Table of Content

24 April 1999, Volume 15 Issue 2

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Articles

Syn thesis, Characterization of CoAPO-11 Molecular Sieve from a Nonaqueous System

JIAO Xiu-ling, YAO You-wei, PANG Wen-qin, XU Ru-ren

1999, 15(2):  96-99. 

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CoAPO-11 molecular sieve with a high crystallinity was prepared by hydro thermal syn thesis from a non-aqueous system(EG) in the presence of Et₂NH or i-Pr₂NH as a structuredirecting agent. The X-ray diffraction(XRD) patterns, scanning electron micrographs(SEM) revealed that the product powder was pure, homogenous in particle-size. The X-ray powder diffraction data, compositional analysis, thermal stability analysis, UV-V is diffuse reflectance spectroscopic analysis showed that Co(Ⅱ) ions were incorporated in the aluminophosphate framework, tetrahedrally coordinated in the lattice of asprepared samples.

Preparation, Characterization of Ternary Europium Complex-Doped Thin Sol-Gel Hybrid Film by Fluorescence Spectroscopy

FU Lian-she, ZHANG Hong-jie, WANG Shu-bin MENG Qing-guo, YANG Kui-yue, NI Jia-zuan

1999, 15(2):  100-104. 

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ernary europium complex with dibenzoylmethane(DBM), 1,10-phenanthroline(phen) was in-situ syn thesized in thin SiO₂/polyvinyl butyral(PVB) hybrid films by a two-step sol-gel process, characterized by means of fluorescence spectroscopy. The luminescence spectra, fluorescence lifetimes, photostability were all investigated. The results showed that the hybrid films exhibited the characteristic emission bands of the central rare earth Eu³⁺. In addition, Eu³⁺ presented longer fluorescence lifetime than in an ethanol solution, the complex had a higher photostability in the hybrid film than in the PVB film containing the corresponding pure complex.

Preparation of LiTi₂(PO₄)₃ by the Solgel Method, Investigation of Its Formation Process

ZHU Ji-shun, Tohge Noboru, Minami Tsutomu

1999, 15(2):  105-109. 

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In this study, a novel sol-gel method has been developed to prepare LiTi₂(PO₄)₃ lithium ion conductor as monophase at relatively low temperature(600℃). According to the XRD, IR analysis, the as-prepared sample remained an amorphous state up to 500℃. The activation energy was calculated to be 252 kJ/mol according to the modified Kissinger equation.

Syn thesis, Characterization of 1,3-Diisopropoxyaloxanes, Their Modification on Calcium Carbonate Filler

ZHENG Chen-mou, LIAO Kai-rong, CHEN Xiao-wu

1999, 15(2):  110-115. 

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Five 1,3-diisopropoxyaloxanes, i. e., (PrⁱO)RO₂AlOAlO₂R(OPrⁱ) [where R=C₁₆H₃₁(Ⅰ)_C₁₈H₃₅(Ⅱ), _C₉H₁₆CH=CHC₇H₁₅(Ⅲ), _P(OCH₂(C₂H₅)CHC₄H₉)₂(Ⅳ), and _C₁₂H₂₃(Ⅴ), respectively] were syn thesized by the hydrolysiscondensation of aluminium isopropoxide with water, exchange reaction with relevant acids. They were characterized by elemental analysis, determination of molecular weight, IR,, ²⁷Al NMR. The results show that the coordination number of Al atom in the compounds is 5, they exist in monomers in benzene. The analyses of TG/DTG, DTA indicated that both the thermal hydrolysis stability, thermal stability of these compounds are in the following order:Ⅰ<Ⅱ<Ⅲ<Ⅳ. The viscosity determinations of light calcium carbonate(L-CaCO₃)/liquid paraffin suspension systems demonstrated that they had an excellent modification effect on the surface of LCaCO₃ filler, the amount needed to form a monomolecular film on the surface of LCaCO₃ particles is in the order:Ⅰ<Ⅱ<Ⅲ<Ⅳ.

