Vesicle binding and movement on microtubules - This is something like the fish melanophore. The blue vesicles (pigment granules) move randomly until they "hit" a microtubule. They move first in the outward (+) direction. They can fall off either spontaneously or when they reach the end of the microtubule. The default spontaneous rate of fall off ("fall off parameter") is 0.97, meaning that for every time step, 97% of the time the vesicle will remain bound to the microtubule while there is a 3% chance it will fall off. You can change this number during the animation. Once the vesicle falls off, it moves randomly until it binds to another microtubule. The default "binding efficiency" of 0.7 means that 70% of the time that a vesicle hits a microtubule it will bind to that microtubule. Once it is bound, it will move in the inward (-) direction, until it spontaneously falls off or reaches a certain set distance from the center ("central no-travel zone"). The vesicles continue to alternate directions as they fall off and re-bind. In the fish melanophore, the cAMP level determines the distribution of the pigment granules. You can change this by using the buttons.

Combination of microtubule dynamic instability and vesicle movements. In this animation there are 40 microtubule nucleation sites. You can specify a subset of microtubules that have different dynamic properties. These microtubules will be in the lower right quadrant of the circle and are colored green.

Axonal transport animation - You can change the number of anterograde and retrograde vesicles and the average length and gap between microtubules. While the animation is running, you can change the speed of the anterograde and retrograde movements, brownian motion when vesicles aren't bound to microtubules, the saltation parameters, and fall off parameters. The rate of vesicles moving out of the field is monitored.


Old actionscript 2 animations: Vesicle binding and movement on microtubules - By pressing the up or down arrows, you can switch the cell between the high and low cAMP states. Another version - no minus end directed movement in the high cAMP state.