Ti-containing phosphate（ Ti-P-O ） catalysts with different molar ratios of P to Ti （0--2. 0 ） were synthesized and characterized by XRD, N2-adsorption/desorption, IR and temperature-programmed desorption （TPD） m...Ti-containing phosphate（ Ti-P-O ） catalysts with different molar ratios of P to Ti （0--2. 0 ） were synthesized and characterized by XRD, N2-adsorption/desorption, IR and temperature-programmed desorption （TPD） methods. The catalytic properties of Ti-P-O samples in the vapor-phase O-methylation of catechol with methanol were also studied. The catechol conversion increases with the increase of the molar ratio of P to Ti in a range of 0-0. 33, while a further increase in the P content leads to a decrease of the catalytic activity. Meanwhile, the selectivities of the catalysts to the main product（guaiacol） increase gradually with the increase of the molar ratio of P to Ti. The presence of relatively strong Lewis acidic and/or basic sites in the P-free catalyst should be responsible for the formation of C-alkylation products. The weak acid-base characteristics of the catalysts are favourable for the mono-O-methylation of catechol. In comparison with the Lewis acidic sites, the Bronsted acidic sites on the catalysts are more active for the title reaction.展开更多
Racemic O-methyl O-pheayl thiophosphoric acid 1 has been successfully resolved through its quinine and brucine salts in methanol solution by fractional crystallization. The absolute configurations of the optically act...Racemic O-methyl O-pheayl thiophosphoric acid 1 has been successfully resolved through its quinine and brucine salts in methanol solution by fractional crystallization. The absolute configurations of the optically active 1 have been established as (+)-R-1 and (-)-S-1 by chemical correlation.展开更多
Currently, levodopa is the most effective and commonly used medication to control motor symptoms in Parkinson’s disease (PD). However, its long-term use is associated with adverse effects (AEs). Combination therapy o...Currently, levodopa is the most effective and commonly used medication to control motor symptoms in Parkinson’s disease (PD). However, its long-term use is associated with adverse effects (AEs). Combination therapy of a monoamine oxidase type B inhibitor (MAOBI) with levodopa or a catechol-O-methyl transferase inhibitor (COMTI) with levodopa provides benefits to PD patients. Direct comparison of efficacy and side effect profiles is complex. The aim of this study is to investigate the different AE profiles of MAOBI and COMTI combination therapies. Data used to analyze the AEs of different PD medications were retrieved from “The Boston University Medical Center’s Parkinson’s Disease and Movement Disorder Database”. Ten categories of AEs were compared between patients receiving MAOBI and COMTI combination treatment. In total, 87 subjects were included in the analysis. Out of ten AEs, the presence of dementia was signifi- cantly different between the MAOBI and COMTI groups with an OR of 6.9 (COMTI vs MAOBI, 95% CI 1.3 - 37.0). Motor fluctuations were also found to be differently distributed in the two medication groups with an OR of 3.1 (COMTI vs MAOBI, 95% CI 1.0 - 9.8). In this retrospective database analysis of patients treated with combination treatment for PD, combination therapy of a COMTI with levodopa was more likely to be associated with dementia and motor fluctuations than a MAOBI with levodopa.展开更多
