Poor fit

Hello. I did this experiment in which I the ligand is a Biotinylated IgG, Fc specific that is immobilized unto a streptavidin chip. I then passed on an antibody as the analyte. Used HBS P+ with 0.01% BSA as the running buffer. I used this running buffer for all dilutions. I am getting very poor fit, high bulk contribution found in the QC section. Are there any suggestions on how I can have a better fit? I do not see any non-specific binding from the reference. Also tried to set RI=0 with no success. Thank you.

Hello,

In the first figure the fitting algorithm adds the bulk to make the chi2 smaller. Also the second fit is not optimal. The conclusion should be that the curves are not 1:1.
Therefore, there will be no better 1:1 fit on these curves.

The absence of non-specific binding (in the reference) is no guarantee that an interaction is 1:1.
Check the analyte (and ligand) for purity.

Arnoud

Thanks Arnoud. I will check...