The location of charge-balancing sodium cations plays an important role in determining the adsorption and catalytic properties of zeolites.Solid-state <sup>23</sup>Na nuclear magnetic resonance （NMR） can...The location of charge-balancing sodium cations plays an important role in determining the adsorption and catalytic properties of zeolites.Solid-state <sup>23</sup>Na nuclear magnetic resonance （NMR） can provide information about the distribution and chemical surroundings of sodium cations in zeolites.A number of papers have been published using various <sup>23</sup>Na NMR techniques to investigate the distribution of sodium cations and their interactions with water molecules in hydrated zeolite A, zeolite Y and sodalites.In addition, Challoner et al. have studied the motion of展开更多
Lansoprazole degradation is accelerated in both acidic and basic medium in water. The present investigation deals with the hydrolytic degradation of Lansoprazole. Acidic medium degradation show all known impurities an...Lansoprazole degradation is accelerated in both acidic and basic medium in water. The present investigation deals with the hydrolytic degradation of Lansoprazole. Acidic medium degradation show all known impurities and degradation products whereas basic degradation studies show new impurity which has higher molecular weight than Lansoprazole. New impurity was identified, isolated using mass based auto purification system and characterised by 1H NMR, 13C NMR, HMBC, HSQC, NOE, COSY and HRMS experiments. Isolated impurity was showing molecular weight of 467.10, molecular formula of C23H16F3N5OS and its name is 7-(3-Methyl-4-(2,2,2-trifluoroethoxy) pyridin-2-yl)-7H-benzo[4,5]imidazo[2,1-b]benzo[4,5]imidazo[2,1-d][1,3,5]thiadiazine.展开更多
The DNA heptamer [d(TCGCGCG)]_2,which has an alternating pyrimidine-purine se- quence and a dangling T residue at the 5′-end has been used as a model for studying conformational charac- teristics of DNA duplexes with...The DNA heptamer [d(TCGCGCG)]_2,which has an alternating pyrimidine-purine se- quence and a dangling T residue at the 5′-end has been used as a model for studying conformational charac- teristics of DNA duplexes with double-single strand junctions that occur during replication and transcription. The proton resonances of the molecule have been assigned by NOESY and TOCSY/HOHAHA experiments. The NOE intensities at seven different mixing times were quantified for calculating distance constraints with the two-spin approximation.The experiments have uncovered the interesting structural features of the molecule.The sugar proton coupling constants were determined by the P.E.COSY experiment for each residue of the duplex to examine the sugar conformations of the DNA heptamer.The structural features of the heptamer in solution have been obtained.The overall structure of the DNA duplex is basically of a B-type DNA,and substantial changes from a standard B-DNA have been observed,especially in the terminal region of the molecule.The dangling T residue was found in an unusual syn-conformation.展开更多
In order to study the action mechanism of cisplatin on DNA,we have used the solution-phase phosphotriester method to synthesize the oligonucleotide d-TGGGT. Prior to investigating the conformational change due to Pt(...In order to study the action mechanism of cisplatin on DNA,we have used the solution-phase phosphotriester method to synthesize the oligonucleotide d-TGGGT. Prior to investigating the conformational change due to Pt(Ⅱ) attachment。展开更多
Two dimensional 1H NMR techniques were used to determine the solution structure of C10, a cyclopeptide synthesized in the laboratory. Complete proton resonance assignments were obtained using 2 D DQF COSY, TOC...Two dimensional 1H NMR techniques were used to determine the solution structure of C10, a cyclopeptide synthesized in the laboratory. Complete proton resonance assignments were obtained using 2 D DQF COSY, TOCSY, and NOESY experiments. The cross peak volumes in the NOESY spectra were used to calculate the C10 structure. The conformation showed that the four side chains of the lysine residues faced the same side of the cyclopeptide ring.展开更多
基金Project supported by the National Natural Science Foundation of China.
文摘The location of charge-balancing sodium cations plays an important role in determining the adsorption and catalytic properties of zeolites.Solid-state <sup>23</sup>Na nuclear magnetic resonance （NMR） can provide information about the distribution and chemical surroundings of sodium cations in zeolites.A number of papers have been published using various <sup>23</sup>Na NMR techniques to investigate the distribution of sodium cations and their interactions with water molecules in hydrated zeolite A, zeolite Y and sodalites.In addition, Challoner et al. have studied the motion of
文摘Lansoprazole degradation is accelerated in both acidic and basic medium in water. The present investigation deals with the hydrolytic degradation of Lansoprazole. Acidic medium degradation show all known impurities and degradation products whereas basic degradation studies show new impurity which has higher molecular weight than Lansoprazole. New impurity was identified, isolated using mass based auto purification system and characterised by 1H NMR, 13C NMR, HMBC, HSQC, NOE, COSY and HRMS experiments. Isolated impurity was showing molecular weight of 467.10, molecular formula of C23H16F3N5OS and its name is 7-(3-Methyl-4-(2,2,2-trifluoroethoxy) pyridin-2-yl)-7H-benzo[4,5]imidazo[2,1-b]benzo[4,5]imidazo[2,1-d][1,3,5]thiadiazine.
文摘The DNA heptamer [d(TCGCGCG)]_2,which has an alternating pyrimidine-purine se- quence and a dangling T residue at the 5′-end has been used as a model for studying conformational charac- teristics of DNA duplexes with double-single strand junctions that occur during replication and transcription. The proton resonances of the molecule have been assigned by NOESY and TOCSY/HOHAHA experiments. The NOE intensities at seven different mixing times were quantified for calculating distance constraints with the two-spin approximation.The experiments have uncovered the interesting structural features of the molecule.The sugar proton coupling constants were determined by the P.E.COSY experiment for each residue of the duplex to examine the sugar conformations of the DNA heptamer.The structural features of the heptamer in solution have been obtained.The overall structure of the DNA duplex is basically of a B-type DNA,and substantial changes from a standard B-DNA have been observed,especially in the terminal region of the molecule.The dangling T residue was found in an unusual syn-conformation.
文摘In order to study the action mechanism of cisplatin on DNA,we have used the solution-phase phosphotriester method to synthesize the oligonucleotide d-TGGGT. Prior to investigating the conformational change due to Pt(Ⅱ) attachment。
文摘Two dimensional 1H NMR techniques were used to determine the solution structure of C10, a cyclopeptide synthesized in the laboratory. Complete proton resonance assignments were obtained using 2 D DQF COSY, TOCSY, and NOESY experiments. The cross peak volumes in the NOESY spectra were used to calculate the C10 structure. The conformation showed that the four side chains of the lysine residues faced the same side of the cyclopeptide ring.
