Application Of Nanopore Sensor In Biomolecular Detection

Nanopore is a single molecule analysis method developed in the 20 th century,which has the advantages of fast,low cost and without any labeling.The nanopore analysis method can obtain the characteristic information such as composition,conformations,sizes,and charges of the analytes at the single molecule level.In this study,?-hemolysin nanopores were used as analysis tools to investigate the effects of changing oligonucleotide sequences on the formation and stability of i-motif structure,which provided new insight for DNA secondary structure analysis at single-molecule level.In the second part,based on aptamer and target specific recognition,a simple and rapid new method for ampicillin detection without any labeling was developed.This paper mainly focuses on the following two aspects:1.Single molecule investigation of i-motif structure based on ?-hemolysin nanoporei-Motifs are DNA secondary structures present in cytosine-rich sequences.These structures are formed in regulatory regions of the human genome and play key regulatory roles.In this study,we analyzed the effect of changing DNA sequence on imotif structures formation and stability by using ?-hemolysin self-assembly to form nanopore.The results suggested that the cytosine tract of three nucleobases is a tipping point for stabilization of the i-motif structure.The i-motif structure becomes more and more stable with the number of cytosines in cytosine tract.Changing the loop sequence and length in the sequences did not affect the formation of the i-motif structure but changed its stability.Meanwhile,the application of all-atom molecular dynamics simulations revealed the structural morphology of all sequences.We further postulated a folding rule for i-motif structure formation,suggesting that thousands of sequences in human genome might fold into i-motif structures by using bioinformatics methods,among which 8.76% located in the promoter region.The results indicating that these structures might play important regulatory roles,which lay a foundation for future studies exploring the biological roles of i-motifs.2.Detection of ampicillin based on ?-hemolysin nanoporeBased on the specific recognition of aptamer and target,a highly specific DNA-based probe was designed.The probe bound to ampicillin to form DNA1-AMP complexes,which interacted with the nanopore to produce characteristic current signals.The frequency of currents events with concentration of ampicillin has good linear relationship,which realized the rapid and sensitive detection of ampicillin.The method was applied to the analysis of antibiotics in complex water samples that showed high selectivity.