Studying Single-Molecule Molecular Motors Paul Selvin John Bardeen Faculty Scholar Dept. of Physics University of Illinois at Urbana-Champaign We have been able to "beat" the diffraction limit of light, i.e., we have achieved 1.5 nm resolution using fluorescence imaging, approximately 300 times better than the diffraction limit of conventional light. We have been able to achieve this with a time resolution to 1-500 msec. Using this time-resolution, we have been able to see single molecular motors moving both in purified systems, and inside living cells. In purified systems, we show that myosin and kinesin, two (out of three) types of molecular motors, walk in a hand-over-hand and not an inchworm fashion. We also show that Myosin VI, which moves in opposite direction to all other myosins, actually walks in a hand-over-hand fashion, despite recent controversy. In living cells, we have been able to see individual cargos being moved by individual kinesin and dynein (the third type of molecular motor). We find that both kinesin and dynein move cargo 8 nm per ATP (the universal food of the cell), in opposite directions in a cell. Amazingly, these two molecular motors do not engage in a tug-of-war, but appear to be cooperative, giving the particle extra speed. Refreshments will be served in Rm. N201 at 2:30 PM