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Atomic force microscopic study on topological structures of pBR322 DNA

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【作者】 张平城白春礼成英俊方晔王中怀黄熙泰

【Author】 ZHANG Pingcheng , BAI Chunli , CHENG YingjunFANG Ye WANG Zhonghuai(STM Laboratory, Institute of Chemistry, Chinese Academy of Sciences. Beijing 100080, China)and HUANG Xitai(Department of Biology, Nankai University, Tianjin 300071, China)

【机构】 STM LaboratoryInstitute of ChemistryChinese Academy of Sciences. Beijing 100080ChinaDepartment of BiologyNankai UniversityTianjin 300071China

【摘要】 <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

【Abstract】 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 intermediates formed from monomer to oligomer.

【基金】 Project supported by the National Natural Science Foundation of China, the Foundation of Chinese Academy of Sciences,and Beijing Nature Scientific Foundation.
  • 【文献出处】 Science in China(Series C:Life Sciences) ,中国科学(C辑:生命科学)(英文版) , 编辑部邮箱 ,1996年01期
  • 【分类号】Q52
  • 【被引频次】1
  • 【下载频次】46
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