Institute for Materials and Processes, School of Engineering, The University of Edinburgh , King's Buildings, Robert Stevenson Road, Edinburgh, EH9 3FB, United Kingdom.
Université Bordeaux, I2M, UMR 5295, F-33400 Talence, France.
Langmuir. 2016 May 3;32(17):4361-9. doi: 10.1021/acs.langmuir.6b00038. Epub 2016 Apr 21.
Small sessile drops of water containing either long or short strands of DNA ("biodrops") were deposited on silicon substrates and allowed to evaporate. Initially, the triple line (TL) of both types of droplet remained pinned but later receded. The TL recession mode continued at constant speed until almost the end of drop lifetime for the biodrops with short DNA strands, whereas those containing long DNA strands entered a regime of significantly lower TL recession. We propose a tentative explanation of our observations based on free energy barriers to unpinning and increases in the viscosity of the base liquid due to the presence of DNA molecules. In addition, the structure of DNA deposits after evaporation was investigated by AFM. DNA self-assembly in a series of perpendicular and parallel orientations was observed near the contact line for the long-strand DNA, while, with the short-stranded DNA, smoother ring-stains with some nanostructuring but no striations were evident. At the interior of the deposits, dendritic and faceted crystals were formed from short and long strands, respectively, due to diffusion and nucleation limited processes, respectively. We suggest that the above results related to the biodrop drying and nanostructuring are indicative of the importance of DNA length, i.e., longer DNA chains consisting of linearly bonded shorter, rod-like DNA strands.
含有长或短 DNA 链的小而无柄的水滴（“生物滴”）被沉积在硅衬底上并允许蒸发。最初，两种类型的液滴的三线（TL）保持固定，但后来后退。TL 后退模式以恒定速度继续，直到短 DNA 链的生物滴的寿命几乎结束，而那些含有长 DNA 链的生物滴则进入 TL 后退速度显著降低的状态。我们基于解锁的自由能障碍和由于 DNA 分子的存在而导致的基础液体粘度的增加，对我们的观察结果提出了一个初步的解释。此外，还通过 AFM 研究了蒸发后 DNA 沉积物的结构。在长链 DNA 附近的接触线附近观察到一系列垂直和平行取向的 DNA 自组装，而对于短链 DNA，则观察到较平滑的环形污渍，具有一些纳米结构但没有条纹。在沉积物的内部，由于扩散和成核受限过程，分别由短和长链形成了树枝状和有面晶体。我们认为，与生物滴干燥和纳米结构有关的上述结果表明 DNA 长度的重要性，即由线性键合的较短、棒状 DNA 链组成的更长 DNA 链。
