AIM: To evaluate whether folate levels in mucosal tissue and some common methylenetetrahydrofolate reductase (MTHFR) variants are associated with the risk of gastric cancer through DNA methylation. METHODS: Real-time ...AIM: To evaluate whether folate levels in mucosal tissue and some common methylenetetrahydrofolate reductase (MTHFR) variants are associated with the risk of gastric cancer through DNA methylation. METHODS: Real-time PCR was used to study the expression of tumor related genes in 76 mucosal tissue samples from 38 patients with gastric cancer. Samples from the gastroscopic biopsy tissues of 34 patients with chronic superficial gastritis (CSG) were used as controls. Folate concentrations in these tissues were detected by the FOL ACS: 180 automated chemiluminescence system. MTHFR polymorphisms were analyzed by PCR-RFLP, and the promoter methylation of tumor-related genes was determined by methylation-specific PCR (MSP). RESULTS: Folate concentrations were significantly higher in CSG than in cancerous tissues. Decreased expression and methylation of c-myc accompanied higher folate concentrations. Promoter hypermethylation and loss of p16INK4A in samples with MTHFR 677CC were more frequent than in samples with the 677TT or 677CT genotype. And the promoter hypermethylation and loss of p21WAF1 in samples with MTHFR 677CT were more frequent than when 677CC or 677TT was present. The 677CT genotype showed a non-significant higher risk for gastric cancer as compared with the 677CC genotype. CONCLUSION: Lower folate levels in gastric mucosal tissue may confer a higher risk of gastric carcinogenesisthrough hypomethylation and overexpression of c-myc.展开更多
An efficient reduction system of benzaldehyde with hydrogen under ambient pressure was developed using facile NiO catalyst. The non-aromatic solvents such as cyclohexane, tetrahydrofuran (THF) and n-hexane, and the ad...An efficient reduction system of benzaldehyde with hydrogen under ambient pressure was developed using facile NiO catalyst. The non-aromatic solvents such as cyclohexane, tetrahydrofuran (THF) and n-hexane, and the addi-tive with strong basicity e.g. KOH, were necessary for smooth conversion of the substrate. That the catalyst can be recov-ered and reused for nine times without loss of catalytic activity indicates that this catalyst is a recyclable one for benzal-dehyde reduction.展开更多
Stable silver nanoparticles were synthesized using polyvinyl alcohol (PVA) as reducing and capping agent. The method of steric stabilization was adopted for the incorporation of silver nanoparticles in the polymer m...Stable silver nanoparticles were synthesized using polyvinyl alcohol (PVA) as reducing and capping agent. The method of steric stabilization was adopted for the incorporation of silver nanoparticles in the polymer matrix. The successful incorporation of silver nanoparticles in a PVA matrix was confirmed by UV–Visible spectroscopy, transmission electron microscopy (TEM) and Fourier transform infrared (FT-IR) spectroscopy. The synthesized silver nanoparticles were characterized by a peak at 426 nm in the UV–Vis spectrum. TEM studies showed the formation of spherical shaped silver nanoparticles of 10-13 nm, following the reduction by UV irradiation. Catalytic properties were studied by means of UV-Visible spectroscopic analysis. The synthesized silver nanoparticles exhibited good catalytic properties in the reduction of methylene blue.展开更多
An industrial electrolytic cell was designed for the electrochemical synthesis of N-methylhydroxylamine hydrochloride (N-MHA). Copper was used as the cathode, graphite as the anode, and a cation membrane as the sepa...An industrial electrolytic cell was designed for the electrochemical synthesis of N-methylhydroxylamine hydrochloride (N-MHA). Copper was used as the cathode, graphite as the anode, and a cation membrane as the separator. The results show that N-MHA with a high purity of 99% can be electrosynthesized directly from nitromethane in HC1 solution. Under a constant current of 1000-2500A.m^-2 in the temperature of 30-50℃, the average yield, current efficiency, and reaction selectivity were 65%, 70%, and 99%, respectively. Graphite electrode and membrane material can be used continuously in the preparative electrolysis for 5000h. Moreover, the effects of the electrode and membrane materials, current intensity, electrolyte temperature, and other associated parameters on the electrosynthesis results were investigated. The direct current power consumption was 8151.3kW-h-(1000kg N-MHA)^ -1. This method is a simple separation process with limited contamination and hence, is a new green synthesis method for the industrial production of N-MHA.展开更多
