tokens: Samples were further incubated with A / G Pluss Agarose beads ( Santa Cruz Biotechnology ) at 4 degrees C for 25 minutes before the beads were removed by centrifugation at 5000g for 4 minutes and the samples were incubated with 1 . 5 micro g anti - V5 ( Invitrogen ) at 4 degrees C for 90 minutes .