1. By Simone Siegel and Avery Baker (Dr. Shubeita)
Molecular Motors
By Simone Siegel and Avery Baker
(Dr. Shubeita)

2. Molecular Motors Move lipid droplets Have two “heads”
Walk along microtubules
Take steps, like humans
Study kinesin and dynein

3. Kinesin vs. Dynein Well known Harder to study because of speed
Transports lipid droplets to positive end of nuclei
Has a step size of 8nm
Harder to study because of speed
Transports lipid droplets to negative end of nuclei
Has an unknown step size

4. Overall Goal: slow down dynein and measure its step size
It is easier to see individual steps when dynein is slowed down
Study at colder temps. In vivo (inside the cell)
Reducing the temp. breaks ATP bonds less often, less energy released, should move slower

5. Procedure: fly embryos
Learned fruit fly embryo preparation techniques (staging, peeling, mounting)
-Peel when about 2.5hrs old
-nuclei are arranged on outside of embryo
-microtubules run to and away from the nuclei
-place on a flow cell, not flattened so embryo doesn’t know it is dead

6. Obtaining Data
Record videos on cold DIC (Differential Interface Contrast) microscope
-you can see the lipid droplets moving
-their direction indicates whether kinesin or dynein is moving them

8. Analyzing With video, position of lipid droplets can be tracked
Excel spreadsheet used to graph the data from the lipid droplet tracked
Data shows the speed of the lipid droplet

9. Graph of distance (nm) vs. time (sec)
-Plateaus indicate one or two dynein molecules
-Difficulty finding the velocity
-Could show dynein taking steps

10. Graph of slopes of multiple lipid droplet tracks
-The y-axis is the velocity of the lipid droplet
-Several moved fairly slowly
-Higher speeds indicate that more dynein molecules were moving the same lipid droplet
-The cooler temperature could have slowed down the speed of movement