Showing papers in "Bulletin of The Korean Chemical Society in 2001"

Intercalation of Functional Organic Molecules with Pharmaceutical, Cosmeceutical and Nutraceutical Functions into Layered Double Hydroxides and Zinc Basic Salts

Abstract: National Nanohybrids Materials Laboratory (NNML)School of Chemistry and Molecular Engineering, Seoul National University, Seoul 151-747, KoreaReceived May 26, 2001Negatively charged functional organic molecules such as retinoic acid, ascorbic acid, indole acetic acid, citricacid, salicylic acid, acidic dye (indigo carmine, Food Blue 1) are intercalatively encapsulated by zinc basic salt(hydrozincite) and layered double hydroxide. Such functional organic-inorganic nanohybrids are realized viacoprecipitation reaction involving simultaneous formation of layered inorganic lattice and intercalation ofanionic species. The heterostructural nature of these nanohybrids, their particle morphology and texturalcharacterizations are mainly discussed on the basis of Powder X-ray Diffraction and Field Emission ScanningElectron Microscopy results. Keywords : Layered double hydroxide (LDH), Zinc basic salt (ZBS), Functional molecules, Intercalation,Nanohybrid.IntroductionIntercalation of organic and biomolecules into lamellarinorganic lattices is of great interest due to its scientific andpractical importance.

Transformations of Aldimines Derived from Pyrrole-2-carbaldehyde. Synthesis of Thiazolidino-Fused Compounds

Abstract: 4-Thiazolidinones which are hetarylsubstituted at the 2-position were prepared by the reaction of mercapto acids with aldimines which were prepared by the condensation of pyrrole-2-carbaldehyde with different aromatic amines. After their benzylide ne derivatives were obtained, we first applied the Wittig reagent on them in the presence of triethylamine, dihydrofurothiazolidines were synthesized. Second, we prepared new pyrazolinothiazolidines by using phenylhydrazine in the presence of sodium acetate. All mentioned compounds have been characterized by their spectral data, and screened for their antimicrobial activities. Some of them exhibit moderate to good antibacterial and tuberculostatic activities.

Effect of Poly(ethylene glycol)Grafting on Polyethylenimine as a Gene Transfer Vector in vitro

Abstract: To evaluate the non-ionic polymer, poly(ethylene glycol) (PEG), as a component in cationic copolymers for non-viral gene delivery systems, PEG was coupled to polyethylenimine (PEI). We present the effects of different degrees and shapes of pegylation of PEI on cytotoxicity, water solubility and transfection efficiency. This work reports the synthesis and characterization of a series of cationic copolymers on the basis of the conjugates of PEI with PEG. The modified molecules were significantly less toxic than the original polymer. Moreover, the chemical modification led to enhancement of their solubility. The comparison of pegylated PEIs with different degrees of derivation showed that all the polymers tested reached comparable levels of transgene expression to that of native PEI. As assessed by agarose gel electrophoresis, even highly substituted PEI derivatives were still able to form polyionic complexes with DNA. However, aside from an increase in solubility and retention of the ability to condense DNA, methoxy-PEG-modified PEIs resulted in a significant decrease in the transfection activity of the DNA complexes. In fact, the efficiency of the copolymer was compromised even at a low degree of modification suggesting that the PEG action resulting from its shape is important for efficient gene transfer. The mode of PEG grafting and the degree of modification influenced the transfection efficiency of PEI.

three binding sets analysis of a - lactalbumin by interaction of tetradecyl trimethyl ammonium bromi

Abstract: The interaction between tetradecyl trimethyl ammonium bromide (TTAB) with bovine has been investigated at pH = 9 and at by isothermal titration calorimetry, equilibrium dialysis and UV-Vis spectrophotometry methods. The binding data from unusual Scatchard plot have been analyzed in terms of the Hill equation for three sets of binding sites. The calorimetric data show that TTAB interacts endothermically with and causes protein unfolding below 2 mM concentration of TTAB, which is confirmed by spectrophotometric data. The unfolding of the protein would be mainly due to occupation of the second set of binding sites.

