Lecture 7 - SDS-PAGE Analysis

Question 1

How does SDS-PAGE work?

Answer 1

• Migration proportional to molecular weight
• Staining w/ Coomassie blue is approximately proportional to total protein quantity
• Minor differences in MW can be detected.
• These differences are real.
• Can be detected with a good control, i.e., unmodified / untagged protein.

Question 2

How is SDS page different from native PAGE?

Answer 2

Native PAGE, run w/o denaturation

• SDS “dominates” the net electrostatics
• Even highly charged proteins migrate according to mass:charge ratio
• Native PAGE reveals the natural charge sign, but not necessarily the exact mass

SDS-PAGE reveals little about 3D structure