The understanding of factors that affect the optical properties of azo dyes sheds insight to the design of novel optoelectronic devices.The effect of the acidity or alkalinity and the solvent on the absorption spectra...The understanding of factors that affect the optical properties of azo dyes sheds insight to the design of novel optoelectronic devices.The effect of the acidity or alkalinity and the solvent on the absorption spectra of ortho-methyl red(o-MR)aqueous solutions was investigated using UV/Vis experiments and density functional theory(DFT)calculations.The spectra of o-MR aqueous solutions showed a red shift of the maximum absorption peak from 430 nm to 520 nm when the pH of the solution was decreased from 13.1 to 0.5.In various acidity or alkalinity conditions,three main forms of o-MR coexisted in the aqueous solutions,i.e.,diprotic o-H2MR^+(strong acid condition),nonionic o-HMR(weak acid condition),and o-MR-(basic condition),whose electronic structures were studied by DFT.The lowest dipole-allowed excitation energies of o-MR in aqueous solutions have been estimated by performing time-dependent density functional theory(TD-DFT)calculations.Both polarized continuum model(PCM)and explicit water cluster model were applied to study the solvent effects on the electronic structures and calculated spectra.The intramolecular hydrogen bond increases the planarity of o-H2MR~and o-HMR,leading to the enhancement of TT-conjugation and,hence,a red shift in the spectra.Significant solvent effects on the calculated UV/Vis spectra of o-MR(under basic condition)were revealed.Strong dipole-dipole interactions between the polar o-MR-and solvent water molecules may contribute to the red shift in the spectra.展开更多
Methyltransferases are pivotal enzymes in the biosynthesis of methylated flavonoids,including(2S)-hesperetin.However,existing flavonoid 4′-O-methyltransferase(F4′OMT)enzymes typically exhibit low substrate specifici...Methyltransferases are pivotal enzymes in the biosynthesis of methylated flavonoids,including(2S)-hesperetin.However,existing flavonoid 4′-O-methyltransferase(F4′OMT)enzymes typically exhibit low substrate specificity and catalytic efficiency,which hinders microbial synthesis.To overcome this limitation,this study screened and identified two novel F4′OMTs,CrcOMT-2 and CgtOMT-3,from Chinese citrus varieties Citrus reticulata‘Cha-chiensis’(CZG)and Citrus grandis Tomentosa(HZY).These enzymes displayed high substrate specificity for(2S)-eriodictyol.A strain capable of de novo synthesis of(2S)-hesperetin was developed by integrating the novel F4′OMTs and other biosynthetic pathway genes at high copy numbers into Yarrowia lipolytica.The engineered strain achieved a remarkable production titre of(2S)-hesperetin(130.2 mg/L),surpassing the yields of previ-ously reported F4′OMTs.Furthermore,availability of the cofactor S-adenosylmethionine(SAM)was optimised to enhance methyltransferase catalytic efficiency,enabling the engineered strain to produce 178.2 mg/L of(2S)-hesperetin during fed-batch fermentation with SAM supplementation,the highest yield reported to date.This study represents the first successful de novo biosynthesis of(2S)-hesperetin in Y.lipolytica,providing valuable insights into the synthesis of other O-methylated flavonoids.展开更多
The facile enantioselective synthesis of the di-O-methyl ethers of （-）-agatharesinol （1b）, （-）-sugiresionl （2b）, （＋）-nyasol （3b） and （＋）-tetrahydronyasol （4） were achieved in high yield. The absolute...The facile enantioselective synthesis of the di-O-methyl ethers of （-）-agatharesinol （1b）, （-）-sugiresionl （2b）, （＋）-nyasol （3b） and （＋）-tetrahydronyasol （4） were achieved in high yield. The absolute configuration of （＋）-3a was confirmed via first total synthesis of （＋）-3b and （＋）-4.展开更多
