Richard Marsh and Dr. James P. Lewis, Department of Physics and Astronomy
In the world today there is an immense interest in the field of nanotechnology. One particularly unique aspect is that of molecular electronics. The ability to take one molecule and use it as a transistor has many applications. While the transistors on our current computers are in the order of micrometer, a molecular wire has the capability of taking transistors into the nanoscale region. Such a development would drastically increase computer speed, and make the next generation of computers more compact and more manageable. One possibility for this nano-wire is DNA. DNA has several electronic properties that could possibly render it into an excellent wire. Our goal is to better understand these properties and see if the idea of DNA as a molecular wire has merit.
In order to verify the electronic properties of DNA, a series of calculations are needed. The brilliance of this project lies in the means of obtaining the desired results. In order to obtain the needed calculations a large amount of time, energy, and computing power is required because we are dealing with many atoms. But through a series of approximations, these same calculations can be obtained in a much more reasonable time. The code to be used is called “FIREBALL”, which began as an improvement on the Sankey-Niklewski method. FIREBALL is distributed and developed by the Lewis group here at BYU. With the continuing increase in computational power and because of better theoretical techniques, FIREBALL now allows the performance of more accurate calculations in more complex systems. The need for this new method arises because when applying certain theoretical considerations to DNA charge-transfer experiments, one must also take into account the dynamics of the DNA structure.
Our previous efforts worked to unmask the electronic properties of dry DNA, with no present environment. However, this theoretical discovery does not translate directly into a real world situation. To make our studies more life like, we begin to study the effects of an environment on the electronic properties of DNA. We will use water as the solvent. Hence, our studies will focus on wet DNA.
We consider a 10-mer poly(A)-poly(T), a 10-mer poly(G)-poly(C), and a 9-mer poly(A)-poly(T)-poly(G)-poly(C) DNA strand for our dry DNA studies. Furthermore, we will study a 10-mer poly(A)-poly(T), and a 10-mer poly(G)-poly(C) in our study of wet DNA. These calculated systems contain over a thousand atoms and are the first ab initio calculation of wet DNA of this magnitude.
We observe 2 eV band gap for the A-T DNA strand, indication semiconducting properties. Our results indicate that the G-C DNA stand is conducting while the combination strand shows a and gap o approximately 1.35 eV. For all three cases the HOMO state is localized to one nitrogenous base. This data suggests that strand composition will have an effect of the electronic properties. Our initial studies of hydrated DNA seems to indicate that the addition of an aquatic environment does not significantly alter the electronic properties of DNA.