• Bulletin of the Korean Chemical Society
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• 제26권11호
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• pp.1875-1877
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• 2005

• 대한화학회지
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• 제29권1호
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• pp.45-51
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• 1985

MeOH-DMSO 혼합용매중에서 t-butyl halide의 가메탄올 분해반응 속도상수 및 활성화 파라미터를 전기전도도법으로 측정하였고, Taft의 분광용매화 변수인 용매의 극성-편극성(${\pi}^{\ast}$), 수소결합주기산도(${\alpha}$) 및 수소결합 받기염기도(${\beta}$)를 분광법에 의해서 5가지의 지시약을 이용하여 측정계산하였다. 분광용매화변수와 반응속도상수로부터 얻은 활성화파라미터를 써서 용매의 부피조성비에 따른 가용매분해반응의 속도상수 변화를 논의한 결과, t-butyl halide의 이온화에 용매의 ${\pi}^{\ast}$, ${\alpha}$ 및 ${\beta}$가 협동적으로 기여했고, 또한 이탈기와 혼합용매사이의 이온-쌍극자 작용과 수소결합주기-받기 작용과 같은 독특한 상호작용이 전이상태의 안정화에 미치는 가장 중요한 용매효과 인자들임을 밝혔다.

• Journal of Microbiology and Biotechnology
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• 제29권2호
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• pp.268-273
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• 2019

The specificity of a Bacillus licheniformis uridine diphosphate (UDP) glycosyltransferase, YjiC, was increased towards thymidine diphosphate (TDP)-sugar by site-directed mutagenesis. The Arg-282 of YjiC was identified and investigated by substituting with Trp. Conversion rate and kinetic parameters were compared between YjiC and its variants with several acceptor substrates such as 7-hydroxyflavone (7-HF), 4',7-dihydroxyisoflavone, 7,8-dihydroxyflavone and curcumin. Molecular docking of TDP-glucose and 7-HF with YjiC model showed pi-alkyl interaction with Arg-282 and His-14, and pi-pi interaction with $His^{14}$ and thymine ring. YjiC (H14A) variant lost its glucosylation activity with TDP-glucose validating significance of His-14 in binding of TDP-sugars.

• 대한화학회지
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• 제35권3호
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• pp.196-203
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• 1991

25$^{\circ}$C 때 벤조산과 메타 및 파라위치에 할로겐(F, Cl, Br)이 치환된 $pK_a$값을 메탄올-물 혼합용매(0∼80% 메탄올) 중에서 Fuoss-Kraus 식에 근거한 전도도법과 Gelb의 전도도법을 이용하여 결정하였다. 할로겐 치환기에 따른 벤조산의 $pK_a$ 변화를 전자받게 유도효과와 전자주게 공명효과로 복합시킨 치환기 상수(${\sigma}_1$ 및 ${\sigma}_R$)로써 논의하였다. ${\sigma}_1$가 $D^{-1}$에 대하여 양(+)의 기울기를 갖는 직선성을 보인 반면 ${\sigma}_R$은 $D^{-1}$에 대하여 음(-)의 기울기를 갖는 직선성을 보이고 있는데, 이를 field effect의 유전상수 의존성과 할로겐 치환기의 ${\pi}$-고립쌍 전자와 이온화 중심간의 through-space ${\pi}$-상호작용으로 해석하였다.

• 대한화학회지
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• 제30권1호
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• pp.9-18
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• 1986

${\alpha}$-치환아세톤($CH_2XCOCH_3$, X = F, Cl, OH, SH 및 $NH_2$)의 상대적 형태안정성을 결정하기 위하여 MNDO 및 STO-3G계산을 수행하였다. 계산결과 cis형이 더 안정한 F 및 $NH_2$ 치환 아세톤의 경우를 제외하고 모두 gauche형에 해당하는 형태이성체가 안정함을 밝혔다. gauche형에 대한 안정성은 ${\sigma}_{cx}$와 ${\pi}_{co}^*$궤도간의 two-orbital-two-electron상호작용에 의한 것으로 생각되며 이것은 gauche형에서의 vicinal overlap이 상당히 크다는 점과 두 궤도간의 에너지간격이 작다는 점에서 비롯된다. 아울러 이러한 에너지간격의 좁힘현상은 ${\sigma}_{cx}^*$-${\pi}_{co}^*$궤도간의 hyperconjugation상호작용 때문에 ${\pi}_{co}^*$궤도가 낮아졌기 때문이다. 또한 gauche형에서의 여러가지 ${\sigma}-{\pi}$상호작용들은 X가 Cl 및 SH인 3주기 원자들에게 더 강함을 보였다. 한편 질소원자의 비결합궤도함수 $n_N$과 인접 C-C ${\sigma}$결합의 상호작용은 cis일 경우 보다 trans배향일 경우에 더 강하였다.

• Environmental Engineering Research
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• 제24권4호
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• pp.608-617
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• 2019

The adsorption of sulfamethoxazole (SMX) onto a NaOH-activated pine wood-derived biochar was investigated via batch experiments and models. Surprisingly, the maximum adsorption capacity of activated biochar for SMX (397.29 mg/g) was superior than those of pristine biochars from various feedstock, but comparable to those of commercially available activated carbons. Elovich kinetic and Freundlich isotherm models revealed the best fitted ones for the adsorption of SMX onto the activated biochar indicating chemisorptive interaction occurred on surface of the activated biochar. In addition, the intraparticle diffusion limitation was thought to be the major barrier for the adsorption of SMX on the activated biochar. The main mechanisms for the activated biochar would include hydrophobic, π-π interactions and hydrogen bonding. This was consistent with the changes in physicochemical properties of the activated biochar (e.g., increase in sp² and surface area, but decrease in the ratios of O/C and H/C).

