I am studying the Protein-peptides interaction using FP assay. But my curve in never saturating even when unlabeled protein concentration is 1 mM. When I increase conc of unlabeled protein from micro molar to 50 or 100 micro molar with fixed nM conc of labeled peptide, the FP values increases form 20 to 50 to 80 but never saturated. What does it indicate,

1.If  there is no interaction then where the increase in FP signal coming from?

2. If there is interaction then why the curve is not saturating even after adding 100 micro molar unlabeled protein to 10 nM labeled peptide?