Dynamic behavior of the single-strand DNA molecules from the hydrophilic to hydrophobic regions on graphene oxide surface driven by heating.

Abstract

Heating affects the interfacial properties of two-dimensional nanomaterials, especially when they interact with biomolecules. Here, we theoretically studied the dynamic processes driving single-strand DNA (ssDNA) molecules from the hydrophilic to hydrophobic regions on the graphene oxide (GO) surface by heating, as reported by recent experiments. This was accomplished by using multi-sample molecular dynamics simulations in the NVT ensemble, with the temperature increasing from 300 K to 350 K. When the temperature increased, the lifetime of hydrogen bonds between water molecule and oxygen-containing groups on the GO surface decreased from 10.04 ps to 6.86 ps, and the end-to-end distance of 4-mer and 8-mer ssDNA molecules also decreased. This indicated that heating facilitated the breaking/formation of hydrogen bonds and enhanced the flexibility of ssDNA molecules. By heating, active hydrogen bonding first led to unbalanced interactions between the ssDNA molecule and GO surface, and the enhanced flexibility allowed the ssDNA molecule to release stress by moving on the GO surface and relaxing its structure. The ssDNA molecule constantly adjusted its structure by a competition between intra and inter π-π stacking structures. With dynamic cooperation of hydrogen bonding and π-π stacking, the ssDNA molecule moved from the hydrophilic to hydrophobic regions. Our results offer fundamental interfacial science insights into the effects of heating on the interactions between biomolecules and two-dimensional nanomaterials.