Study On Spectroscopical Detection Methods Of DNA Concentration And Structure

DNA is the carrier of genetic information and has the function of storing,transmitting and expressing genetic information.Due to its important role in human life process,DNA has become a hot spot in life science.At the meantime,the detection of functional gene sequence is also vitally important in clinical diagnosis,gene therapy and disease prevention.Therefore,it is very important to develop novel analytical methods with high sensitivity,high specificity,and high accuracy for DNA concentration and structure detection.However,the current methods for DNA detection have some problems such as long assay time,complicated procedures,and difficulty in obtaining structural information.Thus,a simple,rapid,convenient and reliable DNA biosensing strategy has become the development goal of DNA detection.In this thesis,the quantitative and structural detections of DNA are realized by UV-visible absorption spectroscopy and surface-enhanced Raman scattering,respectively.Combined with nano technology and signal amplification strategy for target DNA detection in highly sensitive analysis,two novel methods of DNA detection are developed in the following sections:1.Enzymatically driven formation of palindromic DNA-Au nanoparticles for snowball assembly and colorimetric biosensingA strategy for enzymatically driven formation of palindromic DNA-Au nanoparticles(AuNPs)was designed via specific recycling recognition and release of target DNA to/from hairpin DNA functionalized AuNPs(DNA-AuNPs),which led to the snowball assembly of palindromic DNA-AuNPs at single temperature.The assembly was demonstrated with UV-vis spectra,TEM images,dynamic light scattering and PAGE analyses,and could be monitored by substantial red shift of the adsorption peak and the color change of DNA-AuNPs from red to pink and ultimately slight purple,leading to a convenient method for colorimetric detection of target DNA.By combining with AuNPs-catalyzed silver enhancement,sensitive and selective scanometric assay was further achieved.This strategy could be extended to a wide range of analytes by coupling with other strategies releasing tag DNA from a DNA duplex upon the recognition of target analyte for enzymatically driven formation and snowball assembly of palindromic DNA-nanoparticles.As a proof-of-concept,the extended methods for thrombin detection showed excellent biosensing performance,indicating universal applicability of the proposed strategy for colorimetric biosensing of both DNA and proteins.2.Probing structural differences of the same topological G-quadruplexes formed with the same DNA sequences by surface-enhanced Raman scatteringDiscriminating the subtle structural differences of G-quadruplexes with the same topology,which were formed with the same DNA sequences,is a challenging topic,especially in a simple and rapid way.Herein,surface-enhanced Raman scattering is firstly used to distinguish two same topological G-quadruplexes in the presence of sodium or potassium ion and explore the possible mechanism for cation-dependent effects,which is proved by previous atomic scale structures.