Stability values in negatives

Hi,
We have a problem when we run a kinetics method in biacore T100 and Biacore T200.
So we use a capture method, Our kinetic profile and the kinetic parameters are fine but when i look into the bar chart for the stability values, the last concentration goes in negatives. The binding values are also fine,I tried increasing the concentration but then our Chi square value increases.

Thanks

The stability is measured with a report point 10 seconds after the end of the analyte injection.
For a single channel, the values calculated are the difference between the baseline value (before the analyte injection) and the point when the stability is measured.
If you look at the subtracted curves (e.g. ch2-1) the stability value is also subtracted. Thus when the reference channel has a higher value, the stability value for channel 2 will be negative.

Since you use a capture approach I can imagine that you have some dissociation from the capture system leading to differences between reference and active signal. Since increasing the analyte concentration makes things worse I think that is the case in your system. As long as the differences are small compared to the overall signal I would not bother.

Arnoud