PHYS 115 |
| We have been able to measure 1.5 nm in 1-500 msec, using fluorescence imaging. We have seen single molecular motors moving both in purified systems, and inside living cells. In living (Drosophilia) cells, we have seen individual cargos being moved by individual "conventional" kinesin and dynein. We find that both kinesin and dynein move cargo 8 nm per ATP. Amazingly, these two molecular motors do not engage in a tug-of-war, but appear to be cooperative, giving the particle extra speed. 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. Finally, we have also achieved the inverse of this technique on melanophores in frog eggs. These cells are non-fluorescent but contain melanin, an opaque material. Here we use bright-field microscopy and achieve < 2 nm and < 2 msec resolution. We show that a heterotrimeric kinesin, and kinesin II, displays 8 nm steps, and myosin V moves 36 nm, all in vivo. Furthermore, they move farther total distances when intermediate filaments are removed. And for the first time, we have been able to see a cargo being passed between myosin V and kinesin/dynein. |
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Frontiers in Single-Molecule Biophysical Chemistry and Imaging
8:20 AM-12:00 PM, Monday, 11 September 2006 Grand Hyatt San Francisco -- Plaza Ballroom East, Oral
Division of Physical Chemistry |