ions-what-band-pattern-would-you-predict-from-top-near-well-to-bottom-of-the-gel

Question

If three proteins of 20 kDa, 60 kDa, and 120 kDa are loaded in separate lanes on an SDS-PAGE gel under identical conditions, what band pattern would you predict from top (near well) to bottom of the gel?

Accepted Answer

Top: 120 kDa, middle: 60 kDa, bottom: 20 kDa, because larger proteins migrate more slowly through the polyacrylamide matrix while smaller proteins travel farther.

Answer

All three will co-migrate to the same position in the gel because SDS equalizes charge-to-mass ratio so that every protein experiences identical electrophoretic force regardless of size.

Answer

Top: 20 kDa, middle: 60 kDa, bottom: 120 kDa, because SDS reverses the native charge of proteins causing smaller proteins to be retained near the wells while larger ones travel faster.

Answer

The pattern cannot be predicted without knowing the pH of the running buffer since SDS-PAGE separation is dominated by isoelectric focusing which requires pH information to determine migration order.