Research On Logical Computing Model Based On DNA Strand Replacement Technology

DNA not only stores the huge genetic information of life,but also serves as a natural nano-biomaterial and component.And so far,scientists have skillfully used DNA molecules to complete the design and construction of various functional structures and devices.Combining DNA as a nanomaterial with other nanomaterials will definitely bring unprecedented impetus to the development of life sciences,materials science,and environmental science.In this paper,we follow the principle of Watson-Crick base pairing,by means of the characteristics of new nanomaterials such as deoxyribozymes and G-quadruplex,and through the combination of DNA strand replacement technology,fluorescent labeling technology and other DNA nanotechnology,on this basis,the construction of the logical calculation model of DNA molecules is completed.The main research work done in this paper includes the following two aspects:(1)We first proposed a simple DNA probe logic calculation model that can be implemented by DNA probe technology based on strand displacement reactions mediated by streptavidin and DNAzyme.In the first process,a fluorescence quenching device(Al)based on streptavidin-mediated short-range strand migration was constructed.Here,we mainly use the proximity effect triggered DNA strand displacement technology to manipulate the small protein-streptavidin-mediated AND logic operation.Among them,streptavidin can be strongly bound to biotin with high specificity due to the very strong high affinity between them.This will provide guarantee for the implementation of this strategy,and it contributes to the sensitivity and efficiency of this model.Then a signal recovery device(A2)triggered by DNAzyme cleavage is proposed.In this process,only when two split DNA ribozyme fragments are present at the same time,they can have the catalytic activity under the auxiliary action of metal ions,thereby activating the catalytic cleavage reaction,and resulting in the separation of short chains containing quenching groups,along with the enhancement of the fluorescent signal.In order to effectively improve the complexity and practicability of the model,we constructed a cascade logic calculation model by combining streptavidin with DNAzyme to sensitively control the intensity of the signal.At the same time,an intelligent DNA molecular switch for realizing cascaded fluorescence quenching and recovery process was established.Finally,the feasibility of the proposed model was verified by using polyacrylamide gel electrophoresis and fluorescence detection.The model built in the chapter mainly utilizes binding-induced branching transfer of DNA,and introduces streptavidin,deoxyribozyme and other materials,which provides more choices for the construction of DNA logical computing model.(2)In the second study,we have successfully developed a new strategy that integrates DNA logic into a simple and versatile platform for the implementation of advanced arithmetic logic functions including half adders(HA)and half reducers(HS).Among them,the general platform constructed in this strategy is mainly composed of DNAzyme subunit and molecular beacon MB.Based on this general model,the different logic computing elements can be constructed only by changing different input chains.Since the main operational objects of the two logic components,the half adder and the half subtractor,are two one-bit binary numbers,and the output yields two results,that is,the model needs to design two inputs and two outputs.Therefore,in this strategy,we use molecular beacons MB and G-quadruplex as signal reporters.At the same time,the FAM fluorescence signal detection and the color change of the TMB/H2O2 solution(which can be clearly obtained by the naked eye)are separately detected.And as the signal result corresponding to the two logic outputs.The functional requirements of the logical computing model being built are finally met.What makes this logic system unique is that input-mediated assembly and disassembly of the calculation circuit,modularity of the door design,and the visible output that can be obtained by observing the color change of the solution.These provides a new idea for the construction of subsequent complex logic circuits.