Cleavage of Nucleotides by Lanthanide Metal Complexes

ZHU Bing, ZHAO Da-qing, Ni Jia-zuan

1999, 15(2):  116-121. 

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The present work revealed that the praseodymium(Ⅲ) complex of 2-carboxyethylgermanium sesquioxide(Ge-132) promotes the hydrolysis of the phosphodiester linkages of 3',5'-cyclic adenosine monophosphate(cAMP), 3',5'-cyclic deoxyadenosine monophosphate(dcAMP), 5'-adenosine monophosphate(5'-AMP), 5'-deoxyadenosine monophosphate(5'-dAMP) under mild conditions. Both cAMP, dcAMP were hydrolyzed sitespecifically, yielding predominantly 3'-monophosphates, the main products of the cleavage of 5'-AMP, 5'-dAMP included adenosine(Ado), deoxyadenosine(dAdo), free phosphates respectively. A hydrolytic mechanism was proposed for cAMP, dcAMP, 5'-AMP, 5'-dAMP.

Hexacyan oferrate as the Electrochemical Probe for 2-Mercaptobenzothiazole Modified Gold Electrode

XU Jing-juan, FANG Hui-qun, CHEN Hong-yuan

1999, 15(2):  122-127. 

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A gold electrode covered with self-assembled monolayers of 2-mercaptobenzothiazole(Au/MBT) has been developed, its electrochemical characteristics have been investigated in detail. Using hexacyan oferrate as the electrochemical probe for studying the characteristics of the MBT monolayer film, the results, obtained by A. C. impedance spectroscopy technique, show that the electron transfer of hexacyan oferrate(Ⅱ) on Au|MBT in higher pH media was more difficult than that obtained in H₂SO₄ medium or on a bare gold electrode. The electrochemical reversibility of Fe(CN)₆^3-/Fe(CN)₆^4- changed with pH of the solution due to the proton, deproton states of N atom of MBT. The relationship between the coverage of MBT on Au surface or pH, the apparent heterogeneous rate constant was derived, discussed. The double layer capacitance of Au|MBT is (76.4±5.5) μF/cm². The characteristic frequency was dependent on the pH of the solution.

Studies on the Voltammetric Behavior of Nicardipine Hydrochloride, its Voltammetric Determination at the Co/GC Modified Electrode

ZHI Yao, HU Jing-bo, LI Qi-long, HUANG Qing-quan

1999, 15(2):  128-133. 

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To whom correspondence should be addressed. In a 0.02 mol/L BR buffer solution(pH=5.52), the electrochemical behaviour of nicardipine hydrochloride was studied by linearsweep voltammetry, cyclic voltammetry at a Co/GC ion implantation modified electrode. The experiments showed that the electrode had a good stability, reproductivity. The peak height was proportional to the concentration of nicardipine over the range of 4.0×10^-7—1.0×10^-4 mol/L, the detection limit was 1.0×10^-7 mol/L. This method has been used for the direct determination of nicardipine in tablets. Its recoveries were in the range from 95.6% to 103.8%. The reduction of nicardipine at the Co/GC electrode was an irreversible proccess.

Parallel DNA Constrained by "CC⁺ Clamps"

LIU Ke-liang, H. Todd Miles, Frank B. Howard, Joe Frazier, V. Sasisekharan

1999, 15(2):  134-139. 

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Parallel DNA helices with reverse Watson-Crick pairing have been described in several papers. It has been pointed out, however, that the parallel structures may also be in equilibrium with antiparallel Watson-Crick helices due to their closely similar properties. To avoid the problem we have prepared, characterized DNA helices which are constrained to possess parallel polarity by two dC residues, or "CC⁺ clamps", at both the ends of AT oligomer chains. The residues are hemiprotonated below neutral pH, forming two stable CC⁺ base pairs with three hydrogen bonds at each end of the helix. The physical properties of these constructs can then be used to calibrate those of duplexes having the same sequences but lacking the terminal C residues. Though recent studies indicate that dC acid self-structures are four-stranded with intercalated bases, gel electrophoresis indicates that these structures are not present in the molecules described here.

