Jahan Merina, Uline Mark J
Department of Chemical Engineering, University of South Carolina, Columbia, SC 29208, USA.
Biomedical Engineering Program, University of South Carolina, Columbia, SC 29208, USA.
Polymers (Basel). 2018 Dec 18;10(12):1403. doi: 10.3390/polym10121403.
The performance of aptamer-based biosensors is crucially impacted by their interactions with physiological metal ions, which can alter their structures and chemical properties. Therefore, elucidating the nature of these interactions carries the utmost importance in the robust design of highly efficient biosensors. We investigated Mg 2 + binding to varying sequences of polymers to capture the effects of ionic strength and grafting density on ion binding and molecular reorganization of the polymer layer. The polymers are modeled as ssDNA aptamers using a self-consistent field theory, which accounts for non-covalent ion binding by integrating experimentally-derived binding constants. Our model captures the typical polyelectrolyte behavior of chain collapse with increased ionic strength for the ssDNA chains at low grafting density and exhibits the well-known re-entrant phenomena of stretched chains with increased ionic strength at high grafting density. The binding results suggest that electrostatic attraction between the monomers and Mg 2 + plays the dominant role in defining the ion cloud around the ssDNA chains and generates a nearly-uniform ion distribution along the chains containing varying monomer sequences. These findings are in qualitative agreement with recent experimental results for Mg 2 + binding to surface-bound ssDNA.
基于适配体的生物传感器的性能受到其与生理金属离子相互作用的关键影响，这些相互作用会改变其结构和化学性质。因此，阐明这些相互作用的本质对于高效生物传感器的稳健设计至关重要。我们研究了Mg2+与不同聚合物序列的结合，以捕捉离子强度和接枝密度对聚合物层离子结合和分子重组的影响。使用自洽场理论将聚合物建模为单链DNA适配体，该理论通过整合实验得出的结合常数来解释非共价离子结合。我们的模型捕捉到了低接枝密度下单链DNA链随离子强度增加而发生链塌缩的典型聚电解质行为，并展示了高接枝密度下随离子强度增加而出现的拉伸链的著名再入现象。结合结果表明，单体与Mg2+之间的静电吸引在定义单链DNA链周围的离子云方面起主导作用，并在包含不同单体序列的链上产生几乎均匀的离子分布。这些发现与最近关于Mg2+与表面结合的单链DNA结合的实验结果在定性上一致。
