Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California 93106, United States.
School of Materials Science and Engineering, Nanyang Technological University, 639798 Singapore.
Langmuir. 2021 Nov 16;37(45):13346-13352. doi: 10.1021/acs.langmuir.1c01966. Epub 2021 Nov 3.
Using a surface forces apparatus (SFA), we have studied the nanomechanical behavior of short single-stranded and partially and fully double-stranded DNA molecules attached via one end to a self-assembled monolayer on a gold surface. Our results confirm the previously proposed "mushroom-like" polymer structure for surface-attached, single-stranded DNA at low packing density and a "brush-like" structure for the same construct at higher density. At low density we observe a transition to "rigid rod" behavior upon addition of DNA complementary to the surface-attached single strand as the fraction of molecules that are double-stranded increases, with a concomitant increase in the SFA-observed thickness of the monolayer and the characteristic length of the observed repulsive forces. At higher densities, in contrast, this transition is effectively eliminated, presumably because the single-stranded state is already extended in its "brush" state. Taken together, these studies offer insights into the structure and physics of surface-attached short DNAs, providing new guidance for the rational design of DNA-modified functional surfaces.
我们使用表面力仪器（SFA）研究了通过一端连接到金表面自组装单层的短单链和部分及完全双链 DNA 分子的纳米力学行为。我们的结果证实了先前提出的低包装密度下表面附着的单链 DNA 的“蕈状”聚合物结构和更高密度下相同结构的“刷状”结构。在低密度下，当添加与表面附着的单链互补的 DNA 时，我们观察到向“刚性棒”行为的转变，因为双链分子的比例增加，与 SFA 观察到的单层厚度和观察到的排斥力的特征长度同时增加。相比之下，在较高密度下，这种转变实际上被消除了，可能是因为单链状态已经在其“刷状”状态下延伸了。总的来说，这些研究提供了对表面附着的短 DNA 的结构和物理性质的深入了解，为合理设计 DNA 修饰的功能表面提供了新的指导。
