I am performing an inhibition assay. I generally run my control several times throughout the experiment to make sure that the chip is regenerating/functioning properly. I have noticed that over time, I get a decrease in signal when running the control. I thought perhaps the chip was no good, however when I prepare fresh control, it works as well as the initial preparation. My control is an antibody (I have a peptide coupled to BSA coupled to the chip). Could this reflect antibody instability at low concentration? Its only a few hours difference? I am totally baffled. I thought at first it might be a regen issue but that does not seem to be the case. Any thoughts?