Homogeneous and heterogeneous types of catalysis are frequently considered as separate disciplines or even opposed to each other.In the present work,a new type of mixed het-ero-/homogeneous catalysis was demonstrated ...Homogeneous and heterogeneous types of catalysis are frequently considered as separate disciplines or even opposed to each other.In the present work,a new type of mixed het-ero-/homogeneous catalysis was demonstrated for the case of selective alkylarene oxidation by molecular oxygen.The proposed catalytic system consists of two widely available components:N-hydroxyphthalimide(NHPI,a homogeneous organocatalyst for free-radical chain reactions)and nanosized TiO_(2)(heterogeneous UV-active photoredox catalyst).The interaction of NHPI with TiO_(2) allows for a shift from UV to visible light photoredox activity and generation of phthalimide-N-oxyl(PINO)radicals that diffuse into the solution where NHPI/PINO-catalyzed free-radical chain reaction can proceed without the additional light input providing a fundamental increase in energy efficiency.The NHPI/TiO_(2) ratio controls the selectivity of oxidation affording preferential formation of hydroperoxide or ketone from alkylarene.展开更多
Asymmetric synthesis of (-)-1-trimethylsilyl-ethanol with immobilized Saccharomyces cerevisiae cells in water/organic solvent biphasic system was studied. The effects of shake speed, hydrophobicity of organic solvent,...Asymmetric synthesis of (-)-1-trimethylsilyl-ethanol with immobilized Saccharomyces cerevisiae cells in water/organic solvent biphasic system was studied. The effects of shake speed, hydrophobicity of organic solvent, volume ratio of water phase to organic phase, pH value of aqueous phase and reaction temperature on the initial reaction rate, maximum yield and enantiomeric excess (ee) of the product were systematically explored. All the above-mentioned factors had significant influence on the reaction. n-Hexane was found to be the best organic solvent for the reaction. The optimum shake speed, volume ratio of water phase to organic phase, pH value and reaction temperature were 150 r.min-1, 1/2, 8 and 30 ℃ respectively, under which the maximum yield and enantiomeric excess of the product were as high as 96.8% and 95.7%, which are 15% and 16% higher than those of the corresponding reaction performed in aqueous phase. To our best knowledge, this is the most satisfactory result obtained.展开更多
Trifluoromethylation reactions are important transformations in the research and development of drugs, agrochemicals and functional materials. An oxidation/reduction process of trifluoromethyl-containing compounds is ...Trifluoromethylation reactions are important transformations in the research and development of drugs, agrochemicals and functional materials. An oxidation/reduction process of trifluoromethyl-containing compounds is thought to be involved in many recently tested catalytic trifluoromethylation reactions. To provide helpful physical chemical data for mechanistic studies on trifluoromethylation reactions, the redox potentials of a variety of trifluoromethyl-containing compounds and trifluoro- methylated radicals were studied by quantum-chemical methods. First, eoB97X-D was found to be a reliable method in predicting the ionization potentials, electron affinities, bond dissociation enthalpies and redox potentials of trifluoromethylcontaining compounds. One-electron absolute redox potentials of 79 trifluoromethyl substrates and 107 trifluoromethylated radicals in acetonitrile were then calculated with this method. The theoretical results were found to be helpful for interpreting experimental observations such as the relative reaction efficiency of different trifluoromethylation reagents. Finally, the bond dissociation free energies (BDFE) of various compounds were found to have a good linear relationship with the related bond dissociation enthalpies (BDE). Based on this observation, a convenient method was proposed to predict one-electron redox potentials of neutral molecules.展开更多
