AVS 49th International Symposium
    Biomaterials Tuesday Sessions
       Session BI+SS-TuA

Paper BI+SS-TuA9
Characterization of DNA on Gold: A Quantitative Surface Science Approach

Tuesday, November 5, 2002, 4:40 pm, Room C-201

Session: Molecular Recognition Surfaces
Presenter: D.Y. Petrovykh, University of Maryland - College Park / NRL
Authors: D.Y. Petrovykh, University of Maryland - College Park / NRL
H. Kimura-Suda, National Institute of Standards and Technology
M.J. Tarlov, National Institute of Standards and Technology
L.J. Whitman, Naval Research Laboratory
Correspondent: Click to Email
Covalent attachment of thiolated DNA onto gold surfaces is one of the most common methods for immobilizing aqueous DNA onto solid substrates. The formation of the DNA film in this case is thought to closely resemble that of alkanethiol self-assembled monolayers (SAMs). DNA films in modern applications, e.g. DNA microarrays, are < 10 nm thick with submonolayer surface coverage, which means that the traditional surface characterization techniques can be employed to complement biochemical analysis. We are applying XPS, FTIR, and ellipsometry to systematically quantify the chemical structure and coverage of self-assembled single-stranded DNA (ssDNA) films. Thymine (T) has the simplest structure of the four nucleotide bases: a single ring with two N atoms. Moreover, the environment of the two N atoms is so similar that the resulting XPS peak is consistent with a single N1s state in a polymer-like material. Backbone P atoms produce a base-independent single P2p peak. N and P are not subject to significant contamination, so the peak intensities can be used to estimate the coverage of immobilized DNA. N1s chemical shifts together with the base-dependent N/P ratio can confirm the presence of specific polynucleotides on the surface. The coverage determined by XPS is linearly correlated with base-specific IR features and agrees with absolute values obtained from radiolabeling measurements. We will also discuss how the XPS and IR spectra of dT-polynucleotide films can provide information about other basic properties of ssDNA films, such as uniformity and orientation, as well as issues of damage, degradation and contamination.