMM), improved rates of MII and the cleavage in comparison with other studied maturation systems.

• Bulletin of the Korean Chemical Society
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• v.29 no.10
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• pp.1920-1926
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• 2008

We investigated the C-H bond activation mechanism of aldimine by the [RhCl$(PPH_3)_3$] model catalyst using DFT B3LYP//SBKJC/6-31G*/6-31G on GAMESS. Due to their potential utility in organic synthesis, C-H bond activation is one of the most active research fields in organic and organometallic chemistry. C-H bond activation by a transition metal catalyst can be classified into two types of mechanisms: direct C-H bond cleavage by the metal catalyst or a multi-step mechanism via a tetrahedral transition state. There are three structural isomers of [RhCl$(PH_3)_2$] coordinated aldimine that differ in the position of chloride with respect to the molecular plane. By comparing activation energies of the overall reaction pathways that the three isomeric structures follow in each mechanism, we found that the C-H bond activation of aldimine by the [RhCl$(PH_3)_3$] catalyst occurs through the tetrahedral intermediate.

• Bulletin of the Korean Chemical Society
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• v.25 no.11
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• pp.1623-1624
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• 2004

• Journal of Korea Foresty Energy
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• v.17 no.1
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• pp.56-70
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• 1998

This study was carried out to investigate the structural characteristics of kraft lignin and the wood degrading characteristics, the productivity of ligninolytic enzymes and the enzymatic degradation of kraft lignin by white-rot fungi. To purify kraft lignin, precipitation of kraft pulping black liquors of pitch pine meal was done by titration with lN $H_{2}SO_{4}$ reaching to pH 2, and isolation of the precipitates done by centrifugation. The isolated precipitates from pitch pine were redissloved in lN NaOH, reprecipitated by titration with lN $H_{2}SO_{4}$, washed with deionized water, and kept ofr analysis after freeze drying. Fractionation of the precipitates in solution by successive extraction with $CH_{2}Cl_{2}$ and MeOH, and the fractionates were named SwKL, SwKL I, SwKL II, and SwKL III for pitch pine kraft lignin. The more molecular weights of kraft lignin increased, the less phenolic hydroxyl groups and the more aliphatic hydroxyl groups. Because as the molecular weights increased, the ratio of etherified guaiayl/syringyl(G/S ratio) and the percentage were increased. The spectra obtained by 13C NMR and FTIR assigned by comparing the chemical shifts of various signals with shifts of signals from autherized ones reported. The optimal growth temperature and pH of white-rot fungi in medium were $28^{\circ}C$ and 4.5-5.0, respectively. Especially, in temperature and pH range, and mycelial growth, the best white-rot fungus selected was Phanerochaete chrysosporium for biodegradation. For the degradation pathways, the ligninolytic fungus jcultivated with stationary culture using medium of 1% kraft lignin as a substrate for 3 weeks at $28^{\circ}C$. The weight loss of pitch pine kraft lignin was 15.8%. The degraded products extracted successively methoanol, 90% dioxane and diethyl ether. The ether solubles were analyzed by HPLC. Kraft lignin degradation was initiated in $\beta$-O-4 bonds of lignin by the laccase from Phanerochaete chrysosporium and the degraded compounds were produced from the cleavage of $C\alpha$-$C\beta$ linkages at the side chains by oxidation process. After $C\alpha$-$C\beta$ cleavage, $C\alpha$-Carbon was oxidized and changed into aldehyde and acidic compounds such as syringic acid, syringic aldehyde and vanilline. And the other compound as quinonemethide, coumarin, was analyzed. The structural characteristics of kraft lignin were composed of guaiacyl group substituted functional OHs, methoxyl, and carbonyl at C-3, -4, and -5 and these groups were combinated with $\alpha$ aryl ether, $\beta$ aryl ether and biphenyl. Kraft lignin degradation pathways by Phanerochaete chrysosporium were initially accomplished cleavage of $C\alpha$-$C\beta$ linkages and $C\alpha$ oxidation at the propyl side chains and finally cleavage of aromatic ring and oxidation of OHs.

• Journal of Physiology & Pathology in Korean Medicine
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• v.19 no.3
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• pp.802-810
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• 2005

The tetrahydroisoquinolines included potent cytotoxic agents that showed antitumor activity,antimicrobial activity, and other biological properties. We studied the effect of CDST, 1-Chloromethyl-6,7-dimethoxy-3,4-dihydro-1H-isoquinoline-2-sulfonic acid amide, a newly synthesized anti-cancer agent. The cytotoxic activity of CDST in HL-60 cells was increased in a dose-dependent manner. CDST, tetrahydroisoquinolines derivative, was cytotoxic to HL-60 cells, with IC50 of $80{\mu}g/ml$. Treatment of CDST to HL-60 cells showed the fragmentation of DNA in a dose- and time dependent manner, suggesting that thesecells underwent apoptosis. Treatment of HL-60 cells with CDST was induced in a dose- and time-dependent activation of caspase-3, caspase-8 and proteolytic cleavage of poly(ADP-ribose) polymerase. In caspase activity assay, caspase-3 and -8 was activated after 12 h and 6 h posttreatment, respectively. CDST also caused the release of cytochrome c from mitochondria into the cytosol. CDST-induced cytochrome c release was mediated by caspase-8-dependent cleavage of Bid and Bax translocation. These results suggest that caspase-8 induced Bid cleavage and Bax translocation, caused mitochondrial cytochrome c release, and induce caspase-3 activationduring CDST-induced apoptosis in HL-60 cells.

• Korean Journal of Food Science and Technology
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• v.32 no.6
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• pp.1227-1233
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• 2000

Lycopene was subjected to ozonolysis in ice-cold dichloromethane. The ozonolysis products were fractionated with a silica column and the carbonyl fraction was analyzed by ODS-HPLC with a photodiode array detector and by LC-MS. UV-vis spectra and $[M+H]^+$ of the carbonyl compound peaks showed clearly that acycloretinal, apo-14'-lycopenal, apo-12'-lycopenal, apo-10'-lycopenal, apo-8'-lycopenal and apo-6'-lycopenal were formed by ozonolysis of lycopene. Lycopene was solubilized in toluene and aqueous Tween 40, and then oxidized by incubating at $37^{\circ}C$ under atmospheric oxygen. Carbonyl compounds were produced. In comparison with autoxidation and ozonolysis, each compound showed the same retention time and UV-vis spectra are identical to the reference cleavage products prepared by ozonolysis of lycopene. Thus, eccentric cleavage of lycopene was confirmed to occur in vitro under oxidation condition.