From: Michael Morris <michaelm@pharm.usyd.edu.au>
  To  : rasmb@alpha.bbri.org
  Date: Fri, 28 Apr 2000 12:21:39 +1000

Incompetency number XXX

Although you guys in the States are a day behind Australia you are ahead in
terms of business hours which means I come in and see a swag of RASMB emails
piled up on my server. So, I jump in on the end of the discussion of
incompetency for what it is worth.

If you are sure the self-associating sample you have at sedimentation
equilibrium is uncontaminated by other proteins and proteolytic breakdown
products, then a sensible model-independent test for the presence of
incompetent species (incompetent monomer or irreversible aggregates) is to
look at the overlap (or lack of overlap) of weight-average molecular weight
plots or, much better, Omega plots. The model independence of these simple
tests is probably crucial since different K values might be generated for
each channel of data simply because the model being fitted is wrong and not
because incompetent species are present.

Furthermore, the type of lack of overlap of the Omega or Mw,app plots can
provide useful clues as to whether the incompetent species is monomeric or
polymeric.

If the type of incompetent species is known or can be guessed there is no
reason I can think of why it cannot be included in the model to be fitted to
the data. We have dabbled with this although never published and I cannot
think of any published examples.

Michael Morris



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Michael Morris
Senior Lecturer
Pharmaceutical Chemistry	  Tel:	+ 61-2-9351-2359
Department of Pharmacy A15	  Fax:	+ 61-2-9351-4391
University of Sydney 2006	Email:	michaelm@pharm.usyd.edu.au 
Australia			
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