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Need help with NonlinearFit

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  • Subject: [mg1872] Need help with NonlinearFit
  • From: "Timothy W. Weber" <tww5y at>
  • Date: Wed, 9 Aug 1995 22:40:04 -0400
  • Organization: uva

I'm trying to fit two sets of kinetic data using NonlinearFit and I'm having
a lot of difficulty doing so. My reaction is bisubstrate, S1 and S2, let's
say. My rate expression is 

r = a S1 S2/(b + S1 (c + S2))

where a, b and c are my kinetic constants. My problem is that one set of data
is for varying S1 at constant S2, while the other is for varying S2 at constant
S1. There is one crossover point, which unfortunately didn't have the exact 
same value in both studies. What's happening is that I'm getting two sets of 
kinetic parameters for the two different sets of data, and theoretically, they
should be capable to fitting to only set of parameters, right? Any suggestions?
My next step is to average the values for the crossover point and replace the
individual values with the average. Yes? No? I'm in a real quandry and under
somewhat of a time constraint since these are for my dissertation, which is 
coming up in a few short weeks.

Any help would be appreciated. Thanks in advance.


Tim Weber
Graduate Student, Chemical Engineering

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