Can Immunoprecipitation result in the identification of a modified form of a pro - (Mar/14/2014 )

Hi All,

Please does anyone know if immunoprecipation followed by Western blotting can result in the identification of a modified form of a protein that is not otherwise detected via western blotting alone? See attached document. I keep seeing a band at ~130 kDa compared to the ~100 kDa size of my protein when I perform IP/WB compared to when I perform WB alone. I am torn between whether this is a PTM or just unspecificity of my antibody. Also, I am wondering if this is resulting from the PA beads I used?? Any ideas and suggestions are welcome. Thanks.

Phina

What were your controls for the IP?  Did you do a normal serum IP as well as specific antibody?  Did you do a beads only or preclear IP?