From: Borries Demeler <demeler@bioc09.v19.uthscsa.edu>
  To  : rasmb@alpha.bbri.org
  Date: Wed, 26 Apr 2000 11:09:27 -0500 (CDT)

NONLIN question

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