Defect-Induced Double-Stranded DNA Unwinding on Graphene.

Several works have shown that graphene materials can effectively regulate the double-stranded DNA (dsDNA) structures and are used to remove antibiotic resistance genes in the environment, during which the morphology of the graphene surface plays a key role. However, the mechanism of how different graphene surfaces interact with dsDNA is poorly documented. Here, the interactions of dsDNA with defective graphene (D-Gra) and pristine graphene (P-Gra) have been explored by molecular dynamics simulations. Our data clearly showed that both D-Gra and P-Gra were able to attract dsDNA to form stable bindings. However, the structure evolutions of dsDNA are distinctly different. In detail, D-Gra can initiate quick unwinding of dsDNA and cause significant structural disruption. While for P-Gra, it demonstrated a much weaker capability to disrupt the dsDNA structure. This difference is due to the strong electrostatic interaction between defects and DNA nucleotides. Nucleotides can be highly restricted by the defect while the other parts of dsDNA could move along the transverse directions of D-Gra. This effectively introduces a "pulling force" from the defect that causes the breaking of the hydrogen bonds between dsDNA base pairs. Such force finally leads to the serious unwinding of dsDNA. Our present findings could help us to better understand the molecular mechanism of how the dsDNA canonical B-form was lost upon adsorption to graphene. The findings of the key roles of defects on graphene are beneficial for the design of functional graphenic materials for biological and medical applications through nanostructure engineering.