• Bulletin of the Korean Chemical Society
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• 제27권11호
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• pp.1809-1814
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• 2006

The L-Valinate anion coordinating zinc complex, [$Zn(val)_2(H-2O)$], was isolated and structurally characterized by single crystal X-ray crystallography. The crystal possess orthorhombic symmetry with a space group $P2_12_12_1$, Z = 4, and a = 7.4279(2)$\AA$, b = 9.4342(2)$\AA$, c =20.5862(7)$\AA$ respectively. The compound features a penta-coordinate zinc ion in which the two valine anion molecules are directly coordinating the central zinc metal ion via their N (amine) and O (carboxylate) atoms, and an additional coordination to zinc is made by water molecule (solvent) to form a distorted square pyramidal structure. In addition, further synthesis of the valine capped ZnS:Mn nanocrystal from the reaction of [$Zn(val)_2(H-2O)$] precursor with $Na_2S$ and 1.95 weight % of $Mn^{2+}$ dopant is described. Obtained valine capped nanocrystal was water dispersible and was optically characterized by UV-vis and solution PL spectroscopy. The solution PL spectrum for the valine capped ZnS:Mn nanocrystal showed an excitation peak at 280 nm and a very narrow emission peak at 558 nm respectively. The measured and calculated PL efficiency of the nanocrystal in water was 15.8%. The obtained powders were characterized by XRD, HR-TEM, and EDXS analyses. The particle size of the nanocrystal was also measured via a TEM image. The measured average particle size was 3.3 nm.

• Molecular & Cellular Toxicology
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• 제3권4호
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• pp.292-298
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• 2007

Zinc plays indispensable roles in metabolism, including cell growth, apoptosis, proliferation and differentiation. Kidneys are target organs for various regulators of mineral metabolism, and play a key role in zinc balance. To investigate the zinc uptake efficiency, we examined the zinc uptake and accumulation level in vivo and in vitro study. Plasma zinc concentration was peaked out at 1 hr after oral zinc administration. The renal zinc level was peaked out at 12 hr after oral zinc administration, and it was the highest in 40 mg/kg Zn-Asp administrated group in comparison with other groups. In addition, the m-RNA expression level of zinc transporter-1 (ZnT-1), zinc transporter-2 (ZnT-2) and high-affinity L-aspartate transporter (EAAT-3) in Zn-Asp administered group were increased compared with control groups and $ZnSO_4$ group. In order to investigate the intracellular zinc uptake mechanism, we performed the in vitro study by using human embryonic kidney cell line, HEK 293. Intracellular zinc level was peaked out at 3 hr after zinc treatment. In the same way, the mRNA expression level of ZnT-1 and EAAT-3 were increased compared with control group. This study showed that Zn-Asp is effective the zinc uptake into the kidney by increasing the zinc transporter expression.

• Bulletin of the Korean Chemical Society
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• 제34권12호
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• pp.3547-3552
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• 2013

Single crystal EPR and optical studies of a mixed ligand zinc(II) complex doped with VO(II) ion is carried out to establish the structural properties. The angular variation of vanadyl hyperfine lines indicates a single site, with spin Hamiltonian parameters as: $g_{xx}=1.985$, $g_{yy}=1.979$, $g_{zz}=1.943$; $A_{xx}=8.71$, $A_{yy}=6.41$ and $A_{zz}=17.80$ mT. By comparing the direction cosines of principal g and A values with the direction cosines of metalligand bonds, it has been confirmed that the vanadyl ion has entered the lattice interstitially. The exact interstitial position of VO(II) in host lattice has been calculated using the fractional coordinates of atoms in the host lattice out of many assumptions. The EPR and optical data have been confirmed to obtain various bonding parameters, from which the nature of the bonding in the complex is discussed. FT-IR confirms the formation of structure of host lattice.

• 대한화학회지
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• 제68권1호
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• pp.32-39
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• 2024

Glycerol dehydrogenase (GlyDH) plays a crucial role in the glycerol metabolism pathway by catalyzing the oxidation of glycerol to dihydroxyacetone (DHA). Previous studies of GlyDH have predominantly focused on unraveling the structural features of the active site and its binding interactions with ligand. However, the structural details of GlyDH in complex with both NAD⁺ and the substrate bound have remained elusive. In this study, we present the crystal structures of Klebsiella pneumoniae GlyDH (KpGlyDH) in the absence and presence of NAD⁺ at a resolution of 2.1 Å. Notably, both structures reveal the binding of the substrate, ethylene glycol, to the zinc ion. Interestingly, a significant change in the coordination number of the zinc ion is observed, with three in the absence of NAD⁺ and four in its presence. These findings shed light on the structural aspects of GlyDH and its interactions with NAD⁺ and the substrate.

