Table of Content

24 April 2002, Volume 18 Issue 2

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Articles

Single-Molecule FRET Study of DNA G-Quadruplex

Jeremy Green, Li ming Ying, David Klenerman, Shankar Blasubramanian

2002, 18(2):  103-106. 

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The DNA G-quadruplex formed by the human telomeric sequence is a potential target for novel anticancer drugs. We have investigated an intramolecular DNA G-quadruplex using single-molecule fluorescence resonance energy transfer and shown that individual folded quadruplexes can be identified. The mean proximity ratio measured at the single-molecule level was consistent with ensemble measurement.

Applications of Pattern Recognition in Drug Discovery

W. Graham Richards

2002, 18(2):  107-108. 

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This is a brief account of the plenary talk given to the meeting of the Chinese Society of Chemical Science and Technology held in Oxford on 6 October 2001. The talk covered the application of pattern recognition techniques to discover molecules which will bind to the binding sites of proteins. Three situations were considered: the structure of the protein being unknown; the structure known but the binding site unknown; and finally, and this is the most important case for the future, both the structure and nature of the target site available in atomic detail. For this case we have developed a massively distributed computer program using a screensaver which now involves over one million personal computers, including over a thousand in China. The project will involve the screening of 3.5 billion small molecules against 16 protein targets, all of which are implicated in the process of cancer.

Effects of Cryoprotective Agents on the Bovine Articular Chondrocyte Viability

X. Xu, Z. F. Cui

2002, 18(2):  109-112. 

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Cryopreservation is the process of choice for long term preservation of cells and tissues. In this study, the effects of cryoprotective agents, dimethyl sulfoxide(DMSO), glycerol and 1,2-propanediol on the bovine articular chondrocyte viability were examined experimentally. The CPA was added at the concentrations of 0. 6. 0.9, 1.2 and 1.5 mol/I and at 4℃ and 37℃ and removed at 37℃ in one-step. CPA stepwise addition and removal at 0. 6 and 1. 2 mol/L and at 37℃ was also tested as an alternative protocol. Cell volume excursion during DMSO addition and removal was estimated and correlated well with cell survival rates. Solution makeup affects cell survival rate and a stepwise protocol can improve the cell survival rates significantly.

Numerical Simulation of Mixing in a Micro-well Scale Bioreactor by Computational Fluid Dynamics

Hu Zhang, Sally Lamping, Parviz Ayazi Shamlou

2002, 18(2):  113-116. 

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The introduction of the multi-well plate miniaturisation technology with its associated automated dispensers, readers and integrated systems coupled with advances in life sciences has a propelling effect on the rate at which new potential drug molecules are discovered. The translation of these discoveries to real outcome now demands parallel approaches which allow large numbers of process options to be rapidly assessed. The engineering challenges in achieving this provide the motivation for the proposed work. In this work we used computational fluid dynamics(CFD) analysis to study flow conditions in a gas-liquid contactor which has the potential to be used as a fermenter on a multi-well format. The bioreactor had a working volume of 6.5 mL with the major dimensions equal to those of a single well of a 24-well plate. The 6.5 mL bioreactor was mechanically agitated and aerated by a single sparger placed beneath the bottom impeller. Detailed numerical procedure for solving the governing flow equations is given. The CFD results are combined with population balance equations to establish the size of the bubbles and their distribution in the bioreactor, Power curves with and without aeration are provided based on the simulated results.

CFD Model of Dense Gas-solid Systems in Jetting Fl uidized Beds

Kai Zhang, Jiyu Zhang, Biiang Zhang, John Yates

2002, 18(2):  117-120. 

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A CFD code has been developed based on the conservation principles describing gas and solid flow in fluidized beds. This code is employed to simulate not only the spatiotemporal gas- and solid-phase velocities and voidage profiles in a two-dimensional bed but also fluid dynamics in the jet region. The computational results show that gas flow direction is upward in the entire bed accompanied with random local circulations, whilst solid flow direction is upward at the center and downward near the wall. The radical reason of strong back-mixing of solid particles and good transfer behavior between two phases is that the jet entrains solid particles. Numerical calculation indicates that gas velocity, solid velocity and pressure profile have a significant change when the voidage is 0. 8. The simulated time-averaged voidage profiles agree with the experimental results and simulated data reported by Gidaspow and Ettehadieh(1983). Therefore, CFD model can be regarded as a useful tool to study the jet characteristics in dense gas-solid fluidized beds.

