• Bulletin of the Korean Chemical Society
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• 제33권8호
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• pp.2711-2718
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• 2012

The alkylation of the ambident enolates of a methyl glycinate Schiff base with ethyl chloride was studied at B3LYP and MP2 levels with $6-31+G^*$ basis set. The free (E)-enolates and (Z)-enolate are similar in energy and geometry. The transition states for the alkylation of the free (E)/(Z)-enolate with ethyl chloride have similar energy barriers of ~13 kcal/mol. However, with a lithium ion, the (E)-enolate behaves as an ambident enolate and makes a cyclic lithium-complex in bidentate pattern which is more stable by 11-23 kcal/mol than the (Z)-enolate-lithium complexes. And the TS for the alkylation of (E)-enolate-lithium complex coordinated with one methyl ether is lower in energy than those from (Z)-enolate-lithium complexes by 4.3-7.3 kcal/mol. Further solvation model (SCRF-CPCM) and reaction coordinate (IRC) were studied. This theoretical study suggests that the alkylation of ambident enolates proceeds with stable cyclic bidentate complexes in the presence of metal ion and solvent.

• Bulletin of the Korean Chemical Society
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• 제30권12호
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• pp.2973-2978
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• 2009

The decomposition reaction mechanism of $CH_3CF_2O$ radical formed from hydroflurocarbon, $CH_3CHF_2$ (HFC-152a) in the atmosphere has been investigated using ab-initio quantum mechanical methods. The geometries of the reactant, products and transition states involved in the decomposition pathways have been optimized and characterized at DFT-B3LYP and MP2 levels of theories using 6-311++G(d,p) basis set. Calculations have been carried out to observe the effect of basis sets on the optimized geometries of species involved. Single point energy calculations have been performed at QCISD(T) and CCSD(T) level of theories. Out of the two prominent decomposition channels considered viz., C-C bond scission and F-elimination, C-C bond scission is found to be the dominant path involving a barrier height of 12.3 kcal/mol whereas the F-elimination path involves that of a 28.0 kcal/mol. Using transition-state theory, rate constant for the most dominant decomposition pathway viz., C-C bond scission is calculated at 298 K and found to be 1.3 ${\times}$ 10$^4s{-1}$. Transition states are searched on the potential energy surfaces involving both decomposition channels and each of the transition states are characterized. The existence of transition states on the corresponding potential energy surface are ascertained by performing Intrinsic Reaction Coordinate (IRC) calculation.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 신호처리소사이어티 추계학술대회 논문집
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• pp.77-80
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• 2003

본 논문에서는 디지털방송과 인터넷의 융합에 따른 MPEG-2/4/7 방송 및 인터넷 콘텐츠를 비롯한 게임등과 같은 다양한 멀티미디어 서비스를 제공하기 위한 차세대 지능형 고품질 홈 엔터테인먼트 시스템 Platform 개발에서 사용될 MPEG-4 오디오를 개발한다. 인터넷 상에서의 스트리밍 서비스를 위해서는 저 전송률과 고 품질의 비디오/오디오 알고리즘이 필요하다. 이러한 서비스를 제공하기 위하여 MPEG-4 오디오는 음성에서 고품질의 다중 채널의 오디오까지, 그리고 자연음(Natural Sound)에서 합성음에 이르기까지 다양한 알고리즘을 제공한다. 본 논문에서는 지능형 고품질 미디어 에이전트 시스템에 적합한 MPEG-4 AAC, MPEG-1 Layer-3인 MP3, G.723.1을 구현하고, 이 시스템에 알맞은 7㎑ 대역폭을 가지는 광대역(Wideband) 음성신호를 16kbps로 압축하는 음성 압축기를 제안 및 개발한다.

• 한국초지조사료학회지
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• 제38권4호
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• pp.260-265
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• 2018

TMR 급여와 분리급여가 반추위 메탄발생량 변화에 미치는 효과를 연구한 사례가 많지 않다. 본 실험은 1일 실험사료를 체중의 1.8%(실험 1) 그리고 2.4%(실험 2) 수준에서 급여하면서 triplicated $2{\times}2$ Latin square design을 이용하여 실험을 수행하였다. 각 실험에는 6마리의 Holstein steer를 이용하였고 2개의 군으로 나누어 각각 TMR 급여 또는 분리급여를 하였다. 공시 사료의 농후사료와 조사료 비율은 73% 그리고 27%이었다. 두 실험 모두 사료급여 방식 간의 1일 메탄발생량 차이가 없었다. 현재까지 보고된 국내 연구와 본 연구에서 얻어진 개체 별 1일 건물섭취량과 1일 메탄발생량과의 관계를 분석한 결과, 메탄발생량 $(g/d)=11.5({\pm}1.3){\times}$ 건물섭취량(kg/d) + 14.2, $R^2=0.73$, p<0.001의 회귀식을 유도하였다.

