Investigation Of Probe Design And Applying Based On DNA G-quadruplexes

DNA G-quadruplex is a kind of special secondary structure formed by guanine-rich DNA sequences, generally being induced by metal ions such as Na+ and K+. The special secondary structure has excellent physicochemical property just like having special response to metal ions and causing formation change. Cyanine dye aggregate and DNAzyme can recognize special G-quadruplex, causing the change of cyanine dye aggregate state and peroxidase-like activity. Accordingly, the properties, including absorbance, fluorescence and color, of cyanine dye and DNAzyme change. Based on this,we make efforts in a series of studies. The thesis contains the following part:1) Based on cyanine dye MTC recognizing special formation of G-quadruplex, a Pb2+detection probe applying in lake detection and a colorimetric and fluorometric dualmodal DNA logic gate has been designed. MTC can recognize parallel G-quadruplex while has no response to antiparallel G-quadruplex. Pb2+can induce parallel Gquadruplex form into antiparallel G-quadruplex and change MTC aggregates, leading to different signal in absorption spectra and fluorescence spectra. Based on this, a Pb2+detection probe and an INHIBIT DNA logic gate is designed here.2) Based on different response of MTC to DNA duplex and G-quadruplex, a probe used in visual detection of Hg2+ has been constructed. MTC can recognize K+-stabled parallel G-quadruplex while has no response to DNA duplex. Hg2+can bind to thymine residues to form duplex and change the state of MTC aggregate, leading to the change in absorbance spectra and solution color. Based on the principle, the probe is utilized in visual detection of Hg2+and applied in lake detection.3) A sodium probe has been constructed based on DNAzyme. Hemin can bind to special G-quadruplex and form into a kind of peroxidase-like artificial enzymes, which can catalyze H2O2-mediated oxidation ABTS [2, 2-azinobis(3-ethylbenzothiazoline)-6-sulfonic acids], exhibiting different signal in absorption spectra. By utilizing the concentration of Na+ to control G-quadruplex formation and the ABTS-H2O2 system, a colorimetric probe for Na+detection applied in serum has been designed.