protein size change after western blot - (Oct/26/2009 )

My target protein is about 61KD.
But I did the western blot, the band was between 45KD~55KD.
What's the matter? How to explain it?Please give me some advice. Thanks a lot!

proteins don't always migrate to the proper molecular weight. sds-page is not perfect for mw determination. it gives a good approximation but there are a number of factors that may alter mobility.

you should confirm with other techniques (eg gel filtration).