Macrocyclic Corphin Ring-Puckering of 12,13-diepimeric Coenzyme F430 by the Compensated ROESY Experiment

Won, Hoshik 漢陽大學校 基礎科學硏究所 1994 基礎科學論文集 Vol.13 No.-

¹H-¹H 동핵관련 핵자기공명 실험법중에서 핵의 Overhauser 효과(NOESY)와 회전좌표상에서의 Overhauser 효과(ROESY)를 이용한 실험을 실행하여 최근 발견된 전이원소 Ni(Ⅱ)를 함유한 보조인자 F430의 corphin 구조정보가 얻어졌다. ROESY 핵자기공명 실험중 스핀고정 시간에 부가적으로 2개의 90° 펄스를 가함으로서 corphin고리의 포화 탄화수소로 부터 얻어진 해석하기 힘든 signal의 중도를 명확하게 구분할 수 있었다. 기존 2차원적 자기공명 방법으로도 구분하기 힘든 중첩된 methylene기의 signal들에 대하여 선구키랄성이 얻어졌으며 F430의 거대 corphin고리에 관해 주름잡힌 정도를 알아낼 수 있었다. By employing ¹H-¹H homonuclear correlated spectroscopies, including nuclear Overhauser effect spectroscopy (NOESY) and rotating frame NOE spectroscopy (ROESY), corphin structure of the recently discovered nickel(Ⅱ)-containing coenzyme F430 was obtained. Two additional 90° soft pulses applied during the spin-lock period of ROESY(compensated REOSY) were clearly enabled to distinguish multiplets of protons attached to saturated carbon atoms on the D-ring. Results were turned out to be important in the determination of the degree of macrocyclic puckering and in the prochiral assignments.

Studies of Square Pyramidal Nickel(Ⅱ)-Containing Coenzyme F430 Model Complexes

Won, Hoshik,Chun, Hyungphil,Kwak, Bunghun,Chang, Hwanbong,Park, Seunghee 漢陽大學校 基礎科學硏究所 1995 基礎科學論文集 Vol.14 No.-

보조효소 F430은 사각평면의 중앙에 Ni(Ⅱ)원자가 결합하여 있는 tetrapyrrole의 corphin 거대고리 분자이다. 최근 구조연구에 의하면 corphin은 보조효소 B₂에서의 corrin 거대고리와 유사하게 부분적으로 이중결합의 연결되어 있으며 거대고리 전체가 굽혀지고 주름이 잡혀있는 것으로 보고되고 있다. F430의 촉매메카니즘에 관여하는 corphin고리의 역활을 이해하기 위해, 모델착물 Ni((DO)(DOH)pn]I 을 합성하였고 Ni(Ⅱ)[(DO)(DOBF₂)pn]I와 구조적인 비교를 시행하였다. 두착물의 중요한 차이점은 적도방향 리간드가 분자평면으로 부터 다른 굽힘각(α)을 준다는 것이다. Ni((DO)(DOH)pn)I은 평면으로부터 11.6˚의 굽힘각을 나타내고, 반면에 Ni((DO)(DOBF₂)pn)I의 굽힘각은 19.0˚을 나타낸다. 두 화합물에서 결합은 Ni원자는 각각의 diimino 형태들(최대 π-orbital overlap을 유지하기 위해서)과 동일 평면상에 남기위해 수직방향 리간드와 거리가 멀게 위치한다. I방향으로 Ni원자가 4개의 질소평면으로부터 Ni((DO)(DOH)pn)I에서는 0.188Å 만큼 떨어져있고, Ni((DO)(DOBF₂)pn)I에서는 0.23Å 떨어져있다. 또한 Ni((DO)(DOH)pn)I에서 얻어진 긴 Ni-I 결합거리는(DO)(DOH)pn 리간드가 (DO)(DOBF₂)pn보다 더욱 강한 강성(rigidity)을 갖고 있음을 나타낸다. Coenzyme F430 consists of a tetrapyrrole corphin macrocycle with a centrally bound, square planar Ni(Ⅱ) atom. Recent structural studies exhibit that the corphin is not fully conjugated and is thus able to bend or ruffle as in the corrin macrocycle in coenzyme B12. In order to increase the functions of corphin ring in the mechanistic details of F430 - dependent catalysis, model complex Ni [(DO)(DOH)pn] I was synthesized and structural comparison was made with Ni((DO)(DOBF₂)pn) I. Significant difference between complexes was the angle of deviation from planarity of the equatorial ligand (bending angle α). Ni((DO)(DOH)pn) I exhibits deviation from planarity of 11.6˚whereas deviation in Ni((DO)(DOBF₂)pn) I is 19˚. In both compounds, bending is away from the axial ligands such that the Ni atom remains coplanar with each of the diimino moieties(to maintain maximum π-orbital overalp), and is displaced from the 4-N plane towards I by 0.188Å in Ni((DO)(DOH)pn) I and 0.23Å in Ni((DO)(DOBF₂)pn) I. The very long Ni - I bond in Ni((DO)(DOH)pn) I is thus a consequence of the greater rigidity of the (DO)(DOH)pn ligand compared to the (DO)(DOBF₂)pn ligand.