Quantitative Structure-Activity Relationship (QSAR) Study of New Fluorovinyloxyacetamides

Abstract: Quantitative Structure-Activity Relationship (QSAR) have been established of 57 fluorovinyloxyacetamides compounds to correlate and predict EC50 values. Genetic algorithm (GA) and multiple linear regression analy- sis were used to select the descriptors and to generate the equations that relate the structural features to the bio- logical activities. This equation consists of three descriptors calculated from the molecular structures with molecular mechanics and quantum-chemical methods. The results of MLR and GA show that dipole moment of z-axis, radius of gyration and logP play an important role in growth inhibition of barnyard grass.

Preparation and characterization of sol-gel derived SiO2-TiO2-PDMS composite films

Abstract: Thin films of the SiO 2 -TiO 2 -PDMS composite material have been prepared by the sol-gel dip coating method. Acid catalyzed solutions of tetraethoxy silane (TEOS) and polydimethyl siloxane (PDMS) mixed with titanium isopropoxide Ti(O'Pr) were used as precursors. The optical and structural properties of the organically modified 70SiO 2 -30TiO 2 composite films have been investigated with Fourier Transform Infrared Spectroscopy (FT-IR), UV-Visible Spectroscopy (UV-Vis), Differential Thermal Analysis (DTA) and prism coupling technique. The films coated on the soda-lime-silicate glass exhibit 450-750 nm thickness, 1.56-1.68 refractive index and 88-94% transmittance depending on the experimental parameters such as amount of PDMS, thermal treatment and heating rate. The optical loss of prepared composite film was measured to be about 0.34 dB/cm.

Nucleophilic Behaviour of DBU and DBN toward Acetylated Baylis-Hillman Adducts

Abstract: 1,8-Diazabicycl 이 5.4.이 undec-7-ene (DBU) and 1,5diazabicyclo[4.3.0]non-5-ene (DBN) are known as nonnucleophilic, sterically hindered, strong tertiary amine bases.1 They are widely used in organic synthesis, especially in dehydrohalogenation.1 There have been reports where DBU or DBN act as a nucleophilic reagent.2 For example, DBU acts as a nucleophile with 4-halo-3,5-dimethyl-1-nitro-1Hpyrazoles,2a methyl 3,5-dinitrobenzoate and 1,3,5-trinitrobenzene,2b diethyl maleate,2c 2-H heptafluorobut-2-ene,2d 1halocyclopropane 1,2-diesters,2e and 1-bromo-4-benzoyloxyimino-1,2,3,4-tetrahydrophenanthrene.2f The Baylis-Hillman reaction is a well known coupling reaction between aldehydes and activated alkenes, catalyzed by tertiary amines or tertiary phosphines.3-5 The reaction with ethyl acrylate serves a-methylene-Qhydroxy esters, which have been transformed to various useful compounds.4,5 As continuing projects on the chemical transformation of the Baylis-Hillman adducts,5 we have focused recently on the synthesis of 2-substituted naphthalenes from the BaylisHillman acetates 1 and primary nitroalkanes in the presence of a base.6 During our study we found that ^-caprolactam derivatives were isolated in moderate yields when we used DBU as a base. We have investigated the reaction of various Baylis-Hillman acetates 1 with DBU and DBN and report here the results. As shown in Scheme 1 and in Table 1, the reaction of 1a and DBU (2 equiv) in tetrahydrofuran afforded £-caprolactam derivative 2a in 88% isolated yield. Similarly, the

Self-Assembled Monolayers of Alkanethiols on Clean Copper Surfaces

Abstract: Alkanethiols (CH3(CH2)n-1SH) based self-assembled monolayers (SAMs) on the clean copper surfaces have been examined for n = 4, 8, and 16. Using X-ray photoelectron spectroscopy (XPS) and contact angle analysis, it is found that alkanethiolate monolayers similar to those on gold are formed on clean copper surfaces. The monolayers are stable in air up to about 140 Above 160 the monolayers begin to desorb through the oxidation reaction of the thiolate to sulfonate, with the alkyl chains remaining intact. Following this desorption step, the copper surface has begun to oxidize to CuO at about 180 .