The first enantioselective total synthesis of(+)-preussin B and an improved synthesis of the antifungal alkaloid(+)-preussin are described. Our approach relied on the four step-economical synthetic methods developed i...The first enantioselective total synthesis of(+)-preussin B and an improved synthesis of the antifungal alkaloid(+)-preussin are described. Our approach relied on the four step-economical synthetic methods developed in our laboratory:(1) the cis-diastereoselective reductive dehydroxylation of hemiaminals;(2) the direct amide/lactam reductive alkylation;(3) the one-pot N,O-bisdebenzylation-N-methylation; and(4) the one-step synthesis of malimide from malic acid. Both total syntheses are quite concise, which have been achieved in six steps, and gave overall yields of 25.7% and 27.6%, respectively.展开更多
Direct electroreduction of solid cuprous chloride to prepare copper powder in a"neutral"ambient-temperature ionic liquid,1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid(BMIMBF4)was investigated.Cy...Direct electroreduction of solid cuprous chloride to prepare copper powder in a"neutral"ambient-temperature ionic liquid,1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid(BMIMBF4)was investigated.Cyclic voltammetry of the CuCl powder in a Pt-powder cavity microelectrode exhibited that solid CuCl can be electrochemical reduced in the ionic liquid.Chronoamperometry of the salt powder filled Mo-cavity electrode(current collector)in the ionic liquid further demonstrated the conversion of chloride to metal inside the cavity,as confirmed by scanning electron microscopy,energy-dispersive X-ray,and X-ray diffraction spectra.展开更多
A novel phthalocyanine, 2,9(10),16(17),23(24)-tetra(4-benzoyl)phenoxyphthalocyanine, and its complexes with Zn(Ⅱ), Cu(Ⅱ), Co(Ⅱ), and Ni(Ⅱ) have been synthesized and characterized by a combination o...A novel phthalocyanine, 2,9(10),16(17),23(24)-tetra(4-benzoyl)phenoxyphthalocyanine, and its complexes with Zn(Ⅱ), Cu(Ⅱ), Co(Ⅱ), and Ni(Ⅱ) have been synthesized and characterized by a combination of elemental analysis, IR, IH NMR, UV-vis spectroscopy and mass spectrometry. All of the materials are very soluble in common organic solvents such as dichloro- methane, chloroform, tetrahydrofuran, N,N-dimethylformamide and dimethyl sulfoxide. The Q band wavelengths of the com- plexes decrease in the order: Zn 〉 Cu 〉 Ni 〉 Co. Redox processes were observed at -1.06, -0.74, 0.51 and 0.98 V for the free phthalocyanine, at -0.72 and 1.04 V for the Co(Ⅱ) complex, at -1.24, -0.77, -0.24, 0.61 and 0,91 V for the Cu(Ⅱ) complex, and at -0.74 and 1.20 V for the Ni(Ⅱ) complex. The cyclic voltammograms of the phthalocyanine ring of the four species are similar, with reduction and oxidation couples each involving a one-electron transfer process.展开更多
基金Supported by the National Basic Research Funds of China 973 Project, No. 2005CB522400 grants from the National Natural Science Foundation of China, No. 30470781 grants from Shanghai Municipal Commission for Science and Technology, No. 04DZ14006 and Doctoral Funds from the Ministry of Education of China, No. 20050266013
文摘AIM: To evaluate whether folate levels in mucosal tissue and some common methylenetetrahydrofolate reductase (MTHFR) variants are associated with the risk of gastric cancer through DNA methylation. METHODS: Real-time PCR was used to study the expression of tumor related genes in 76 mucosal tissue samples from 38 patients with gastric cancer. Samples from the gastroscopic biopsy tissues of 34 patients with chronic superficial gastritis (CSG) were used as controls. Folate concentrations in these tissues were detected by the FOL ACS: 180 automated chemiluminescence system. MTHFR polymorphisms were analyzed by PCR-RFLP, and the promoter methylation of tumor-related genes was determined by methylation-specific PCR (MSP). RESULTS: Folate concentrations were significantly higher in CSG than in cancerous tissues. Decreased expression and methylation of c-myc accompanied higher folate concentrations. Promoter hypermethylation and loss of p16INK4A in samples with MTHFR 677CC were more frequent than in samples with the 677TT or 677CT genotype. And the promoter hypermethylation and loss of p21WAF1 in samples with MTHFR 677CT were more frequent than when 677CC or 677TT was present. The 677CT genotype showed a non-significant higher risk for gastric cancer as compared with the 677CC genotype. CONCLUSION: Lower folate levels in gastric mucosal tissue may confer a higher risk of gastric carcinogenesisthrough hypomethylation and overexpression of c-myc.
基金Supported by the National Natural Science Foundation of China (Nos.20576045, 20306009 and 202225620).
