| Deoxyribonucleic acid(DNA)is the carrier of life genetic information,and plays an important role in many biological systems and activities.DNA has a unique double helix structure,and its bases have a unique ionization potential.In addition,DNA is one of the few nanomaterials that can be reproducibly produced with high precision.Therefore,the electrical properties of DNA sequences with specific base composition have attracted widespread attention.In addition,electrical methods offer potential possibilities for sequencing technologies based on individual DNA molecules.Many studies have found that electrical methods for disease detection based on the current flowing through DNA are feasible.However,the modeling of current flowing in DNA molecules is very complicated.That is because the model is based on atomic-level contacts between DNA molecules and metals and cannot be established in a reproducible way,however,the conductivity of DNA is easily affected by the constantly changing external environment.The environment is affected;the DNA molecule itself is soft.In view of the problems in modeling the electrical properties of DNA molecules,this thesis proposes a decoherent transport model and uses this model to study the effect of cytosine hydroxymethylation on the charge transport of DNA,as well as the four common types of mutations.The changes in the electrical properties of breast cancer No.1 gene are studied.The main research contents are as follows:1.Based on density functional theory,Green's function formula,Landauer-Büttiker theory and Büttiker phenomenological probes,a quantum chemical decoherent transport model is established.This model takes into account the coupling effect of the two electrodes and the external environment on the DNA molecule,so that the theoretical calculation simulates the real experimental environment to a greater extent.2.The research for studying the changes of small internal modifications of DNA bases-the effect of cytosine hydroxymethylation on its charge transmission properties indicates that the conductance of the hydroxymethylated DNA sequence is about 20%lower than that of the methylated sequence,which is only 50%of the original sequence.In addition,the charge transmission properties of the hydroxymethylated DNA sequence under different sequence lengths,different environmental temperatures,and different molecular configurations are studied.It is found that the hydroxymethylated DNA sequence has properties of length-dependent,temperature-dependent,and molecular configuration-dependent.3.Study the influence of DNA structural variation-duplication,single nucleotide variation,deletion,indel on the electrical properties of breast cancer No.1 gene.The study found that for replication mutations and single nucleotide mutations,the charge transfer rate after mutation decreased from 2.48×10-5 and 1.38×10-3 to 6.02×10-6 and5.95×10-6,respectively.For deletion mutations and indel mutations,the charge transfer rate after mutation increased from 5.01×10-6 and 7.49×10-6 to 1.61×10-5 and 2.93×10-4,respectively.In addition,their electrical conductivity and density of states have the same changing trend as the charge transfer rate. |
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