Preparation, Antioxidative Effects of Soybean Peptides

MENG Xian-ju, ZHANG Xue-zhong, WANG Huai-yu

1999, 15(2):  140-145. 

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In this work an alkaline protease, alcalase, was used to hydrolyze the separated soybean protein at 50℃, pH 8.0. The dependence of hydrolysis time on hydrolysis degree, relative antioxidative activity was examined. The antioxidative activity of the hydrolysate reached the maximum after the hydrolysis for two hours, then decreased. The hydrolysate hydrolyzed for two hours was isolated on a Sephadex G-25 column. The range of molecular weight for the collected fractions was 100-1 300. A fur ther purification of the isolated antioxidative peptides was conducted on a CM-Cellulose column. Two active peaks were observed. One of them was taken to investigate the antioxidative properties for in vitro model systems. It was found that the autoxidation rate of pyrogallol under the alkaline condition was decreased by, at least, 10%, indicating that some free radicals in the tested system were removed. In the experiment of the antihemolysis of erythrocyte, it was observed that the hemolysis degree of erythrocyte caused by hydroxyl free radicals was decreased obviously. This result indicates the protective effect of the antioxidative peptides on the cell membrane damage of erythrocyte. Moreover, it was also found that the membrane fluidity could be depressed after a solution of the antioxidative peptides was mixed with a liposome solution, indicating that the antioxidative peptides could fur ther inhibit the membrane damage caused by lipid peroxidation when the small molecules of antioxidative peptides were embedded in liposome.

Autooxidation Mechanism of Pyrogallol, Its Free Radical Effects Studied by Means of ESR, UV, NMR

LIU Shan-lin, ZHAO Bao-lu, SHI Dong-yun, XIN Wen-juan

1999, 15(2):  146-151. 

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Pyrogallol(pyrogallic acid) is easy to be auto-oxidized, forming a free radical under alkaline condition, but the mechanism has not been clear. The mechanism of the auto-oxidation of pyrogallol was studied with ESR, UV, NMR techniques, it was found that pyrogallol was autooxidized to a quinone radical under alkaline condition. And at the same time oxygen recieved an electron from the reaction to form superoxide anions, the hydroxyl free radical was then produced by Haber-Weiss reaction. The oxygen free radicals generated from this process promoted the auto-oxidation of pyrogallol.

Quantum Chemical Investigations on the Structures, Stabilities, Decompositions of Trinitrobenzenes, Their Chloro Derivatives

GONG Xue-dong, XIAO He-ming, DONG Hai-shan

1999, 15(2):  152-157. 

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he molecular geometries, heats of formation, electronic structures of three trinitrobenzenes(1,2,3-TNB, 1,2,4-TNB, 1,3,5-TNB), their chloro derivatives were studied by using the quantum chemical MO AM1 method at the RHF level, ab initio method at the HF/3-21G level. The decompositions of the title compounds were investigated by using the AM1 method at the UHF level. The decomposition activation energies were obtained, the order of the relative stabilities of the title compounds is found. The substituent effects on the structures, properties, on the decompositions of the title compounds are discussed in the present paper.

The Structure, Sizeeffect of Calcium Modified Lead Titanate Nanocrystal, Pb_0.85Ca_0.15TiO₃

FU Hong-gang, QIANG Liang-sheng, XU Chong-quan, ZHAN Zhi-qian, ZHANG Xin, YU Hai-tao, ZHANG Yan-yi, huang Li

1999, 15(2):  158-162. 

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Calcium modified lead titanate nanocrystal material Pb_0.85Ca_0.15TiO₃ was syn thesized by means of a sol-gel method. The changes of crystal structure, grain-size of the samples were investigated under different conditions of heat treatment. the results show that the tetragonal symmetry is reduced, the ferroelectricparaelectric phase transformation temperature is decreased with the reduce of the grainsize of the sample. the critical grain-size for the ferroelectric-paraelectric phase transformation at room temperature was calculated. The change regularities of the lattice constant, tetragonality with the grain-size are discussed.

