Proteins which run high on SDS-PAGE

[sam simons]

I believe that the "kinks" introduced by proline would create a larger 
apparent size in three dimensions. A long rod would be relatively thin 
in the third dimension. Of course this is dependent on the rigidity of 
an SDS bound, linearized polypeptide. This could also explain why 
multiple prolines in a domain would have more effect than one or a few 
spread through the protein as it would tend to give a more extensive 
deviation into the third dimension. As I said before, I'm not sure how 
much may be due to charge distribution differences, they could be 
significant. I would also point out that Enrique Jose Labadan Frio 
described this in much better biophysical terms in his reply. He may 
also be suggesting that rigidity introduced into the structure by the 
prolines may inhibit movement through a gel. 

Sam

Pfizer assumes no responsibility for statements I make, be they lucid or 
no.