Using DNA as Scaffolding to Better Understand Surface Plasmon Enhancement of FRET

Our lab is utilizing customizable DNA to better understand the surface plasmon enhancement of fluorescence. Currently, we are investigating the enhancement of Förster resonance energy transfer (FRET) with surface plasmons excited on gold nanogratings. FRET is the transfer of energy between a donor and acceptor fluorescent molecule. Enhancements to the FRET efficiency from surface plasmon excitations depend on the spacing of the fluorescent molecules relative to each other and the surface of the grating. We developed a protocol to attach the donor and acceptor molecules to the grating surface using single-stranded, 20 monomer oligonucleotides. One strand contained a six-carbon thiol group on the terminal end, and a complementary strand contained a fluorescent Cyanine group (Cy3). Once annealed, the double-stranded DNA molecule has a thiol group on one end and the Cy3 molecule on the other. This double-stranded DNA is then deposited dropwise onto the gold surface along with a mercaptohexanol (MCH) spacer molecule. The MCH ensures that the DNA orients itself normal to the surface. This protocol allows us to more accurately position fluorescent molecules in such a way that surface plasmon FRET enhancement can be better understood