• Preventive Nutrition and Food Science
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• 제8권4호
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• pp.383-389
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• 2003

This study was conducted to investigate the antioxidative effects of Paeonia lactiftora Pall. (PL) seed extracts and Forsythia viridissima Lindl. (FVL) extracts on the antioxidative defense system and lipid peroxidation in the erythrocytes of rats fed a high-cholesterol diet. Sprague-Dawley male rats weighing 100 10 g were randomly assigned to nine experimental groups and fed 0.5 % cholesterol. The HC group did not receive any supplement, while the MP group was supplemented with 0.1 % methanol extract of PL seed, the MP2 group with 0.2 % methanol extract of PL seed, the EP1 group with 0.05 % ether-soluble fraction of PL seed, the EP2 group with 0.1 % ether-soluble fraction of PL seed, the MS1 group with 0.05 % methanol extract of FVL, the MS2 group with 0.1 % methanol extract of FVL, the ES group with 0.025% ethyl acetate-soluble fraction of FVL, and the ES2 group with 0.05 % ethyl acetate-soluble fraction of FVL. The experimental diets were fed ad libitum for 3 weeks. The erythrocyte SOD activity in the EP1 and EP2 groups increased 38% and 59%, respectively, when compared with the HC group, while the erythrocyte GSHpx activity in the EP1, EP2, and ES2 groups increased 30%, 31 %, and 29%, respectively, when compared with the HC group. The level of erythrocyte TBARS was significantly lower in the MP2, EP1, and EP2 groups than in the HC group, yet the level of serum TBARS was significantly lower in the all supplemented groups than in the HC group. The level of serum HDL- TBARS was significantly lower in the EP1 and EP2 groups than in the HC group, while the level of serum LDL- TBARS was significantly lower in the all the supplemented groups than in the HC group. Accordingly, the results indicated that the PL seed extracts and FVL extracts reduced oxidative damage by activating the antioxidative defense system in the erythrocytes of rats fed a high-cholesterol diet.

• Childhood Kidney Diseases
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• 제6권1호
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• pp.75-84
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• 2002

목 적 :성장기 신장에서의 급성신우신염은 신반흔으로 진행된다. 신반흔의 형성에는 세균자체보다도 숙주의 염증반응과 면역반응의 산물인 TGF-${\beta}1$이 세포 고사를 증가시키고 세포증식을 억제함으로서 섬유화를 촉진한다고 하였다. 이에 저자는 항염증제인 methyl-prednisolone (MP)이 실험적으로 급성신우신염을 일으킨 이유기 백서에서 신반흔 형성에 미치는 영향을 관찰하고자 하였다. 대상 및 방법 : 생후 3주(체중 50-60g)된 이유기 Sprague-Dawley 백서의 방광에 삽입된 16 guage의 실리콘 도관내로 107/mL 농도의 E coli (ATCC No. 25922, pili형)를 5 mL씩 주입하여 급성신우신염을 유발하였다. 실험군은 1군 (ceftriaxone 단독투여, n=31)과 2군 (MP와 ceftriaxone투여, n=28)으로 나누었고 대조군 (n=43)에는 약제를 투여하지 않았다. 실험 1주와 3주에 실험동물을 희생하여 병리 조직학적 소견상 염증점수, 세포고사 지수와 TGF-${\beta}1$ 발현점수 및 섬유화 점수를 관찰하였다. 결 과 : 사망률은 II군이 $21.4\%$였으나 대조군 $41.9\%$, I군 $32.3\%$와 유의한 차이는 없었다. 염증 점수는 실험 1주에 II군에서 $0.8{\pm}0.87$로 대조군의 $2.3{\pm}0.87$, I군의 $1.7{\pm}0.79$에 비하여 유의하게 낮았다 (P<0.05. 세포고사 지수는 실험 1주에 II군에서 $2.9{\pm}2.15$로 대조군의 $10.0{\pm}1.95$, I군의 $8.3{\pm}2.53$에 비하여 유의 하게 낮았다 (P<0.05). TGF-${\beta}1$발현도 실험 1주에 II군에서 $0.8{\pm}0.72$로 대조군의 $1.90{\pm}67$, I군의 $1.8{\pm}0.60$에 비하여 유의하게 낮았다 (P<0.05). 섬유화 지수는 실험 3주에 II군에서 $0.8{\pm}0.63$로 대조군의 $1.8{\pm}0.83$에 비하여 유의하게 낮았다 (P<0.05) 결 론 : 성장기 백서의 실험적 급성 신우신염에서 MP는 ceftriaxone단독 투여에 비하여 염증 반응, 세포고사, TGF-${\beta}1$발현, 섬유화를 모두 감소 시켰다. 즉 항생제 외에 항염증제의 병용투여가 신반흔의 정도를 감소시킬 수 있으므로 치료지연등 신반흔의 위험인자가 있는 경우에 고려할 수 있을 것으로 생각된다.

