Espejo R T, Canelo E S, Sinsheimer R L
Proc Natl Acad Sci U S A. 1969 Aug;63(4):1164-8. doi: 10.1073/pnas.63.4.1164.
The DNA molecules isolated from mature bacteriophage PM2 are closed double-stranded rings of a molecular weight of six million. Direct evidence for the circularity and supercoiling of PM2 DNA was obtained by electron microscopy. Other properties, such as sedimentation behavior at neutral and alkaline pH, unusually high buoyant density in alkaline CsCl, and stability upon heating, are consistent with this structure. Only the four common nucleotides are found after hydrolysis and chromatographic analysis of PM2 DNA.
从成熟噬菌体PM2中分离出的DNA分子是分子量为六百万的闭合双链环。通过电子显微镜获得了PM2 DNA呈环状和超螺旋结构的直接证据。其他特性，如在中性和碱性pH下的沉降行为、在碱性氯化铯中异常高的浮力密度以及加热稳定性，都与这种结构相符。对PM2 DNA进行水解和色谱分析后，仅发现了四种常见的核苷酸。
