I just start to work on coIP. I am studying the interaction between a small menbrane protein A (17kd), and a big menbrane protein B (75kd). I precipitate B, and detect A by WB. I found the control (normal IgG+beads) can be detect protein A. Even I use beads as control, the band is still clear. I doubt the beads can trap small hydrophobic protein.
The beads is produced by Santa Cruz.
Should I use a stringent condition to wash beads? Or I should change another beads.