Surface Modification by Atmospheric Pressure DBDs Plasma: Application to Electroless Ni Plating on ABS Plates

Song, Hoshik,Choi, Jin Moon,Kim, Tae Wan The Korean Institute of Electrical and Electronic 2013 Transactions on Electrical and Electronic Material Vol.14 No.3

Acrylonitrile-butadiene-styrene (ABS) plastic is a polymer material extensively used in electrical and electronic applications. Nickel (Ni) thin film was deposited on ABS by electroless plating, after its surface was treated and modified with atmospheric plasma generated by means of dielectric barrier discharges (DBDs) in air. The method in this study was developed as a pre-treatment for electroless plating using DBDs, and is a dry process featuring fewer processing steps and more environmentally friendliness than the chemical method. After ABS surfaces were modified, surface morphologies were observed using a scanning electron microscope (SEM) to check for any physical changes of the surfaces. Cross-sectional SEM images were taken to observe the binding characteristics between metallic films and ABS after metal plating. According to the SEM images, the depths of ABS by plasma are shallow compared to those modified by chemically treatment. The static contact angles were measured with deionized (DI) water droplets on the modified surfaces in order to observe for any changes in chemical activities and wettability. The surfaces modified by plasma showed smaller contact angles, and their modified states lasted longer than those modified by chemical etching. Adhesion strengths were measured using 3M tape (3M 810D standard) and by 90° peel-off tests. The peel-off test revealed the stronger adhesion of the Ni films on the plasma-modified surfaces than on the chemically modified surfaces. Thermal shock test was performed by changing the temperature drastically to see if any detachment of Ni film from ABS would occur due to the differences in thermal expansion coefficients between them. Only for the plasma-treated samples showed no separation of the Ni films from the ABS surfaces in tests. The adhesion strengths of metallic films on the ABS processed by the method developed in this study are better than those of the chemically processed films.

공정공시가 주식유동성에 미치는 영향에 대한 연구: 중소기업과 대기업 비교

심호식 ( Hoshik Shim ) 한국중소기업학회 2015 기업가정신과 벤처연구 Vol.18 No.3

본 연구는 한국의 공정공시제도 도입 이후의 공시자료를 이용하여 기업별로 공정공시 빈도가 주식유동성에 미치는 영향에 대하여 연구하였다. 공시이론에서는 공시의 빈도가 높을수록 해당기업의 정보비대칭 현상이 해소되어 유동성이 증가하고, 그 결과 자기자본 비용이 감소한다고 밝히고 있다. 그러나 한국과 같은 신흥시장에서는 공시 이전의 정보 유출현상 때문에 공시의 효과를 예측하기가 어려운 실정이다. 공정공시제도의 도입으로 인해 한국의 상장회사들은 해당되는 항목에 대하여 모든 시장참여자에게 동시에 그정보를 공개하도록 의무화되었다. 따라서 공정공시제도의 시행은 과거 사전적인 정보 유출현상을 효과적으로 방지할 수 있는 제도적 틀을 마련한 것으로 기대할 수 있다. 본 연구는 이러한 점에 착안하여 공정공시제도가 자본시장에 미치는 영향 중 주식유동성과의 관련성에 대해 실증적으로 분석하였다. 분석결과, 공시빈도가 많을수록 주식의 유동성이 증가하는 것을 확인하였다. 구체적으로 공시빈도가 많을수록 해당기업주식의 거래량 및 변동성이 증가하였으며, 거래비용이 감소하여 무수익(zero-return) 거래일의 빈도가 감소하는 것으로 나타났다. 한편 이러한 공시효과는 중소기업과 대기업에서 모두 발견되지만, 개별 유동성 변수에 미치는 영향이 다른 것으로 나타났다. 강건성 분석으로 도구변수를 이용하여 내생성을 통제하였을 경우에도 이러한 결과는 유지되었다. 본 연구의 결과는 공시가 자본시장에 미치는 영향, 특히 공시와 자기자본비용 간의 관계를 연구할 때 시장유동성의 영향과 기업규모에 따른 정보환경의 영향을 반드시 고려해야 함을 시사한다. This paper investigates the impact of disclosure activity on the stock market liquidity under the Regulation Fair Disclosure in Korea. Economic theories generally support that more disclosures reduce the level of information asymmetry, increase stock liquidity, and thus decrease the costs of equity capital. A series of empirical studies examine the impact of disclosure policy, however, they mainly focus on the relationship between disclosure and costs of equity capital, but not on the relationship between disclosure and liquidity especially in Korea. Since the disclosure theory is driven with a joint hypotheses, it is needed to investigate the relationships by stage. Using various measures of market liquidity, this study finds that disclosure activity is positively related with market liquidity. And the comparative analysis shows that both SMEs and large firms have disclosure impacts, but they affect this relation differently. Various sensitivity tests show that the relation is robust. The findings of this paper have an implication that the impact of liquidity and also the impact of information environment (i.e., SMEs vs. large firms) should be considered in examining the relation between disclosure and costs of equity capital.

