Forum :: Curve Fitting

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This forum is intended for questions about kinetics, Surface Plasmon Resonance and the instruments related to these techniques.

TOPIC: Curve Fitting

Curve Fitting 18 Nov 2015 16:51 #1


When I run the fitting in BiaEvaluation I always get sharp lines, I mean the lines don't go smoothly with the curve, always go with right angles around the curve without any curvature (Fig 1), do you know why and how can I resolve this

I want the fitting to be something like Fig 2

Curve Fitting 18 Nov 2015 19:52 #2

Hi Ahmed,

First make sure that the concentration values you put in are right.
Then choose the proper parts for association and dissociation.
Select a 1:1 model.

What you can try is to do the fitting in little steps.

1) fit the dissociation only.
2) fit the association and dissociation but use the value of 1 and set it constant. In addition, set the RI and drift to constant zero.
3) repeat 2) but change the initial value for ka a factor 10 up or down
4) when the fitting looks better, repeat with the reported values from 3) and let float the RI and drift if necessary or add a mass transport component.

All the contributions of RI, drift and mass transport should be small.

I hope this will help you.

Kind regards


Curve Fitting 18 Nov 2015 22:01 #3

Thanks a lot Arnoud for the assistance.

When you said "use the value of 1 and set it constant." you mean use the 1:1 model?

The problem is that when I am trying the Biaevaluation handbook procedure for fitting of the model file came with Biacore, I still get the same right angle fit although I am following the same procedure mentioned in the handbook?

Best Regards

Curve Fitting 18 Nov 2015 22:13 #4


I ment the dissociation of value of step 1).

The reason why fittings sometimes go wrong is that the initial values are too far from the actual values and the fitting procedure gets stuck in the wrong values.
Please look at for more explanation.

Last Edit: 18 Nov 2015 22:16 by Arnoud.
Moderators: Arnoud