The Study Of Charge Transport Properties Of Different DNA Molecule Configurations

Desoxyribo-Nucleic-Acid (DNA) is a complicated biomolecule, which encodes the fundamental nature of living species. The DNA is made up of two pieces of mucleoside chains, which are made from base pairs to a kind of helix structure. Every chain always connects with the pyridine in the other chain by the hydrogen bond. It's more important that Adenine (A) must connect with Thymine (T) and Guanine (G) must connect with Cytosine (C).The study of DNA's conductivity has become the focus of biology, physics, chemistry and their cross-discipline. The progress of the electronic industry in the past few decades was based on the delivery of smaller and smaller devices, The trend give birth to the molecular electronics. DNA becomes a candidate for molecular devices as its two of the most unique and appealing properties:double-strand recognition and self-assembly. In addition, it is important to study the structure of electrons in DNA molecule and the transfer of electric charge through its structure, for discover the regularity of vital movement, the damnification and treatment of gene, the transfer of information and so on. Electric conductivity of DNA has been investigated widely both in experiment and theoretic calculation, but the results and the mechanism of charge transport in DNA molecular is are inconsistent and even contradictory.controversial. The experiments of charge transport in DNA molecular have shown that DNA molecular may be conductor, semiconductor or insulator. So how to interpret these controversial experiment phenomena and ravel the mechanism of charge transport in DNA molecular has important significance for using DNA as a molecular device and understanding of DNA mutation and repairing of the damaged DNA.DNA is a large soft biomolecule. The charge transport in DNA is affected by many factors, which the effect of molecular structure of the DNA on molecule charge transport properties is the focus of this thesis. Three kinds of biological activity of the double helix structure DNA are A-DNA, B-DNA, Z-DNA, of which the most common DNA is the B-DNA. Experimental results shows that in a different environment and the effect of people the B-DNA have the trends to A or Z-DNA. In order to reflect the effect of molecular structure of the DNA for charge transport properties, we describe the DNA molecule using three-dimensional tight-binding model, and computed different molecular structure of DNA impact on its transport properties by transfer matrix method. The primary content and results are given as follows:1. The effects of helix angle on transport properties of Poly(dG)-Poly (dC)DNA moleculeIn single degree of freedom three-dimensional tight-binding model calculate the effects of spiral angle on electrical conductivity of DNA molecules and found that:With the increase of helix angle, DNA molecular states have tended to spread, open voltage was changed and for the better conductivity.2. The effects of base pares and horizontal angle on transport properties of Poly(dG)-Poly (dC)DNA moleculeCalculated under different axial angle of the IV curve and the conductivity of molecules, the results showed that with increasing of the axial angel, DNA molecular conductivity increases first slowly and then decrease rapidly. Finally, we compared the A-DNA, B-DNA and Z-DNA in the transport properties, B-DNA conductivity is better than other configurations DNA, this consistent with the experimental and theoretical analysis.3. The effects of thermal structural fluctuations on different configuration Poly(dG)-Poly(dC)DNA moleculeIn the frame of three-dimensional tight binding model, effects of temperature on the charge transport properties of DNA molecule are studied through thermal fluctuations. Adopting a Gaussian distribution to simulate thermal structural fluctuations, we studied effects of thermal fluctuations on charge transport properties of different configurations Poly (dG)-Poly (dC) DNA. The results indicate that either configuration thermal fluctuations of the hydrogen bond length have effects on the charge transport of Poly (dG)-Poly (dC) DNA. Torsion angle on the molecular transport properties of thermal fluctuation had no significant effect, but DNA of different configurations for the influence of thermal fluctuations in torsion angle are not the same, Z-DNA thermal fluctuations of the smallest.