The catalytic structure of a hammerhead ribozyme is composed of 3 helixes and10-nucleotide residue single strand regions (numbered 3—9. 12—14). In our previous pa-pers, three double strand regions were called stems....The catalytic structure of a hammerhead ribozyme is composed of 3 helixes and10-nucleotide residue single strand regions (numbered 3—9. 12—14). In our previous pa-pers, three double strand regions were called stems. and now they are called helixes uponthe suggestion of Hertel et al.The previous stem Ⅰ is now called helix Ⅲ, stem Ⅲ iscalled helix Ⅰ,and stem Ⅱ is called helix Ⅱ. The study on the catalytic mechanism ofribozyme in our laboratory indicated that the base pairing strength and property in展开更多
A facile approach for the first total synthesis of prenylated flavonoids, （±）-abyssinone-VI-4-O-methyl ether 1, （±）-abyssinone- IV-4＇-O-methyl ether 2, （±）-abyssinone-V-4＇-O-methyl ether 3 and ...A facile approach for the first total synthesis of prenylated flavonoids, （±）-abyssinone-VI-4-O-methyl ether 1, （±）-abyssinone- IV-4＇-O-methyl ether 2, （±）-abyssinone-V-4＇-O-methyl ether 3 and （±）-sigmoidin E 4 has been described. The key intermediate 4-hydroxy-3,5-di-（3-methylbut-2-enyl）benzaldehyde 6 was also first synthesized that features regioselective prenylation of 4-hydroxybenzaldehyde and crystallizing with petroleum ether from the reaction mixture by freeze-out effect.展开更多
甲基化儿茶素具有显著的抗过敏等生理活性,且其稳定性和肠道吸收率高于未甲基化的儿茶素。然而天然具有高甲基化儿茶素含量的茶树种质资源相对稀缺。通过测定447份来自不同地区且遗传背景广泛的茶树种质资源中表没食子儿茶素3-O-(3-O-甲...甲基化儿茶素具有显著的抗过敏等生理活性,且其稳定性和肠道吸收率高于未甲基化的儿茶素。然而天然具有高甲基化儿茶素含量的茶树种质资源相对稀缺。通过测定447份来自不同地区且遗传背景广泛的茶树种质资源中表没食子儿茶素3-O-(3-O-甲基)没食子酸酯(EGCG3″Me)含量,发现2份高EGCG3″Me含量的特异茶树种质资源‘金秀2-2’(JX)和‘品明茶’(PM)。以高EGCG3″Me含量茶树资源JX、PM、‘红富贵’(BFK),以及EGCG3″Me含量低于检测限的茶树资源‘舒茶早’(SCZ)为研究材料,分析茶树黄酮醇和花青素O-甲基转移酶(Flavonol and anthocyanin O-methyltransferase,CsFAOMT)基因表达量,结果显示,JX、PM和BFK中的CsFAOMT1相对表达水平无显著差异,均显著高于SCZ。进一步在4份茶树资源中克隆出4种CsFAOMT1等位基因,均含有CsFAOMT1.3。酶活性分析结果显示,3份高EGCG3″Me含量茶树资源所含的CsFAOMT1等位基因编码蛋白的活性都较高,且相互间差异较小。结果表明,JX、PM能富集EGCG3″Me,是其CsFAOMT1表达水平高导致的。本研究通过发掘高EGCG3″Me含量特异茶树种质,解析其特异性状形成的分子机制,为培育高甲基化儿茶素茶树新品种提供了材料和理论基础。展开更多
基金Supported by the Development Project of Science and Technology of Jilin Province(Nos. 20050309-1 and 20040563), the Spe-cialized Research Fund for the Doctoral Program of Higher Education(No.20040183003), CNPC(No.JTGS 20040010), and the Na-tional Natural Science Foundation of China(No.20403006)
文摘Ti-containing phosphate（ Ti-P-O ） catalysts with different molar ratios of P to Ti （0--2. 0 ） were synthesized and characterized by XRD, N2-adsorption/desorption, IR and temperature-programmed desorption （TPD） methods. The catalytic properties of Ti-P-O samples in the vapor-phase O-methylation of catechol with methanol were also studied. The catechol conversion increases with the increase of the molar ratio of P to Ti in a range of 0-0. 33, while a further increase in the P content leads to a decrease of the catalytic activity. Meanwhile, the selectivities of the catalysts to the main product（guaiacol） increase gradually with the increase of the molar ratio of P to Ti. The presence of relatively strong Lewis acidic and/or basic sites in the P-free catalyst should be responsible for the formation of C-alkylation products. The weak acid-base characteristics of the catalysts are favourable for the mono-O-methylation of catechol. In comparison with the Lewis acidic sites, the Bronsted acidic sites on the catalysts are more active for the title reaction.
