Events
SINGLE-MOLECULE FLUORESCENCE STUDIES OF PROTEIN FOLDING
00:00 11-04-2006
Fluorescence spectroscopy on the single-molecule level can provide a unique real-time view of the heterogeneous dynamics of fold- ing proteins. We have recently developed a method, based on trapping of single molecules within surface-tethered lipid vesicles, which all- owed us to obtain for the first time folding and unfolding trajectori- es of individual protein molecules. Fluorescence resonance energy transfer studies with two proteins exposed dissimilarities in the shape of their energy landscapes, and allowed us to observe large het- erogeneity of folding pathways. First steps towards characterization of the transition state ensembles of these molecules were also made. We also used single-molecule spectroscopy of freely-diffusing proteins to study their denatured states. In particular, FRET histograms were used to measure the size of the unfolded proteins as a function of a denaturation coordinate. The denatured proteins expanded significantly as their solvent ‘improved’, a well-known phenomenon in polymer physics. Indeed, using the theory of the globule-coil transition of polymers, we extracted from these measurements the solvation energe- tics of the denatured proteins, as well as their radius of gyration in the absence of denaturant, a somewhat elusive property.
