• BMB Reports
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• 제33권1호
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• pp.49-53
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• 2000

PMAP-23 is a 23-residue antimicrobial peptide derived from porcine myloid cells. In order to investigate the effects of two Pro residues at positions 12 and 15 of PMAP-23 on antibiotic activity, two analogues in which Ala was substituted for Pro residue at position 12 or 15 were synthesized. $Pro^{12}{\rightarrow}Ala$ (PMAPl) or $Pro^{15}{\rightarrow}Ala$(PMAP2) substitution in PMAP-23 caused a significant reduction on antitumor and phospholipid vesicle-disrupting activities, but did not cause a significant effect on antibacterial activity. PMAP-23 displayed the type I ${\beta}-turn$ structure with a negative ellipticity at near 205 om in SDS micelle, whereas PMAP1 and PMAP2 had a somewhat ${\alpha}-helical$ propensity in TFE solution, as compared to PMAP-23. These results suggest that two Pro residues of positions 12 and 15 in PMAP-23 play important roles in the formation of ${\beta}-turn$ structure on lipid membrane and its ${\beta}-turn$ structure may be essential for antibiotic activity including phospholipid vesicle-disrupting property.

• 대한화학회지
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• 제27권2호
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• pp.95-101
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• 1983

여러가지 수용성 혼합용매와 에탄올-TFE 혼합용매에서 시안화 벤조일의 가용매분해반응에 대한 유사-1차반응속도상수를 1, 5, 10, 15, $20^{\circ}C$에서 구하였다. Kivinen polt의 n값, Grunwald-Winstein polt의 m값, Leffler 관계식의 $\beta$값, 확정된 Grunwald-Winstein식의 m 및 l값을 구하였다. More O'Ferrall polt와 양자역학적 해석 방법을 이용하여 용매 변화에 따른 전이상태 변화를 논의하였으며 본 반응은 associative $S_N2$ 반응 메카니즘으로 진행됨을 알 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제30권2호
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• pp.383-388
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• 2009

Rates of solvolyses of diphenyl thiophosphorochloridate ($(PhO)_2$PSCl, 1) in ethanol, methanol, and aqueous binary mixtures incorporating ethanol, methanol, acetone and 2,2,2-trifluoroethanol (TFE) are reported. For four representative solvents, studies were made at several temperatures and activation parameters were determined. The 30 solvents gave a reasonably precise extended Grunwald-Winstein plot, correlation coefficient (R) of 0.989. The sensitivity values (l = 1.29 and m = 0.64) of diphenyl thiophosphorochloridate ($(PhO)_2$PSCl, 1) were similar to those obtained for diphenyl phosphorochloridate ($(PhO)_2$POCl, 2), diphenylphosphinyl chloride ($Ph_2$POCl, 3) and diphenylthiophosphinyl chloride ($Ph_2$PSCl, 4). As with the previously studied of 3~4 solvolyses, an $S_N$ pathway is proposed for the solvolyses of diphenyl thiophosphorochloridate (1). The activation parameters, ${\Delta}H^{\neq}\;(=11.6{\sim}13.9\;kcal{\cdot}mol^{-1})\;and\;{\Delta}S^{\neq}\; (=\;-32.1\;{\sim}\;-42.7\;cal{\cdot}mol^{-1}{\cdot}K^{-1})$, were determined, and they were in line with values expected for an $S_N$2 reaction. The large kinetic solvent isotope effects (KSIE, 2.44 in MeOH/MeOD and 3.46 in $H_2O/D_2$O) are also well explained by the proposed $S_N$2 mechanism.

• 반도체디스플레이기술학회지
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• 제20권3호
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• pp.22-26
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• 2021

Thin-film encapsulation (TFE) technology is most effective in preventing water vapor and oxygen permeation in the organic light emitting diodes (OLED). Of those, a laminated structure of Al₂O₃ and MgO were applied to provide efficient barrier performance for increasing the stability of devices in air. Atomic layer deposition (ALD) method is known as the most promising technology for making the laminated Al₂O₃/MgO and is used to realize a thin film encapsulation technology in organic light-emitting diodes. Atomic layer deposited inorganic films have superior barrier performance and have advantages of excellent uniformity over large scales at relatively low deposition temperatures. In this study, the control system of the MgCP₂ precursor for the atomic layer deposition of MgO was established in order to deposit the MgO layer stably by the injection time of second level and the stable heating temperature. The deposition rate was obtained stably to be from 4 to 10 Å/cycle using the injection pulse times ranging from 3 to 12 sec and a substrate temperature ranging from 80 to 150 ℃.

