AVS 50th International Symposium
    Applied Surface Science Tuesday Sessions
       Session AS+BI-TuA

Paper AS+BI-TuA8
Spectroscopic Quantification of Covalently Immobilized Oligonucleotides

Tuesday, November 4, 2003, 4:20 pm, Room 324/325

Session: Biomaterials Characterization
Presenter: A.V. Saprigin, Naval Research Laboratory
Authors: A.V. Saprigin, Naval Research Laboratory
C.W. Thomas, Naval Research Laboratory
C.H. Patterson, Naval Research Laboratory
M.S. Spector, Naval Research Laboratory
Correspondent: Click to Email
Quantitative determination of surface coverage, film thickness, and molecular orientation of DNA oligomers covalently attached to aminosilane monolayers has been obtained using complementary infrared and photoelectron studies. Spectral variations between the different nucleic acids are observed in surface immobilized oligomers for the first time. Carbodiimide condensation was used to covalently attach phosphorylated oligonucleotides to silanized aluminum substrates. Fourier-transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to characterize the surfaces after each modification step. Infrared reflection-absorption spectroscopy of covalently bound DNA provides orientational information. Surface density and layer thickness are extracted from XPS data. The surface density of immobilized DNA, 2-3×10^13 molecules/cm^2, was found to depend on base composition. Comparison of antisymmetric to symmetric phosphate stretching band intensities in reflection-absorption spectra of immobilized DNA and transmission FTIR spectra of DNA in KBr pellet indicates that the sugar-phosphate backbone is predominantly oriented with the sugar-phosphate backbone lying parallel to the surface, in agreement with the 10-20 Å DNA film thickness derived from XPS intensities.