基金This project was supported by National Natural Science Foundation of China
文摘Racemic O-methyl O-pheayl thiophosphoric acid 1 has been successfully resolved through its quinine and brucine salts in methanol solution by fractional crystallization. The absolute configurations of the optically active 1 have been established as (+)-R-1 and (-)-S-1 by chemical correlation.
文摘Currently, levodopa is the most effective and commonly used medication to control motor symptoms in Parkinson’s disease (PD). However, its long-term use is associated with adverse effects (AEs). Combination therapy of a monoamine oxidase type B inhibitor (MAOBI) with levodopa or a catechol-O-methyl transferase inhibitor (COMTI) with levodopa provides benefits to PD patients. Direct comparison of efficacy and side effect profiles is complex. The aim of this study is to investigate the different AE profiles of MAOBI and COMTI combination therapies. Data used to analyze the AEs of different PD medications were retrieved from “The Boston University Medical Center’s Parkinson’s Disease and Movement Disorder Database”. Ten categories of AEs were compared between patients receiving MAOBI and COMTI combination treatment. In total, 87 subjects were included in the analysis. Out of ten AEs, the presence of dementia was signifi- cantly different between the MAOBI and COMTI groups with an OR of 6.9 (COMTI vs MAOBI, 95% CI 1.3 - 37.0). Motor fluctuations were also found to be differently distributed in the two medication groups with an OR of 3.1 (COMTI vs MAOBI, 95% CI 1.0 - 9.8). In this retrospective database analysis of patients treated with combination treatment for PD, combination therapy of a COMTI with levodopa was more likely to be associated with dementia and motor fluctuations than a MAOBI with levodopa.
文摘The understanding of factors that affect the optical properties of azo dyes sheds insight to the design of novel optoelectronic devices.The effect of the acidity or alkalinity and the solvent on the absorption spectra of ortho-methyl red(o-MR)aqueous solutions was investigated using UV/Vis experiments and density functional theory(DFT)calculations.The spectra of o-MR aqueous solutions showed a red shift of the maximum absorption peak from 430 nm to 520 nm when the pH of the solution was decreased from 13.1 to 0.5.In various acidity or alkalinity conditions,three main forms of o-MR coexisted in the aqueous solutions,i.e.,diprotic o-H2MR^+(strong acid condition),nonionic o-HMR(weak acid condition),and o-MR-(basic condition),whose electronic structures were studied by DFT.The lowest dipole-allowed excitation energies of o-MR in aqueous solutions have been estimated by performing time-dependent density functional theory(TD-DFT)calculations.Both polarized continuum model(PCM)and explicit water cluster model were applied to study the solvent effects on the electronic structures and calculated spectra.The intramolecular hydrogen bond increases the planarity of o-H2MR~and o-HMR,leading to the enhancement of TT-conjugation and,hence,a red shift in the spectra.Significant solvent effects on the calculated UV/Vis spectra of o-MR(under basic condition)were revealed.Strong dipole-dipole interactions between the polar o-MR-and solvent water molecules may contribute to the red shift in the spectra.
基金supported by the Shenzhen Science and Technology Innovation Committee(project no.KCXFZ20211020174805009).
文摘Methyltransferases are pivotal enzymes in the biosynthesis of methylated flavonoids,including(2S)-hesperetin.However,existing flavonoid 4′-O-methyltransferase(F4′OMT)enzymes typically exhibit low substrate specificity and catalytic efficiency,which hinders microbial synthesis.To overcome this limitation,this study screened and identified two novel F4′OMTs,CrcOMT-2 and CgtOMT-3,from Chinese citrus varieties Citrus reticulata‘Cha-chiensis’(CZG)and Citrus grandis Tomentosa(HZY).These enzymes displayed high substrate specificity for(2S)-eriodictyol.A strain capable of de novo synthesis of(2S)-hesperetin was developed by integrating the novel F4′OMTs and other biosynthetic pathway genes at high copy numbers into Yarrowia lipolytica.The engineered strain achieved a remarkable production titre of(2S)-hesperetin(130.2 mg/L),surpassing the yields of previ-ously reported F4′OMTs.Furthermore,availability of the cofactor S-adenosylmethionine(SAM)was optimised to enhance methyltransferase catalytic efficiency,enabling the engineered strain to produce 178.2 mg/L of(2S)-hesperetin during fed-batch fermentation with SAM supplementation,the highest yield reported to date.This study represents the first successful de novo biosynthesis of(2S)-hesperetin in Y.lipolytica,providing valuable insights into the synthesis of other O-methylated flavonoids.