• Bulletin of the Korean Chemical Society
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• 제19권3호
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• pp.349-353
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• 1998

Solvolysis rates of substituted 2-aryl-1,1-dimethylethyl bromides (1) were determined in a variety of solvents such as aqueous mixtures of ethanol, acetone, 2,2,2-trifluoroethanol, and also mixtures of ethanol and TFE at 25 ℃, 35 ℃, and 45 ℃. The solvent effects were analyzed in terms of Winstein-Grunwald equation. The solvent effects of 1-4-MeO failed to give a single linear correlation against either Y or YCl (YBr), but exhibited a wide split pattern which could not be related to the solvent nucleophilicity. On the other hand 1-4-CH3 and 1-H gave a fairly good linearity. In the case of 1-4-MeO, a fairly good linearity was observed against YΔ defined from the solvolysis of 4-methoxyneophyl tosylate. It is assumed that resonance interaction between reaction site and aryl-π-system operates to give charge delocalization regardless of the different solvolysis mechanisms. The Hammett-Brown treatment of the solvolytic rate constant of compounds 1 was obtained non-linear two separated lines of - 1.06 to - 1.46, suggesting of mechanistic changeover from kc-ks to kΔ on going from electron-withdrawing to electron-donating substituents as a basis of 4-CH3 group.

• Bulletin of the Korean Chemical Society
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• 제24권4호
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• pp.431-436
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• 2003

Solvolytic rate constants at 25℃ are reported for solvolyses of cinnamyl bromide (1) in binary mixtures of water with acetone, ethanol, methanol, methanol-d, and 2,2,2-trifluoroethanol. Product selectivities are reported for solvolyses of 1 in aqueous ethanol and methanol. Rate ratios in solvents of the same $Y_{Br}$ value and different nucleophilicity provide measures of the minimum extent of nucleophilic solvent assistance (e.g. $[k_{40EW}/k_{97TFE}]$Y = 2.88, EW = ethanol-water). With use of the extended Grunwald-Winstein equation, the l and m values are similar to the values of 0.43 and 0.88 obtained for the solvolyses of 1 using the equation (see below) which includes a parameter (I) for solvation of aromatic rings. The magnitude of l and m values associated with a change of solvent composition predicts the $S_{N1}$ reaction mechanism rather than an $S_{N2}$ channel. Product selectivities (S), defined by S = [ether product]/[alcohol product]×[water]/[alcohol solvent] are related to four rate constants for reactions involving one molecule of solvent as nucleophile and another molecule of solvent as general base catalyst. A linear relationship between 1/S and molar ratio of solvent is derived theoretically and validated experimentally for solvolyses of the above substrates from water up 75% 1/S = $(k_{wa}/k_{aw})$([alcohol solvent]/[water]) + $k_{ww}/k_{aw}$ alcohol-water. The results are best explained by product formation from a “free” carbocation intermediate rather than from a solvent-separated ion pair.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.180-180
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• 2016

최근 디스플레이 시장의 주요 키워드는 flexible organic light emitting diode (OLED) 이다. OLED 소자의 수명을 결정하는 가장 큰 요인 중의 하나는 공기 중의 O2와 H2O에 의한 유기물의 열화이다. 따라서 공기 중의 O2나 H2O가 유기물에 쉽게 침투하는 것을 막는 것은 소자의 수명 향상을 위하여 필수적이라 할 수 있다[1-3]. SiNx 박막은 경질로 투과성이 우수하며, 화학적 불활성인 특성으로 이러한 Barrier 역할로 연구되어 산업분야에 다양하게 응용되고 있다[4]. SiNx 박막은 일반적으로 plasma enhanced chemical vapor deposition (PECVD) 기술을 이용하여 증착되는데 기존의 PECVD 기술을 이용한 SiNx 박막은 낮은 water vapor transmission rate (WVTR) 등의 문제점들로 인해 한계점이 들어났다. 본 연구에서는, flexible display의 thin film encapsulation (TFE) 공정에서의 적용을 알아보기 위해 $370{\times}470$ size를 증착할 수 있는 In-line 장비를 이용하였으며, 기존의 PECVD 기술의 문제점으로 지적되고 있는 낮은 WVTR을 해결하기 위하여 저온 (<$100^{\circ}C$) 선형 PECVD 기술을 이용하여 WVTR을 개선하고자 하였다. 공정가스로는 SiH4와 NH3를 사용하였으며, SiH4 Carrier 가스로 He을 추가적으로 사용하였다. 또한 공정 압력은 100mTorr를 유지하였다. 증착된 SiNx 박막의 물리적, 화학적 특성 분석을 위해 분광엘립소메타, field emission electron microscopy (FESEM), X-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS) 등을 이용하여 측정하였으며, 박막에 투습되는 수분의 양은 MOCON사의 AQUATRAN 2(W)로 측정하였다. OLED 소자를 구현하기 위해서는 기본적으로 봉지층에 투습되는 양을 $10-6g/m2{\cdot}day$ 이하로 막아줘야 한다고 알려져 있으나, 기존의 PECVD 기술을 이용하여 제작된 SiNx 박막의 WVTR은 $10-2{\sim}10-3g/m2{\cdot}day$ 레벨의 WVTR 결과를 보이고 있다. 본 연구에서 사용된 저온 선형 PECVD 기술을 이용하여 제작된 SiNx 박막의 WVTR은 $5.0{\times}10-5g/m2{\cdot}day$ 이하의 개선된 결과를 확인 할 수 있었다. 또한 flexible display에 적용하기 위해 SiNx 박막의 두께를 최소화한 100nm의 두께에서도 WVTR은 $5.0{\times}10-5g/m2{\cdot}day$ 이하의 결과가 유지됨을 알 수 있었다.

