Redox-state modulated ORR activity of Cd-based Prussian blue analog frameworks transformed <i>via</i> anion exchange with controlled redox-state from CdCO₃ cuboids

Shrestha, Nabeen K.,Bui, Hoa Thi,Yoon, Seog Joon,Patil, Supriya A.,Bathula, Chinna,Lee, Kiyoung,Noh, Yong-Young,Han, Sung-Hwan Elsevier 2019 Journal of electroanalytical chemistry Vol.847 No.-

<P><B>Abstract</B></P> <P>This work reports a facile solution based chemical transformation of thin film of CdCO<SUB>3</SUB> cuboids into Cd-based Prussian blue analogue structured thin film with controlled redox-state by manipulating the anion exchange reaction between the solid film and the aqueous solution of K<SUB>3</SUB>[Fe(CN)<SUB>6</SUB>] at 60°C. The progress of the transformation reaction is monitored <I>via</I> electron microscopy, X-ray difractometry and X-ray photoelectron spectroscopy. Based on the scenario of the reaction progress revealed by these analysis, the CdCO<SUB>3</SUB> cuboids are first found to be transformed into the smaller cuboids of cadmium ferricyanide, which, on further reaction, are transformed into the cadmium ferrocyanide cuboids. Thus, by controlling the redox-state of the Fe-metal center on the frameworks, the electrocatalytic activity of the frameworks on oxygen reduction reaction (ORR) is studied. The electrocatalytically inert CdCO<SUB>3</SUB> cuboids after transformation to the frameworks with Fe<SUP>3+</SUP>-centers demonstrate an enhanced catalytic activity on ORR, while the Fe<SUP>2+</SUP>-centers of the frameworks are found to relegate the catalytic activity, thereby manifesting the redox-sate modulated ORR activity of the frameworks. To the best of the authors' knowledge, this is the first report of this kind on redox-state specific ORR activity.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Conversion of CdCO<SUB>3</SUB> cuboid film into Cd-HCF frameworks <I>via</I> anion exchange </LI> <LI> Controlling reaction time to achieve Fe (III)-or Fe(II)- based Cd-HCF frameworks </LI> <LI> Fe(III) based Cd-HCF frameworks demonstrate electrocatalytic activity towards ORR. </LI> <LI> Fe(II) based Cd-HCF frameworks relegate the ORR catalytic activity. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Change of electrical properties of (K_0.5Na_0.5) (Mn_0.005Nb_0.995)O₃ thin films induced by gamma-ray irradiation

Kim, B.H.,Yang, S.A.,Kang, S.W.,Choi, G.P.,Cho, S.Y.,Han, J.K.,Lee, G.J.,Lee, M.K.,Seog, H.J.,Kim, I.W.,Bu, S.D. Elsevier 2016 CURRENT APPLIED PHYSICS Vol.16 No.5

<P>We investigated the effects of gamma-ray (gamma) irradiation on the electrical properties of (K0.5Na0.5) (Mn0.005Nb0.995)O-3 (KNMN) thin films. The KNMN thin films were prepared on Pt/Ti/SiO2/Si substrate using a chemical solution deposition method through a spin-coating process and were subject to gamma radiation at various total doses from 0 to 3000 kGy. The structural properties as well as the ferroelectric and dielectric properties of the prepared films were examined before and after gamma irradiation. We found that their crystalline quality did not vary significantly with an increase in the total dose. It was also observed that the remnant polarization value of the films decreased by similar to 10%, but the films maintained ferroelectricity even after irradiation up to 3000 kGy. In addition, the dielectric constant of the films decreased with the total dose. The observed variation of the electrical properties on the total dose might be mainly associated with the mobile defects in Mn-doped KNN thin films such oxygen vacancy and the stored energy gained from gamma-rays. (C) 2016 Elsevier B.V. All rights reserved.</P>

Mechanisms of Oxidation of Guanine in DNA by Carbonate Radical Anion, a Decomposition Product of Nitrosoperoxycarbonate

Lee, Young ,Ae,Yun, Byeong ,Hwa,Kim, Seog ,K.,Margolin, Yelena,Dedon, Peter ,C.,Geacintov, Nicholas ,E.,Shafirovich, Vladimir WILEY-VCH Verlag 2007 Chemistry Vol.13 No.16

