Title: Quiz: What Factors Influence Protein Migration?
Course: BTEC-2020-301-302-303-F21 > Section: Protein Gels

Q: If this umbrella were a protein, would it travel faster through a gel when closed or open? (Note that the umbrella has the same mass regardless of its shape.)
A: (a choice with no text)
Feedback: Incorrect. Think back to the way that supercoiled vs. relaxed plasmids move through an agarose gel; while both plasmids have the same number of base pairs and therefore the same mass, the supercoiled goes through the gel faster because it is compact. Similarly, the more compact a protein is, the faster it will move through a gel.
Feedback: Correct! More compact molecules tend to move faster through a gel.

Q: Which protein runs faster in a nondenaturing gel?
- A globular (spherical shape) protein with a mass of 25 kD, and a strong negative charge (Correct. The more negative a protein is, the faster it will move toward the positive pole.)
- A globular (spherical shape) protein with a mass of 25 kD, and a very weak negative charge (Incorrect. Remember that charges are attracted to their opposite charge. In this case, a weakly negative protein will be less attracted to the positive pole than a more negative protein, which will move faster through the gel.)
A: A globular (spherical shape) protein with a mass of 25 kD, and a strong negative charge

Q: Which protein runs faster in a gel?
- A globular (spherical shape) protein with a mass of 25 kD, and a strong negative charge (Correct. Small proteins are able to move more rapidly through a gel than larger ones of similar charge and shape.)
- A globular (spherical shape) protein with a mass of 87 kD, and a strong negative charge (Incorrect. Recall the way that linear DNA moves through an agarose gel; small fragments of DNA are able to pass through the gel matrix faster than large fragments. Similarly, small proteins are able to move through the gel more rapidly than large proteins.)
A: A globular (spherical shape) protein with a mass of 25 kD, and a strong negative charge

Q: Based on the selections you made in the learning activity and the feedback you received, write in your own words how mass, shape, and charge affect how proteins migrate through a gel.
Feedback: Hopefully you noted that less massive proteins tend to move more quickly through a gel than more massive proteins, that more compact proteins move through the gel more quickly than less compact proteins, and that more negatively charged proteins move more quickly than less negatively charged (or positively charged) proteins.