Fitting steady state concentration vs response values - Forum


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TOPIC: Fitting steady state concentration vs response values

Fitting steady state concentration vs response values 18 Oct 2020 19:42 #1

I'm trying to fit concentrations vs. observed responses to a Langmuir 1:1 model but have not discovered any straight forward method. Does anyone have a suggestion on how to fit this data to obtain Rmax and KD?
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Fitting steady state concentration vs response values 19 Oct 2020 09:12 #2

Hi,

Use the steady state model.
The requirement for this model is that the response measure point is at steady state.
Kind regards

Arnoud

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Fitting steady state concentration vs response values 19 Oct 2020 19:00 #3

Thanks Arnoud for the response. I left out a few details that may have better framed the question.

I captured a his-tagged receptor and injected over its binding partner for 120 seconds. The his/anti-his interaction decayed about 35% during the association so I took the max response just a few seconds after injection (very fast on-rate). I then plotted those responses on the attached chart as they are more representative of the response at that concentration. I’m wondering if there is a way to fit this curve to obtain the rmax and KD as I can’t change the response point the Biacore software uses for determining response and would prefer not to repeat experiment with shorter associate time. Many thanks in advance !

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Fitting steady state concentration vs response values 20 Oct 2020 19:57 #4

Hi,
The formula for fitting the steady state is: Y = Conc*Rmax/(KD+Conc).
It can be done in Excel. Search for 'excel fitting with solver' on the web and you get some tutorials.
Also most commercial graph-software can do this fitting, so you are not dependent on your SPR software.
The model is often one site binding or hyperbola.

Kind regards
Arnoud

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Fitting steady state concentration vs response values 20 Oct 2020 22:58 #5

Thank you Arnoud. What I’m struggling with is that I am trying to calculate both KD and Rmax from this response vs concentration plot. I couldn’t find a straightforward solver tutorial either for fitting this curve. Thanks for your help.

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