Study Of Electronic Structure And Transport Properties Of Dna Molecules

In recent years, the nature of DNA-mediated charge migration has triggered extensive attention among physics, chemistry and biology communities, and has been the subject of intense debate since the original discussion by Eley and Spivey in 1962 that DNA might be conductors, owing to their potential applications in molecular electronic engineering and understanding the damage recognition process and protein binding. Nevertheless, direct charge transport measurements of DNA do not yet yield a consensus that they might be conductors, semiconductors, or insulators. These controversial results need to be explained reasonably and lead to simulate DNA from a theoretical perspective, that will further our understanding of the conduction mechanism and dynamical feature of DNA. These, however, motivate us to study the intrinsic feature of DNA.The chemical composition and geometrical structure are presented in chapter one, while the advance and approaches in DNA are introduced in chapter two. Since DNA's structure and sequence are intricate, a simple but effective tight-binding model is constructed. In this model, DNA are considered as one-dimensional binary disordered system, where a new method for creating the sequence is proposed. With the help of Dean's negative eigenvalue theory and Wu's infinite order perturbation method, the density of state, localization length and electron wave-function are calculated and compared by considering different DNA sequences and temperature. And our results indicate that: (1) The electron wave-function of long DNA molecules is localized and electrons can only hop among these localization state. (2) The conducting behaviors depend on DNA's sequence and may range from conductors, semiconductors to insulators. (3) The off-diagonal disorder effect will be more obvious with increasing temperature due to stronger thermal structure fluctuations. (4) There exists a crossover of temperature. Below the crossover, the localization length dramatically decreases with increasing temperature and electron states will be further localized, whereas above it, the localization length tends toward temperature-independence. (5) An original formula is put forward to describe the relationship between localization length and temperature, which is in good agreement with the theoretical results. (6) With increasing temperature, the effect of phonon becomes more obvious and will be favorable for conveying charge carriers through DNA chains. Meanwhile, the conductivity of DNA increases with temperature and the conduction mechanism may be the variable range hopping.On the other hand, the transmission coefficient and localization length are computed by considering the sequence length, base pair's percentage and off-diagonal correlation using the transfer matrix method. And the results show that: (1) The resonant phenomenon will be gradually disappeared with increasing length for random DNA chains. (2) The transmission ability of DNA will firstly increase with P and then decrease with it. (3) Since the golden correlation and local correlation can considerably enhance the transmission ability of DNA, we conclude that these correlations are stronger than others. While for the Anderson model, the ability will dramatically decrease with increasing length.