AVS 52nd International Symposium
    DNA Topical Conference Tuesday Sessions
       Session DN+BI-TuM

Paper DN+BI-TuM1
First-principles Calculations of DNA Core Level Energies

Tuesday, November 1, 2005, 8:20 am, Room 311

Session: DNA Surface Characterization
Presenter: J.M. Sullivan, Northwestern University and Naval Research Laboratory
Authors: J.M. Sullivan, Northwestern University and Naval Research Laboratory
D.Y. Petrovykh, University of Maryland and Naval Research Laboratory
G.C. Schatz, Northwestern University
L.J. Whitman, Naval Research Laboratory
Correspondent: Click to Email
X-ray photoelectron spectroscopy (XPS) is emerging as a powerful method for characterizing DNA on surfaces.@footnote 1@ The relative positions of core electron binding energies (CBEs) suggest likely binding geometries and strength of chemical bonds, and the peak areas provide a quantitative measure of the coverage. Although CBEs for simple molecules can often be readily assigned to specific adsorption sites and bonding configurations based on historical data, such interpretation for CBEs of DNA is not possible. As a start to developing a comprehensive ab initio understanding of DNA-surface interactions, we are using density functional theory to determine the geometric and electronic configuration of DNA nucleobases, nucleosides, and nucleotides in the generalized gradient approximation. We have initially focused on the nitrogen spectra because these are the easiest to interpret experimentally, arising solely from the nucleobases. Binding energies of core-electrons are evaluated in a variety of standard methodologies including spin-restricted and spin-unrestricted versions of Slater's and generalized transition state methodologies, and a @Delta@KS-type approach in which the CBE is determined directly by the difference between the total energy of the molecule with and without the core hole. We find the theoretical XPS spectra for isolated nucleic components are surprisingly similar to experimental spectra measured on DNA films, suggesting that-although the films are adsorbed on the surface-the underlying electronic structure of the nucleobases is "free-like". @FootnoteText@ @footnote 1@D. Y. Petrovykh, et al., J. Am. Chem. Soc. 125, 5219 (2003); D. Y. Petrovykh, et al., Langmuir 20, 429 (2004).