Dependence of DNA electronic structure on environmental and structural variations.

We present experimental and theoretical evidence that varying the local environment and physical structure of dried DNA has a direct impact on its electronic structure. By preparing samples of DNA in various solutions, it was possible to alter the type of ions present during the production of the DNA samples. These variations resulted in differences in the local chemical environment of the dried DNA molecules. X-ray absorption spectroscopy (XAS) and X-ray emission spectroscopy (XES) were used to probe the variations in the electronic structure of DNA samples. DFT calculations of a stack of 10 adenine (A)-thymine (T) nucleobase pairs show that slight structural variations in stacking height have a direct influence on the electronic structure and result in changes to the HOMO-LUMO gap. The effects of these differences in the local environment on the electronic structure are discussed and are related to the results of conductivity measurements of DNA.