Research On The Self-assembly Structures Of G-rich Oligonucleotide

Self-assembly properties of biomolecules, especially nano-assembles of DNA have attracted considerable interests recently due to their potential roles in cancer chemotherapy, biosensor technology. Besides the canonical duplex helix structure, DNA can form multi-stranded structures such as the triplex, the quadruplex and the frayed wire etc., which make it possible to design novel nano-materials with special geometries, and to orient the organization of other nanoparticles beyond the assembled templates.This thesis first studied the thermodynamic properties of the G-rich DNA in the presence of different ions, the related thermodynamic parameters were obtained. Then based on the sequence of A8G12, the self-assembled structure of the G-rich sequence and its influence on the assembly of silver nanocluster and nano-gold were investigated through Ultraviolet Visible Spectrum (UV), Fluorescence Spectrum (FS), Atomic Force Microscope (AFM) and Transmission Electron Microscope (TEM).It is indicated by using CD and AFM that A8G12 can form the structure of Frayed wire containing the G-quadruplex building block, the dimension of this structure depends on the cations, concentration, and the incubation time. Using the assembly of A8G12 as the template to synthesize silver nanocluster, it is suggested that silver nanoclusters interact directly with the base of the sequence and they have greater affect on the A8 section of the sequence rather than the G-quadruplex. The silver nanoclusters show special light-absorption and fluorescence property. Based on the studies of the assembly of nano-gold and A8G12, it is indicated that addition of the SH-T15 results in the formation of perpendicular wire structures while the consequent addition of A8G12 leads to non-perpendicular wire structures. Under the similar conditions, addition of MPS results in snow-flake shaped structures.