• Bulletin of the Korean Chemical Society
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• 제31권9호
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• pp.2613-2617
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• 2010

Chloroprene is a chlorine substituent of 1,3-butadiene. Butadiene rubber (BR) and chloroprene rubber (CR) composites were thermally aged at 60, 70, 80, and $90^{\circ}C$ for 2 - 185 days in a convection oven and changes of the crosslink densities by the accelerated thermal aging were investigated. The crosslink densities increased as the aging time elapsed and as the aging temperature became higher. Degrees of the crosslink density changes of the BR composite were on the whole larger than those of the CR one except the short-term thermal aging at 60 and $70^{\circ}C$. The crosslink densities abnormally increased after themal aging at high temperatures for a long time. Activation energies for the crosslink density changes of the rubber composites tended to increase with increase of the aging time and the variation showed a local minimum. The activation energies of the CR composite were lower than those of the BR one. The experimental results were explained with a role of ligand of chlorine atom of CR in a zinc complex, steric hindrance by chlorine atom of CR, and oxidation of rubber chain.

• Bulletin of the Korean Chemical Society
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• 제22권7호
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• pp.743-747
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• 2001

New azomethine metal complexes were synthesized systematically and characterized. Beryllium, magnesium, or zinc ions were used as a central metal cation and aromatic azomethines (L1-L4) were employed as a chelating anionic ligand. Emission peaks o f the complexes in both solution and solid states were observed mostly at the region of 400-500 nm in the luminescence spectra, where blue light was emitted. Three of them (BeL1 (Ⅰ), ZnL2 (Ⅱ), and ZnL3 (Ⅲ)) were sublimable and thus were applied to the organic light-emitting devices (OLED) as an emitting layer, respectively. The device including the emitting layer of Ⅰ exhibited white emission with the broad luminescence spectral range. The device with the emitting layer of Ⅱ showed blue luminescence with the maximum emission peak at 460 nm. Their ionization potentials, electron affinities, and electrochemical band gaps were investigated with cyclic voltammetry. The electrochemical gaps of 2.98 for I, 2.70 for Ⅱ, and 2.63 eV for Ⅲ were found to be consistent with their respective optical band gaps of 3.01, 2.95 and 2.61 eV within an experimental error. The structure of OLED manufactured in this study reveals that these complexes can work as electron transporting materials as well.

• 대한화학회지
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• 제44권5호
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• pp.403-409
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• 2000

1,4,7,10-tetraaza13,16-dioxacyclooctadecane-N,N',N",N'"-tetraacetic acid (1), 1,4,7,10-tetraaza-13,16-dioxactclootadecane-N,N',N",N'"-tramethylacetic acid (2), 및 1,4,7,10-tetraaza-13,16-dixacyclooc-tedecane-N,N',N",N'"-tetrapropionic acid (3)와 $Zn^{2+}$ 착물의 형성 및 해리 속도를 멈춤-흐름법 및 분광학적방법으로 측정하였다. 측정 조건을 온도 25.0$\pm$0.1 $^{\circ}C$ 및 이온강도 0.10 M NaClO4 이었다. $Zn^{2+}$이온과 1과 2의 형성 반응은 빠르게 중간 생성물($ZnH_3L^+$)를 형성한다. 여기서 $Zn^{2+}$ 이온은 부분적으로 배위되어 있고 속도 결정 단계는 최종 생성물이었다. pH범위 4.76-5.76에서, 2가 양성자($H_2L^{2-}$) 형태가 매우 낮은 농도임에도 불구하고 속도론적으로 활성화종임을 알 수 있었다. 또한 중간체 착물의 안정도 상수(log$K_{(ZnH_3L^+)}$)와 고유 물분자-보조 속도상수(KOH)가 속도론적 자료로부터 계산되었다. $Zn^{2+}$이온과 1,2, 및 3의 해리 반응은 아세테이트 완충 용액 하에서 청소군 $Cu^{2+}$ 이온을 이용하여 측정하였다. 모든 착물의 해리 반응은 산-무관 및 산-촉매 반응으로 진행됨을 알 수 있었다. $Zn^{2+}$ 착물의 해리 속도에 영향을 미치는 완충 용액 및 $Cu^{2+}$농도의 효과를 알아보았으며, 아울러 리간드 효과를 곁가지에 매달려있는 치환기와 킬레이트 고리크리로 논하였다.