COLL 141 |
| James C. Weisshaar and Michael Konopka. Department of Chemistry, U. Wisconsin-Madison, 1101 University Ave, University of Wisconsin-Madison, Madison, WI 53706 |
| Total internal reflectance fluorescence microscopy can track secretory vesicles in live PC12 cells in three dimensions with 5-10 nm spatial resolution and 25 ms time resolution for 10 s. The cells are stably transfected to express the neuropeptide fusion protein ANF-GFP, permitting bright images and high spatial accuracy. Within the actin cortex, some vesicles dwell in sub-25 nm diameter "traps", moving from trap to trap in directed fashion. Others sample large regions of space seemingly without trapping. Some trajectory segments exhibit dwell times, step lengths, and speeds consistent with the known properties of the myosin-V motor, whose steps in vivo may be imaged here for the first time. Effects of actin-altering drugs are under study. Comparison of the statistics and structure factors of the trajectories with random walks and with models combining processive walks with diffusive motion reveal much about both active and passive vesicle transport mechanisms. |
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Nanoscale Imaging of Biological Systems
Division of Colloid and Surface Chemistry |