The prevailing theories describing DNA confinement in a nanochannel are predicated on the assumption that wall-DNA electrostatic interactions are sufficiently short-ranged such that the problem can be mapped to an equivalent neutral polymer confined by hard walls with an appropriately reduced effective channel size. To determine when this hypothesis is valid, we leveraged a recently reported experimental data set for the fractional extension of DNA molecules in a 250-nm-wide poly(dimethyl siloxane) (PDMS) nanochannel with buffer ionic strengths between 0.075 and 48 mM. Evaluating these data in the context of the weakly correlated telegraph model of DNA confinement reveals that, at ionic strengths greater than 0.3 mM, the average fractional extension of the DNA molecules agree with theoretical predictions with a mean absolute error of 0.04. In contrast, experiments at ionic strengths below 0.3 mM produce average fractional extensions that are systematically smaller than the theoretical predictions with a larger mean absolute error of 0.15. The deviations between experiment and theory display a correlation coefficient of 0.82 with the decay length for the DNA-wall electrostatics, linking the deviations with a breakdown in approximating the DNA with an equivalent neutral polymer.

中文翻译：

---

描述纳米通道限制 DNA 的理论的等效中性聚合物假设的局限性。

描述纳米通道中 DNA 限制的流行理论基于这样的假设：壁-DNA 静电相互作用足够短程，因此可以将问题映射到由硬壁限制的等效中性聚合物，并适当减小有效通道尺寸。为了确定这一假设何时有效，我们利用了最近报道的实验数据集，用于在 250 nm 宽的聚二甲基硅氧烷 (PDMS) 纳米通道中进行 DNA 分子的分数延伸，缓冲液离子强度在 0.075 至 48 mM 之间。在 DNA 限制的弱相关电报模型的背景下评估这些数据表明，在离子强度大于 0.3 mM 时，DNA 分子的平均延伸分数与理论预测一致，平均绝对误差为 0.04。相比之下，离子强度低于 0.3 mM 的实验产生的平均延伸分数系统地小于理论预测，平均绝对误差更大，为 0.15。实验与理论之间的偏差显示，DNA 壁静电衰减长度的相关系数为 0.82，将偏差与用等效中性聚合物近似 DNA 时的故障联系起来。