State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, 130012, PR China.
Langmuir. 2010 Jun 15;26(12):9491-6. doi: 10.1021/la100037z.
Single-stranded DNA binding proteins (SSB) interact with single-stranded DNA (ssDNA) specifically. Taking advantage of this character, we have employed Bacillus subtilis SSB protein to investigate the nature of force-induced conformation transition of double-stranded DNA (dsDNA) by using AFM-based single molecule force spectroscopy (SMFS) technique. Our results show that, when a dsDNA is stretched beyond its contour length, the dsDNA is partially melted, producing some ssDNA segments which can be captured by SSB proteins. We have also systematically investigated the effects of stretching length, waiting time, and salt concentration on the conformation transition of dsDNA and SSB-ssDNA interactions, respectively. Furthermore, the effect of proflavine, a DNA intercalator, on the SSB-DNA interactions has been investigated, and the results indicate that the proflavine-saturated dsDNA can be stabilized to the extent that the dsDNA will no longer melt into ssDNA under the mechanical force even up to 150 pN, and no SSB-DNA interactions are detectable.
单链 DNA 结合蛋白（SSB）特异性地与单链 DNA（ssDNA）相互作用。利用这一特性，我们采用枯草芽孢杆菌 SSB 蛋白，利用原子力显微镜（AFM）单分子力谱（SMFS）技术研究了力诱导双链 DNA（dsDNA）构象转变的性质。结果表明，当 dsDNA 被拉伸超过其轮廓长度时，dsDNA 部分解链，产生一些 ssDNA 片段，这些片段可以被 SSB 蛋白捕获。我们还系统地研究了拉伸长度、等待时间和盐浓度对 dsDNA 构象转变和 SSB-ssDNA 相互作用的影响。此外，还研究了嵌入剂吖啶黄对 SSB-DNA 相互作用的影响，结果表明，即使在 150pN 的机械力下，吖啶黄饱和的 dsDNA 也可以稳定到 dsDNA 不再解链成 ssDNA 的程度，并且无法检测到 SSB-DNA 相互作用。
