Title: Quiz: Pouring SDS-PAGE Gels
Course: BTEC-2020-301-302-303-F21 > Section: Protein Gels

Q: Which chemical(s) in SDS-PAGE is a neurotoxin?
- DTT (Incorrect. Acrylamide, in the liquid unpolymerized form, is a neurotoxin.)
- SDS (Incorrect. Acrylamide, in the liquid unpolymerized form, is a neurotoxin.)
- APS and TEMED (Incorrect. Acrylamide, in the liquid unpolymerized form, is a neurotoxin.)
- Acrylamide (Correct. Acrylamide, in the liquid unpolymerized form, is a neurotoxin.)
A: Acrylamide

Q: Which chemical(s) should not be added until you are ready to pour the gel because they initiate polymerization?
- Tris-HCl (Incorrect. APS and TEMED initiate the polymerization reaction.)
- SDS (Incorrect. APS and TEMED initiate the polymerization reaction.)
- APS and TEMED (Correct. APS and TEMED initiate the polymerization reaction.)
- Acrylamide (Incorrect. APS and TEMED initiate the polymerization reaction.)
A: APS and TEMED

Q: Why is it important that the separating gel be made with Tris-HCl pH 8.8, while the stacking has pH 6.8?
- The different pH values are required for the stacking process. (Correct. The stacking gel’s pH of 6.8 causes the proteins to be squeezed between chloride and glycine ions, creating a tight band of proteins. The separating gel’s pH of 8.8 allows the glycine ions to move ahead of the proteins. The proteins are then separated only by mass.)
- The different pH values help denature the proteins. (Incorrect. While extreme pH values can cause denaturation, the pH values of 6.8 and 8.8 are unlikely to do so. Instead, the different pH values promote stacking. The stacking gel’s pH of 6.8 causes the proteins to be squeezed between chloride and glycine ions, creating a tight band of proteins. The separating gel’s pH of 8.8 allows the glycine ions to move ahead of the proteins. The proteins are then separated only by mass.)
- The different pH values help eliminate the effects of charge. (Incorrect. While pH can affect charge, remember that large amounts of SDS have been added to make all proteins strongly negatively charged. The effects of pH values 6.8 and 8.8 are negligible. Instead, the different pH values promote stacking. The stacking gel’s pH of 6.8 causes the proteins to be squeezed between chloride and glycine ions, creating a tight band of proteins. The separating gel’s pH of 8.8 allows the glycine ions to move ahead of the proteins.)
- The different pH values help eliminate the effects of mass. (Incorrect. The different pH values promote stacking. The stacking gel’s pH of 6.8 causes the proteins to be squeezed between chloride and glycine ions, creating a tight band of proteins. The separating gel’s pH of 8.8 allows the glycine ions to move ahead of the proteins. The proteins are then separated only by mass.)
A: The different pH values are required for the stacking process.