Fluorescence imaging is used to probe the molecular and morphological changes in tissue upon cancerous transformation. Spectrally and time-resolved fluorescence spectroscopy generates direct information about the heterogeneous microenvironments in the stationary phase and the molecular distribution in these environments. The influences of high voltage, stationary phase, pH, and solvent composition on molecular distribution are investigated. We are currently studying the folding mechanism with fluorescence spectroscopy of intrinsic tryptophan residues and extrinsic probes. The changes in the protein structure upon unfolding are revealed by solvent exposure of the probe molecules, and the distance between a donor-acceptor pair through fluorescence resonance energy transfer.
Conformational fluctuation is probed by fluorescence lifetime distributions.
Time-resolved fluorescence emission spectra reveal the reorientation kinetics of protein structure. We are pursuing methods of single molecule spectroscopy to monitor the conformational fluctuation and to dissect folding pathways. Structures of single protein molecules at different folding stages will be probed spectroscopically.