Organic Light Emitting Diodes with Lithium Contained Alq3 as Electron Injection Layer

Zugang Liu, J. L. Pinto

2002, 18(2):  121-123. 

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Novel lithium doped tris-8-hydroxylquinoline aluminium (Alq3:Li) layer is deposited between emission layer and electron injection aluminium electrode as an electron injection assistant layer in different organic light emitting diodes(OLED) to lower the electron injection barrier. In these devices, Alq3 is used as emission layer, and a bilayer film of N, N' -bis- ( 1-naphhyl)-N, N' -diphenyl- 1,1' -biphenyle-4,4" -diamine (NPB) and 4,4' , 4" -tris (3-methyl-phenylphenylamino) triphenylamine(m-MTDATA) used as hole transport layer(HTL). The electroluminescent performance of devices with different thicknesses of Alq3: Li shows that the insertion of the lithium doped Alq3 layer can reduce the turn on voltage by at least 2 volts, and the stability of devices with this lithium doped Alq3 layer is improved too. It can also change the efficiency of devices. Compared with an ultra-thin lithium fluoride(IiF) layer, Alq3 : Li sheet gives similar effects but higher efficiency and can be much thicker and hence it is easier to control the deposition.

Ultra-thin Oxide Films on SiO₂: An STM Study of Their Thermal Stability in the Presence of Au Deposit

Jun Wang, C. E. J. Mitchell, R. G. Egdell, J. S. Foord

2002, 18(2):  124-129. 

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The annealing of Au particles deposited onto the ultrathin layers of SiO₂ on Si(111 ) has been studied in realtime with a high temperature scanning tunnelling microscopy. Annealing did not create significant changes to themorphology of the surface until the surface was heated up to more than 920 K when the gold particles started todisplay a preference for the step edge. Further heating caused the decomposition of the oxide layer with the for-mation of voids on the surface in the surface step edge area. Comparison between the gold assisted oxide decom-position and pure oxide decomposition indicates that the two decomposition routes proceed with different mecha-nisms.

Purification of Single-walled Carbon Nanotubes Grown by a Chemical Vapour Deposition (CVD) Method

Cigang Xu, Emmanuel Flahaut, Sam R. Bailey, Gareth Brown, Jeremy Sloan, Karl S. Coleman, V. Clifford Williams, Malcolm L. H. Green

2002, 18(2):  130-132. 

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A procedure for purification of single-walled carbon nanotubes(SWNTs) grown by the chemical vapour deposition (CVD) of carbon monooxide has been developed. Based on the result from TGA/DTA of as-prepared sample, the oxidation temperature was determined. The process included sonication, oxidation and acid washing steps. The purity and yield after purification were determined and estimated by TEM. Moreover, for the first time, a loop structure for CVD SWNTs has been observed.

Development and Electrochemical Studies of Ruthenium Based Mixed Oxide Catalyst Electrodes for Chlorine Evolution

L. X. Yang, J. P. G. Farr

2002, 18(2):  133-138. 

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Experimental results are presented which allow comparison of the electrochemical performance of RuO₂/Ti, Ru_0.3V_0.7O₂/Ti and Ru_0.3V_0.7O₂/Ti catalysts prepared on a titanium substrate by thermal decomposition from respective precursors. The highest activity for chlorine evolution is observed on the Ru_0.3V_0.7O₂/Ti electrode, lower on Ru_0.3V_0.7O₂/Ti and least on RuO₂/Ti. Voltammograms obtained in the polarisable region are used to characterize the different electrodes. Further more an analysis of the catalytic activity and reaction kinetics of the developed electrodes in NaCl are presented.

Effects of Thermal Activation on the El ectrocatalysis of the Ru(O001) Surface

Wenfeng Lin, Jiamei Jin, Paul A. Christensen

2002, 18(2):  139-145. 

