• Bulletin of the Korean Chemical Society
• /
• 제6권4호
• /
• pp.206-209
• /
• 1985

The gas phase reactions of the photochemically generated t-butoxy radicals with phosphine ($PH_3$) were studied in the temperature range of $35-80^{\circ}C.$ We found the significant differences between high temperature thermal reactions and low temperature photo reactions. In comparison with the reactions of t-butoxy radicals with other hydrogen donors, some possible mechanistic suggestions were made for the explanation of the results.

• The Korean Journal of Physiology and Pharmacology
• /
• 제17권3호
• /
• pp.181-187
• /
• 2013

Reactive oxygen species (ROS) are generated in various cells, including vascular smooth muscle and endothelial cells, and regulate ion channel functions. $K_{Ca}3.1$ plays an important role in endothelial functions. However, the effects of superoxide and hydrogen peroxide radicals on the expression of this ion channel in the endothelium remain unclear. In this study, we examined the effects of ROS donors on $K_{Ca}3.1$ expression and the $K^+$ current in primary cultured human umbilical vein endothelial cells (HUVECs). The hydrogen peroxide donor, tert-butyl hydroperoxide (TBHP), upregulated $K_{Ca}3.1$ expression, while the superoxide donors, xanthine/xanthine oxidase mixture (X/XO) and lysophosphatidylcholine (LPC), downregulated its expression, in a concentration-dependent manner. These ROS donor effects were prevented by antioxidants or superoxide dismustase. Phosphorylated extracellular signal-regulated kinase (pERK) was upregulated by TBHP and downregulated by X/XO. In addition, repressor element-1-silencing transcription factor (REST) was downregulated by TBHP, and upregulated by X/XO. Furthermore, $K_{Ca}3.1$ current, which was activated by clamping cells with 1 ${\mu}M$ $Ca^{2+}$ and applying the $K_{Ca}3.1$ activator 1-ethyl-2-benzimidazolinone, was further augmented by TBHP, and inhibited by X/XO. These effects were prevented by antioxidants. The results suggest that hydrogen peroxide increases $K_{Ca}3.1$ expression by upregulating pERK and downregulating REST, and augments the $K^+$ current. On the other hand, superoxide reduces $K_{Ca}3.1$ expression by downregulating pERK and upregulating REST, and inhibits the $K^+$ current. ROS thereby play a key role in both physiological and pathological processes in endothelial cells by regulating $K_{Ca}3.1$ and endothelial function.

• 통합자연과학논문집
• /
• 제5권3호
• /
• pp.195-197
• /
• 2012

Halogen atoms in a molecule are traditionally considered as electron donors, since they have unshared electrons. Normally when they are bonded, there are three lone pair electrons. These lone pairs can function as Lewis bases. However, when they are bound to electron withdrawing groups, they can act as Lewis acids. Since the situation is similar hydrogen bonding (HB), this type of interaction is named as halogen bonding (XB). This mainly comes from the uneven distribution of electron density around the halogen atoms. Since the electron density around halogen atom opposite to ${\sigma}$-bond is depleted, its electropositive region is called ${\sigma}$-hole. This ${\sigma}$-hole can attract halogen bond acceptors, requiring more stringent directionality compared to HB. Since this interaction mainly comes from electrostatic origin, the geometry tends to be linear. Since the XB energy is comparable to corresponding HB. Still in its infancy, XB shows a broad range of applicability, with potentially more useful properties, compared to corresponding HB.

• 한국미생물·생명공학회지
• /
• 제11권3호
• /
• pp.211-216
• /
• 1983

R. sphaeroides K- 7에 의한 수소생성과 질소고정효소(nitrogenase)와의 연관성을 조사한 결과 수소생성은 질소고정효소에 의해 이루어지는 것으로 나타났다. 또한 수소생성은 수소효소(hydrogenase)와 무관하며 박테리오클로로필의 농도와도 무관한 것으로 나타났다. 글루타민산이 in vivo에서 질소고정효소의 활성도를 조절하는데 중요한 역할을 할 수 있는 것으로 나타났으며 질소개스를 이용해 키운 세균을 글루타민산 존재하로 옮겼을때 보다 큰 정도의 수소생성능 및 질소고정효소 활성도가 나타났다.

