Department of Physics, University of Basel, Klingelbergstrasse 82, 4056, Basel, Switzerland.
Departamento de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid, E-28049, Madrid, Spain.
Nat Commun. 2019 Feb 8;10(1):685. doi: 10.1038/s41467-019-08531-4.
Cryo-electron microscopy can determine the structure of biological matter in vitrified liquids. However, structure alone is insufficient to understand the function of native and engineered biomolecules. So far, their mechanical properties have mainly been probed at room temperature using tens of pico-newton forces with a resolution limited by thermal fluctuations. Here we combine force spectroscopy and computer simulations in cryogenic conditions to quantify adhesion and intra-molecular properties of spray-deposited single-strand DNA oligomers on Au(111). Sub-nanometer resolution images reveal folding conformations confirmed by simulations. Lifting shows a decay of the measured stiffness with sharp dips every 0.2-0.3 nm associated with the sequential peeling and detachment of single nucleotides. A stiffness of 30-35 N m per stretched repeat unit is deduced in the nano-newton range. This combined study suggests how to better control cryo-force spectroscopy of adsorbed heterogeneous (bio)polymer and to potentially enable single-base recognition in DNA strands only few nanometers long.
冷冻电子显微镜可以确定玻璃态液体中生物物质的结构。然而，仅仅结构本身不足以理解天然和工程生物分子的功能。到目前为止，它们的机械性能主要是在室温下使用几十皮牛的力进行探测的，分辨率受到热涨落的限制。在这里，我们在低温条件下结合力谱学和计算机模拟来量化喷射沉积在 Au(111)上的单链 DNA 寡聚物的粘附和分子内性质。亚纳米分辨率的图像揭示了折叠构象，这些构象通过模拟得到了证实。提起实验显示，测量的刚度随每 0.2-0.3nm 出现的急剧下降而衰减，这与单个核苷酸的顺序剥离和分离有关。在纳米牛顿范围内推断出伸展重复单元的刚度为 30-35N m。这项联合研究表明如何更好地控制吸附异质（生物）聚合物的冷冻力谱学，并有可能使只有几纳米长的 DNA 链能够实现单个碱基的识别。
