中文摘要：

基于原子力显微镜（AFM）的分子操纵技术能通过AFM针尖将云母表面的单个DNA分子分离（拾取）,通过单分子PCR和Sanger法测序,可以得到任何感兴趣的单个DNA片段的序列。然而在实际操作中,由于针尖-DNA吸附力不足以克服云母表面-DNA吸附力,衬底表面的DNA分子被分离的成功率往往较低。本文改进了原子力显微镜（AFM）针尖对云母表面单个DNA分子的分离（拾取）方法,通过对导电的AFM针尖施加正偏压,使针尖与负电荷的DNA分子形成较强的静电吸引力。结果表明,在针尖施加偏压后,表面的DNA分子能被高效的分离;而在未施加偏压的情况下,表面的DNA分子容易被针尖＂搓揉＂成球状的颗粒,但比较难分离。说明该方法能明显提高DNA分子从云母表面的分离效率。此外,被AFM针尖分离的DNA可通过单分子PCR技术成功扩增,说明对AFM探针施加正偏压来分离DNA不会影响其生物活性。

英文摘要：

The atomic force microscope（AFM） can image and manipulate native biological samples on surfaces on the single-molecule level,including cutting,pushing and picking-up.By applying a positive bias to AFM tip,we have developed a new method for DNA isolation（picking-up） from chemically-modified mica surface.The positive bias on the AFM tip produces electrostatic attraction force between the negatively charged DNA molecules and the tip,which increases DNA picking-up efficiency.By single-molecule PCR,the picked-up DNA can be successfully amplified,indicating the DNA molecules keep their biological activities after the manipulation by the biased AFM tip.