Q: When using any of your Fab-Zap product line, the recommended final concentration is 4.5 nM. Is this based on experiments you have done? I question if at 4.5 nM my primary antibody will be saturated with Fab-ZAP secondary conjugate?
A: Yes, the 4.5 nM concentration is what we use to quality-control test our Fab-ZAP conjugates and why we recommend it in the literature. We also recommend only titrating your primary antibody. The 4.5 nM of Fab-ZAP should be enough to saturate your primary antibody. If you have a test of ~10 nM of primary antibody and you experience less cell death than ~1 nM, this will indicate “antibody competition” (i.e., your primary antibody is not saturated). The data sheet shows a cytotox with a nice example of this. (Fab-ZAP data sheet)