Variety of molecular conformation of plasmid pUC18 DNA and solenoidally supercoiled DNA |
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Authors: | HUANG Xitai WANG Zhaoqing WU Yongwen FAN Tingyu WANG Shurong WANG Xukun |
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Institution: | Department of Biochemistry and Molecular Biology; Nankai University; Tianjin 300071; China |
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Abstract: | The plasmid pUC18 DNA isolated from Escherichia coli HB101 were analyzed by two-dimensional agarose gel electrophoresis and hybridization. The results show that the DNA sample can be separated into six groups of different structural components. The plectonemically and solenoidally supercoiled pUC18 DNA coexist in it. These two different conformations of supercoiled DNA are interchangeable with the circumstances (ionic strength and type, etc.). The amount of solenoidally supercoiled pUC18 DNA in the samples can be changed by treatment of DNA topoisome rases. Under an electron microscope, the solenoidal supercoiling DNA has a round shape with an average diameter of 45 nm. The facts suggest that solenoidaUy supercoiled DNA be a structural entity independent of histones. The polymorphism of DNA structure may be important to packing of DNA in vivo. |
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Keywords: | DNA topological structure DNA topoisomerases two-dimensional agarose gel electrophoresis electron microscopy digoxiginine |
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