Question

Imagine that you have just run protein gel electrophoresis using the same protein ladder that we used in this experiment as your molecular weight standard. In the test sample (in the lane just to the right of the ladder), after running the gel you stain for a protein band that is positioned almost exactly halfway between the Phosphorylase and BSA bands on the ladder. A colleague in the lab points to the band and says it must have a molecular weight of 80kDa since it is halfway between 62 and 98kDa. Do you agree with their reasoning? Why or why not?

Answer 1

The reason given is correct in my opinion and says that the test sample must have a molecular weight of 80kDa since it is halfway between 62 and 98kDa.

We know that Phosphorylase and BSA bands are of molecular weight 62 and 98kDa on the ladder which will be the reason for the same.The test sample (in the lane just to the right of the ladder), after running the gel is positioned almost exactly halfway between the Phosphorylase and BSA bands on the ladder.The distance between the 62 and 98kDa bands is (98-62) =36kDa.Now the test sample band is exactly the halfway of this.That means the test sample band is 36/2 =18 KDa far from both the 98kDa and 62kDa bands.So, (98-18)kDa = 80kDa and( 62+18) kDa = 80kDa band is the test sample band.