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
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
The functional impact of modifications of cellular RNAs,including m RNAs,mi RNAs and lnc RNAs,is a field of intense study.The role of such modifications in cancer has started to be elucidated.Diverse and sometimes opp...The functional impact of modifications of cellular RNAs,including m RNAs,mi RNAs and lnc RNAs,is a field of intense study.The role of such modifications in cancer has started to be elucidated.Diverse and sometimes opposite effects of RNA modifications have been reported.Some RNA modifications promote,while ot-hers decrease the growth and invasiveness of cancer.The present manuscript reviews the current knowledge on the potential impacts of N6-Methyladenosine,Pse-udouridine,Inosine,2’O-methylation or methylcytidine in cancer’s RNA.It also highlights the remaining qu-estions and provides hints on research avenues and potential therapeutic applications,whereby modulating dynamic RNA modifications may be a new method to treat cancer.展开更多
Caprolactam is treated with dimethyl sulfate in benzene medium under conditions of various molar ratios to yield two different methylatcd products. The homogeneous reaction of caprolactam with dimethyl sulfate without...Caprolactam is treated with dimethyl sulfate in benzene medium under conditions of various molar ratios to yield two different methylatcd products. The homogeneous reaction of caprolactam with dimethyl sulfate without any medium can only givc one methylated derivative. In a similar condition to that mentioned above, the reaction of caprolactam with diethylsulfate forms also one product, O-ethyl caprolactim. In this articlc NMR spectrum is applied to further identify the molecular structures of two methylated derivatives held by predecessors, and, applied the chemical shift reagent to induce the NMR and combined the field scanning and decoupling method to confirm the classification of signals, as a consequence the preferred conformation of caprolactam and its alkyl derivatives are proposed.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
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 University of Zurich:"URPP:Translational Cancer research"the"MERIT"project supported by the FP7 European Union’s ResearchInnovation Funding program
文摘The functional impact of modifications of cellular RNAs,including m RNAs,mi RNAs and lnc RNAs,is a field of intense study.The role of such modifications in cancer has started to be elucidated.Diverse and sometimes opposite effects of RNA modifications have been reported.Some RNA modifications promote,while ot-hers decrease the growth and invasiveness of cancer.The present manuscript reviews the current knowledge on the potential impacts of N6-Methyladenosine,Pse-udouridine,Inosine,2’O-methylation or methylcytidine in cancer’s RNA.It also highlights the remaining qu-estions and provides hints on research avenues and potential therapeutic applications,whereby modulating dynamic RNA modifications may be a new method to treat cancer.
文摘Caprolactam is treated with dimethyl sulfate in benzene medium under conditions of various molar ratios to yield two different methylatcd products. The homogeneous reaction of caprolactam with dimethyl sulfate without any medium can only givc one methylated derivative. In a similar condition to that mentioned above, the reaction of caprolactam with diethylsulfate forms also one product, O-ethyl caprolactim. In this articlc NMR spectrum is applied to further identify the molecular structures of two methylated derivatives held by predecessors, and, applied the chemical shift reagent to induce the NMR and combined the field scanning and decoupling method to confirm the classification of signals, as a consequence the preferred conformation of caprolactam and its alkyl derivatives are proposed.
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.
