The New Methods Based On Lead Ion Induced Conformational Change Of Functional Nucleic Acids For Determining The Radon Concentration

Radon is a radioactive gas which produced by the decay of radium. It is a natural radionuclides could be found in all rocks and soils. The geotectonic movement and human activities make more ways for radon to get into the atmosphere, and endanger human health. Radon had become the second major cause of lung cancer, which always alerts us. The existing methods of radon measurement have the problems of long cycle, expensive equipment, and radiation damage to the inspectors. So it is very urgent to establish an economical and applicable method with high sensitivity, stable, reliable results and no radiation hazard for radon measurement.The second chapter: a new method for detection of the specific non labeled fluorescence sensing of inert gas radon was established, which based on the Pb2+-PW17-OG system. OG generating high intensity of fluorescence after combined with the free curl PW17; Pb2+ can induce PW17 to form a stable G-quadruplexe structure, which inhibit PW17 interact with the free dye OG, that is obviously decreasing the fluorescence intensity of the system after the introduction of radon decay product into the system. In the lead ion concentration range from 0.5 to 10?g/L, the fluorescence intensity of the system shows a good linear relationship with it,while shows an exponential attenuation relationship with radon concentration(D). LOD for lead ions detection was 129.69ng/L. This sensitive and accurate method avoid radiation damage from site sampling, and explores a new field in biological analysis by using aptamers to detect inorganics, gases and radioactive substances.The third chapter: we established a new method for the detection of radon concentration by studying the mutual transformation of G-quadruplexe, which under the interaction of Thioflavin T and radon decay product. Without Pb2+, Thioflavin T bind with the aptamer to form a parallel structure G-quadruplexe. Once the lead ions or lead standard solution introducing into the system, they would replace the Thioflavin T and change the conformation of G-quadruplexe, resulting in decreased fluorescence which is inversely proportional to the Pb2+concentration. In the lead ion concentration range from 0.06 to 24?g/L, the fluorescence intensity of the system shows a good linear relationship with it, while shows an exponential attenuation relationship with radon concentration(D). The LOD of lead ion was 23.03ng/L; the LOD of radon was 766.55Bq·h/m3.The fourth chapter: studying the new method based on DNAzyme for detection of radon concentration. Lead ions activate the lead specific DNAzyme, resulting in the substrate chain break and single-stranded DNA release; Thioflavin T combining two single-stranded DNA to form G-quadruplexe which could enhance fluorescence. In the lead ion concentration range from 0.12 to 4?g/L, the fluorescence intensity of system shows a good linear relationship with it, LOD was 97.14ng/L. While the intensity of fluorescence shows logarithmic growth with radon concentration, and LOD was 947.50Bq·h/m3.