Our research involves the application of single-molecule fluorescence and Raman spectroscopy to study molecular dynamics. We are interested in a diverse set of problems, from protein folding to charge transfer at metal surfaces.
Here are some examples of what we do (click Research above to see more)
The ability of red blood cells to meander through small blood vessels depends on their sub-membrane skeleton. We develop optical methods that allow us to study the dynamics of the spectrin filaments comprising this skeleton.
GroEL is a biomolecular machine which assists other proteins in their folding. It undergoes transitions between multiple conformations. Single-molecule fluorescence spectroscopy facilitates studying the dynamics of this machine.
The way membrane proteins insert into lipid membranes, move within them and interact with each other is still poorly understood. By tracking the motion of individual peptide molecules within membranes we are able to shed new light on their reactions and interactions.
Vesicle encapsulation facilitates studies of individual molecules and their dynamics. However, vesicles are not permeable to many different molecules which one might want to add, e.g. substrates for an enzyme molecule. We are developing methods to overcome the permeability barrier by including various porous proteins in the vesicular membranes.
The interaction of nanometer-scale metal particles with light leads to interesting new phenomena, due to surface-plasmon excitations. This is the realm of plasmonics. We use Raman scattering from molecules situated within metal clusters to study their unusual properties. For example, we found that nanoparticle trimers can rotate the polarization of emitted light.
The folding of large proteins may involve complex energy landscapes and multiple steps. Single-molecule spectroscopy is particularly well-poised to study such complex dynamics. Using FRET, we measure time-dependent trajectories of folding and unfolding of individual molecules trapped within large lipid vesicles. Statistical analysis enables characterization of the folding reaction, the number of intermediates and their inter-conversion rates.