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Variable-temperature in-situ FTIR spectroscopy has been used as the primary tool to investigate the effects of temperature (10 to 50 C ) on formaldehyde dissociative adsorption and electro-oxidation on the Ru (0001) electrode in perchloric acid solution, and the results were interpreted in terms of the surface chemistry of the Ru (0001) electrode and compared to those obtained during our previous studies on the adsorption of CO under the same conditions. It was found that formaldehyde did undergo dissociative adsorption, even at -200 mV vs. Ag/AgCl, to form linear (COL) and 3-fold-hollow(CO_H) binding CO adsorbates. In contrast to the adsorption of .CO, it was found that increasing the temperature to 50℃ markedly increased the amount of CO adsorbates formed on the Ru(0001) surface from the adsorption of formaldehyde. On increasing the potential, the electrooxidation of the CO adsorbates to CO₂ took place via reaction with the active (1×1)-O oxide. A significant increase in the surface reactivity was observed on the RuO₂(100) phase formed at higher potentials. Formic acid was detected as a partial oxidation product during formaldehyde electro-oxidation. The data obtained at 50℃are markedly different from those collected at 10 and 25℃ in terms of the amount of both CO₂ and formic acid formed and the adsorbed CO_L and CO_H species observed. These results were rationalized by the thermal effects on both the loosening of the CO adlayer and the activation of surface oxide on increasing the temperature.

Facile Syntheses of (6S)-6-Fluoroshikimic Acid and (6R)-6-Hydroxyshikimic Acid

Chuanjun Song, Shende Jiang, Gurdial Singh

2002, 18(2):  146-152. 

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(6S)-6-Fluoroshikimic acid 2 and (6R)-6-hydroxyshikimic acid 3 have been synthesized via an OsO₄-catal-ysed dihydroxylation of diene 7, which was derived from (-)-shikimic acid 1.

Contamination by Organochlorine Pesticides in the Estuaries of Southeast China* 06 A

Z. L. Zhang, H. S. Hong, J. L. Zhou, M. H. Dai, K. Maskaouib, W. Q. Chen

2002, 18(2):  153-160. 

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Persistent organic pollutants(POPs) such as organochlorine pesticides are of global concern due to their widespread occurrence and persistence. This paper reports recent research studying the distribution and fate of organochlorine pesticides in the Jiulong River, the Minjiang River and the Pearl River estuaries in Southeast China. Eighteen organochlorine pesticides were extracted from water, pore water and sediment samples, followed by analysis by GC-ECD. The results showed that the contamination levels were similar in these three estuaries.The levels of the total organochlorine pesticides in porewater were significantly higher than those in surface water, due to the high affinity of these hydrophobic compounds for sediment phase. Among the hexachlorocyclohexane (HCH) compounds, β-HCH was found to be the most important isomer. The analysis of 1, 1,1-trichloro-2,2-bis-chlorophenyl-ethane(DDT) and its metabolites showed that 1, 1-dichloro-2[o-chlorophenyl]-2[p-chlorophenyl]-ethylene (DDE) was dominant in the group.Koywords Organochlorine insecticides, DDT, Lindane, Jiulong River Estuary, Minjiang River Estuary, Pearl River Estuary, Water, Sediment

Recent Advance in the Electrochemical Detection of Sulphide and Sulphhydryl Species

Nathan S. Lawrence, Timothy G. J. Jones, Richard G. Compton, Li Jiang

2002, 18(2):  161-168. 

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This article aims at providing a critical review of some most recent developments in the electrochemical detection and measurement of hydrogen sulphide and the related species, which are of great significance to a variety of industries and in environmental moitoring. The molecular recognition processes are initiated by using either an organic precursor or a catalytic complex, leading to extensive ranges of detection. A series of advanced chemical and simulation techniques are used to probe the mechanistic details of the analytical chemistry involved.

Preparation of MCM-41 in Industrial Scale and Its Application in Heavy Oil Processing

Jianwen Da, Tiancun Xiao, Jianming Su, Xingzhong Xu, Malcolm. L. H. Green

2002, 18(2):  169-174. 

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A series of MCM-41 molecular sieves have been prepared on an industrial scale, and the effect of preparation factors such as aging temperature, pH values on the structure and pore distribution of the MCM-41 product have been studied by using X-ray diffraction(XRD), thermogravimetric(TG) and electron microscopy (TEM). It is shown that the pH values have a significant effect on the crystallinity of the synthesized product. Under proper conditions, the MCM-41 prepared on an industrial scale has the same performance as the samples prepared on an Lab-scale. The prepared MCM-41 was used as a modifier of zeolite Y for fluid catalytic cracking (FCC) of residual oil. It is shown that the addition of the MCM-41 in the zeolite Y catalyst increases the pore size, and surface area of the catalysts, which helps to increase the yield of gasoline and diesel and decrease the production of gaseous product and carbon deposition in the catalyst. The better performance of the MCM-41 modified zeolite Y catalyst is believed to be due to its adjustment on the acidity and increase of the pore size.