文摘An efficient reduction system of benzaldehyde with hydrogen under ambient pressure was developed using facile NiO catalyst. The non-aromatic solvents such as cyclohexane, tetrahydrofuran (THF) and n-hexane, and the addi-tive with strong basicity e.g. KOH, were necessary for smooth conversion of the substrate. That the catalyst can be recov-ered and reused for nine times without loss of catalytic activity indicates that this catalyst is a recyclable one for benzal-dehyde reduction.
文摘Stable silver nanoparticles were synthesized using polyvinyl alcohol (PVA) as reducing and capping agent. The method of steric stabilization was adopted for the incorporation of silver nanoparticles in the polymer matrix. The successful incorporation of silver nanoparticles in a PVA matrix was confirmed by UV–Visible spectroscopy, transmission electron microscopy (TEM) and Fourier transform infrared (FT-IR) spectroscopy. The synthesized silver nanoparticles were characterized by a peak at 426 nm in the UV–Vis spectrum. TEM studies showed the formation of spherical shaped silver nanoparticles of 10-13 nm, following the reduction by UV irradiation. Catalytic properties were studied by means of UV-Visible spectroscopic analysis. The synthesized silver nanoparticles exhibited good catalytic properties in the reduction of methylene blue.
文摘An industrial electrolytic cell was designed for the electrochemical synthesis of N-methylhydroxylamine hydrochloride (N-MHA). Copper was used as the cathode, graphite as the anode, and a cation membrane as the separator. The results show that N-MHA with a high purity of 99% can be electrosynthesized directly from nitromethane in HC1 solution. Under a constant current of 1000-2500A.m^-2 in the temperature of 30-50℃, the average yield, current efficiency, and reaction selectivity were 65%, 70%, and 99%, respectively. Graphite electrode and membrane material can be used continuously in the preparative electrolysis for 5000h. Moreover, the effects of the electrode and membrane materials, current intensity, electrolyte temperature, and other associated parameters on the electrosynthesis results were investigated. The direct current power consumption was 8151.3kW-h-(1000kg N-MHA)^ -1. This method is a simple separation process with limited contamination and hence, is a new green synthesis method for the industrial production of N-MHA.
文摘Homogeneous and heterogeneous types of catalysis are frequently considered as separate disciplines or even opposed to each other.In the present work,a new type of mixed het-ero-/homogeneous catalysis was demonstrated for the case of selective alkylarene oxidation by molecular oxygen.The proposed catalytic system consists of two widely available components:N-hydroxyphthalimide(NHPI,a homogeneous organocatalyst for free-radical chain reactions)and nanosized TiO_(2)(heterogeneous UV-active photoredox catalyst).The interaction of NHPI with TiO_(2) allows for a shift from UV to visible light photoredox activity and generation of phthalimide-N-oxyl(PINO)radicals that diffuse into the solution where NHPI/PINO-catalyzed free-radical chain reaction can proceed without the additional light input providing a fundamental increase in energy efficiency.The NHPI/TiO_(2) ratio controls the selectivity of oxidation affording preferential formation of hydroperoxide or ketone from alkylarene.
基金Supported by the National Natural Science Foundation of China(No.20076019)the Natural Science Foundation of Guang-dong Province(No.000444).
文摘Asymmetric synthesis of (-)-1-trimethylsilyl-ethanol with immobilized Saccharomyces cerevisiae cells in water/organic solvent biphasic system was studied. The effects of shake speed, hydrophobicity of organic solvent, volume ratio of water phase to organic phase, pH value of aqueous phase and reaction temperature on the initial reaction rate, maximum yield and enantiomeric excess (ee) of the product were systematically explored. All the above-mentioned factors had significant influence on the reaction. n-Hexane was found to be the best organic solvent for the reaction. The optimum shake speed, volume ratio of water phase to organic phase, pH value and reaction temperature were 150 r.min-1, 1/2, 8 and 30 ℃ respectively, under which the maximum yield and enantiomeric excess of the product were as high as 96.8% and 95.7%, which are 15% and 16% higher than those of the corresponding reaction performed in aqueous phase. To our best knowledge, this is the most satisfactory result obtained.
