Separates denatured proteins by size/charge
Typically 6-8 M urea is added into the gel
A great technique to study protein modifications!
Example of Urea PAGE
SDS PAGE
Due to high density of binding of SDS to proteins, the ratio size/charge is nearly the same for many SDS denatured proteins. Hence proteins are separated only by length of their polypeptide chains (but not by differences in charge).
Great separation. Allows estimation of the size of polypeptide chains
SDS gradient PAGE
3
IEF
Separates proteins by their isoelectric points (pI)
Each protein has own pI = pH at which the protein has equal amount of positive and negative charges (the net charge is zero)
