摘要
采用原子力显微镜（ＡＦＭ）在无水乙醇中成象了ｐＢＲ３２２质粒ＤＮＡ。在不同温度范围加热云母表面的ＤＮＡ溶液，并在相应温度下干燥使ＤＮＡ充分展开地固定在云母基底上。ＡＦＭ观察结果表明：在３０～４０℃，质粒ＤＮＡ主要是超螺旋和环状分子；在４０～５０℃，环状分子开环形成线形分子； 在７０～８０℃，这些线形分子全部变性，解链形成无规线团。我们通过测定ｐＢＲ３２２质粒ＤＮＡ的熔融曲线，发现了两个突变点，对应于ＡＦＭ所观察到的质粒ＤＮＡ在加热过程中由环状变成线形、双螺旋解开成单链的两个结构变化过程。这是首次通过ＡＦＭ直接观察到质粒ＤＮＡ在不同温度下的结构变化。
An improved method has been developed for imaging pBR322 plasmid DNA in ethanol with the atomic force microscopy (AFM). DNA solution on freshly cleaved mica was heated in different ranges of temperature (30～40, 40～50, 50～60, 60～70, 70～80 and > 80℃),and dried at the corresponding temperature to fix the extended DNA molecules on mica surface. The typical structural features were directly observed with AFM. The superhelical and circular DNA molecules were found at 30～40℃. At 40～50℃, the circular DNA werebroken to form linearized molecules, which could be denatured to form supercoiled structure at 70～80℃. We also determined the temperature-absorbancy curve of the PBR322 plasmid DNA. The two Tin points proved that there are two changes during heat - denaturation,corresponding to the changes of circular→linear, double - stranded→single- stranded structure.
出处
《生物物理学报》
CAS
CSCD
北大核心
1996年第4期554-558,共5页
Acta Biophysica Sinica
