Antimicrobial peptide-membrane

I am trying to find the kinetic parameters for antimicrobial peptide with membrane mimetics. I have tried both L1 and HPA sensor chips. However, both shows non-specific binding. I tried following methods for melitin that was published and tried reproducing binding curves for melitin (Niv Papo and Yechiel Shai, Biochemistry 2003, 42, 458-466). However, it wasn't possible to get the same curves. Could someone please explain why I am not able to obtain sensorgrams as shown on the paper without any non-specific binding.

I tried to achieve coverage on these chips as indicated in Biacore protocols for the reference, mammalian mimetic, and also for the sample, bacterial mimetic. BSA at 0.1 mg/mL is not showing any binding. However, I see non specific binding with both systems. I used both, phosphate and PBS at pH 7.4.