Research On The Model Of Several DNA Logic Gates

Molecular devices are micro-systems that utilize the intrinsic diversity of molecules to perform computational functions at the molecular level.As the most representative molec-ular system in molecular devices,molecular logic gate has made great progress in the past few decades.At present,molecular logic gate is a very active research area and is expected to solve the bottleneck of the development of modern electronic computers.The speci-al molecular structure and diversified functions of DNA have naturally become the application materials of molecular logic gate.In this thesis dissertation,we applied Watson-Crick base pairing principle and used G-quadruplexes to enhance the fluorescence intensity of NMM.We constructed the DNA logic gate model by means of DNA strand displacement and fluorescent labeling.The main research contents are as follows:1)Using circular DNA as the basic unit,we constructed a one-bit binary half-adder calculation model.In this calculation model,the two single-stranded DNAs modified with the fluorescent molecule FAM and the quenching molecule Dabcyl are complementarily paired with the circular DNA,respectively,and fluorescence resonance energy transfer occurs between FAM and Dabcyl due to the characteristics of the circular DNA.As a result,the fluores-cence of FAM quenched.First,two complementary guanine-rich DNA single strands are designed to serve as two input signals for the half adder,and then DNA strand replacement technology is used to release the single-stranded DNA chain of modified FAM or Dabcyl on the circular DNA and enriched the G-quadruplex structure formed by the guanine fragment,the final output signal detected the relative change in the fluorescence intensity of the FAM and NMM,thus achieving the half-adder calculation.2)Using complementary double-stranded DNA as the basic unit,we constructed a one-bit binary half-substracter calculation model.In this calculation model,one of the double-stranded DNAs as a basic unit not only modified the annihilation molecule Dabcyl but also was designed to contain a guanine-rich fragment that can form a G-quadruplex,and the other is a modified fluorescent molecule FAM.Complementary pairing of the basic units on the one hand causes FAM to interact with Dabcyl to quench fluorescence and on the other hand to disrupt the formation of G-quadruplexes.First,design two simple complementary pairs of DNA single-strands as the two input signals of the half-subtractor device,then destroy the composition of the basic unit through DNA strand displacement,and finally use the relative change in the fluorescence intensity of FAM and NMM as the output signal,and then complete half-subtractor calculations.3)Using single-stranded DNA/graphene oxide as the basic unit,we constructed a one-bit binary half adder-half subtracter computation model.In this calculation model,we use graphene oxide with a special structure for its excellent fluorescence quenching characteristics and the property of adsorbing single-stranded DNA to release double-stranded DNA,combining single-stranded DNA which is modified by the fluorescent molecule FAM and the quenching molecule Dabcyl to form the basic unit.First,we design two special complementary DNA single strands as input signals.One of the input strands modifies the fluorescent molecule HEX and the other is rich in guanine.Both DNA single strands as input signals can be complemented with graphene oxide-adsorbed single-stranded DNA to form a double-stranded structure to release it from the graphene oxide surface.We then designed the third single strand of DNA rich in guanine segments to regulate whether the model performs a half-adder function or a half-subtractor function.Finally,we use the combination of FAM and HEX fluorescence signals as the output signal of the half-adder and the combination of FAM and NMM fluorescence signals as the output signal of the half-reduction device.This model can achieve both half-adder calculation and half-subtraction calculation.