핵자기공명법에 의한 신경호르몬 LHRH의 입체구조 연구

원호식,원영도,김대성 漢陽大學校 基礎科學硏究所 1995 基礎科學論文集 Vol.14 No.-

Luteinizing Hormone Releasing Hormone(LHRH)는 신경전달 물질로서 10개의 아미노산으로서 이루어져 있다. 고등동물에서 80%정도 동종성을 가지고 있어, 유사한 기능을 가지고 있거나 LHRH를 조절할 수 있는 물질에 관심이 집중되고 있다. 본 연구에서는 핵자기공명 실험의 결과 및 distance geometry(DG)를 이용하여 LHRH의 액상상태 3차원구조를 구하였다. Nuclear Overhauser effect 분광법(NOESY)에서 얻어진 수소쌍들의 거리 정보를 분자구조 결정에 사용하였다. 얻어진 구조를 기존의 에너지 계산법 및 분광학적인 방법에 의해 예측된 구조에 대한 연구결과와 비교하였다. 본 연구에서 얻어진 구조는 10개의 아미노산중 잔기서열 2∼7범위에서 α - 나선 구조로 - 특이한 회전을 나타내고 있고, 에너지 계산에 의해 얻어진 구조와 유사한 고리 형태를 이루고 있다. Luteinizing Hormone Releasing Hormone (LHRH) is composed of 10 amino acids, and is best known as a neurotransmitter. Because of the 80% homology in animals, much more concerns have focused on the substances that have similar functions or can control LHRH. Solution-state structure determination of LHRH was accomplished by using NMR results and NMR-based distance geometry(DG). Interproton distances from nuclear Overhauser effect spectroscopy(NOESY) were utilized for the molecular structure determination. Results were compared with previous structures obtained from energy minimization and other spectroscopic methods. Structure obtained in this study has a cyclic conformation which is similar to that of energy minimized, and exhibits a specific α-helical turn with residue numbers(2∼7) out of 10 amino acids.

보조효소 F430의 모델 착물 Ni((PMO)(PMOH)pn)Ⅰ 와 Ni((PEO)(PMOH)pn)Ⅰ 합성 및 구조적 특성 연구

원호식 한양대학교 이학기술연구소 2007 이학기술논문지 Vol.10 No.-

F430 의존 촉매 메카니즘에 관여하는 corphin 고리의 역할을 이해하기 위해, 다양한 alkyl과 aryl 작용기를 가지는 imine/oxime type의 거대고리 리간드와 축 방향 리간드 (X=Ⅰ)를 가지는 사각 피라밋 구조의 Ni(Ⅱ) 착물을 합성하였다. 합성된 리간드 및 착물은 질량 분석을 이용하여 확인하였고, NMR, UV-Vis, X-ray, CV 등의 기기를 이용하여 구조 및 물리화학적인 특성을 규명하였다. 구조 분석 결과, Ni((PMO)(PMOH)pn)Ⅰ 착물과 Ni((PEO)(PMOH)pn)Ⅰ 착물에 대하여 5.88°과 6.63° bending 각과 금속이온의 평면으로 부터의 편차 d 값이 각각 0.19 Å, 0.22 Å으로 얻어졌다. In order to understand the functions of corphin ring in F430-dependent catalysis, Ni(Ⅱ)-containing square pyramidal macrocylic model complexes which have imine/oxime type macricyclic ligands including various alkyl, aryl groups and axial ligands(X=Ⅰ) were synthesized. Ligands and metal complexes synthesized were identified with Mass spectrometry, and futher studies including structure and physicochemical properties were accomplished by utilizing NMR, UV-Vis, CV, and X-ray, respectively. The bending angle(5.880°, 6.63°), and the deviation of metal ion from plnarity d value (0.19 Å, 0.22 Å ) were obtained for Ni((PMO)(PMOH)pn)Ⅰ and Ni((PEO)(PMOH)Pn)Ⅰ complexes.