• 대한가정학회지
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• 제42권11호
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• pp.167-187
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• 2004

This study investigated the post-divorce adjustment level, by focusing on life satisfaction, health, stress and resource factors, for divorced men and women in their 20s and 30s. Also, it examined how these factors affect life satisfaction and health. For this empirical analysis, data were collected from 114 divorced men and 112 divorced women, living in the Seoul metropolitan area, from 23rd Sep. to 20th Oct., 2002. The questionnaire for the survey dealt with demographic information, life satisfaction, health, stress and resource factor scales. The major findings of the research project were as follows.: first, the life satisfaction and health levels of the divorced men and women were low. Especially, divorced women had more physical and psychological problems than men. Second, the divorced men's satisfaction was affected by pre-divorce life events and education level, whereas the divorced women's satisfaction was affected by subjective economic dissatisfaction, pre-divorce tfe events, everyday life level when they were divorced, and social support. Finally, the attitude toward divorce of significant others and pre-divorce life events were important variables for the divorced men's health, whereas attachment toward ex-spouse, pre-divorce life events, pre-divorce marital conflict and social support were affectable variables for the divorced women's health. The results of current research are expected to contribute to the divorce adjustment programs according to gender.

• Journal of Microbiology and Biotechnology
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• 제8권6호
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• pp.595-600
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• 1998

In order to investigate a relationship of the structure-antifungal and hemolytic activities between cecropin A(1-8)-magainin 2(1-12) and cecropin A(1-8)-melittin(1-12) hybrid peptides, several analogues with amino acid substitution at positions 10 (Ile) and 16 (Ser) were designed and synthesized. The increase of the hydrophobicity by substituting with Leu, Phe, and Trp at position 16 in cecropin A(1-8)-magainin 2(1-12) did not have a significant effect on antifungal activity but caused a remarkable increase in hemolytic activity. These results indicate that the hydrophobic property at position 16 of cecropin A(1-8)-magainin 2(1-12) is more correlated to hemolytic activity than to antifungal activity. Replacement with Pro at position 10 of cecropin A(1-8)- magainin 2(1-12) and cecropin A(1-8)-melittin (1-12) caused a remarkable decrease in a-helical contents in the 50% TFE solution and induced a reduction in lytic activity against Aspergillus flavus, and Aspergillus fumigatus. These results demonstrate that flexibility at the central hinge region is essential for lytic activity against fungal cells and $\alpha$-helicity of the peptides.

• Bulletin of the Korean Chemical Society
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• 제28권12호
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• pp.2377-2381
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• 2007

Solvolyses of 3,4-dimethoxybenzenesulfonyl chloride (DSC) in water, D2O, CH3OD, and in aqueous binary mixtures of acetone, acetonitrile, 1,4-dioxane, ethanol, methanol, and 2,2,2-trifluoroethanol (TFE) have been investigated at 25.0 oC. Kinetic solvent isotope effects (KSIE) in water and in methanol and product selectivities in alcohol-water mixtures are also reported. The Grunwald-Winstein plot of first-order rate constants for the solvolyic reaction of DSC with YCl shows marked dispersions into separated lines for various aqueous mixtures. With use of the extended Grunwald-Winstein equation, the l and m values obtained are 1.12 and 0.58 respectively for the solvolyses of DSC. The relatively large magnitude of l is consistent with substantial nucleophilic solvent assistance. From Grunwald-Winstein plots the rate data are dissected approximately into contributions from two competing reaction channels. This interpretation is supported for alcohol-water mixtures by the trends of product selectivities, which show a maximum for ethanol-water mixtures. From the KSIE of 1.45 in methanol, it is proposed that the reaction channel favored in methanolwater mixtures and in all less polar media is general-base catalysed and/or is possibly (but less likely) an addition-elimination pathway. Also, the KISE value of 1.35 for DSC in water is expected for SN2-SN1 processes, with minimal general base catalysis, and this mechanism is proposed for solvolyses in the most polar media.