• 대한임상검사과학회지
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• 제39권3호
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• pp.249-255
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• 2007

While respiratory burst enhances neutrophil glucose utilization, many neutrophil functions are critically influenced by extracellular matrix interaction and phosphoinositide-3-OH kinase (PI3K) signaling. We thus evaluated the role of RGD integrin occupancy and PI3K inhibition on respiratory burst and [18F]FDG uptake of stimulated neutrophils. Human neutrophils were stimulated by 100 ng/mL phorbol-myristate-acetate (PMA), and respiratory burst was measured by cumulative luminescence with lucigenin. [18F]FDG uptake and total hexokinase activity was measured 20 min after PMA stimulation in the presence or absence of soluble RGD peptides (200 g/mL) and/or the PI3K inhibitor wortmannin (200 nM). PMA induced a 71.70.9 fold increase in neutrophil oxygen intermediate generation. [18F]FDG uptake was increased to $194.6{\pm} 3.7%$ and hexokinase activity to $145.0{\pm}2.0%$ of basal levels (both p<0.0005). RGD peptides attenuated respiratory burst activation to $35.6{\pm}0.2%$ (p<0.005), but did not inhibit stimulated [18F]FDG uptake or hexokinase activity. In contrast, without affecting respiratory burst activation, wortmannin inhibited PMA stimulated [18F]FDG uptake to $66.9{\pm}1.6%$ and hexokinase activity to $81.0{\pm}4.2%$ (both P<0.0005), demonstrating its dependence on PI3K activity. Neither RGD nor wortmannin reversed the other's inhibitory effect on stimulated [18F]FDG uptake and hexokinase activity or respiratory burst, which suggests the involvement of distinct signaling pathways. Neutrophil [18F]FDG uptake is enhanced by PMA through a mechanism that requires PI3K activity but is independent of integrin receptor occupancy or respiratory burst activation.

• Bulletin of the Korean Chemical Society
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• 제23권2호
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• pp.221-224
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• 2002

Nucleophilic addition reactions of benzylamines (BA; $XC_6H_4CH_2NH_2$) to ethyl-${\alpha}$-cyanocinnamates (ECC;$YC_6H_4CH$=C(CN)COOEt) have been investigated in acetonitrile at $30.0^{\circ}C$. The rate is first order with respect to BA and ECC. The rate is slower than that expected from the additive effect of ${\sigma}^-$ or $R^-$ for the activating groups (CN and COOEt). Natural. bond orbital ${\pi}^{\ast}_{c=c}$ calculations show that the contribution of COOEt group may not be fully effective despite the coplanar molecular structure. The selectivity parameters including the cross-interaction constant (${\rho}_{xy}$ = -0.22) indicate that the addition occurs in a single step. The kinetic isotope effects ($k_H/k_D$=2.5-2.8) involving deuterated BA ($XC_6H_4CH_2ND_2$) nucleophiles and activation parameters (${\Delta}H^{\neq}=4{\sim}6\;kcal\;mol^{-1};{\Delta}S^{\neq}=-45{\sim}-52\;e.u.$) suggest a cyclic transition state in which N-$C_{\alpha}$ and H-$C_{\beta}$ bonds are formed concurrently.

• Biotechnology and Bioprocess Engineering:BBE
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• 제9권4호
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• pp.241-244
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• 2004

Protein A molecular thin film was fabricated as a platform of antibody-based biosensor. For the immobilization of the protein A thin film, a viologen multilayer was built up using the Langmuir-Blodgett (LB) technique, and then, protein A was adsorbed on the viologen LB film by an electrostatic interaction force, which was formed as a hetero-film structure. For the deposition of viologen, surface pressure area ($\pi$-A) isotherm was investigated. The fabricated protein A-viologen hetero LB film was investigated using atomic force microscopy (AFM). Using the developed molecular film, antibody immobilization and fluorescence measurement was carried out.

• Composites Research
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• 제24권6호
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• pp.1-6
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• 2011

본 연구에서는 탄소나노튜브를 물상에서 균일하게 분산시키기 위하여 물에 녹으면서 분자 내에서 자체 도핑이 가능한 새로운 종류의 그래프트 공중합체(PSSA-g-PANI, poly(styrenesulfonic acid-graft-aniline))를 합성하였고, 그 분산 능력을 실험해 보았다. PANI 고분자는 벤조이드와 퀴노이드 구조가 반복되어 존재하는 판상구조로 탄소나노튜브와 같은 탄소나노 소재의 벽에 강하게 결합할 수 있고, 따라서 짧은 시간의 sonication 처리 만으로 나노튜브를 분산시킬 수 있었고 그 분산 용액의 장시간 안정성은 다른 상용화된 분산제보다 뛰어났다. 또한 PSSA-g-PANI 그래프트 고분자/탄소나노튜브 복합 필름은 대략 1.5-2.5 S/cm의 전도도를 기록하였다.