| Since the discovery of graphene,due to its excellent mechanical,optical,electrical and thermal properties,it has shown wide application prospects in many fields such as electrochemistry,catalysts,decontamination,nanocomposites and biomedicine field.In the field of biomedicine,graphene-based nanomaterials play a key role in drug delivery,genome sequencing platform,biological imaging,biosensors.A significant feature of graphene is the huge specific surface area,which can absorb a variety of biomolecules,and cause the distortion of the structure of biomolecules and the loss of function.It is well known that various defects usually occur on the surface of graphene due to material preparation method and experimental environment,and the defects usually cause some new physical and chemical properties of the material itself.Although the interaction between graphene and various biomolecules has been widely reported in theory and experiment,there are few studies on the interaction between defects and biomolecules.Based on the method of molecular dynamics simulation,we conducted an in-depth study on the interaction characteristics,structural changes and interaction mechanism between graphene materials and two kinds of nucleic acid molecule.The main research contents of this thesis are as follows:1.We have studied the binding mode,structure evolution and interaction mechanism of dsDNA on two kinds of graphene material,defective graphene and graphene.Our research results have shown that the structural changes of dsDN A on the surface of two kinds of graphene material are obviously different.The existence of defects on graphene surface can promote the unwinding and structural destruction of dsDNA,while the defect-free graphene shows much weaker ability to destroy the structure of dsDNA.This difference is due to the strong electrostatic interaction between the defect and dsDNA.Nucleotides can be highly restricted by the defect while the other parts of dsDNA could move along the transverse directions of defective graphene.This effectively introduces a "pulling force" from the defect that causes the breaking of the hydrogen bonds between dsDNA base pairs.Such kind of force finally leads to the serious unwinding of dsDNA.2.We have studied the binding mode,structural stability,diffusion characteristics and related interaction mechanisms of G-quadruplex on the surface of graphene materials.Our research results have shown that the existence of defects can effectively regulate the binding mode of G-quadruplex on defective graphene,so that only the loop nucleotides are adsorbed onto the surface of graphene materials through π-π stacking interaction.Thus,a weaker vertical binding is formed and the structural integrity of G-quadruplex is maintained.In contrast,when there is no defect,the G-quadruplex is adsorbed on the surface of graphene through the strongerπ-π stacking interaction between the quartet and graphene,leading to a stronger horizontal binding and unwinding of G-quadruplex.In addition,the Na+can bridge the phosphate group of the G-quadruplex with the defective carboxyl group,resulting in a weaker vertical binding mode.This pattern resulted in the lack of stronger stacking to cause structural expansion and steady loss of intra-quartet bonding of G-quadruplex.In summary,we systematically investigated the important role of defects on graphene materials in modulating the structure of nucleic acid molecules.Our study has provided the indepth understanding of the biotoxicity of nanomaterials,and we have elucidated the physical mechanism that the defects of the two-dimensional nanomaterials can enhance the destructive effect for DNA molecules.And our new findings may also provide some new ideas for the application of bio-detection sensors targeting G-quadruplex. |