<P>Peroxynitrite is produced during inflammation and combines rapidly with carbon dioxide to yield the unstable nitrosoperoxycarbonate, which decomposes (in part) to CO<SUB>3</SUB><SUP>.−</SUP> and <SUP>.</SUP>NO<SUB>2</SUB> radicals. The CO<SUB>3</SUB><SUP>.−</SUP> radicals oxidize guanine bases in DNA through a one-electron transfer reaction process that ultimately results in the formation of stable guanine oxidation products. Here we have explored these mechanisms, starting with a spectroscopic study of the kinetics of electron transfer from 20–22mer double-stranded oligonucleotides to CO<SUB>3</SUB><SUP>.−</SUP> radicals, together with the effects of base sequence on the formation of the end-products in runs of one, two, or three contiguous guanines. The distributions of these alkali-labile lesions were determined by gel electrophoresis methods. The cascade of events was initiated through the use of 308 nm XeCl excimer laser pulses to generate CO<SUB>3</SUB><SUP>.−</SUP> radicals by an established method based on the photodissociation of persulfate to sulfate radicals and the oxidation of bicarbonate. Although the Saito model (Saito et al., J. Am. Chem. Soc. 1995, 117, 6406–6407) predicts relative ease of one-electron oxidations in DNA, following the trend 5′-⋅⋅⋅GGG⋅⋅⋅ > 5′-⋅⋅⋅GG⋅⋅⋅ > 5′-⋅⋅⋅G⋅⋅⋅, we found that the rate constants for CO<SUB>3</SUB><SUP>.−</SUP>-mediated oxidation of guanines in these sequence contexts (k<SUB>5</SUB>) showed only small variation within a narrow range [(1.5–3.0)×10<SUP>7</SUP> M<SUP>−1</SUP> s<SUP>−1</SUP>]. In contrast, the distributions of the end-products are dependent on the base sequence context and are higher at the 5′-G in 5′-⋅⋅⋅GG⋅⋅⋅ sequences and at the first two 5′-guanines in the 5′-⋅⋅⋅GGG⋅⋅⋅ sequences. These effects are attributed to a combination of initial hole distributions among the contiguous guanines and the subsequent differences in chemical reaction yields at each guanine. The lack of dependence of k<SUB>5</SUB> on sequence context indicates that the one-electron oxidation of guanine in DNA by CO<SUB>3</SUB><SUP>.−</SUP> radicals occurs by an inner-sphere mechanism.</P> <B>Graphic Abstract</B> <P>Rates of one-electron oxidation of guanine in DNA by carbonate radicals do not depend on sequence context: The sequence-dependent damage at guanine sites (see figure) is attributed to a combination of initial hole distributions among the contiguous guanines and the subsequent differences in chemical reaction yields at each guanine. <img src='wiley_img/09476539-2007-13-16-CHEM200601434-content.gif' alt='wiley_img/09476539-2007-13-16-CHEM200601434-content'> </P>

전하 재사용 저전력 SRAM 설계

박노경,차균현,이주석,김형곤,주병권,강용섬 대한전자공학회 1996 CAD 및 VLSI 설계연구회지 Vol.5 No.1

The proposed SRAM reusing charge operate in 3.3 voltage and we obtain 33.3% power save efficiency compared to the conventional wordline access method due to resuing the current of first actived wordline gate capacitance at second actived wordline gate capacitance. In the case of this SRAM reusing charge, described in this paper, we obtained 5ns(200MHz) operation speed result in the HYUNDAI 0.6um CMOS technology. In this paper power saving is 30.75mW compaired to the conventional wordline access for one clock.

Label-free emission assay of mercuric ions using DNA duplexes of poly(dT)

Oh, Byul Nim,Park, Sangji,Ren, Jun,Jang, Yoon Jung,Kim, Seog K.,Kim, Jinheung Royal Society of Chemistry 2011 Dalton Transactions Vol.40 No.24

