• Macromolecular Research
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• 제17권10호
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• pp.739-745
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• 2009

N,N'-(bicyclo[2,2,2]oct-7-ene-tetracarboxylic)-bis-L-amino acids 3a-g were synthesized by the condensation reaction of bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride 1 with two equimolars of Lalanine 2a, L-valine 2b, L-leucine 2c, L-isoleucine 2d, L-phenyl alanine 2e, L-2-aminobutyric acid 2f and L-histidine 2g in an acetic acid solution. Seven new poly(amide-imide)s PAIs 5a-g were synthesized through the direct polycondensation reaction of seven chiral N,N'-(bicyclo[2,2,2]oct-7-ene-tetracarboxylic)-bis-L-amino acids 3a-g with bis(3-amino phenyl) phenyl phosphine oxide 4 by two different methods: direct polycondensation in a medium consisting of N-methyl-2-pyrrolidone (NMP)/triphenyl phosphite (TPP)/calcium chloride ($CaCl_2$/pyridine (py), and direct polycondensation in a tosyl chloride (TsCl)/pyridine (py)/N,N-dimethylformamide (DMF) system. The polymerization reaction produced a series of flame-retardant and thermally stable poly(amide-imide)s 5a-g with high yield. The resulted polymers were fully characterized by FTIR, $^1H$ NMR spectroscopy, elemental analyses, inherent viscosity, specific rotation and solubility tests. Data obtained by thermal analysis (TGA and DTG) revealed that the good thermal stability of these polymers. These polymers can be potentially utilized in flame retardant thermoplastic materials.

• Bulletin of the Korean Chemical Society
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• 제12권2호
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• pp.178-181
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• 1991

The crystal structure of dehydrated fully $Cd^{2+}$-exchanged zeolite A evacuated at $2{\times}10^{-6}$ Torr and $450^{\circ}C (a = 12.225(2){\AA})$ and of its ethylene sorption complex (a = 12.219(2) ${\AA}$) have been determined by single crystal X-ray diffraction techniques in the cubic space group Pm3m at $21(1)^{\circ}$. The structures were refined to final error indices, $R_1$ = 0.063 and $R_2$ = 0.065 with 266 reflections and $R_1$ = 0.055 and $R_2$ = 0.062 with 260 reflections, respectively, for which $I{\gg}3{\sigma}(I)$. In both structures, six $Cd^{2+}$ ions lie at two distinguished three-fold axes of unit cell. Dehydrated $Cd_6$-A sorbs 4 ethylene molecules per unit cell at $25^{\circ}C$ (vapor pressure of ethylene is ca. 100 Torr). Each $Cd^{2+}$ ion forms a lateral ${pi}$ complex with an ethylene molecule. Four $Cd^{2+}$ ions exist in a nearly tetrahedral environment, 2.210(7)${\AA}$ apart from three framework oxygen ions (considering ethylene molecule as a monodentate ligand) and $2.67(6){\AA}$ from each carbon atom of ethylene molecule.

• Bulletin of the Korean Chemical Society
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• 제20권3호
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• pp.355-361
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• 1999

To improve the volatility and stability of lead complexes, the principle of stabilization by saturating the metal coordination sphere by intramolecular coordination through a β-diketonates with an ethereal group has was tested. Several new lead complexes with alkoxyalkyl-substituted β-diketonates, Pb(R1C(O)CHC(O)(CH2)3OR2)2(Rl=t-Bu, Me, OMe, i-Pr, R2=Me, Et), or carboxylate, Pb(OC(O)(CH2)3OEt)2, were prepared by the reaction between Pb(OAc)2 and corresponding alkoxyalkyl-substituted β-diketonates, and they were found to have a viscous liquid phase. The nature of the head (β-diketonate or carboxylate) or tails and substituents of β-diketonates appeared not to be important for the formation of the liquid phase. It is worth mentioning that Pb(OAc)2, which has limited use due to its low solubility, was successfully adopted as a starting material for the preparation of new lead complexes. Easy hydrolysis, reaction with HCl, and 13C NMR spectra indicated that tail portions were not coordinated to the metal as a copper derivative, Cu(t-BuC(O)CHC(O)(CH2)3OMe)2. All these complexes were not volatile enough for the MOCVD experiments, but a methyl derivative, Pb(MeC(O)CHC(O)(CH2)3OEt)2, showed some sublimation. The methoxy derivative, Pb(MeOC(O)CHC(O)(CH2)3OEt)2, was thermally unstable due to possible equilibrium between species coordinating with a keto oxygen atom and an ethereal atom of a methoxy group, which was confirmed by IR and 13C NMR spectra.

