Study On The Aggregation Of Lable-free Nucleic Acid Probe Induced By DNA

Nucleic acid is the main genetic material and it carries genetic information, any one of the organism's cells has a complete set of genetic information. The functional unit of genetic is the smallest fragment of DNA, which is called as genes, and DNA-related research is to reveal the mysteries of bio-genetic basis. And now tens of thousands of diseases are related to DNA. So the nucleic acid detection will promote the development of diagnostic method. In recent years, the nucleic acid sequence, shape and characteristics has become the focus of biological research, and the corresponding new type of nucleic acid biosensor has been developing at home and abroad.Now the analytical techniques for nucleic acid are so many, such as chemiluminescence, high-performance liquid chromatography, capillary electrophoresis, resonance light scattering method, hybridization, PCR, as well as fluorescent probe technology. Some of these have been much useful in the quantitative and qualitative analysis of nucleic acids. However, the most of these methods need for specific equipment, which will be inconvenient for the detection of nucleic acid. And it is difficult to achieve real-time, simple and convenient. At present, spectrum is more common in nucleic acid analysis. The reason is that spectral analysis can be much more direct, accurately to reflect the content of nucleic acids, nucleic acid structure or conformation changes in space. Fluorescence analysis has been widely used in the analysis of life due to its high sensitivity, high selectivity, simple, fast, etc. However, fluorescence analysis must detect the nucleic acid with the molecular probes. And the most of the molecular probe must be labeled to the nucleic acid which greatly increased the difficulty and the cost to detect the DNA. Our study is focused on to develop an efficient, sensitive, simple, and economic method to detect nucleic acid. 1 the synthesis of the label-free DNA probe and the study of its optical propertiesFirst of all, we synthesized a fluorescence compound which contains a group of pyrene and a five-carbon chain. In the end of the five-carbon chains is a trimethy amine which carries a positive charge. The optical character was detected by Carry-50 UV-Vis spectrophotometer and Ls-55 fluorescence spectrophotometer. Fluorescence intensity of probe has the direct ratio with the concentration of probe. According to fluorescence spectra, the emission peak was at 377 nm. However, when adding polyanion, the fluorescent emission peak was shift to 480 nm. It is mainly due to probe molecules has a positive charge, when there has Polyanionic, the pyrene probe molecules can be self-assembly induced by polyanion, and formed excitant complex. When stimulate by UV light the complex' emission light will shift to long wave area, according to changes of fluorescence research nucleic acid' information of sequence, structure, and content.2 The interaction of Lable-free DNA probe with nucleic acidIn this chapter, we used the fluorescence spectrophotometer, UV spectrophotometer and circular dichroism spectroscopy to research the molecular conformation and structure of nucleic acid when added difference concentration of probe. We identified physical optical properties of probes based on the spectra of UV, circular dichroism and fluorescence changes. First of all, we researched the impact of buffer and ionic on the fluorescence of probe, and chose a best environment for experimentation. And then change the concentration of probe or nucleic acids to research the relationship of fluorescence intensity and the concentration of probe. And then change the length of nucleic acid to see the relationship between the fluorescence intensity of probe to the length of nucleic acid. Through these studies, we received the mechanism of probe combined to DNA. Through this research we provided enough data to design a new type probe.3 study on the applied research of Label-free probe In this chapter we mainly introduces the uses of small molecule probes based on the changes of fluorescence spectra. First of all, we research the changes of fluorescence intensity when the concentration of probe increasing, based on this point we can detect the concentration of nucleic acid. We can also detect the micro-surrounding of solution by the changes of fluorescence intensity. By the character of direct relationship between the length of nucleic acid and the probe we also can detect the activity of nuclease. We also used this character and the character of S1 nuclease developed a new method to detect SNP.To sum up, our research has developed a new probe which needn't labeled to the nucleic acid chain. Just because we omit labeling to the nucleic acid chain lets the detection more conveniently and more economically .we get the mechanism of probe linking to nucleic acid and optimized the detecting condition. Moreover, according to the experiment we get the purpose to detect the concentration of nucleic acid, to detect the micro-surrounding of solution, to detect the activity of nuclease and to detect SNP. It can also be used to detect the telomerase because of its high affinity to guanine.