This Data Analysis Problem does not appear in the textbook.

Source:  Millonig, R., H. Salvo, U. Aebi. 1988. Probing actin polymerization by intermolecular cross-linking. J. Cell Biol. 106: 785–796.

Corresponding chapter(s) in the textbook: Chapter 14 (and 1)

Review the following terms before working on the problem: skeletal muscle, G- and F-actin, cytoskeleton, electron microscopy


Rabbit skeletal muscle G-actin was isolated and purified. G-actin was dissolved in a buffer containing 2 mM MgCl2 and 50 mM KCl. Samples were taken 30 seconds (a) and 5 minutes (b) after the addition of the salt solution and processed for electron microscopic analysis; uranyl formate was used for staining (scale bars, 100 nm).


© 1988 Millonig, R., H. Salvo, U. Aebi. Originally published in Journal of Cell Biology.


1. What kind of contrast enhancement was used in this experiment? Explain how this type of enhancement works.

2. Compare the two micrographs. What process was stimulated by salt treatment?

3. Determine the diameter of the filaments in micrograph b.