Spectrophotometric Determination of Cadmium and Copper with Ammonium Pyrrolodinedithiocarbamate in Nonionic Tween 80 Micellar Media

Abstract: The determination of Cd2+ and Cu2+ with ammonium pyrrolidinedithiocarbamate (APDC) in Tween 80 micellar media has been studied. The UV-visible spectrum of Cd(PDC)2 complex in Tween 80 media had more sensitivity tha n in chloroform. Although the UV-visible spectrum of the Cu(PDC)2 complex in Tween 80 media had somewhat less sensitivity than that in chloroform, absorbance data of Cu2+ were more reproducible in Tween 80 media. The Cd(PDC)2 and Cu(PDC)2 complexes were very stable at pH 7.0 for up to 100 minutes and could be quantitatively chelated if APDC were added to the sample solution more than 30 times the moles of Cd2+ and Cu2+ . The optimum concentration of Tween 80 was 0.1%. The calibration curves of Cd(PDC)2 and Cu(PDC)2 complexes with good linearity were obtained in 0.1% Tween 80 media. The detection limits of Cd2+ and Cu2+ were 0.0493 ㎍mL-1 and 0.0393 ㎍mL-1 , respectively. Recovery yields of Cd2+ and Cu2+ ions in the spiked real samples were almost 100%. Based on experimental results, this proposed method could be applied to the rapid and simple determination of Cd2+ and Cu2+ in real samples.

Static Dielectric Constant and Relaxation Time for the Binary Mixture of Water, Ethanol, N. N-Dimethylformamide, Dimethylsulphoxide, and N, M-Dimethylacetamide with 20Hethoxyethanol

Abstract: Frequency spectra of the complex permittivity of 2-methoxyethanol (2-ME) with water, ethanol, dimethylsulphoxide (DMSO), N,N-dimethylformamide (DMF) and N,N-dimethylacatamide (DMA) have been determined over the frequency range of 10 MHz to 20 GHz at 25 , using the Time domain reflectometry method, for 11 concentrations for each system. The static dielectric constant, dielectric constant at microwave frequency, relaxation time, excess dielectric parameters, and Kirkwood correlation factor have been determined. The relaxation in these systems within the frequency range can be described by a single relaxation time constant, using the Debye model. The parameters show a systematic change with the concentration.

Effect of Metal Ions on the Degradation and Adsorption of Two Cellobiohydrolases on Microcrystalline Cellulose

Abstract: Ba ++ , Pb ++ , and Cd ++ . The addition of Mn ++ , Ba ++ , and Ca ++ (10 mM) during the hydrolysis of Avicel PH 101 caused an increase in the total reducing sugar (TRS) for CBH I by 142, 135, and 114 percent, respectively. Those for CBH II increased by 177, 175, and 115 percent, respectively. The Mn ++ was the most stimulatory metal ion, whereas Hg ++ was the most inhibitory metal ion. The adsorption experiments were performed to investigate how the influence of Mn ++ and Hg ++ on the hydrolysis is related to the adsorption of cellobiohydrolases on cellulose. The increase in TRS during hydrolysis by adding Mn ++ caused an increase in adsorption affinity ( Kad) and tightness (ΔHa). While, the decrease of TRS during hydrolysis by adding Hg ++ caused a decrease in the adsorption affinity ( Kad) and tightness (ΔHa). These results indicate the changes in the tightness and affinity of adsorption by adding metal ions play a crucial role in the degradation of the microcrystalline cellulose.

