Marcia Levitus


Overview Nucleosome dynamics Photophysics   FCS-FRET

Research in the Levitus Group

My research interests involve the use of state-of-the-art techniques of Single Molecule Detection in solution to study conformational changes of biologically interesting macromolecules.

In contrast with the more conventional fluorescence techniques, where billions of molecules are sampled simultaneously, Single Molecule Techniques allow the observation of subpopulations and rare events that would otherwise be hidden in the measured average. More importantly, the observation of an individual molecule allows the study of dynamical aspects of conformational changes without the need to synchronize the entire sample.

A related technique, Fluorescence Correlation Spectroscopy, is based on the analysis of the fluctuations in the fluorescent signal of a small number of molecules. Correlation analysis of the fluorescence fluctuations yields kinetic information about the dynamical processes that cause the changes in the fluorescent signal.

I am also interested in studying the photochemical and photophysical properties of fluorescent dyes that are commonly used for single-molecule applications. Photophysical processes are a source of artifacts that have not been thoroughly explored in many cases. Photochemical reactions, such as isomerizations, produce results that can be interpreted as conformational changes of the macromolecule to which the fluorophore is attached. A careful characterization of the photophysical properties of these fluorophores is critical for correct interpretation of experimental results.