• Rapid Communication in Photoscience
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• 제2권2호
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• pp.42-45
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• 2013

Natural photosynthesis utilizes solar energy to convert carbon dioxide and water to energy-rich carbohydrates. Substantial use of sunlight to meet world energy demands requires energy storage in useful fuels via chemical bonds because sunlight is intermittent. Artificial photosynthesis research focuses the fundamental natural process to design solar energy conversion systems. Nicotinamide adenine dinucleotide ($NAD^+$) and $NADP^+$ are ubiquitous as electron transporters in biological systems. Enzymatic, chemical, and electrochemical methods have been reported for NADH regeneration. As photochemical systems, visible light-driven catalytic activity of NADH regeneration was carried out using platinum nanoparticles, molecular rhodium and cobalt complexes in the presence of triethanolamine as a sacrificial electron donor. Pt nanoparticles showed photochemical NADH regeneration activity without additional visible light collector molecules, demonstrating that both photoactivating and catalytic activities exist together in Pt nanoparticles. The NADH regeneration of the Pt nanoparticle system was not interfered with the reduction of $O_2$. Molecular cobalt complexes containing dimethylglyoxime ligands also transfer their hydrides to $NAD^+$ with photoactivation of eosin Y in the presence of TEOA. In this photocatalytic reaction, the $NAD^+$ reduction process competed with a proton reduction.

• 한국결정학회지
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• 제17권2호
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• pp.41-45
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• 2006

[ $cis-[Co(13-aneN_4)(N_3)_2]Cl{\cdot}H_2O$ ] (1) (13-ane$N_4$ = 1,4,7,10-tetraazacyclotridecane) 착물(錯物)을 합성(合成)하고 구조(構造)를 규명(糾明)하였다. 이 착물(錯物)은 단사정계(單斜晶系), 공간군(空間群) Pbca, a = 7.8282(4) ${\AA}$, b = 14.3197(7) ${\AA}$, c = 29.9021(15) ${\AA}$, V= 3351.9(3) ${\AA}^3$, Z = 8로 결정화(決定化) 되었다. 착물(錯物) 1의 코발트(III)이온은 거대(巨大)고리 리간드의 4개(個)의 질소원자(窒素原子)와 시스 위치에 2개(個)의 azide 리간드가 결합(結合)한 고천(若干) 일그러진 팔면체(八面體) 구조(構造)를 갖는데, 착물(錯物)의 양이온, 염소(鹽素) 음이온 및 물분자(分子)를 통하여 1차원의 수소결합(水素結合)을 형성(形成)한다.

• BMB Reports
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• 제38권5호
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• pp.584-590
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• 2005

Glucose 6-phosphate dehydrogenase (EC 1.1.1.49) was purified from Aspergillus aculeatus, a filamentous fungus previously isolated from infected tongue of a patient. The enzyme, apparently homogeneous, had a specific activity of $220\;units\;mg^{-1}$/, a molecular weight of $105,000{\pm}5,000$ Dal by gel filtration and subunit size of $52,000{\pm}1,100$ Dal by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The substrate specificity was extremely strict, with glucose 6-phosphate (G6P) being oxidized by nicotinamide adenine dinucleotide phosphate (NADP) only. At assay pH of 7.5, the enzyme had $K_m$ values of $6\;{\mu}m$ and $75\;{\mu}m$ for NADP and G6P respectively. The $k_{cat}$ was $83\;s^{-1}$. Steady-state kinetics at pH 7.5 produced converging linear Lineweaver-Burk plots as expected for ternary-complex mechanism. The patterns of product and dead-end inhibition suggested that the enzyme can bind NADP and G6P separately to form a binary complex, indicating a random-order mechanism. The enzyme was irreversibly inactivated by heat in a linear fashion, with G6P providing a degree of protection. Phosphoenolpyruvate (PEP), adenosinetriphosphate (ATP), and fructose 6-phosphate (F6P), in decreasing order, are effective inhibitors. Zinc and Cobalt ions were effective inhibitors although cobalt ion was more potent; the two divalent metals were competitive inhibitors with respect to G6P, with $K_i$ values of $6.6\;{\mu}m$ and $4.7\;{\mu}m$ respectively. It is proposed that inhibition by divalent metal ions, at low NADPH /NADP ratio, is another means of controlling pentosephosphate pathway.

• Bulletin of the Korean Chemical Society
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• 제25권4호
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• pp.471-475
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• 2004

The solubility of N,N'-Bis(salicylidene) ethylenediamine (n-salen) and N,N'-bis(3,5-di-tert-butylsalicylidene) ethylenediamine (t-butyl-salen) was studied with in-situ UV-VIS spectrometer. n-Salen is 3-5 times more soluble than t-butyl-salen in liquid or supercritical $CO_2$. This behavior may be attributed to Lewis acid-base interaction between salen and $CO_2$. The chelation of salen with $Co^{++}$ ion in supercritical condition was confirmed to be fast enough above room temperature. However, the metal ion extraction capability of t-butyl salen is relatively poor because of its low solubility and ionic nature of complex.