An Adsorption Process Study on the Self-Assembled Monolayer Formation of Octadecanethiol Chemisorbed on Gold Surface

Abstract: The self-assembled formation of octadecanethiol (CH3(CH2)17SH) on a gold substrate was studied using a quartz crystal microbalance (QCM) and a scanning tunneling microscope (STM). From the QCM measurements at vario us concentrations of octadecanethiol solutions in hexane and alcohol, the adsorption process of octadecanethiol onto Au was confirmed to consist of two steps as follows: (i) fast but disordered adsorption and (ii) a thermodynamically controlled rearrangement for uniform packing of octadecanethiol. Also, it was revealed that the adsorption rate became faster in ethanol than in hexane since less solubility of octadecanethiol in ethanol could help the formation of the monolayers. At 5 10-7 M solution, the monolayer formation was monitored by STM. The morphology of monolayer region was initially circular (diameter size: 7.26 2.1 nm) and gradually changed to a stripe type after several minutes. At higher concentration, the self-assembled monolayer was formed immediately after the solution was introduced to a substrate.

Synthesis and Application of the Novel Azomethine Metal Complexes for the Organic Electroluminescent Devices

Abstract: Department of Science, Chemical Engineering, and Research Institute for Science and Technology,Hong-Ik University, Seoul 121-791, KoreaReceived March 2, 2001New 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 achelating anionic ligand. Emission peaks of the complexes in both solution and solid states were observedmostly 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-emittingdevices (OLED) as an emitting layer, respectively. The device including the emitting layer of I exhibited whiteemission with the broad luminescence spectral range. The device with the emitting layer of II showed blueluminescence with the maximum emission peak at 460 nm. Their ionization potentials, electron affinities, andelectrochemical 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, 2.95and 2.61 eV within an experimental error. The structure of OLED manufactured in this study reveals that thesecomplexes can work as electron transporting materials as well. Keywords : Azomethine metal complex, Organic electroluminescent devices, Blue and white emission, Bandgap.IntroductionSince the electroluminescence (EL) of a multi-layer deviceusing AlQ

Preparation and Characterization of Solvent Induced Dihydrated, Anhydrous, and Amorphous Paclitaxel

Abstract: The control of solid drug properties is one of the current issues in the pharmaceutical industry. 1,2,3 Many drugs have different applications according to characteristics of their different solid states. 4,5,6,7 Sometimes, the solubility of a drug in water or other solvents is largely dependent on its solid properties, such as the degree of hydration. 6,7,8 Moreover, the stability of the drug may have a close relationship with the interconversion of the drug among morphologically different states. Therefore the control of solid states and their characterization of a drug have practical as well as academic importance. 2,3 Paclitaxel, which is one of the most potent anticancer drugs, is relatively complex organic drug having several solid structures. In relation to this, Burt and et al. reported the solid-state characterization of the different paclitaxel in their recent studies. 1 According to the studies, there are four different states of solid paclitaxel and these can be characterized using solid-state analytical tools, such as X-ray powder diffractometer (XRPD) and differential scanning calorimetry (DSC). Among these four solid states, only three solid forms are considered to be stable under ambient condition. We will refer to them as dihydrated, anhydrous, and amorphous paclitaxel according to the paper. 1 In the paper, they described the methods to control the morphologies of paclitaxel, in which they used some severe experimental conditions. These methods, however, are not suitable for industrial application because they are not practical for large-scale production. Moreover, the large amount of heat used in some of their schemes can cause degradation of the drug. Therefore, a systematic study is needed to find a new way to control the morphologies of paclitaxel, considering the importance of drug. In this study, we tried to control the morphology of paclitaxel and prepare morphologically different paclitaxels using several common solvents not exposing the system to high temperature. The resulting morphologies were identified by comparing X-ray powder diffraction (XRPD) pattern as well as differential scanning calorimetry (DSC) data with previous ones. 1 The additional powerful and simple methods, solid NMR and infrared spectroscopy (IR) were used to characterize the solid state of paclitaxel. Despite the recent increasing utilization of these methods for characterization of solid drugs, this is the first study to use these methods for solidstate paclitaxels. Experimental Section

Shock Tube and Modeling Study of the Ignition of Propane

Abstract: The ignition of propane was investigated behind reflected shock waves in the temperature range of 1350-1800 K and the pressure range of 0.75-1.57 bar. The ignition delay time was measured from the increase of pressure and OH emission in the C3H8-O2-Ar system. The relationship between the ignition delay time and the concentrations of propane and oxygen was determined in the form of mass-action expression with an Arrhenius temperature dependence. The numerical calculations were also performed to elucidate the important steps in the reaction scheme of propane ignition using various reaction mechanisms. The ignition delay times calculated from the mechanism of Sung et al.1 were in good agreement with the observed ones.