Ab Initio Study on The Influence of Spin State upon Bonding, Interaction in Fe—CO

XU Xin, LÜ Xin, XIAN Hui, CAI Yu, WANG Nan-qin, ZHANG Qian-er

1999, 15(2):  163-168. 

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Four Fe—CO states with 3d_σ-4s, 3d_δ-3d_δ electrons spin-paired or spinunpaired were examined to investigate the influences of pairing versus unpairing mechanisms upon the bonding, interaction in Fe—CO. The calculation results show that the Fe—CO bonding, interaction are determined by a balance between the bonding stabilization, the exchange stabilization with 3d_σ-4s electron spinpairing or without it. The 3d_δ-3d_δ electron spinpairing versus unpairing has a surprised effect on the Fe—CO bonding properties even though the 3d_δ orbitals are usually considered as non bonding ones.

An EPR Study on Intramolecular Spin Exchange, Rotational Mobility of Nitroxides Linked by a Long-chain

Yoshimi Sueishi, Katsumi Noritake, LIU Ying-jin

1999, 15(2):  174-181. 

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The effects of pressure, solvent on the intramolecular spin exchange of biradicals having two nitroxide fragments linked by a long flexible chain were studied by means of highpressure EPR technique. It was found that the intramolecular exchange interaction between nitroxides of biradical took place through the direct contact between them. By analyzing the observed EPR spectra, we have estimated the ratio(Τ_in/Τ_out) value of the average lifetime of the radical fragments inside a cage(Τ_in) to that outside the cage(Τ_out). The Τ_in/Τ_out values decreased with decreasing temperature, increasing pressure. The results suggest that the nearly cyclic conformation in a cage is favorable in solution. Fur ther, the rotational correlation time of individual nitroxide was estimated from the anisotropic EPR signal,, the information on the segmental motion of the nitroxide group in biradical was obtained.

Reduction of Aromatic Aldehydes, Ketones with Acyloxy Substituent at the Ortho-position by NaBH₄ in the Presence of Waters

WAN Xin-hua, ZHOU Hong-bing, XIE Ren, ZHANG Dong, FENG Xin-de, ZHOU Qi-Feng

1999, 15(2):  182-187. 

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n unusual reduction of some aromatic aldehydes, ketones by sodium borohydride was discovered. In a THF/H₂O or DMSO/H₂O solvent system the aromatic aldehydes, ketones with acyloxy substituent on the ortho-position to the carbonyl group can be reduced to the corresponding alkyl phenols. This unusual reduction is applicable also to the corresponding alcohols of all the above aldehydes, ketones. A putative mechanism was suggested. In addition to the above aldehydes, ketones, benzyl alcohols, certain 4-acyloxybenzyl esters(probably also the 2-substituted analogues) such as 4-benzoyloxybenzyl benzoate was also found to be reduced to methylphenol by this unusual reduction.

Benzoylation of Toluene over Alpromoted SO₄^2-/M_xO_y(M=Zr, Ti, Fe) Catalysts

XIA Yong-de, HUA Wei-ming, GAO Zi

1999, 15(2):  188-190. 

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Fragmentation of Some Substituted Phthalimides on Electron Impact Ionization

WEI Jun-hua, DONG De-wen, LIU Zhi-qiang, LIU Shu-ying, JIN Dan-hong

1999, 15(2):  191-195. 

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Rapid, Catalytic Hydrolysis of DNA by Copper(Ⅱ) Complexes

REN Rui, YANG Pin, GAO Dong

1999, 15(2):  196-199. 

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Effects of Ligands in Novel Non-titanocene on Syndiotactic Polymerization of Styrene

ZHOU Nai, YAN Wei-dong, XIE Guang-hua, HU You-liang

1999, 15(2):  200-203. 

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