• 한국산업융합학회 논문집
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• 제8권3호
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• pp.155-160
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• 2005

Kinetic studies were carried out for aquation of carbonatobis(ethylenediamine)cobalt(III) complexes in [H+] aqueous solution by UV/VIS-spectrophotometry. The rate law that in deduced from rate data is $rate=k_H{^+}[H^+]^{1.4}$ {$[Co(en)_2(CO_3)]^+$}1.0 where $k_H{^+}$ is the rate constant considering acidic catalyst, $H^+$ ion whose value is $0.241l{\cdot}mol^{-1}{\cdot}sec^{-1}$. The values of activation parameters Ea, ${\Delta}H^{\ast}$ and ${\Delta}S^{\ast}$ were $15.33Kcal{\cdot}mol^{-1}$, $14.52Kcal{\cdot}mol^{-1}$ and -57.49 e.u. respectively. On the basis of kinetic data and the observed activation parameters, we have proposed the mechanism that proceeds with two step protonations. The rate equation derived from the proposed mechanism has been in agreement with the observed rate equation. It has been seen that our modified mechanism for Harris's proton freequilibrium one prefer to the his concerted mechanism, and more the last product substitute $H_2O$ for $OH^-$ the Harris's mechanism in the acidity range 2 < pH < 5.

• 보존과학회지
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• 제38권1호
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• pp.1-13
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• 2022

Colour consistency is an important consideration when selecting pigments used on works of art. In this study, we analyse the colour difference between two sets of synthetic blue glass pigments acquired at least 8 years apart from the same manufacturer in Japan. The old pigment set (unused, dry powder with four different grain sizes) appears faded compared to the new set. These pigments are made available for artistic use, commonly in Nihonga or Japanese paintings. Raman spectroscopy and SEM-EDS results characterize these pigments as cobalt aluminate spinels dissolved in leaded glaze, a special class of complex coloured inorganic pigments that is not well-understood in the field of conservation. Colour difference between the old and new pigments with four different grain sizes were quantified by analysing photomicrographs with image analysis software. Blue pigments with coarse and extremely fine grains showed significant colour change compared to pigments with medium and fine grain sizes. The high occurrence of crystallites in the finer grains give a final colour that is bluer and lighter. Possible causes for the colour difference including manufacturing methods and storage environment are discussed.

• 한국산업융합학회 논문집
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• 제1권1호
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• pp.43-49
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• 1998

The SS-phpm 4HCl(N,N'-bis-[2(S)-pyrrolidinylmethyl]phenylene-l,2-diamine-4-Hydrochloride) ligand having stereospecificity has been prepared and reacted with trans-[$Co(pyridine)_4Cl_2]$Cl. The resultants are purple crystals, which are identified to be ${\Delta}$-cis-${\beta}$-[$Co(SS-phpm)Cl_2$]Cl by elemental analysis and UV/Vis- and CD-absorption spectra, The conformation of SS-phpm in ${\Delta}$-cis-${\beta}$ complex is ${\delta}$ ${\varepsilon}$ ${\lambda}$ (SSSS) for each of the five-membered chelated ring. Futhermore, according to orientation of secondary amine, total strain energy on each isomers was calculated by molecular mechanics(MM) to verify structural characterization and spectral data. As the result, the most stabilized isomer was ${\Delta}$-cis-${\beta}$(SSSS). The value of total strain energy(U) of ${\Delta}$-cis-${\beta}$(SSSS) isomer was 63.21 kcal/mol, respectively.

• Bulletin of the Korean Chemical Society
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• 제33권4호
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• pp.1297-1302
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• 2012

The interaction between carbon monoxide (CO) and a cobalt-salen complex (Co(salen)) was studied and applied to detect CO. The metal complex doped PEDOT:PSS film exhibited good sensitivity to CO and differentiate CO from other gases. The response of the composite to CO was reversible (RSD < 5%) change in resistance upon removal of CO gas from the test chamber. The effects of adding Co(salen) in the probe film on the response of the sensor were investigated using AFM, XPS, and FT-IR spectroscopy. The sensitivity of the sensor increased as the Co(salen) concentration enhanced as it increased from 0.0 to 1.5 wt. %, where the highest sensitivity ($%{\Delta}R/R_o$) of $-25.0{\pm}0.05%$ was achieved with 1.0 wt. % Co(salen). The sensor containing probe exhibited a linear response ($R^2$ = 0.983) in the range of 0.5 to 10.0% CO (v/v) $N_2$, and the detection limit was 1.74% CO (v/v) in $N_2$.

