AVS 45th International Symposium
    Biomaterial Interfaces Group Tuesday Sessions
       Session BI-TuM

Paper BI-TuM9
Structure of Single- and Double-Stranded DNA Monolayers on Gold from Neutron Reflectivity

Tuesday, November 3, 1998, 11:00 am, Room 326

Session: Biosensor-Biology Interface
Presenter: M.J. Tarlov, National Institute of Standards and Technology
Authors: R. Levicky, National Institute of Standards and Technology
T.M. Herne, National Institute of Standards and Technology
M.J. Tarlov, National Institute of Standards and Technology
S.K. Satija, National Institute of Standards and Technology
Correspondent: Click to Email
Neutron reflectivity was used to determine the concentration profiles of oligomeric DNA monolayers on gold under conditions of high salt (1M NaCl). These monolayers are of interest as model DNA probe systems used in diagnostic devices. To facilitate its attachment, the DNA was functionalized at the 5' end with a thiol group connected to the oligonucleotide by a hexamethylene linker. Concentration profiles determined from neutron reflectivity indicate that adsorbed layers of single-stranded DNA (HS-ssDNA) on bare gold are compact, suggesting the presence of multiple contacts between a DNA strand and the surface. After treatment with mercaptohexanol, a short alkanethiol with a terminal hydroxy group, the DNA "stands-up" and extends farther into the solvent phase. These changes are consistent with the DNA remaining attached through its thiol endgroup while contacts between DNA backbones and the surface are limited by the formation of a mercaptohexanol monolayer. The end-tethered HS-ssDNA layer readily hybridizes to its complementary sequence, resulting in DNA helices with a preferred orientation toward the substrate normal.