<P>In this study, an assay to quantify the presence of mercuric ions and methyl mercury by double-stranded DNA containing a poly(dT) sequence was developed using a light switch compound, Ru(phen)<SUB>2</SUB>(dppz)<SUP>2+</SUP> (1), which is known to intercalate into double-stranded DNA. Upon treatment with mercuric ions, the metal-to-ligand charge transfer (MLCT) emission derived from the intercalation of 1 was reduced due to the formation of DNA duplexes containing T–Hg<SUP>2+</SUP>–T base pairs by the dehybridization of poly(dT)–poly(dA) duplexes at room temperature. As the concentration of Hg<SUP>2+</SUP> was increased, the emission of 1 gradually decreased. This label-free method had a detection limit of 5 nM. Other metal ions, such as K<SUP>+</SUP>, Ag<SUP>+</SUP>, Ca<SUP>2+</SUP>, Mg<SUP>2+</SUP>, Zn<SUP>2+</SUP>, Mn<SUP>2+</SUP>, Co<SUP>2+</SUP>, Ni<SUP>2+</SUP>, Cu<SUP>2+</SUP>, Cd<SUP>2+</SUP>, Cr<SUP>3+</SUP>, Fe<SUP>3+</SUP>, had no significant effect on reducing emission. This emission method can differentiate matched and mismatched poly(dT) sequences based on the dehybridization rate of dsDNA and the rate decreased in the order of T<SUB>10</SUB>C·A<SUB>11</SUB> ∼ T<SUB>10</SUB>A·A<SUB>11</SUB> > T<SUB>10</SUB>G·A<SUB>11</SUB> > T<SUB>11</SUB>·A<SUB>11</SUB>.</P> <P>Graphic Abstract</P><P>An assay to quantify the presence of mercuric ions by double-stranded DNA containing a poly(dT) sequence was developed using the metal-to-ligand charge transfer emission derived from the intercalation of a light switch Ru complex. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c1dt10083a'> </P>

RecA requires two molecules of Mg ²⁺ ions for its optimal strand exchange activity <i>in vitro</i>

Kim, Raeyeong,Kanamaru, Shuji,Mikawa, Tsutomu,Pré,vost, Chantal,Ishii, Kentaro,Ito, Kentaro,Uchiyama, Susumu,Oda, Masayuki,Iwasaki, Hiroshi,Kim, Seog K,Takahashi, Masayuki Oxford University Press 2018 Nucleic acids research Vol.46 No.5

<P><B>Abstract</B></P><P>Mg<SUP>2+</SUP> ion stimulates the DNA strand exchange reaction catalyzed by RecA, a key step in homologous recombination. To elucidate the molecular mechanisms underlying the role of Mg<SUP>2+</SUP> and the strand exchange reaction itself, we investigated the interaction of RecA with Mg<SUP>2+</SUP> and sought to determine which step of the reaction is affected. Thermal stability, intrinsic fluorescence, and native mass spectrometric analyses of RecA revealed that RecA binds at least two Mg<SUP>2+</SUP> ions with K<SUB>D</SUB> ≈ 2 mM and 5 mM. Deletion of the C-terminal acidic tail of RecA made its thermal stability and fluorescence characteristics insensitive to Mg<SUP>2+</SUP> and similar to those of full-length RecA in the presence of saturating Mg<SUP>2+</SUP>. These observations, together with the results of a molecular dynamics simulation, support the idea that the acidic tail hampers the strand exchange reaction by interacting with other parts of RecA, and that binding of Mg<SUP>2+</SUP> to the tail prevents these interactions and releases RecA from inhibition. We observed that binding of the first Mg<SUP>2+</SUP> stimulated joint molecule formation, whereas binding of the second stimulated progression of the reaction. Thus, RecA is actively involved in the strand exchange step as well as bringing the two DNAs close to each other.</P>