• Bulletin of the Korean Chemical Society
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• 제29권7호
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• pp.1335-1343
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• 2008

Theoretical studies on the un-catalyzed and catalyzed aminations of ketene with $NH_3$ and $(NH_3)_2$, respectively, were studied using MP2 and hybrid density functional theory of B3LYP at the 6-31+G(d,p) and 6- 311+G(3df,2p) basis sets in the gas phase and in benzene and acetonitrile solvents. In the gas phase reaction, the un-catalyzed mechanism was the same as those previously reported by others. The catalyzed mechanism, however, was more complicated than expected requiring three transition states for the complete description of the C=O addition pathways. In the un-catalyzed amination, rate determining step was the breakdown of enol amide but in the catalyzed reaction, it was changed to the formation of enol amide, which was contradictory to the previous findings. Starting from the gas-phase structures, all structures were re-optimized using the CPCM method in solvent medium. In a high dielectric medium, acetonitrile, a zwitterions formed from the reaction of $CH_2$=C=O with $(NH_3)_2$, I(d), exists as a genuine minimum but other zwitterions, I(m) in acetonitrile and I(d) in benzene become unstable when ZPE corrected energies are used. Structural and energetic changes induced by solvation were considered in detail. Lowering of the activation energy by introducing additional $NH_3$ molecule amounted to ca. −20 $\sim$ −25 kcal/mol, which made catalyzed reaction more facile than un-catalyzed one.

• Bulletin of the Korean Chemical Society
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• 제20권9호
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• pp.1067-1072
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• 1999

Structures of unprotonated [(NH3)n+(n = 1-6)] and protonated [NH4+(NH3)n-1(n = 1-6)] ammonia cluster cations have been optimized with ab initio Hartree-Fock (HF) and second-order MФller-Plesset (MP2)/6-31+G ** levels and the harmonic vibrational frequencies have also been evaluated. In unprotonated cluster cations, NH3+ forms as a central core of the first ammonia solvation shell. In protonated cluster cations, NH4+ forms as a central core. In unprotonated dimer and trimer cations, there are two types of isomers (hydrogen-bonded and head-to-head interactions). In both cluster cations, the hydrogen-bonded isomers are more stable. In the hydrogen-bonded dimer cation, the proton transfer reaction takes place from (NH3-HN+H2) to (NH4+-NH2). But in the other unprotonated cluster cations, the proton transfer does not take place. In unprotonated pentamer and hexamer, a NH3+ core has both interactions in a complex. On the other hand, in unprotonated tetramer a core has only the hydrogen-bonded type combined with neutral ammonia molecules. With increasing cluster cation size, the bond lengths [R(NN)] between two nitrogen atoms and the distances [R(N ...H)] of the hydrogen-bond increase reg-ularly. In the calculated infra-red absorption bands for ammonia cluster cations, the characteristic peaks of the bridged NH vibration of the hydrogen-bonded clusters appear near 2500 cm-1 . With increasing size, the peaks shift from 2306 cm-1 to 2780 cm-1 .

• 대한화학회지
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• 제59권2호
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• pp.117-124
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• 2015

Hydrogen polyoxide, $H_2O_n-H_2O_m$(n=1-4, m=1-4) 이중합체(dimer)의 분자 구조 변화에 따른 수소결합(H-bonding) 효과를 순 이론적(ab initio) 방법과 밀도 범함수 이론(DFT)으로 계산하였다. 분자 구조는 B3LYP, CAM-B3LYP, MP2의 양자역학적 방법들을 사용하여 최적화하였으며, 진동주파수를 계산하여 최저에너지(true local minimum) 구조인 것을 확인하였다. 보다 정확한 수소결합 에너지(${\Delta}E$) 계산을 위하여 CCSD(T) 이론수준에서 한 점(single-point) 에너지 계산을 하였으며, 영점 진동에너지(ZPVE) 보정과 바탕집합 중첩에러(BSSE) 보정을 하였다. CCSD(T)/cc-pVTZ 이론 수준에서 $H_2O_4-H_2O_3$이 8.18 kcal/mol로 가장 강한 결합을 나타내었으며, 물 이중합체($H_2O-H_2O$)는 3.00 kcal/mol로 가장 약한 결합에너지를 나타내었다.

• Journal of Photoscience
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• 제9권3호
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• pp.49-50
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• 2002

N-Nitrosoproline(NPRO) is endogenously formed from proline and nitrite. NPRO has been reported to be nonmutagenic and noncarcinogenic. In this study, we have detected the direct mutagenicity of NPRO with UVA and UVB towards S. typhimurium. Formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), a mutagenic lesion, was observed in calf thymus DNA treated with NPRO plus simulated sunlight. Furthermore, the treatment with NPRO and sunlight induced single strand breaks in the superhelical replicative form of phage M13mp2 DNA. An analysis using scavengers suggested that both reactive oxygen species and NO radical mediate the strand breaks. The formation of nitric oxide was observed in NPRO solution irradiated with UVA. The co-mutagenic and co-toxic actions of NPRO and sunlight merit attention as possible mechanisms increasing the carcinogenic risk from UVA irradiation.