<正> Plasmid pBR322 DNA (0.5mg/mL) isolated from Escherichia coli HB101 was suspended in Tris-HCl-EDTA (1 mol/L - 0.1 mol/L, pH8.5); then a drop of the above solution was deposited on freshly cleaved mica substr...<正> Plasmid pBR322 DNA (0.5mg/mL) isolated from Escherichia coli HB101 was suspended in Tris-HCl-EDTA (1 mol/L - 0.1 mol/L, pH8.5); then a drop of the above solution was deposited on freshly cleaved mica substrate. After adsorption for about 1 min, the sample was stained with phosphotungstic acid. The residua] solution was removed with a piece of filter paper. Afterwards the sample was imaged with a home-made atomic force microscope (AFM) in air. The AFM images of pBR322 DNA with a molecular resolution have been obtained. These images show that pBR322 DNA exists in several different topological structures: (i) relaxed circular DNA with a different diameter; (ii) supercondensed DNA with different particle sizes; (iii) dimeric catenane connected by one relaxed circular molecule and another dose-compacted molecule which might be either supercoiled or intramolecular knotted form; (iv) oligomeric catenane with multiple irregular molecules in which DNA is interlocked into a complex oligomer; (v) possibly-existing展开更多
A series of metal complexes were designed and synthesized and a novel binuclear magnesium complex has been selected, namely [Mg-2(dien)Cl(OH2)(2)]Cl-2 . H2O (dien=diethylene-triamine), which can cleave the plasmid pBR...A series of metal complexes were designed and synthesized and a novel binuclear magnesium complex has been selected, namely [Mg-2(dien)Cl(OH2)(2)]Cl-2 . H2O (dien=diethylene-triamine), which can cleave the plasmid pBR322 DNA effectively in close to physiological condition without adding any external materials. Through biological and chemical methods, especially the comparative experiments, we find the interaction between the complex and DNA belongs to hydrolytic mechanism.展开更多
基金Project supported by the National Natural Science Foundation of China, the Foundation of Chinese Academy of Sciences,and Beijing Nature Scientific Foundation.
文摘<正> Plasmid pBR322 DNA (0.5mg/mL) isolated from Escherichia coli HB101 was suspended in Tris-HCl-EDTA (1 mol/L - 0.1 mol/L, pH8.5); then a drop of the above solution was deposited on freshly cleaved mica substrate. After adsorption for about 1 min, the sample was stained with phosphotungstic acid. The residua] solution was removed with a piece of filter paper. Afterwards the sample was imaged with a home-made atomic force microscope (AFM) in air. The AFM images of pBR322 DNA with a molecular resolution have been obtained. These images show that pBR322 DNA exists in several different topological structures: (i) relaxed circular DNA with a different diameter; (ii) supercondensed DNA with different particle sizes; (iii) dimeric catenane connected by one relaxed circular molecule and another dose-compacted molecule which might be either supercoiled or intramolecular knotted form; (iv) oligomeric catenane with multiple irregular molecules in which DNA is interlocked into a complex oligomer; (v) possibly-existing
文摘A series of metal complexes were designed and synthesized and a novel binuclear magnesium complex has been selected, namely [Mg-2(dien)Cl(OH2)(2)]Cl-2 . H2O (dien=diethylene-triamine), which can cleave the plasmid pBR322 DNA effectively in close to physiological condition without adding any external materials. Through biological and chemical methods, especially the comparative experiments, we find the interaction between the complex and DNA belongs to hydrolytic mechanism.