공기업 조직구성원의 변혁적·거래적 리더십과 리더신뢰

권석균(Seog K. Kwun),이춘우(Choonwoo Lee) 한국인사관리학회 2004 조직과 인사관리연구 Vol.28 No.1

This study aims to investigate the differentiated effects of transformational and transactional leadership on the follower's trust in leader Since trust in leader has been defined as singe-dimensional in most prior leadership studies, the complicated relationships between leadership and the follower's trust have not been highlighted yet. For the reason, we defined in this study the follower's trust in leader as multidimensional: calculus-based, knowledge-based and identification-based. The results of empirical analyses showed positive effects of charisma and individual consideration and negative effects of management by exception on all of the three types of trust in leader. But the intelligent stimulus factor of transformational leadership exerted positive effects only on calculus-based trust in leader The factor of contingent rewards in transactional leadership showed no effects on any types of trust in leader Finally, transformational leadership showed the augmentation effects on the follower's trust in leader beyond the effects of transactional leadership, whereas the vise versa was not the case. 본 연구는 명령지시-복종의 조직위계관계가 상대적으로 강하며 보수적인 조직풍토를 나타내는 우리나라 공기업에서 상사의 변혁적 · 거래적 리더십이 부하의 리더신뢰 수준에 미치는 효과를 조직내 위계적 관계를 고려한 현실적인 연구모델을 통해 연구하였다. 종속변수인 리더신뢰는 신뢰의 다차원 개념에 관한 논의에 기초하여 계산적 신뢰, 지식적 신뢰, 동일화 신뢰의 세 가지 수준의 유형으로 구분하고, 이에 대해 변혁적 거래적 리더십의 구성요소들이 개별적으로 어떻게 영향을 미치는지를 살펴보았다. 특히 변혁작 ·거래적 리더십 연구의 핵심 이슈가 되고있는 변혁적 리더십의 부가효과가 리더신뢰를 다차원 개념으로 정의한 경우에서도 확인되는지를 검증해 보았다. 자료는 국내 세 개 주요 공기업의 종업원 300명을 대상으로 설문지를 통해 수집하였으며, 이 중 252개의 자료를 회귀분석 하였다. 분석결과 공기업 조직내에서도 변혁적 리더십의 카리스마와 개인적 배려 수준이 높을수록 부하의 리더에 대한 계산적 신뢰, 지식적 신뢰, 동일화 신뢰 수준이 높아지는 것을 확인할 수 있었다. 그러나 지적 자극 활동은 계산적 신뢰를 높이는 데에만 부분적으로 기여할 뿐, 오히려 리더에 대한 지식적 신뢰 수준을 저하시킬 가능성도 있는 것으로 나타났다. 그리고 거래적 리더십의 예외관리가 많아질수록 부하의 리더신뢰 수준이 저하될 수 있으며, 특히 주로 사기업체직원을 대상으로 한 선행연구결과와 달리 공기업 조직구성원들에게 있어서 상황적 보상은 리더신뢰를 높이는데 기여하지 못하였다. 한편 변혁적 리더십의 부가효과는 모든 유형의 리더신뢰에서 일관되게 나타났다. 이 같은 연구결과는 변혁적 거래적 리더십의 각 요인들이 부하의 리더신뢰를 높이는데 있어서 각기 다른 기능을 한다는 점을 말해준다. 변혁적 리더십의 카리스마나 개인적 배려가 공기업 조직상황에서도 일관되게 리더신뢰 수준을 높여주는 요인인 반면, 지적 자극이나 거래적 리더십의 예외관리, 상황적 보상은 공기업 상황에서 리더신뢰 수준 제고에 기여하지 못하거나 오히려 저하시킬 수 있는 요인으로 나타났다. 우리나라의 공기업에서는 민간기업에 비해 한국의 전통 사회문화적 가치가 남아 강하게 작용하고 있다는 점을 감안하면, 한국의 사회문화적 상황에서는 상사의 카리스마나 부하에 대한 배려행동과 같은 정서적이거나 인간적인 리더행동이 부하의 리더신뢰 수준을 제고시키는데 효과적일 수 있다는 시사점을 얻을 수 있다.

한국의 기업문화와 이문화관리 ; 한국의 벤처 기업문화에 대한 규범적 제언: 보편주의와 특수주의의 조화 관점에서

권석균 ( Seog K. Kwun ) 한국외국어대학교 국제지역연구센터 2000 국제지역연구 Vol.4 No.3

부하의 상급자 신뢰에 상급자의 행동특성과 능력 , 사회적 유사성 및 교환관계 특성이 미치는 영향

권석균(Seog K . Kwun) 한국경영학회 2000 經營學硏究 Vol.29 No.1

This study investigates the antecedents of the subordinate`s trust in leader in organizational contexts. Trust in leader was operationalized in terms of three types: calculus-based, knowledge-based, and identification-based trust. Regression analyses of the survey data from 349 employees in 16 medium-sized firms indicated that all three types of trust were significantly affected by the amount of care, openness, and competence that the leader had shown to the subordinates. The temporal length of the subordinate-leader relationship was correlated positively with knowledge-based trust, but negatively with calculus-based trust. Age and gender similarities exerted marginal influence on knowledge-based trust and identification-based trust as well. Interestingly, similarity in regional origins contributed significantly to identification-based trust, but also marginally to knowledge-based trust. Calculus-based trust was strongly influenced by the expected amounts of gains resulting from the future relationship. Based on the findings, managerial implications are derived. Suggestions for future research also follow.

KIF21A-Mediated Axonal Transport and Selective Endocytosis Underlie the Polarized Targeting of NCKX2

Lee, K.-H.,Lee, J.S.,Lee, D.,Seog, D.-H.,Lytton, J.,Ho, W.-K.,Lee, S.-H. Society for Neuroscience 2012 The Journal of neuroscience Vol.32 No.12