From: Karen Fleming <kgf@mail.csb.yale.edu>
  To  : Borries Demeler <demeler@bioc09.v19.uthscsa.edu>
  Date: Wed, 26 Apr 2000 12:41:34 -0400

Re: NONLIN question

Borries,

Separating the LnK2 channel can also mean incompetent dimer. It just depends on
the concentration dependence of the apparant LnK2 value. I frequently see higher
order incompetent something. A common model in my system is 1<->2 <->incompetent
tetramer. This is why I NEVER use the Beckman software because one cannot
separate the Ks in a global fit.

Hope this makes sense.

-Karen

Borries Demeler wrote:

> Dear RASMB'ers,
>
> I have a question that keeps popping up - I never really thought about it
> much, but maybe someone has already:
>
> Sometimes, when fitting a monomer-dimer fit for example, one can obtain a
> substantially better variance by turning on the multi-channel option for
> LnK2 in Nonlin. I suppose one possible interpretation for this would be
> the presence of a portion of the sample being in incompetent monomer state
> the rest can reversibly associate like a normal M/D system.
>
> What other possible interpretations exist for this symptom? And what
> models have people used to fit that?
>
> I suppose for the case of an incompetent monomer an additional exponential
> term with the monomer MW and an amplitude proportional to the fraction of the
> incpt. monomer would work, where the fraction of the total concentration
> would be an adjustable (floating) parameter. Seems like something quite
> sensitive to cross-correlation.
>
> Anyway, if you have dealt with such a system previously, I'd be interested
> to hear from you.
>
> Thanks in advance for any comments and suggestions, -Borries

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