Do Earnings Manipulations Matter Differently in Different Markets of China? Cost of Capital Consequences

Sohn, Byungcherl Charlie,Shim, Hoshik Kyung Hee University Management Research Institute 2019 Asia pacific journal of business review Vol.4 No.1

This study investigates whether and how a firm's cost of equity capital is influenced by the extent of a firm's real earnings management (REM). Using a large sample of Hong Kong and Chinese firms over the 9-year period 2009-2017, we find that our implied cost of equity estimates are positively associated with both the extent of REM and the extent of accrual-based earnings management (AEM), but the positive association is stronger for REM than for AEM. We also provide evidence suggesting that the effect of AEM and REM on the cost of equity is more pronounced for Hong Kong firms than Chinese firms, and within Chinese firms, it is less pronounced for the state-owned enterprises (SOEs). Collectively, our results suggest that while both REM and AEM exacerbate the quality of earnings used by outside investors, REM does so to a greater extent than AEM, and thus the market demands a higher risk premium for REM activities than for AEM activities and that this cost of capital-increase effect is more prominent in a developed market like Hong Kong and mitigated by state ownership in China because of investors' expectations for a lower level of detriments to firm fundamentals by REM due to government's protection in a less developed market like China.

Correlation of the Rates of Solvolyses of Carbomethoxybenzyl Bromides Using the Grunwald-Winstein Equation

Jin Burm Kyong*,Hoshik Won,이영훈,Dennis N. Kevill 대한화학회 2005 Bulletin of the Korean Chemical Society Vol.26 No.4

위성체 태양전지판 구조물의 열적 플러터 해석

윤일성(Ilsoung Yoon),강호식(Hoshik Kang),정남희(Namheui Jeong),송오섭(Ohseop Song) 한국항공우주학회 2005 韓國航空宇宙學會誌 Vol.33 No.7

본 논문에서는 위성체 태양전지의 진동응답을 분석하였다. 태양전지는 복합재료 얇은 벽보와 태양전지 판 및 보조 바로 구성되어 있다. 복합재료 앓은 벽보는 전단 변형, 1ㆍ2차 와핑, 회전 관성과 재료의 방향성 등을 고려해야 한다. 태양전지 판은 z 방향으로 일정한 장력이 가해지는 앓은 막이며 보조 바는 강체 구조물이다. 열적 구배에 따른 구조 변형에 의한 영향을 고려하여 연성된 열적 구조 해석을 수행하였으며, 열적 불안정성 조건이 되는 안정성 기준 인자들을 분석하였다. In this paper, the vibration response of the spacecraft solar array is investigated. The solar array model consists of composite thin walled beam and solar blanket, spreader bar. The composite thin walled beam incorporates a number of nonclassical effects of transverse shear, primary and secondary warping, rotary inertia and anisotropy of constituent materials. The solar blanket is a membrane subjected to uniform tension in the z direction. The spreader bar is a rigid member. A coupled thermal structure analysis that includes the effects of structural deformations on heating and temperature gradient is investigated. A stability criterion given in parameters for establishes the conditions for thermal flutter.

Synthesis of α-oximinoketones, Precursor of CO₂ Reduction Macrocyclic Coenzyme F430 Model Complexes

Kim, Gilhoon,Won, Hoshik Korean Magnetic Resonance Society 2017 Journal of the Korean Magnetic Resonance Society Vol.21 No.4

Ni(II) containing coenzyme F430 catalyzes the reduction of $CO_2$ in methanogen. Macrocyclic Ni(II) complexes with N,O shiff bases have been received a great attention since metal ions play an important role in the catalysis of reduction. The reducing power of metal complexes are supposed to be dependent on oxidoreduction state of metal ion and structural properties of macrocyclic ring moiety that can enhance electrochemical properties in catalytic process. Six different ${\alpha}$-oximinoketone compounds, precursor of macrocyclic ligands used in $CO_2$ reduction coenzyme F430 model complexes, were synthesized with yields over 90% and characterized by NMR. The molecular geometries of ${\alpha}$-oximinoketone analogues were fully optimized at Beck's-three-parameter hybrid (B3LYP) method in density functional theory (DFT) method with $6-31+G^*$ basis set using the ab initio program. In order to understand molecular planarity and substitutional effects that may enhance reducing power of metal ion are studied by computing the structure-dependent $^{13}C$-NMR chemical shift and comparing with experimental results.