Leaching from Heterogeneous Heck Catalysts: A Computational Approach

Peter. M. Jenkins, Shik Chi Tsang

2002, 18(2):  175-177. 

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The possibility of carrying out a purely heterogeneous Heck reaction in practice without Pd leaching has been previously considered by a number of research groups but no general consent has yet arrived. Here, the reaction was, for the first time, evaluated by a simple computational approach. Modelling experiments were performed on one of the initial catalytic steps: phenyl halides attachment on Pd (111) to (100) and (111) to (111) ridges of a Pd crystal. Three surface structures of resulting [PhPdX] were identified as possible reactive intermediates. Following potential energy minimisation calculations based on a universal force field, the relative stabilities of these surface species were then determined. Results showed the most stable species to be one in which a Pd ridge atom is removed from the Pd crystal structure, suggesting Pd leaching induced by phenyl halides is energetically favourable.

Organic-inorganic Hybrids Towards the Preparation of Nanoporous Composite Thin Films for Microelectronic Application

DuanLi Ou, Pierre M. Chevalier

2002, 18(2):  178-182. 

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Silicon containing materials have traditionally been used in microelectronic fabrication. Semiconductor devices often have one or more arrays of patterned interconnect levels that serve to electrically couple the individual circuit elements forming an integrated circuit. These interconnect levels are typically separated by an insulating or dielectric film. Previously, a silicon oxide film was the most commonly used material for such dielectric films having dielectric constants(k) near 4. 0. However, as the feature size is continuously scaling down, the relatively high k of such silicon oxide films became inadequate to provide efficient electrical insulation. As such, there has been an increasing market demand for materials with even lower dielectric constant for Interlayer Dielectric (ILD) applications, yet retaining thermal and mechanical integrity. We wish to report here our investigations on the preparation of ultra-low k ILD materials using a sacrificial approach whereby organic groups are burnt out to generate low k porous ORMOSIL films. We have been able to prepare a variety of organically modified silicone resins leading to highly microporous thin films, exhibiting ultra-low k from 1.80 to 2.87, and good to high modulus, 1.5 to 5.5 Gpa. Structure property influences on porosity, dielectric constant and modulus will be discussed.

Highly Sensitive Spectrofluorimetric Determination of Trace Amounts of Indium(Ⅲ) with Salicylaldehyde Salicyloylhydrazone

HAN Fang, WANG Hongjian, TANG Bo

2002, 18(2):  183-188. 

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The fluorescent reaction of salicylaldehyde salicyloylhydrazone (SASH) with indium (Ⅲ) was studied in detail. Based on this chelation reaction, a sensitive spectrofluorimetric method was developed for the determination of indium in a water-ethanol(volume ratio 3: 7) medium at pH 4.0. Under the condition, the InSASH complex displays an excitation and emission maxima at 396 and 461 nm, respectively. The linear range of the method is from 4. 7 to 1000 ng/mL and the detection limit is 0. 94 ng/mL. The molar ratio of indium to the reagent is 1 : 1. The interferences of other ions were studied. The method was successfully applied to the determination of indium in the chemical reagents of lead, tin, zinc, zinc chloride and geological samples by standard addition method.

Crystal Structure of a New Cembranolide Diterpene

LIN Cui-wu, SU Jing-yu, ZENG Long-mei

2002, 18(2):  189-191. 

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A new cembranoide deterpene was isolated from the soft coral Sinularia Tenella. The crystal and chemical structure of the title compound were determined by means of spectroscopic methods and X-ray diffraction analysis as (1R^* , 4R^* , 5S^* , 12S^* , 12R^* )-9-acetoxy-cembr-8E, 15 (17)-dien-16,4-olide. It shows a moderate cytotoxicity against P 388 and L 1210 cell lines.

Studies of the Catalytic Activity and Deactivation of Calcined Layered Double Hydroxides in the Reaction of Ethanol with Propylene Oxide

JIAO Qing-ze, ZHAO Yun, ZHANG Yi-qing, DUAN Xue, Evans D. G., ZHOU Zi-niu

2002, 18(2):  192-195. 