• 한국전기전자재료학회논문지
• /
• 제28권1호
• /
• pp.17-20
• /
• 2015

The physical effects of H-plasma treatment on ZnO thin film have been studied using photoluminescence(PL) spectroscopy. Four characteristic peaks have been identified: (i) $D^0X$ peak (neutral donor-bound exciton), showing relatively small integrated intensity after H-plasma treatment, indicates that H-plasma passivates the neutral donors in ZnO at low temperatures. The rapid decrease in the integrated intensity of the peak as the temperature goes up is considered to be due to the ionization of neutral donors. (ii) H-related complex-bound exciton peak appears at the low temperatures (10 K~80 K) after H-plasma treatment, showing the same thermal evolution as $D^0X$ peak. (iii) FX (free exciton) peak starts to show up at 60 K and grows more and more as the temperature goes up, which is considered to be related to the increase in free electron concentration in the film. (iv) violet band is intensified after H-plasma, which means more defects and impurities are generated by H-plasma process.

• 반도체디스플레이기술학회지
• /
• 제9권1호
• /
• pp.35-40
• /
• 2010

We have investigated the effects of hydrogen injection via in-situ gas addition ($O_2$, $H_2$, or $O_2$ + $H_2$ gas) and plasma post-treatment (Ar or Ar + H plasma) on material properties of ZnO that is considered to be as a channel layer in transparent thin film transistors. The variations in the electrical resistivity, optical transmittance and bandgap energy, and crystal quality of ZnO thin films were characterized in terms of the methods and conditions used in hydrogen injection. The resistivity was significantly decreased by injection of hydrogen; approximately $10^6\;{\Omega}cm$ for as-grown, $1.2\;{\times}\;10^2\;{\Omega}cm$ for in-situ with $O_2/H_2\;=\;2/3$ addition, and $0.1\;{\Omega}cm$ after Ar + H plasma treatment of 90 min. The average transmittance of ZnO films measured at a wavelength of 400-700 nm was gradually increased by increasing the post-treatment time in Ar + H plasma. The optical bandgap energy of ZnO films was almost monotonically increased by decreasing the $O_2/H_2$ ratio in in-situ gas addition or by increasing the post-treatment time in Ar + H plasma, while the post-treatment using Ar plasma hardly affected the bandgap energy. The role of hydrogen in ZnO was discussed by considering the creation and annihilation of oxygen vacancies as well as the formation of shallow donors by hydrogen.

• 대한화학회지
• /
• 제39권11호
• /
• pp.837-841
• /
• 1995

사염화탄소 속에서 티오프로피온아미드(TPA)와 triethylphosphine oxide(TEPO), triethylphosphine oxide(TPPO), trimethylphosphate(TMP), 그리고 tributyl phosphate(TBP)간의 수소 결합에 대한 열역학적 상수들을 근적외선 분광법을 이용하여 구하였다. TPA의 .nu./.alpha./+amide 2 조합띠는 TPA 단위체 및 수소 결합을 이룬 TPA의 띠로 이루어져 있음이 확인되어 이 띠를 두 개의 Lorentzian-Gaussian 곱함수의 띠로 분해하였다. 온도 및 농도의 변화에 따른 이 조합띠의 변화기로부터 TPA와 TEPO, TPPO, TMP, TBP의 수소 결합 엔탈피는 각각 -21.4, -16.8, -12.8, -12.9kJ/mol이었다. 이 결과는 치환기의 inductive effect 및 steric effect로 설명할 수 있다.

