Danilevich V N, Kadykov V A, Grishin E V
Bioorg Khim. 2010 Jul-Aug;36(4):535-46. doi: 10.1134/s1068162010040084.
An electron microscopy study of large-sized DNA microparticles produced in PCR with different gene-specific primers and plasmid DNAs is described. DNA microspheres of two distinct types were revealed in the all studied samples, namely smooth moderately electron-dense microspheres, and highly electron-dense particles with large thorns and offshoots. Singular microspheres have the average diameter of 1 mum, and their aggregates were up to 3 mum in dimensions. In addition, rare so-called three-dimensional net-like structures with various size (up to several micrometers) were observed. They consisted of different amounts of DNA nanoparticles, having the special compact topology. In some studied samples the discs (nanodiscs) of several dozens nm in thickness and up to 3 mum in diameter were revealed. It was shown that the quantity of net-like structures and nanodiscs sharply increases in asymmetric PCR. We also observed DNA nanowires of different length and thickness, nanodots, nanoparticles in the form of shits of paper as well as electron-dense spherical nanoparticles of big size. Aqueous suspensions of DNA microparticles were heated at 94 degrees C for 5 min and analyzed by electron microscopy. It was shown that microspheres in heated suspensions underwent partial melting; they lost a part of DNA, therefore details of their structure (ultrastructure) can be recognized. At the some time numerous tangles of nanowires appeared. Molecular mechanisms of the DNA micro- and nanoparticles formation are discussed.
本文描述了一项关于在聚合酶链反应（PCR）中使用不同基因特异性引物和质粒DNA产生的大尺寸DNA微粒的电子显微镜研究。在所有研究样本中均发现了两种不同类型的DNA微球，即表面光滑、电子密度适中的微球，以及带有大刺和分支的高电子密度颗粒。单个微球的平均直径为1微米，其聚集体尺寸可达3微米。此外，还观察到了罕见的各种尺寸（高达几微米）的所谓三维网状结构。它们由不同数量的DNA纳米颗粒组成，具有特殊的紧密拓扑结构。在一些研究样本中，发现了厚度为几十纳米、直径达3微米的圆盘（纳米盘）。结果表明，在不对称PCR中，网状结构和纳米盘的数量急剧增加。我们还观察到了不同长度和厚度的DNA纳米线、纳米点、呈纸片状的纳米颗粒以及大尺寸的电子致密球形纳米颗粒。将DNA微粒的水悬浮液在94℃加热5分钟，然后进行电子显微镜分析。结果表明，加热悬浮液中的微球发生了部分熔化；它们失去了一部分DNA，因此可以识别其结构细节（超微结构）。与此同时，出现了大量纳米线缠结。本文讨论了DNA微颗粒和纳米颗粒形成的分子机制。