The Effect of Metallothionein on the Activity of Enzymes Invelved in Remival of Reactive Oxygen Species

Abstract: To show the effects of metallothionein (MT) on the activity of enzymes involved in the removal of reactive oxygen species, MT has been added to the assay systems of superoxide dismutase (SOD), catalase and peroxidase. We have used assay systems of SOD based on NADPH oxidation and nitrite formation from hydroxylammonium chloride as an assay of superoxide breakdown rate. The two assay systems showed different results at the high concentration of MT. MT showed the scavenging of superoxide in the SOD assay system in the presence and absence of SOD. MT added to the SOD assay system behaved as an activator of SOD, but apo-MT behaved as an inhibitor. When MT was added to the assay system in the presence of a fixed amount of SOD, the breakdown rate of superoxide increased. The effects of MT on the decomposition of hydrogen peroxide and the activity of catalase and peroxidase decomposing hydrogen peroxide were evaluated. MT decreased the activities of catalase and peroxidase. We have concluded that the function of MT as an antioxidant might effect the level of superoxide scavenging and not the level of hydrogen peroxide.

Hydrogen Production from Methane Reforming Reactions over Ni/MgO Catalyst

Abstract: The catalyst Ni/MgO (Ni : 15 wt%) has been applied to methane reforming reactions, such as steam reforming of methane (SRM), partial oxidation of methane (POM), and oxy-steam reforming of methane (OSRM) It showed high activity and good stability in all the reforming reactions Especially, it exhibited stable catalytic performance even in stoichiometric SRM (H2O/CH4 = 1) From TPR and H2 pulse chemisorption results, a strong interaction between NiO and MgO results in a high dispersion of Ni crystallite Pulse reaction results revealed that both CH4 and O2 are activated on the surface of metallic Ni over the catalyst, and then surface carbon species react with adsorbed oxygen to produce CO

Two Anhydrous Zeolite X Crystal Structures, $Pd_{18}Ti_{56}Si_{100}Al_{92}O_{384} and Pd_{21}Tl_{50}Si_{100}Al_{92}O_{384}$

Abstract: The crystal structures of fully dehydrated - and -exchanged zeolite X, , a = and a = , have been determined by single-crystal X-ray diffraction methods in the cubic space group Fd3 at The crystals were prepared using an exchange solution that had a mole ratio of 50 : 1 and 200 : 1, respectively, with a total concentration of 0.05M for 4 days. After dehydration at and 2 Torr in flowing oxygen for 2 days, the crystals were evacuated at for 2 hours. They were refined to the final error indices = 0.045 and = 0.038 with 344 reflections for , and = 0.043 and = 0.045 with 280 reflections for ; I > In the structure of dehydrated , eighteen ions and fourteen ions are located at site I'. About twenty-seven ions occupy site II recessed into a supercage from the plane of three oxygens. The remaining fifteen ions are distributed over two non-equivalent III' sites, with occupancies of 11 and 4, respectively. In the structure of , twenty and ten ions occupy site I', and one ion is at site I. About twenty-three ions occupy site II, and the remaining seventeen ions are distributed over two different III' sites. ions show a limit of exchange (ca. 39% and 46%), though their concentration of exchange was much higher than that of ions. ions tend to occupy site I', where they fit the double six-ring plane as nearly ideal trigonal planar. ions fill the remaining I' sites, then occupy site II and two different III' sites. The two crystal structures show that approximately two and one-half I' sites per sodalite cage may be occupied by ions. The remaining I' sites are occupied by ions with Tl-O bond distance that is shorter than the sum of their ionic radii. The electrostatic repulsion between two large ions and between and ions in the same pushes each other to the charged six-ring planes. It causes the Tl-O bond to have some covalent character. However, ions at site II form ionic bonds with three oxygens because the super-cage has the available space to obtain the reliable ionic bonds.

