Same protein, different size on Western and IP ? - (Nov/14/2005 )

Hi, I would like to ask if anyone has seen this happen:
Comparing the size of the protein in the flow through(or original lysate)and
the ones IPed by protein G beads,
I see a slight shift in size between them. This really confuses me.
This happened on more than one protein I worked on.

I am wondering if there is an explanation for this other than nonspecificity?
Thank you!

Maybe you have two species of the same protein (microheterogeneity) in the lysate, and only one of them can be IP'd.

Hi, I would like to ask if anyone has seen this happen:
Comparing the size of the protein in the flow through(or original lysate)and
the ones IPed by protein G beads,
I see a slight shift in size between them. This really confuses me.
This happened on more than one protein I worked on.

I am wondering if there is an explanation for this other than nonspecificity?
Thank you!

Thanks for the reply.

In this case, should I be seeing both of the species in the lysate?

The size difference must come from the sample itself? or could it be from the process of IP?
Confused.