基金Projet supported by-the-Speei-al Doctorial Program Funds of the Ministry of Education of China （No. 20040730008）, Gansu Science Foundation （No. 3ZS051-A25-004）.
文摘The facile enantioselective synthesis of the di-O-methyl ethers of （-）-agatharesinol （1b）, （-）-sugiresionl （2b）, （＋）-nyasol （3b） and （＋）-tetrahydronyasol （4） were achieved in high yield. The absolute configuration of （＋）-3a was confirmed via first total synthesis of （＋）-3b and （＋）-4.
文摘The catalytic structure of a hammerhead ribozyme is composed of 3 helixes and10-nucleotide residue single strand regions (numbered 3—9. 12—14). In our previous pa-pers, three double strand regions were called stems. and now they are called helixes uponthe suggestion of Hertel et al.The previous stem Ⅰ is now called helix Ⅲ, stem Ⅲ iscalled helix Ⅰ,and stem Ⅱ is called helix Ⅱ. The study on the catalytic mechanism ofribozyme in our laboratory indicated that the base pairing strength and property in
基金financially supported by the National Natural Science Foundation(Nos.21162021,20962016)Ningxia Natural Science Foundation(No.NZ1006)+1 种基金Program for New Century Excellent Talents in University(No. NCET-09-0860)the National Basic Research Program 973 of China(No.2010CB534916)
文摘A facile approach for the first total synthesis of prenylated flavonoids, （±）-abyssinone-VI-4-O-methyl ether 1, （±）-abyssinone- IV-4＇-O-methyl ether 2, （±）-abyssinone-V-4＇-O-methyl ether 3 and （±）-sigmoidin E 4 has been described. The key intermediate 4-hydroxy-3,5-di-（3-methylbut-2-enyl）benzaldehyde 6 was also first synthesized that features regioselective prenylation of 4-hydroxybenzaldehyde and crystallizing with petroleum ether from the reaction mixture by freeze-out effect.
文摘甲基化儿茶素具有显著的抗过敏等生理活性,且其稳定性和肠道吸收率高于未甲基化的儿茶素。然而天然具有高甲基化儿茶素含量的茶树种质资源相对稀缺。通过测定447份来自不同地区且遗传背景广泛的茶树种质资源中表没食子儿茶素3-O-(3-O-甲基)没食子酸酯(EGCG3″Me)含量,发现2份高EGCG3″Me含量的特异茶树种质资源‘金秀2-2’(JX)和‘品明茶’(PM)。以高EGCG3″Me含量茶树资源JX、PM、‘红富贵’(BFK),以及EGCG3″Me含量低于检测限的茶树资源‘舒茶早’(SCZ)为研究材料,分析茶树黄酮醇和花青素O-甲基转移酶(Flavonol and anthocyanin O-methyltransferase,CsFAOMT)基因表达量,结果显示,JX、PM和BFK中的CsFAOMT1相对表达水平无显著差异,均显著高于SCZ。进一步在4份茶树资源中克隆出4种CsFAOMT1等位基因,均含有CsFAOMT1.3。酶活性分析结果显示,3份高EGCG3″Me含量茶树资源所含的CsFAOMT1等位基因编码蛋白的活性都较高,且相互间差异较小。结果表明,JX、PM能富集EGCG3″Me,是其CsFAOMT1表达水平高导致的。本研究通过发掘高EGCG3″Me含量特异茶树种质,解析其特异性状形成的分子机制,为培育高甲基化儿茶素茶树新品种提供了材料和理论基础。
