Plasmonic hotspots for single-molecule biophysics

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Supported by the DFG, the Acuna and Tinnefeld labs developed and characterized single-molecule fluorescence from optical antennas. These optical antennas are comprised of two noble metal nanoparticles with a defined gap that are self-assembled using DNA origami nanostructures as scaffold. In addition to the structural organization of nanoparticles, the DNA origami enables placing specific molecular moieties in the antenna’s hotspot. After clarifying many spectroscopic characteristics of fluorescent dyes placed in the optical antennas including fluorescence enhancement up to 5000 fold and first proofs of biocompatibility, the Tinnefeld lab now aims at exploring DNA origami nanoantennas as novel detection volume in single-molecule biophysics. The higher achievable count rates and increased photostability of the dye molecules in the hotspot will be used to study fast biomolecular processes with increased time resolution. DNA origami nanoantennas will be optimized for reduced steric hindrance and single-molecule FRET from the red spectral region to the near infrared will be established adapted to the spectral profile of the nanoantennas. Biomolecular systems of interest will be placed in the antenna’s hotspot and fast conformational changes of proteins will be studied and transition path times of binding induced protein folding as well as of nucleic acid hairpins will be revealed. Above that, a DNA strand displacement tug-of-war will be visualized at single-nucleotide resolution hoping to reveal subtle sequence dependent kinetic variations such as those occurring in epigenetic nucleotide modifications. In summary, we aim at establishing DNA origami antennas as new detection volume of single-molecule research opening a novel window into fast biomolecular processes.