Effects of fluid flow on the oligonucleotide folding in single-walled carbon nanotubes

This paper presents molecular-dynamics (MD) simulations of DNA oligonucleotide and water molecules translocating through carbon nanotube (CNT) channels. An induced pressure difference is applied to the system by pushing a layer of water molecules toward the flow direction to drive the oligonucleotide and other molecules. This MD simulation investigates the changes that occur in the conformation of the oligonucleotide due to water molecules in nanochannels while controlling the temperature and volume of the system in a canonical ensemble. The results show that the oligonucleotide in the (8,8)-(12,12) CNT channel forms a folded state at a lower pressure, whereas the oligonucleotide in the (10,10)-(14,14) CNT channel forms a folded state at a higher pressure instead. The van der Waals forces between the water molecules and the oligonucleotide suggest that the attraction between these two types of molecules results in the linear arrangements of the bases of the oligonucleotide. For a larger nanotube channel, the folding of the oligonucleotide is mainly dependent on the solvent (water molecules), whereas pressure, the size of the nanotube junction, and water molecules are the considering factors of the folding of the oligonucleotide at a smaller nanotube channel. For a folded oligonucleotide, the water distribution around the oligonucleotide is concentrated at a smaller range than that for the distribution around an unfolded oligonucleotide.