I expect a protein at 206kDa. The band seems to be in both wild-type and transgenic samples for tomato and maize . I was wondering if this size is just not documented as a common non-specific FLAG-like sequence in plants. In M2 (monoclonal, anti-mouse) I regularly receive nonspecific bands around 205 and 120. Any suggestions for alternative antibodies to test?

I do not believe it is an issue with blocking buffer. I incubate at RT for 1 hour with 5%NFDM. Should I play around more with the primary concentration? It doesn't seem fruitful since this non-specific band will still be there. Any help would be greatly appreciated!