Single-molecule spectroscopy goes beyond ensemble-averaged information to uncover asynchronous and heterogeneous behavior. We use single-molecule methods to investigate samples ranging from biological receptors to artificial light harvesting systems.
Schematic representation of SM2P measurement
Single-molecule pump-probe (SM2P) spectroscopy. We have combined ultrafast spectroscopy with single-molecule spectroscopy to probe energy transfer at the single particle level. By incorporating a two-pulse pump-probe like excitation, we measure fluorescence intensity, which provides single-molecule sensitivity, as a function of the delay between pulses, which provides femtosecond temporal resolution. SM2P enables measurements of heterogeneity in the ultrafast dynamics for a range of molecular and material systems.
2D fluorescence lifetime correlation (2DFLC) spectroscopy. We have also developed correlation-based analyses of single-molecule data that enable microsecond temporal resolution and resolution of parallel dynamics. By applying this method to light-harvesting complexes, we can identify local protein motions that control quenching of excess sunlight, which is a photoprotective effect. Our analytical approach enables a structure-based understanding of how conformation influences photophysics in light-harvesting complexes.
Example smFRET trace with the donor fluorescence marked in red and acceptor fluorescence in green.
Single-molecule Förster resonance energy transfer (smFRET). We use smFRET to measure nanoscale distances, revealing important structural dynamics of transmembrane receptor proteins. In this method, we measure the efficiency of energy transfer between two conjugated dyes, which depends on the distance between them. These distances report on protein conformations and change with protein dynamics.