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标题：Supercoiled circular DNA of an insect granulosis virus
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作者：Kathleen A. Tweeten ; Lee A. Bulla ; Richard A. Consigli 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1977
卷号：74
期号：8
页码：3574-3578
DOI：10.1073/pnas.74.8.3574
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The DNA of the granulosis virus of the Indian meal moth, Plodia interpunctella, was characterized by physical chemical and electron microscopic techniques. Twenty-five percent of the DNA extracted from purified virus was isolated as supercoiled circular molecules. The remaining 75% consisted of relaxed circular molecules. These molecular forms were indicated by the production of two radioactive bands during sedimentation of 3H-labeled granulosis virus DNA in alkaline sucrose gradients or in equilibrium density gradients of neutral cesium chloride/propidium iodide. Electron microscopic visualization of the DNA that banded at the higher density in the latter gradients revealed supercoiled structures whereas that of DNA that banded at the lower density demonstrated relaxed circular molecules. The superhelical molecules were converted to relaxed circles by treatment with pancreatic DNase. The molecular weight of the viral DNA was calculated to be 81 x 106 by sedimentation in neutral sucrose and 78 x 106 by sedimentation in alkaline sucrose. The molecular weight estimated from length measurements in electron micrographs was 76 x 106. The buoyant density of the granulosis virus DNA was 1.703 g/cm3 and that of its insect host DNA was 1.697 g/cm3. Equilibrium sedimentation in cesium chloride and thermal denaturation indicated G + C contents of 44% and 39% for the viral and host DNA, respectively.
关键词：high-molecular-weight DNA ; electron microscopy ; physical chemical characterization