基金supported by the National Natural Science Foundation of China(21325208,21172209,21361140372,21202006)Specialized Research Fund for the Doctoral Program(20123402110051)+5 种基金Fundamental Research Funds for the Central Universities(WK2060190025)Chinese Academy of Sciences(KJCX2-EW-J02)Fok Ying Tung Education FoundationAnhui Provincial Natural Science Foundation(1308085QB38)China Grid project funded by Ministry of Education of Chinathe supercomputer center of Shanghai and University of Science and Technology of China
文摘Trifluoromethylation reactions are important transformations in the research and development of drugs, agrochemicals and functional materials. An oxidation/reduction process of trifluoromethyl-containing compounds is thought to be involved in many recently tested catalytic trifluoromethylation reactions. To provide helpful physical chemical data for mechanistic studies on trifluoromethylation reactions, the redox potentials of a variety of trifluoromethyl-containing compounds and trifluoro- methylated radicals were studied by quantum-chemical methods. First, eoB97X-D was found to be a reliable method in predicting the ionization potentials, electron affinities, bond dissociation enthalpies and redox potentials of trifluoromethylcontaining compounds. One-electron absolute redox potentials of 79 trifluoromethyl substrates and 107 trifluoromethylated radicals in acetonitrile were then calculated with this method. The theoretical results were found to be helpful for interpreting experimental observations such as the relative reaction efficiency of different trifluoromethylation reagents. Finally, the bond dissociation free energies (BDFE) of various compounds were found to have a good linear relationship with the related bond dissociation enthalpies (BDE). Based on this observation, a convenient method was proposed to predict one-electron redox potentials of neutral molecules.
基金supported by the National Natural Science Foundation of China(21332007)the Program for Changjiang Scholars and Innovative Research Team in University(PCSIRT)of Ministry of Education,China
文摘The first enantioselective total synthesis of(+)-preussin B and an improved synthesis of the antifungal alkaloid(+)-preussin are described. Our approach relied on the four step-economical synthetic methods developed in our laboratory:(1) the cis-diastereoselective reductive dehydroxylation of hemiaminals;(2) the direct amide/lactam reductive alkylation;(3) the one-pot N,O-bisdebenzylation-N-methylation; and(4) the one-step synthesis of malimide from malic acid. Both total syntheses are quite concise, which have been achieved in six steps, and gave overall yields of 25.7% and 27.6%, respectively.
基金the financial support of the National Natural Science Foundation of China(51204080,51274108,21263007)the Natural Science Foundation of Yunnan Province(2011FA009)the Application Foundation Research of Yunnan Province(2011FZ020)
文摘Direct electroreduction of solid cuprous chloride to prepare copper powder in a"neutral"ambient-temperature ionic liquid,1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid(BMIMBF4)was investigated.Cyclic voltammetry of the CuCl powder in a Pt-powder cavity microelectrode exhibited that solid CuCl can be electrochemical reduced in the ionic liquid.Chronoamperometry of the salt powder filled Mo-cavity electrode(current collector)in the ionic liquid further demonstrated the conversion of chloride to metal inside the cavity,as confirmed by scanning electron microscopy,energy-dispersive X-ray,and X-ray diffraction spectra.
基金supported by the Application Foundation of the Science and Technology Office of Jilin Province (20080901)the Fundamental Research Funds for the Central Universities (09SSXT030)
文摘A novel phthalocyanine, 2,9(10),16(17),23(24)-tetra(4-benzoyl)phenoxyphthalocyanine, and its complexes with Zn(Ⅱ), Cu(Ⅱ), Co(Ⅱ), and Ni(Ⅱ) have been synthesized and characterized by a combination of elemental analysis, IR, IH NMR, UV-vis spectroscopy and mass spectrometry. All of the materials are very soluble in common organic solvents such as dichloro- methane, chloroform, tetrahydrofuran, N,N-dimethylformamide and dimethyl sulfoxide. The Q band wavelengths of the com- plexes decrease in the order: Zn 〉 Cu 〉 Ni 〉 Co. Redox processes were observed at -1.06, -0.74, 0.51 and 0.98 V for the free phthalocyanine, at -0.72 and 1.04 V for the Co(Ⅱ) complex, at -1.24, -0.77, -0.24, 0.61 and 0,91 V for the Cu(Ⅱ) complex, and at -0.74 and 1.20 V for the Ni(Ⅱ) complex. The cyclic voltammograms of the phthalocyanine ring of the four species are similar, with reduction and oxidation couples each involving a one-electron transfer process.