Research Overview

Our group develops and applies ultrahigh-resolution, ultrahigh-sensitivity fluorescence imaging and spectroscopy tools to solving outstanding problems in biology.

The ability to watch one molecule at a time helps us obtain unique information on distribution functions of relevant observables, resolve subpopulations in heterogeneous samples, and record asynchronous time trajectories of observables that would otherwise be hidden. Single molecule techniques resolve important phenomena that are otherwise "averaged out" by ensemble measurements.

Of particular relevance is our application of single molecule techniques to studying conformational changes of macromolecules. Several of our techniques make use of small, inert labels which are attached to molecules of interest to detect changes in their conformations. For example, dynamic distance changes between two sites on a macromolecule (or between two different molecules) can be measured via single-pair fluorescence resonance energy transfer (spFRET) by following spectral changes in the emission of a single donor-acceptor pair. Orientational changes can be detected via single-molecule fluorescence polarization anisotropy (smFPA) by following changes in the dipole orientation of a rigidly-attached or tethered probe. Having spent years developing and improving these tools, we now actively use them to study protein folding and transcription on the single-molecule level. In addition, we study the folding reaction energy landscape, pathways, conformational distributions and folding intermediates.