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The reaction of ethanol with propylene oxide over calcined layered double hydroxides(CLDH) was investigated. The results show that CLDH has a good activity and a good selectivity, but the activity and the selectivity of CLDH decrease when CLDH reforms LDH- the so called "memory effect". The influence of the "memory effect" on the CLDH returning to LDH was studied by the hydration reaction. It is shown that the "memory effect" is not complete, and the decreases of the Mg/Al molar ratio of LDH and the crystallite size due to the increase of the hydration reaction time result in the drop of the activity and the selectivity.

Studies on the Catalytic Properties of Magnesia Supported on γ-Alumina

JIAO Qing-ze, ZHAO Yun, LI Xiao-dan, DUAN Xue, EVANS D. G.

2002, 18(2):  196-199. 

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We have shown that MgO can be dispersed on γ-Al₂O₃ with different loadings. The observed dispersion capacity of MgO on the surface of γ-Al₂O₃ is higher than the theoretical monolayer dispersion value. The surface area and the maximum in the pore size distribution gradually decrease with the increase in MgO content at low loadings. The surface area and the maximum in the pore size distribution of MgO/γ-Al₂O₃ decrease more rapidly when the MgO content is large because the pores of γ-Al₂O₃ become blocked. When small amounts of MgO are dispersed on the surface of γ-Al₂O₃, the catalyst is very active and shows a good selectivity for the synthesis of glycol ethers.

Synthesis of Highly ordered Large Size Mesoporous Silica and Effect of Stabilization as Enzyme Supports in Organic Solvent

LI Bo, Inagaki S., Miyazaki C., Takahashi H.

2002, 18(2):  200-205. 

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FSM-16, MCM-41 and SBA-15 types of hexagonal mesoporous silica with a highly ordered 2-dimensional structure were synthesized by using different silicon sources and surfactants. In the 2-dimensional silicate framework, pore size can be uniformly controlled by the combined use of the surfactants having different alkyl chain lengths and the swelling agents(triisopropyl benzene). The pore-diameter of FSM-16 and MCM-41 can be expanded to be 10 nm, SBA-15 to be 15 nm. The crystal regularity was decreased with the increase of the porediameter. In FSM-16 derived from kanemite (silicon source) and MCM-41 from water glass, their anionic characteristics on the pore-wall may be stronger than those of SBA-15 derived from oligomeric tetramethoxysilane(TMOS). We have successfully used FSM-16 and MCM-41 to immobilize the enzyme having cationic residues below isoelectric point. The level of adsorption of enzymes in FSM-16 and MCM-41 was relatively high, but was low in SBA-15 support. The mechanism of enzyme to be adsorbed in mesoporous silica was suggested to be the ionic interactions. In aqueous solutions, horseradish peroxidase(HTP) was immobilized in FSM-16 with 8. 9 nm mesopores and the highest loading amount (183 mg/mg FSM) was obtained, but for the FSM-16 of pore diameter 30 nm only an amount of 28 mg/mg FSM was obtained. The catalytic activity in the organic solvent was high when HRP was immobilized in FSM-16 and MCM-41, but it was low in case of SBA-15.

Surface Activities of Calix[4] resorcinarenes Bearing Four Hydrophobic Chains and Its Sol ubilization for Organic Compounds

LI Bo, Yoshifumi KOIDE, Kunio ESUMI

2002, 18(2):  206-210. 

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Calix [4] resorcinarenes bearing four hydrophobic side chains (4] Ar-Rn, [4] Ar-Ph, and [4] Ar-N) orient stably on water oil interface and show high solubilization capacities for organic compounds, such as long-chain alcohols, benzene, toluene and dyes. The capacities are high even near the omc of polyalkylated calix [4] resorcinarenes, but the solubilities of organic compounds(solubilizates) decrease with the increase of the size of the solubilizates. [4] Ar-R6, with a chain-length of six carbons, is the most effective among [4] Ar-Rn,[4] Ar-Ph, and [4] Ar-N; 11-fold mol of hexanol is dissolved in 2×10^-3 mol/I [4]Ar-R6. Moreover,[4] Ar-Rn bearing four alkyl side chains solubilizes the chain alcohols of the same chain length mostly. The solubilization capacities are presumably brought by inclusion in a large cavity of the polyalkylated calix[4] resorcinarcnes and by an efficient orientation of the solubilizates.