• 한국지하수토양환경학회지:지하수토양환경
• /
• 제11권2호
• /
• pp.22-37
• /
• 2006

생물벽체(biobarrier) 또는 원위치 미생물 필터(in situ microbial filter) 기술을 이용한 염소계 유기용매로 오염된 지하수의 복원 가능성을 회분식 실험을 통하여 살펴보았다. PCE의 환원성 탈염소화의 효율과 속도는 수소 농도에 의존하는 것으로 알려져 있다. 본 연구에서는 분변토와 토탄을 생물벽체로 이용한 PCE의 환원성 탈염소화시 전자공여체의 영향을 살펴보았다. 유기산(lactate, butyrate benzoate)과 yeast extract, 비타민 $B_{12}$가 PCE의 환원성 탈염소화에 미치는 영향을 조사하였다. 생물벽체 담체 비존재시, 전자공여체를 투여하지 않은 control 실험에 비해, 전자공여체의 첨가는 PCE의 탈염소화 속도를 촉진하였다. 전자공여체를 투여한 실험 중에서 lactate 또는 lactate/benzoate를 수소 공여체(hydrogen donor)로 첨가된 경우, 탈염소화 속도가 가장 빨랐다($k_1=0.0260{\sim}0.0266\;day^{-1}$). 분변토를 생물벽체로 사용한 경우, lactate/benzoate 첨가시 탈염소화 속도가 가장 빨랐으며, 겉보기 1차 분해속도상수($k_1$)는 $0.0849day^{-1}$였다. 반면, Pahokee peat을 생물벽체로 사용하였을 경우, butyrate 또는 lactate의 첨가시 탈염소화 속도가 가장 빨랐으며 $k_1$ 값은 각각 0.1092, $0.1067\;day^{-1}$로 나타났다. 본 연구결과로부터 분변토 또는 토탄을 원위치 생물벽체로 사용하여 염소계 유기용매로 오염된 지하수 처리의 잠재적인 응용 가능성을 알 수 있었다.

• Bulletin of the Korean Chemical Society
• /
• 제29권8호
• /
• pp.1479-1484
• /
• 2008

Protein tyrosine phosphatase (PTP) 1B is the superfamily of PTPs and a negative regulator of multiple receptor tyrosine kinases (RTKs). Inhibition of protein tyrosine phosphatase 1B (PTP1B) has been proposed as a strategy for the treatment of type 2 diabetes and obesity. Recently, it has been reported that amentoflavone, a biflavonoid extracted from Selaginella tamariscina, inhibited PTP1B. In the present study, docking model between amentoflavone and PTP1B was determined using automated docking study. Based on this docking model and the interactions between the known inhibitors and PTP1B, we determined multiple pharmacophore maps which consisted of five features, two hydrogen bonding acceptors, two hydrogen bonding donors, and one lipophilic. Using receptor-oriented pharmacophore-based in silico screening, we searched the biflavonoid database including 40 naturally occurring biflavonoids. From these results, it can be proposed that two biflavonoids, sumaflavone and tetrahydroamentoflavone can be potent allosteric inhibitors, and the linkage at 5',8''-position of two flavones and a hydroxyl group at 4'-position are the critical factors for their allosteric inhibition. This study will be helpful to understand the mechanism of allosteric inhibition of PTP1B by biflavonoids and give insights to develop potent inhibitors of PTP1B.

• Bulletin of the Korean Chemical Society
• /
• 제28권3호
• /
• pp.379-385
• /
• 2007

Receptor-oriented pharmacophore-based in silico screening is a powerful tool for rapidly screening large number of compounds for interactions with a given protein. Inhibition of the enzyme catechol-Omethyltransferase (COMT) offers a novel possibility for treating Parkinson's disease. Bisubstrate inhibitors of COMT containing the adenine of S-adenosylmethionine (SAM) and a catechol moiety are a new class of potent and selective inhibitor. In the present study, we used receptor-oriented pharmacophore-based in silico screening to examine the interactions between the active site of human COMT and bisubstrate inhibitors. We generated 20 pharmacophore maps, of which 4 maps reproduced the docking model of hCOMT and a bisubstrate inhibitor. Only one of these four, pharmacophore map I, effectively described the common features of a series of bisubstrate inhibitors. Pharmacophore map I consisted of one hydrogen bond acceptor (to Mg2+), three hydrogen bond donors (to Glu199, Glu90, and Gln120), and one hydrophobic feature (an active site region surrounded by several aromatic and hydrophobic residues). This map represented the most essential pharmacophore for explaining interactions between hCOMT and a bisubstrate inhibitor. These results revealed a pharmacophore that should help in the development of new drugs for treating Parkinson's disease.