Unsual Cytotoxic Phenethylamides form Xenerhabdus nemetophilus

Abstract: Three simple carboxamides incorporating the phenethylamine moiety have been isolated from strain XR-NC of a symbiotic bacterium Xenorhabdus nematophilus. Their structures were identified by spectroscopic data and synthesis. The compounds exhibited significant cytotoxicities against human cancer-cell line, viz. the gastric adenocarcinoma, colon adenocarcinoma and lung adenocarcinoma.

Two Anhydrous Zeolite X Crystal Structures, Mn 28 Cs 36 -X and Mn 21.5 Rb 49 -X

Abstract: ion exchanges were 39% and 53%, respectively. Because these cations were toolarge to enter the small cavities and their charge distributions in the zeolite structure may have beenunfavorable, cation-sieve effects were shown. Keywords : Structure, Zeolite X, Manganese, Cesium, Rubidium.IntroductionThe catalytic importance of zeolite X has promptednumerous investigations into the physical and chemicalnature of this crystalline aluminosilicate. The role played incatalysis by cations associated with the zeolite frameworkalso has received considerable attention.

Synthesis and SAR of Benzimidazole Derivatives Containing Oxycyclic Pyridine as a Gastric $H^+/K^+$-ATPase Inhibitors

Abstract: A series of benzimidazole derivatives containing oxycyclic pyridine was prepared and evaluated for their gastric H+ /K+ -ATPase inhibitory activity. Several of the synthesized compound exhibited potent antisecretion in pylorus-ligated rats when administered intradoudenally. Their inhibitory activities were equivalent or comparable to omeprazole.

Preparation of Porous Silica-Pillared Montmorillonite: Simultaneous Intercalation of Amine-Tetraethylorthosilicate into H-Montmorillonite and Intra-Gallery Amine-Catalyzed Hydrolysis of Tetraethylorthosilicate

Abstract: Porous silica-pillared montmorillonites were prepared by simultaneous intercalation of dodecylamine-TEOS [tetraethylorthosilicate, Si(OC2H5)4] into the H-montmorillonite and intragallery amine-catalyzed hydrolysis of TEOS. Mixtures of the H-montmorillonite, dodecylamine and TEOS at molar ratios of 1 : 2 : 15-30 and 1 : 2-6 : 20 resulted to swollen and viscous gel once at room temperature, allowing intercalation compounds which dodecylamine and TEOS were simultaneously intercalated into interlayer of H-montmorillonite. The hydrolysis of the gallery TEOS was conducted in water solution for 40 min at room temperature, affording siloxane-pillared H-montmorillonite. Calcination of samples at 500 in air resulted in silica-pillared montmorillonite with large specific surface areas between 403 and 577 m2 /g, depending on the reaction stoichiometry. The reaction at H-montmorillonite : dodecylamine : TEOS reaction stoichiometries of 1 : 2 : 15 and 1 : 4 : 20 resulted in high specific surface areas and mesopores with a narrow pore size distribution. Result indicates that the intragallery-amine catalyze the hydrolysis of gallery-TEOS and simultaneously have a role of gallery-templated micellar assemblies.

Fermi Resonance and Solvent Dependence of the νC=O Frequency shifts of Raman Spectra: Cyclohecanone and 2-Cyclohexen-1-one

Abstract: The carbonyl stretching vibration, νC=O of 2-cyclohexene-1-one, is in Fermi resonance with a combination tone. The amount of Fermi resonance interaction between these two modes is dependent upon the amount of solute/ solvent interaction due to hydrogen bonding between the carbonyl oxygen and the solvent proton. The corrected νC=O frequency of 2-cyclohexene-1-one occurs at a lower frequency than the observed νC=O mode of cyclohexanone, possibly caused by expanded conjugation effects. The carbonyl stretching modes of cyclic ketones were also affected by interaction with the ROH/CCl 4 mixed solvent system.