Special Colloquium, February 12, 2004

Quantitative Imaging Strategies for Studying Intermolecular and Intracellular Dynamics

Loling Song, Ph.D
Post Doctoral Associate

Cornell University, Department of Physics

A large number of biological applications utilize fluorescence microscopy to image, either statically or dynamically, what cannot be seen directly by ordinary light microscopy. However, the potential of fluorescence microscopy extends far beyond the generation of high-resolution images. A variety of photophysical parameters can be analyzed, yielding a wealth of quantitative information about the immediate molecular environment of a fluorescently labeled macromolecule, its interaction with other molecules, or conformational changes; all with nanometer resolution.

My research has been primarily concerned with these photophysical parameters. My talk will concentrate on two areas. First, I will describe methods that quantify fluorescence resonance energy transfer (FRET), and discuss how these methods are used in studies of conformational changes and intermolecular interactions. A special focus will be given to my research on the use of a photochromic molecule as a light-driven molecular switch to modulate the FRET process. This unique strategy has provided, for the first time, the possibility of observing FRET in a repeated, light-modulated, and non-photodestructive manner. Secondly, I will discuss my ongoing research combining the unique capabilities of two-photon excitation microscopy and microfluidic devices to study the functional roles of signaling molecules important in chemotaxis of Dictyostelium discoideum. The advantage of the microfluidic channels is the ability to generate temporally and spatially well-defined chemical gradients. The latest biological experiments have provided the experimental proof that chemical gradients in such a microfluidic device can indeed elicit a chemotactic response from the cells. Well-defined chemical gradients in micro-channels provide the opportunity to characterize how GFP-tagged PH domain signaling proteins re-distribute inside the living cells as a response to extracellular cAMP and thus deduce their functional roles in chemotaxis.

9:00 a.m., Smith Laboratory, Room 1094

Refreshments served in Smith 1094 at 8:30 a.m.