Twelve 23-esterified silybin derivatives with different patterns of substituents such as aromatic and aliphatic groups （1-12） were designed and synthesized. The antioxidative properties of these compounds were evalu...Twelve 23-esterified silybin derivatives with different patterns of substituents such as aromatic and aliphatic groups （1-12） were designed and synthesized. The antioxidative properties of these compounds were evaluated. The modifed silybin analogues exhibited improved inhibitory effects against rat liver homogenate lipid peroxidation compared to silybin, with exception of the trimethoxylated ester （5） and the aliphatic one （9）. Compounds 3, 5, 7, 8 and 11 displayed their protective properties on DNA cleavage in a dose-dependent manner. 2009 Xiao Kun Li. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.展开更多
The salt-gradient operation mode used in ion-exchange simulated moving bed chromatography (SMBC) can improve the efficiency of protein separations. A detailed model that takes into account any kind of adsorption/ion-e...The salt-gradient operation mode used in ion-exchange simulated moving bed chromatography (SMBC) can improve the efficiency of protein separations. A detailed model that takes into account any kind of adsorption/ion-exchange equilibrium, salt gradient, size exclusion, mass transfer resistance, and port periodic switching mechanism, was developed to simulate the complex dynamics. The model predictions were verified by the experimental data on upward and downward gradients for protein separations reported in the literature. All design and operating parameters (number, configuration, length and diameter of columns, particle size, switching period, flow rates of feed, raffinate, desorbent and extract, protein concentrations in feed, different salt concentrations in desorbent and feed) can be chosen correctly by numerical simulation. This model can facilitate the design, operation, optimization, control and scale-up of salt-gradient ion-exchange SMBC for protein separations.展开更多
The DNA nuclease-like activity of a water soluble manganese corrole 5, 10, 15-tris（N-methyl-4-pyridyl）- corrolatomanga- nese（III） （MnⅢTMPyC） has been investigated. MnⅢMPyC may bind strongly to DNA via outside ...The DNA nuclease-like activity of a water soluble manganese corrole 5, 10, 15-tris（N-methyl-4-pyridyl）- corrolatomanga- nese（III） （MnⅢTMPyC） has been investigated. MnⅢMPyC may bind strongly to DNA via outside groove binding mode as indicated by absorption spectra, viscosity measurements and CD spectra. MnInTMPyC exhibited excellent catalytic activity in the DNA oxidative cleavage in the presence of hydroperoxide.展开更多
DTPA and its two derivatives were synthesized and used as catalysts in DNA cleavage. Under physiological conditions, a series of experiments have been done. The effects of DNA cleavage with three ligands were studied ...DTPA and its two derivatives were synthesized and used as catalysts in DNA cleavage. Under physiological conditions, a series of experiments have been done. The effects of DNA cleavage with three ligands were studied under different concentrations, cleavage time, and pH values. The results strongly suggested that the plasrnid DNA （pUC 19） can be cleaved efficiently by CITC- DTPA. For the cleavage reaction catalyzed by CITC-DTPA, Form I DNA could convert to Form II mostly, and the DNA-cleavage mechanism involved an oxidative pathway. 2009 Chuan Qin Xia. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.展开更多
We aimed to explore the role of chitosan-based metal complexes in catalyzing the hydrolysis of phosphodiesters To this end, we performed detailed studies on the kinetics of the chitosan copper complex （CSCu）-catalyz...We aimed to explore the role of chitosan-based metal complexes in catalyzing the hydrolysis of phosphodiesters To this end, we performed detailed studies on the kinetics of the chitosan copper complex （CSCu）-catalyzed hydrolysis of bis（4-nitrophenol） phosphate （BNPP） in Tris-H＋ buffer and in an organic solvent. A significant enhancement in the rate of reaction （up to 3 X 105-fold acceleration） was observed at pH 8.0 （25 ℃）. The pH depend- ence of BNPP hydrolysis at pH 5.5-9.5 and the UV spectra revealed that the copper-bounded water molecules un- derwent deprotonation to form the active catalytic species CSCu-OH. The kinetic behavior of BNPP catalytic hydrolysis in the Tris-H＋ buffer was consistent with that predicted by the Michaelis-Menten kinetics model. An in-ramolecular nucleophilic attack by the copper-bonded hydroxide group on the same activated phosphodiester substrate was proposed as the catalytic mechanism for CSCu-catalyzed reaction system. The results of DNA binding and cleavage experiments indicated electrostatic binding mode of CSCu to DNA as well as the strong capability of CSCu to disturb the supercoiled strand of DNA and cleave it to nicked circular form.展开更多
