| Nucleic acid is a vital substance and it is the basic taker and gene expression of the descendiblity information.It dominates the composition of protein,the growth,manifold, aberrance and heredity of all flesh.So it is of special value to study the interaction between small molecules and nucleic,acids,the quantitative analysis of nucleic acids with high sensitivity and low detection limit are important in life science,biochemical medicament, food analysis and clinical analysis,which is helpful to design the new type of drug and study the toxicity of drug.This project is the forward position and hot point in biochemical and biophysical researches.This thesis focus on the development of new probes for nucleic acids and to establish sensitive methods for the quantitative determination of them,using the fluorescence and resonance light scattering(RLS) as the primary technique.The UV-visible spectrometry, circular dichroism(CD),flu(o|¨)rescence lifetime,electrophoresis by TV,transmission electron microscopy(TEM) techniques are also used to study the interaction mechanism.The main conclusions are listed as follows:In the first section,we summarize the recent development of fluorescence and RLS probes for nucleic acids and the analytical application,and comment on the progress of nanoparticle probes for nucleic acid.In the second section,silver nanoparticles(AgNPs) are prepared and they are utilized in the study of the interaction between AgNPs,Al(Ⅲ) and nucleic acids.From the research, we fred that when Al(Ⅲ) is added to AgNPs solution,the RLS intensity is quenched, however,the RLS intensity of AgNPs-Al(Ⅲ) system is greatly enhanced when fsDNA or ctDNA or yRNA is added to the system.Based on this,a new RLS method for the determination of nucleic acids is proposed.Under optimum conditions,the enhanced RLS intensity is proportion to the concentration of nucleic acids in the range of 1.0×10-9-1.0×10-7,1.0×10-7-2.0×10-6g mL-1 for fish sperm DNA(fsDNA),1.0×10-9-7.0×10-8g mL-1 for calf thymus DNA(ctDNA) and 1.0×10-9-1.0×10-7Tg mL-1 for yeast RNA(yRNA).The detection limits(S/N=3) of fsDNA,ctDNA and yRNA are 4.1×10-10 g mL-1,4.0×10-10g mL-1 and 4.5×10-10g mL-1,respectively.The studies indicate that the RLS enhancement effect should be ascribed to the formation of AgNPs-Al(Ⅲ)-fsDNA aggregations through electrostatic attraction and adsorption bridging action of Al(Ⅲ).And the sensitivity and stability of the AgNPs-fsDNA system could be enhanced by Al(Ⅲ).In the third section,the RLS quenching effect of AgNPs-EBT-nucleic acids is studied. It is found that nucleic acids could obviously quench the intensity of RLS of AgNPserichrome black T(EBT) system.Based on this,a new method for the determination of nucleic acids is proposed in this paper.Under optimum conditions,there are linear relationships between the quenching extent of RLS intensity and the concentration of nucleic acids over a range(e.g.fsDNA and yRNA),with detection limits at the ng mL-1 level.The results indicate that AgNPs can form wire-like aggregates and nanoslices in the presence of the EBT.However,in the AgNPs-EBT-fsDNA system,AgNPs are well dispersed and their sizes decrease,resulting in the RLS intensity of AgNPs-EBT system quenching.Moreover,experiment indicates that the quenching extent is different when different nucleic acids are added to AgNPs-EBT system.And the phenomenon is also studied.In the fourth section,it is found that AgNPs can further enhance the fluorescence intensity of curcumin(CU) - cetyltrimethylammonium bromide(CTAB) - nucleic acids and improve its anti-photobleaching activity.Under optimum conditions,the enhanced fluorescence intensity is proportion to the concentration of nucleic acids in the range of 2.0×10-8- 1.0×10-6 g mL-1 for fsDNA,2.0×10-8- 1.0×10-6 g mL-1 for ctDNA, 1.0×10-8-1.0×10-6 g mL-1 for yRNA,and their detection limits(S/N = 3) are 8.0ng mL-1, 10.5ng mL-1 and 5.8ng mL-1,respectively.This method is used for determining the concentration of DNA in actual sample with satisfactory results.The reasons for the fluorescence enhancement of the system of AgNPs-CU-CTAB-fsDNA may be that an optimum hydrophobic environment with low polarity and large microviscosity for CU is provided by AgNPs-CTAB- fsDNA system;Because of the synergistic effect of CTAB and fsDNA,an optimum distance between CU and the surface of the AgNPs is formed,making the energy transfer from AgNPs to the chromophore of CU.In the five section,from the research,we find that when AgNPs is added to berberine (BER) solution,the intrinsic fluorescence of berberine is not obvious change,however,the fluorescence intensity of AgNPs-BER is greatly enhanced when fsDNA or ctDNA or yRNA are added to the system.Based on this,a new fluorimetric method for the determination of nucleic acids is proposed.Under optimum conditions,the enhanced fluorescence intensity is proportion to the concentration of nucleic acids in the range of 4.0×10-8-6.0×10-6 g mL-1 for fsDNA,4.0×10-8- 1.0×10-5g mL-1 for ctDNA and 1.0×10-8-4.0×10-6g mL-1 for yRNA, their detection limits(S/N = 3) are 2.3×10-8 g mL-1,2.2×10-8 and 7.9×10-9 g mL-1, respectively.The interaction mechanism of the system is studied using fluorescence, Resonance light scattering(RLS) and transmission electron microscope(TEM) technology. The chief characteristics of this thesis are as follows:1.It is found that nucleic acids can further enhance the RLS intensity of AgNPs-Al(Ⅲ) system and provide a stable,sensitive and improvement against foreign substances RLS method for the determination of nucleic acids.2.It is found that nucleic acids can obviously quench the RLS intensity of AgNPs-EBT system,Based on this,a new method for the determination of nucleic acids is proposed in this paper.This method is simple,stable and quick.Moreover,experiment indicates that the quenching extent is different when different nucleic acids are added to AgNPs-EBT system.And the phenomenon is also studied.3.It is found that AgNPs can further enhance the fluorescence intensity of CU-CTAB-nucleic acids system and provide a simple and sensitive fluorimetric method for the determination of nucleic acids.Experiments indicate that the new system has better stability and stable against fluorescence photobleaching property when AgNPs are added to the system of CU-CTAB-nucleic acid.The interaction mechanism of the system is also studied.4.It is found that nucleic acids can obviously enhance the fluorescence intensity of BER-AgNPs system,this system has been applied in the determination of DNA in actual samples and the result is satisfactory.Compared with other fluorimetric method,this method is simple,quick and it has a larger range.
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