• Bulletin of the Korean Chemical Society
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• 제19권4호
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• pp.457-462
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• 1998

A chiral pentadentate bis-amide ligand, 1,9-bis(S)-pyrrolidinyl-2,5,8-triazanonane-1,9-dio ne$(S,S-prodienH_2)$ has been synthesized from the reaction of bis(2-aminoethyl)amine(dien) and S-proline, and the structure of $[Co(S,S-prodien)H_2O]ClO_4$ has be en determined by single crystal X-ray diffraction. The geometrical structure of the Co(III) complex has been an αβ -form, where the dien moiety of ligand chelates to a facial in metal center, and the aqua ligand coordinates a cis site to the secondary nitrogen of dien. The Co-N(1), Co-N(3) distances of two amide moiety in S,S-prodien are shorter than the other Co-N(2), Co-N(4), and Co-N(5) distances because of the increased basicity of nitrogen in amide. The complex crystallizes in the monoclinic space group $P2_1$(#4), with a=7.838(1), b=12.675(1), c=9.710(1) Å, β=100.39(1) and z=2. Refinement gives the final R and $R_w$ values of 0.045 and 0.057, respectively for 2130 observed reflections. Based upon the CD and X-ray data, it is identified that the absolute configuration of the αβ -$[Co(S,S-prodien)H_2O]ClO_4$ has a Λ-form.

• 자원환경지질
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• 제30권4호
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• pp.289-301
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• 1997

보국 코발트 광산은 백악기 경상분지내에 위치하며, 셰일로 구성된 건천리층을 천부 관입한 암주상의 미문상 화강암내에 국한하여 배태된다. 광상은 열극 충진형 석영${\pm}$액티놀라이트${\pm}$탄산염 광물맥으로 이루어지며, 광석광물로는 함코발트광물 (비독사석, 휘코발트석, 글로코도트), 함코발트 유비철석과 소량의 황화광물 (자류철석, 황동석, 황철석, 섬아연석) 및 미량의 산화광물 (자철석, 적철석)이 산출된다. Rb-Sr 절대연령 측정 결과, 화강암의 관입 및 이와 관련된 광화작용은 후기 백악기 (85.98 Ma)에 이루어진 것으로 판단된다. 산출광물종은 다소 복잡한 양상을 보이며, 시간에 따라 다음과 같이 변화한다: 액티놀라이트, 탄산염광물 및 석영에 수반되는 함코발트 광물의 정출 (광화시기 I, II)${\rightarrow}$석영에 수반되는 황화광물, 금 및 산화광물의 정출 (광화시기 III)${\rightarrow}$탄산염광물의 정출(광화시기 IV, V). 고온성 광물 (함코발트 광물, 휘수연석, 액티놀라이트)과 더불어 저온성 광물 (황화광물, 금, 탄산염광물)이 산출되는 점으로 보아 열수광화작용은 xenothermal 환경에서 형성되었다. 화강암은 특징적으로 높은 코발트 함유량 (평균 50.90 ppm)을 나타내며, 이는 코발트가 냉각하는 화강암 암주에서 기원하였음을 지시한다. 반면, 건천리층 셰일의 높은 동 및 아연 함유량은 이들 원소가 주로 셰일로부터 유래되었음을 지시한다. 열수용액의 온도 감소와 더불어 산소분압이 감소 (광화 I, II기의 코발트광물 형성, $T=560^{\circ}C-390^{\circ}C$, log $fO_2=$ > -32.7 to -30.7 atm at $350^{\circ}C$; 광화 III기의 황화광물 형성, $T=380^{\circ}-345^{\circ}C$, log $fO_2={\geq}-30.7$ atm at $350^{\circ}C$함은 열수계가 시간이 지남에 따라 초기 마그마성 계로부터 천수로 지배되는 열수계로 전이되었음을 나타낸다. 광화 II기의 유황 동위원소 값은 초기 함코발트 열수 용액이 화성기원 ($${\delta}^{34}S_{{\Sigma}S}{\sim_=}3-5$$‰)으로부터 기원하였음을 증거한다. 열수용액의 ${\delta}^{34}S_{H_2S}$ 값은 광화 II기의 코발트 형성기 (3-5‰)로부터 황화광물 형성 시기인 광화 IV기 (최대 약 20‰)까지 크게 증가하였다. 이는 후기로 갈수록 천수가 우세한 열수계로 진화하면서 주위의 퇴적암을 순환하는 과정에 동위원소적으로 무거운 유황 (퇴적기원의 황산염)과 천금속 (Cu, Zn 등) 및 금을 용해, 농집시켰음을 시사한다. 후기에 천수의 유입이 없었더라면, 보국 광상은 단순히 액티놀라이트 + 석영 + 함코발트 광물로 구성된 광맥으로만 형성되었을 것이다. 또한, 마그마 기원의 열수계가 형성된 이후에 천수 순환계가 형성됨으로 인하여 고온 광물과 저온 광물이 함께 산출되는 xenothermal 한 광상의 특성을 나타내게 되었다.