• Bulletin of the Korean Chemical Society
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• 제23권7호
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• pp.948-952
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• 2002

Three-dimensional terbium coordination polymers with the formulas of [Tb4(NDC)6(H2O)5]${\cdot}$2H2O (1) and [Tb2(BPDC)3(H2O)3]${\cdot}$H2O (2) (NDC = 2,6-naphthalenedicarboxylate; BPDC = 2,2'-bipyridine-4,4'-dicarboxy-late) were prepared by hydrothermal reactions. Both compounds were structurally characterized by X-ray diffraction. Compound 1 has a polymeric structure that contains four distinct Tb metals. Three Tb metals have a square-antiprismatic structure, and the remaining one has a 9-coordinate, triply capped trigonal-prismatic structure. Compound 2 is also a polymer with two distinct Tb metals, both of which have a square-antiprismatic structure. The pyridine nitrogen atoms of the BPDC 2- ligand do not coordinate to the metal centers in compound 2.

• 청정기술
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• 제23권1호
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• pp.104-112
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• 2017

해조류로부터 수열 액화 반응을 통해 생성된 원료를 이용하여 수소가스를 생산하기 위해 개질 반응용 상용화 촉매와 $K_2Ti_xO_y$가 첨가된 니켈(Ni) 제조 촉매를 사용하여 반응온도에 따른 수증기 개질 반응을 수행하였다. 반응원료는 해조류 바이오매스를 503 K의 반응온도에서 2시간 동안 수열 액화를 통해 생성된 액화 원료를 사용하였으며, 상용화 촉매(FCR-4-02)와 제조 촉매($Ni/K_2Ti_xO_y-Al_2O_3$, $Ni/K_2Ti_xO_y-SiO_2$, $Ni/K_2Ti_xO_y-ZrO_2/CeO_2$, Ni/$K_2Ti_xO_y$-MgO) 및 반응온도에 따른 수증기 개질 반응의 활성을 비교 연구하였다. 실험결과 제조 촉매 4종 모두 상용화 촉매와 비교하여 반응활성이 높게 나타나는 것이 확인되었으며, 제조 촉매의 지지체에 따라 생성되는 가스의 조성이 달라지는 것이 확인되었다. 특히, 산성이나 염기성을 띄는 $Al_2O_3$와 MgO의 지지체와 중성을 띄는 $SiO_2$의 지지체에서는 CO가 선택적으로 높게 생성이 되었으며 환원성을 띄는 $CeO_2$를 포함하는 지지체에서는 수성가스 전환 반응이 일어나 $CO_2$가 높게 생성됨을 보였다.

• 한국안광학회지
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• 제17권1호
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• pp.91-97
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• 2012

목적: 본 연구는 노인성 황반변성(age-related macular degeneration, AMD)의 병인으로 잘 알려진 A2E의 광산화가 자외선 차단렌즈나 brown 착색렌즈에 의해 억제되는가를 알아보고자 하였다. 방법: 두 분자의 all-trans-retinal과 한 분자의 ethanolamine을 합성하여 만든 A2E에 청색광(420~470 nm, $94mW/cm^2$)을 3분 동안 조사하여 광산화를 유도하였다. UV 차단 및 brown 착색 안경렌즈의 A2E의 광산화 저해 효과는 광산화되지 않고 남아있는 A2E의 흡광도와 HPLC chromatogram 분석을 통하여 확인하였다. 결과: 자외선 차단렌즈는 청색광 조사로 유발되는 A2E의 광산화를 억제하지 못하였다. 반면 Brown 착색렌즈에서는 가시광선 차단율이 15%인 경우 A2E의 광산화율에는 별차이가 없었지만, 55%와 86% 차단된 렌즈에서는 각각 9.98%, 16.55%의 A2E 광산화 억제 효과를 보였다. HPLC로 분석한 잔존 A2E량을 확인해 보면 렌즈로 차단하지 않은 A2E의 잔존량은 $199.29{\pm}26.53{\mu}M$ 이었으나, 55% 차단율을 가진 brown 렌즈는 $264.58{\pm}31.91{\mu}M$, 86% 차단율을 가진 렌즈에서는 $402.93{\pm}26.68{\mu}M$의 A2E 잔존량을 보여 A2E 광산화 억제효과가 있음을 확인하였다. 반면, 자외선 차단렌즈의 경우에는 잔존량 분석에서도 광산화 억제효과가 없는 것으로 나타났다. 결론: 본 연구결과를 통하여 brown 착색 안경렌즈는 노인성 황반변성의 원인물질인 A2E의 광산화를 억제하는 효과가 있는 것으로 알 수 있었다.

