| DNA is an important functional macromolecule in the life, as the carrier of genetic information in the vast majority of biological species. There are different secondary structures of DNA, including triple helix DNA, G-quadruplex and i-motif sequences, etc.. It is of great significance to investigate the relationship between DNA structure and function, which could help us to deepen the understanding on the essence of life and expand the applications of DNA in various fields.DNAzyme, formed by hemin and G-quadruplex DNA, has demonstrated peroxidase-like activities, and it can catalyze the oxidation of 2,2'-azinobis(3-ethylbenzothiozoline)-6-sulfonic acid (ABTS) by H2O2 as color-changed reaction. This dissertation studied the relationship between the structure and function of DNAzyme, and designed a DNAzyme-based biosensor for the detection of adenosine.1. By the strategy that mutated the end of the DNA sequence of DNAzyme, using ultraviolet spectroscopy, circular dichroism and other experimental methods, this paper systematically studied the relationship between the structure of DNAzyme and its peroxidase activity. We found that adding dTn to the end of the DNA sequence of the enzyme would make great influence on the peroxidase activity. And the more stable the assembled DNAzyme was, the more conducive the binding of enzyme and substrate (H2O2) could be, which showed a higher peroxidase activity, and vice versa, the lower.2. And then we designed a DNAzyme-based biosensor that employed the aptamer as the receptor, restriction enzyme Fok I as the signal controller, DNAzyme as the resultant output device. This DNA biosensor had good sensitivity and selectivity, only to have identified the present of adenosine with the limit of detection (LOD) of 0.5μM, and there was no response to other nucleosides. This biosensor can achieve the optical detection through the color change of the enzymatic reaction, instead of relying on the instrument.
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