Web Release Date: August 19,
A Multistep Chemical Modification Procedure To Create DNA Arrays on Gold Surfaces for the Study of Protein-DNA Interactions with Surface Plasmon Resonance Imaging
Contribution from the Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706-1396
Received May 13, 1999
Abstract:
A multistep surface modification procedure for the creation of DNA arrays on chemically modified
gold surfaces that can be used in surface plasmon resonance (SPR) imaging studies of protein-DNA interactions
is demonstrated. The multistep procedure is required to create an array of spots that are surrounded first by a
hydrophobic background which allows for the pinning of aqueous DNA solutions onto individual array elements
and then to replace that hydrophobic background with one that resists the nonspecific adsorption of proteins
during in situ SPR imaging measurements. An amine-terminated alkanethiol monolayer is employed as the
base layer, and Fmoc and PEG modifiers are used to create the sequentially hydrophobic and protein adsorption-resistant surfaces, respectively. Specifically, the chemical modification steps are the following: (1) the adsorption
and self-assembly of an 11-mercaptoundecylamine (MUAM) monolayer on an evaporated gold thin film, (2)
the reaction of the MUAM monolayer with an Fmoc protecting group to create a hydrophobic surface, (3) the
photopatterned removal of the alkanethiol followed by (4) the readsorption of MUAM to create an array of
MUAM squares (750 × 750 
m) surrounded by a hydrophobic MUAM-Fmoc background that can pin drops
of aqueous solution, (5) the attachment of oligonucleotide sequences onto the MUAM squares by the reaction
of the amine-terminated surface with the heterobifunctional cross linker SSMCC followed by a coupling reaction
to a small volume (0.1 L) of thiol-modified DNA, and (6) the removal of the Fmoc protecting group followed
by (7) a pegylation reaction of the MUAM with PEG-NHS to create a protein adsorption-resistant background.
A combination of polarization-modulation FTIR spectroscopy, contact angle, and scanning angle SPR
measurements is used to characterize the surface modification procedure. An SPR imaging measurement of
the adsorption of single-stranded DNA binding protein (SSB) onto an oligonucleotide array created by this
procedure is used to demonstrate the utility of these surfaces.
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