Novel optical techniques for cell biology

Tuesday, October 27, 2009 - 3:15pm - 4:30pm
Reiss 502
Daniel Axelrod, Professor Emeritus
Department of Physics, The University of Michigan

Although optical microscopy has been an invaluable tool in cell biology for many decades, recent modifications and advances have permitted exploration of some previously inaccessible cellular phenomena. One example is secretion from cells. Packages of specific chemicals (known as secretory granules) stored in the cell interior must migrate to the membrane at the cell surface, fuse with it upon triggering, dump their contents outside, and regenerate. These phenomena are all difficult to observe because the vast majority of granules do not get released, all of them are submicroscopic in size, they move around, and they are naturally clear and colorless. By inserting genes that make these granules fluorescent and then observing them with the evanescent field of total internal reflection fluorescence (TIRF), we can visualize individual granules. By additionally labeling the membrane with a fluorescent dye and combining TIRF with excitation and emission polarization optics, nanometer-scale granule tracking in three dimensions, and spatiotemporal image correlation, much about granule motion near the membrane and local membrane folding before, during, and after fusion can be revealed. These optical combination approaches will be discussed both theoretically and practically with a view toward their possible applications to a wide variety of cell and molecular biological problems. (The experiments on chromaffin secretory cells were done in close collaboration with the laboratory of Dr. Ronald Holz of the University of Michigan.)

Host: Rhonda Dzakpasu
Discussion Leader: Rhonda Dzakpasu