Crystal Structure and Characterization of a Dye with Two-photon Pumoed Frequency-upconverted Lasing Properties

TIAN Yu-peng, YU Wen-tao, FANG Qi, WU Jie-ying, JIANG Min-hua, WANG He-zhou, ZHENG Xi-guang

2002, 18(2):  211-215. 

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The title compound, trans-4-[ p-( N-ethyl-N-(hydroxyethyl ) amino) styryl ]-N-methylpyridiniumtetraphenylborate (abbreviated as ESMT, C₄₆H₄₉N₄O) crystallizes in a space group P1 with a= 0.983 23 (15)nm, b=1.410 73(16) nm, c=1.54 21(12) nm, a=95.252(13)°, β=91.959(17)°, γ= 107.421(12)°, Z=2, F(000)=712, μ= 0.1 mm^-1 Mo Ka radiation, R=0. 093 8. The result shows that the cation of themolecule almost lies in one plane, the hydroxyethyl group is perpendicular to the plane, the anion takes a slightdistorted tetrahedral geometry. Also the thermal stability, two-photon fluorescence, two-photon pumped lasingproperty for the title compound were studied.

Study of Static Adsorption Capacity of ACF for Xenon at 201 K

WANG Ya-long, ZHANG Hai-tao, WANG Xu-hui, ZHANG Li-xing, CHEN Li-yun, XIE Jin-chuan

2002, 18(2):  216-220. 

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The static adsorption performances of a series of active carbon fiber (ACF)for xenon at 201 K were measured with a model ASAP2010M specific surface area and aperture distribution instrument by changing the working gas of instrument from N₂ to Xenon. Compared with grain active carbon(GAC): (1) the adsorption performance of Viscose-based ACF(VACF) adsorbents is better than that of GAC; (2) owing to the difference of aperture distribution, the adsorption performance of ACF with different radicales is different under the same experiment conditions though the specific surface area is similar; (3) there is no definite relationship between adsorption performance and specific surface area; (4) the VACF-A2 is the superior xenon adsorbent at the experimental temperature.Keyworls Active carbon fiber, CTBT, Xenon, Static adsorption, Adsorptive capacity, Adsorptive velocity

CuSO₄ Micro-crystal Lattice Produced by Microcontact Printing

PAN Li-jia, CHEN Lei, HE Ping-sheng, TAO Xiao-ming, QIAN Yi-tai, XIA You-nan

2002, 18(2):  221-222. 

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An elastic stamp was produced by molding poly(dimethylsiloxane)(PDMS) against a master with micropatterns on the surface. Then a procedure named microcontact printing was carried out on the glass substrate with the ink of an octadecylsiloxane(OTS) solution. The OTS reacted with the glass and formed a self-assembly monolayer, and the process produced hydrophobic micro-patterns on hydrophilic substrate. Owing to a simple hydrophobic interaction between the CuSO₄ solution and the monolayer, a regular CuSO₄ micro-crystal lattice could be produced.

Letters

Microporous Silica-supported Poi yoxometal ate Catalyst H₃PW₁₂O₄₀/SiO₂ with High Activity for Acetal Reaction between Benzaldehyde and Ethylene Glycol

YANG Yu-lin, WANG Yong-hui, HU Chang-wen, WANG En-bo, FENG Shou-hua

2002, 18(2):  223-225. 

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Research Notes

Two Brominated-sesquiteroene from Alga Laurencia Majuscula

XU Xiao-hua, YAO Guang-min, LU Jian-hua, LI Yan-ming, CHANG Jiang-lin, KONG Chui-hua

2002, 18(2):  226-227. 

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Two brominated-sesquiterpenes were isolated from the Alga Laurencia majuscula collected from the Xisha Islands in the South China Sea. Compound 1 was first reported, and determined, on spectral evidence, to be 8-bromo-l-en-chamigrene.

Synthesis and Structural Characterization of Chiral[(n-Bu)₄N]₂[MO₂O₅(OC₁₀H₆O)₂]

LU Xiao-ming, ZHOU Yin-zhaung, LIU Shun-cheng, MAO Xian, BU Xian-he

2002, 18(2):  228-232. 

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