Institut für Werkstoffwissenschaft and Max-Bergmann-Zentrum für Biomaterialien, Technische Universität Dresden, Dresden, Germany.
Nanotechnology. 2011 Jan 21;22(3):035304. doi: 10.1088/0957-4484/22/3/035304. Epub 2010 Dec 9.
λ-DNA as well as plasmids can be successfully deposited by molecular combing on hydrophobic surfaces, for pH values ranging from 4 to 10. On polydimethylsiloxane (PDMS) substrates, the deposited DNA molecules are overstretched by about 60-100%. There is a significant influence of sodium ions (NaCl) on the surface density of the deposited DNA, with a maximum near to 100 mM NaCl for a DNA solution (28 ng µl(-1)) at pH 8. The combing process can be described by a micromechanical model including: (i) the adsorption of free moving coiled DNA at the substrate; (ii) the stretching of the coiled DNA by the preceding meniscus; (iii) the relaxation of the deposited DNA to the final length. The sticky ends of λ-DNA cause an adhesion force in the range of about 400 pN which allows a stable overstretching of the DNA by the preceding meniscus. The exposing of hidden hydrophobic bonds of the overstretched DNA leads to a stable deposition on the hydrophobic substrate. The pH-dependent density of deposited DNA as well as the observed influence of sodium ions can be explained by their screening of the negatively charged DNA backbone and sticky ends, respectively. The final DNA length can be derived from a balance of the stored elastic energy of the overstretched molecules and the energy of adhesion.
λ-DNA 和质粒可以在 pH 值为 4 到 10 的范围内成功地通过分子梳理沉积在疏水性表面上。在聚二甲基硅氧烷（PDMS）基底上，沉积的 DNA 分子被拉伸约 60-100%。钠离子（NaCl）对沉积 DNA 的表面密度有显著影响，在 pH 值为 8 时，对于 28ngμl(-1) 的 DNA 溶液，NaCl 的浓度接近 100mM 时达到最大值。梳理过程可以用一个包括以下三个步骤的微机械模型来描述：（i）自由卷曲 DNA 在基底上的吸附；（ii） 前缘月牙对卷曲 DNA 的拉伸；（iii）沉积 DNA 的松弛至最终长度。λ-DNA 的粘性末端产生约 400pN 的粘附力，这使得前缘月牙能够稳定地拉伸 DNA。伸展 DNA 中隐藏的疏水性键的暴露导致 DNA 在疏水性基底上的稳定沉积。沉积 DNA 的 pH 依赖性密度以及观察到的钠离子的影响可以分别用它们对带负电荷的 DNA 骨架和粘性末端的屏蔽作用来解释。最终的 DNA 长度可以通过伸展分子的储存弹性能量与粘附能量之间的平衡来推导。
