Can the molecular weight of modified proteins be determined by SDS-PAGE?

Question

If yes, how is this done?

Answer 1

Yes, basically by using the same methods as for regular proteins. Depending on what type of modifications you are dealing with, you need to run a series of similarly modified proteins where you already know their molecular weight. By comparing the movement of your unknown proteins with the known one, you can determine the molecular weight with reasonable accuracy.

Answer 2

The first answer is completely correct. Normally you would use a marker which produces bands on th SDS gel which specific molecular weights and compare those to your protein. You can not be certain that your protein is exactly say... 30 kDa but you can see it is close and if you want to be sure could send it for mass spec analysis which will provide you with the exact molecular weight.

Hope that helps