基金supported by 985 foundation from Zhejiang University and intramural foundation from Wenzhou Medical College
文摘Twelve 23-esterified silybin derivatives with different patterns of substituents such as aromatic and aliphatic groups （1-12） were designed and synthesized. The antioxidative properties of these compounds were evaluated. The modifed silybin analogues exhibited improved inhibitory effects against rat liver homogenate lipid peroxidation compared to silybin, with exception of the trimethoxylated ester （5） and the aliphatic one （9）. Compounds 3, 5, 7, 8 and 11 displayed their protective properties on DNA cleavage in a dose-dependent manner. 2009 Xiao Kun Li. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
文摘The salt-gradient operation mode used in ion-exchange simulated moving bed chromatography (SMBC) can improve the efficiency of protein separations. A detailed model that takes into account any kind of adsorption/ion-exchange equilibrium, salt gradient, size exclusion, mass transfer resistance, and port periodic switching mechanism, was developed to simulate the complex dynamics. The model predictions were verified by the experimental data on upward and downward gradients for protein separations reported in the literature. All design and operating parameters (number, configuration, length and diameter of columns, particle size, switching period, flow rates of feed, raffinate, desorbent and extract, protein concentrations in feed, different salt concentrations in desorbent and feed) can be chosen correctly by numerical simulation. This model can facilitate the design, operation, optimization, control and scale-up of salt-gradient ion-exchange SMBC for protein separations.
基金supported by the National Natural Science Foundation of China(Nos.20771039,20871122, 20971046)National Key Foundation Research Development Project(973)Item of China(No.2007CB815306)
文摘The DNA nuclease-like activity of a water soluble manganese corrole 5, 10, 15-tris（N-methyl-4-pyridyl）- corrolatomanga- nese（III） （MnⅢTMPyC） has been investigated. MnⅢMPyC may bind strongly to DNA via outside groove binding mode as indicated by absorption spectra, viscosity measurements and CD spectra. MnInTMPyC exhibited excellent catalytic activity in the DNA oxidative cleavage in the presence of hydroperoxide.
基金supported by the National Natural Science Foundation of China(No.20301011)
文摘DTPA and its two derivatives were synthesized and used as catalysts in DNA cleavage. Under physiological conditions, a series of experiments have been done. The effects of DNA cleavage with three ligands were studied under different concentrations, cleavage time, and pH values. The results strongly suggested that the plasrnid DNA （pUC 19） can be cleaved efficiently by CITC- DTPA. For the cleavage reaction catalyzed by CITC-DTPA, Form I DNA could convert to Form II mostly, and the DNA-cleavage mechanism involved an oxidative pathway. 2009 Chuan Qin Xia. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
基金Project supported by the National Natural Science Foundation of China （Nos. 20403002, 20773008）, the Beijing Novel Program （No. 2008B 12） and the National High-Tech R＆D Program （No. 2007AA05Z146）.
文摘We aimed to explore the role of chitosan-based metal complexes in catalyzing the hydrolysis of phosphodiesters To this end, we performed detailed studies on the kinetics of the chitosan copper complex （CSCu）-catalyzed hydrolysis of bis（4-nitrophenol） phosphate （BNPP） in Tris-H＋ buffer and in an organic solvent. A significant enhancement in the rate of reaction （up to 3 X 105-fold acceleration） was observed at pH 8.0 （25 ℃）. The pH depend- ence of BNPP hydrolysis at pH 5.5-9.5 and the UV spectra revealed that the copper-bounded water molecules un- derwent deprotonation to form the active catalytic species CSCu-OH. The kinetic behavior of BNPP catalytic hydrolysis in the Tris-H＋ buffer was consistent with that predicted by the Michaelis-Menten kinetics model. An in-ramolecular nucleophilic attack by the copper-bonded hydroxide group on the same activated phosphodiester substrate was proposed as the catalytic mechanism for CSCu-catalyzed reaction system. The results of DNA binding and cleavage experiments indicated electrostatic binding mode of CSCu to DNA as well as the strong capability of CSCu to disturb the supercoiled strand of DNA and cleave it to nicked circular form.
