Computational studies investigating the effect of sequencing and environment on the conductance of DNA nanowires
- PDF / 506,121 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 79 Downloads / 281 Views
Computational studies investigating the effect of sequencing and environment on the conductance of DNA nanowires Gareth Jones1, Watheq Elias1,2 , M. Elliott1 and C. C. Matthai1 1 School of Physics and Astronomy Cardiff University, The Parade, Cardiff, UK CF24 3AA 2 Dept of Physics, Koya University, Erbil, Iraq. E-mail: [email protected]
ABSTRACT Understanding electron transfer in molecular systems is important, especially in the context of molecular electronics. With the desire to incorporate biological molecules in molecular electronic devices, there is a need to establish the relative importance of the various factors like the environment and the molecular structure (DNA sequence) on the electrical conduction. There has been much debate about mechanisms of electron transfer in biological molecules. We have conducted a systematic study of electron conduction across DNA molecular segments using the non-equilibrium Green function (NEGF) method. The Hamiltonian matrix elements were determined within the framework of the Extended Hückel Approximation. In considering (CG) base pair sequences, we find that the conductance decreases with segment length and that the substitution of (AT) base-pairs also reduces the conductance. When the DNA segments are in aqueous solution, the conductance is found to almost double in magnitude. INTRODUCTION Over twenty years ago, it was reported that it was possible to measure charge motion across a double helix DNA segment [1]. The charge transfers were found to occur over large distances (4nm) leading to the possibility of using DNA in nanodevices. However, many of the subsequent experimental results appeared to give seemingly contradictory results. It is now generally agreed that these discrepancies may be explained by the differences in the details of the DNA segments used in the experiment [2]. There is some consensus that the conduction in DNA does depend on the base sequence and the structure of the DNA (A or B type) as well as on the length of the segment. The first two dependences point to the importance of the electronic structure and correspondingly on the orbital overlap across the molecule. The length dependence of the conductance gives some clues as to the mechanism for charge transport. With much interest in exploiting the functionality of biomolecules in molecular electronics, the selfassembling and self-recognition properties of DNA lends itself to being an important molecule in this field. Molecular conduction may be viewed at many different levels of complexity. At its simplest, it is simply the tunnelling of carriers from one electrode to another across the molecule. The transport can be band-like or, in some instances, might be described by hopping. Most of the theoretical investigations to date have utilized a Landauer description of the tunnelling across the
molecule. These are effectively within the framework of the one electron picture and the transport occurs through the molecular orbitals on a single electronic potential energy surface. Within this descri
Data Loading...
