Research On Molecular Devices Based On DNA Nanotechnology

DNA molecules can be assembled into predesigned shapes or patterns by hybridization of sequence complementation domains.The folding structure of DNA has high spatial addressing ability and can be used as operating platform or active ingredient in a large number of biotechnology applications.DNA is a truly programmable material and thus exploits various possibilities for the development of new biosensors and molecular devices^[1,2].Based on the above advantages of DNA,three kinds of molecular devices based on DNA nanotechnology have been fabricated in this paper.Related works and the research results is mainly carried out as follows:1.Research on p H-Dependence of Duplex-Triplex Interconversion and build dynamic pattern on DNA origami.We innovatively apply p H-Dependence of Duplex-Triplex Interconversion to the construction of dynamic structures and build molecular device that carrying biological information on the DNA origami platform.Select the appropriate directions and sites on the DNA origami to modify according to right-handed spiral rule and anti-parallel law of DNA double helix,design the sequences of staple stands due to the Watson-Crick base pairing principle,so that the short staple strands are bind to the long scaffold strand to form a double-stranded structure,generate rectangular DNA origami with an area of 100×70 nm² and different patterns on origami.When the p H value is 7.8,pattern 1 appears,and when the p H value is adjusted to 5.0,pattern 1 disappears and pattern0 shows up.In addition,the DNA origami pattern is dynamic and controllable because of the reversibility of Duplex-Triplex Interconversion controlled by p H values.2.Preparation and Characterization of Large-cavity 3D DNA Crystals.The conditions of DNA double-strand hybridization,formation of stable tensegrity triangle,DNA crystal culture conditions and characterization methods of DNA crystal were studied.The crystal formed by the 4T7 tensegrity triangle motif designed in this paper has an unprecedented huge cavity with a cell volume of 2409 nm³,twice larger than the largest lattice reported in the past,space group is R3 and the cell parameters are a=b=c=135.8（?）,α=β=γ=98.6°.3.Research on 4T28（4-turn symmetric tensegrity triangle with 28 inter-junction nucleotide pairs）tensegrity triangle.We introduced Triplex Forming Oligonucleotides（TFOs）into tensegrity triangle and studied the crystallization conditions of four kinds of motifs of 4T28 symmetric tensegrity triangle,4T28 symmetric tensegrity triangle with TFOs,asymmetric unit system contained two different 4T28 tensegrity triangle molecules A and B（asymmetric AB system）,and asymmetric AB system with TFOs.Crystals with these four different motifs were successfully prepared,proved the feasibility of controlling the crystal color by combining TFOS modified with dyes into the crystal.finally obtain the diffraction data of the asymmetric AB system,space group is R3 and cell parameters are a=141.986（?）,b=142.924（?）,c=145.173（?）,α=105.712°,β=106.051°,γ=106.155°.4.An enzyme-free fluorescence biosensor for micro RNA detection based on a combined cascade amplification by catalytic hairpin assembly reaction and entropy-driven amplification.We proposed an enzyme-free fluorescence biosensor combined cascade amplification by catalytic hairpin assembly reaction and entropy-driven amplification for mi RNA-21 detection.The fluorescence response has a linear relationship with the logarithmic of mi RNA-21 concentration from 50f M to 1p M.And the novel biosensor provided a LOD as low as 1.3f M,which is about 100-fold lower than that of CHA,exhibit good sensitivity and selectivity and hold great promising in clinical application.