UA Biophysics:Protocols:Tubulin Polymerization with AlexaFluor 488 staining

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The objective of this protocol is to artificially polymerize microtubules from tubulin and to stain them for fluorescence microscopy.


Microtubules depolymerize extremelly rapidly even in the pressence of Taxol. These samples must be imaged the same day they are prepared.


  1. Biotin-labeled tubulin (Cytoskeleton Inc., Denver, CO)
  2. Taxol (Sigma, Saint Louis MO)
  3. GTP [100mM]
  4. BRB80 buffer
  5. MgCl2 [50mM]
  6. DMSO
  7. AlexaFluor 488
  8. PBS-BSA 0.1%
  9. β-mercaptoethanol [14M]
  10. Wet chamber
  11. Coverslips and slides
  12. Nail polish


  1. Prepare 1 ml PBS+β-mercaptoethanol 14mM. Put aside.
  2. Prepare 13.0 μl of growth solution by adding in an eppendorf
    1. MgCl2 [50mM]: 1.04 μl
    2. GTP [25mM]: 2.00 μl
    3. DMSO [100%]: 0.65 μl
    4. BRB80: 9.40 μl
  1. From this growth solution extract 6.5 μl and pour 20μg of biotin-labeled tubulin (Cytoskeleton Inc., Denver, CO) in it. Incubate for 30min at 37°C. Discard the other 6.5μl .
  2. Prepare 500μl BRB80 + Taxol 10μM.
  3. Disolve the 6.5 μl of growth solution + polymerized microtubules in the 500μl BRB80 + Taxol 10μM.
  4. From the 506.5μl take 20μl and deposit it on a thin slide.
  5. Let dry.
  6. Rinse with PBS-BSA 0.1% and leave for 30min at room temperature.
  7. Add 20μl of Alexa 488 2000x in PBS.
  8. Leave in a humid petri dish at room temperature for 30min.
  9. Put a droplet of PBS+β-mercaptoethanol (~20μl).
  10. Immediately put on a thick slide. Then seal with nail polish so PBS+β-mercaptoethanol does not evaporate.
  11. Let dry. Do not expose to light. Ready to be imaged.

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