• 대한화학회지
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• 제36권5호
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• pp.764-769
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• 1992

Strigol은 목화의 뿌리에서 추출된 천연물로서 벼, 옥수수, 사탕수수 등에 기생하는 피류(striga species) 등의 씨앗을 발아시키는데 월등한 효능을 보인다 $(10^{-12} ∼ 10^{-11}M, 80% 발아)$. 그런데 이러한 잡초는 오랜기간(15∼20년) 동안 흙속에서 휴면하고 있기 때문에 이들의 방제가 매우 어렵다. 이들을 방제할 수 있는 제초제 개발을 위해서 여러가지 strigol 유사체들인 3-methyl-4-(2-oxo-3,3a,6,6a-tetrahydro-2H-cyclopenta[b]furan-3-ylidenemethoxy)-but-2-en-4-olide(21), 4-(2-oxo-3,3a,6,6a-tetrahydro-2H-cyclopenta[b]furan-3-ylidenemethoxy)but-2-en-4-oilde(22), 3-methyl-4-(2-oxotetrahydrofuran-3-ylidenemethoxy)-but-2-en-4-olide(23), 4-(2-oxotetrahydrofuran-3-ylidenemethoxy)-but-2-en-4-olide(24)등을 합성하였다.

• The Korean Journal of Physiology and Pharmacology
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• 제18권2호
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• pp.155-161
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• 2014

Overexpression of amyloid precursor protein with the Swedish mutation causes abnormal hyperphosphorylation of the microtubule-associated protein tau. Hyperphosphorylated isoforms of tau are major components of neurofibrillary tangles, which are histopathological hallmarks of Alzheimer's disease. Protein phosphatase 2A (PP2A), a major tau protein phosphatase, consists of a structural A subunit, catalytic C subunit, and a variety of regulatory B subunits. The B subunits have been reported to modulate function of the PP2A holoenzyme by regulating substrate binding, enzyme activity, and subcellular localization. In the current study, we characterized regulatory B subunit-specific regulation of tau protein phosphorylation. We showed that the PP2A B subunit PPP2R2A mediated dephosphorylation of tau protein at Ser-199, Ser-202/Thr-205, Thr-231, Ser-262, and Ser-422. Down-regulation of PPP2R5D expression decreased tau phosphorylation at Ser-202/Thr-205, Thr-231, and Ser-422, which indicates activation of the tau kinase glycogen synthase kinase 3 beta ($GSK3{\beta}$) by PP2A with PPP2R5D subunit. The level of activating phosphorylation of the $GSK3{\beta}$ kinase Akt at Thr-308 and Ser-473 were both increased by PPP2R5D knockdown. We also characterized B subunit-specific phosphorylation sites in tau using mass spectrometric analysis. Liquid chromatography-mass spectrometry revealed that the phosphorylation status of the tau protein may be affected by PP2A, depending on the specific B subunits. These studies further our understanding of the function of various B subunits in mediating site-specific regulation of tau protein phosphorylation.

• Archives of Pharmacal Research
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• 제24권1호
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• pp.16-20
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• 2001

2-(Allylthio)pyrazine derivatives were designed as a novel cancer chemopreventive agent that functions through selective inhibtion of cytochrome P-450 and induction of phase 11 enzymes involved in the detoxification of carcinogens. A practical preparation method of 2-(allylthio) pyrazine derivatives was established by the reaction of 2-mercaptopyrazine and allylbromides in the presence of a catalytic antioxidant, DABCO (1,4-diazabicyclo[2,2,2] octane), in dimethyl-formamide at below $50^{\circ}C$.

• 대한수학회보
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• 제60권1호
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• pp.75-81
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• 2023

If a multiplicative function f is commutable with a quadratic form x² + xy + y², i.e., f(x² + xy + y²) = f(x)² + f(x) f(y) + f(y)², then f is the identity function. In other hand, if f is commutable with a quadratic form x² - xy + y², then f is one of three kinds of functions: the identity function, the constant function, and an indicator function for ℕ ＼ pℕ with a prime p.