[RASMB] Overspeeding to establish equilibrium

[John Correia]

Thanks to Allen for the Chatelier reference on overspeeding - an
insightful & productive guy during his US stay - the analysis in this
paper answers the question for simply monodisperse systems and maybe
self-associating systems, eg. given was 1-2-4 and the suggestion was
made to use the dimer in the calculations.  For real cases the loading
concentraions are varied in an attempt to span a range of degree of
association.  Thus 10% associated should be different than 90% in both
Teq and thus Tos.  Don't know in practise if this is correct, seems
right, although the ability to scan that wide a conc range (? 89x ?) may
actually be difficult depending upon the degree of cooperativity.  For
larger spans in size heterogeneity mentioned in the question the big
stuff may selectively or kinetically spin out and be lost; good for
aggregates but not so good for reversible polymers.  Unfortunately
unstable often means during the run and the whole curves seem to loose
signal at a continuous pace.  Do note his smallest delta R is 0.4 cm
while a typical 6 channel centerpiece using 120 ul will be ~0.3 cm which
by itself saves ~44% of Teq while providing plenty of data for complex
global analysis..  To avoid aggregation problems we typically load 60-65
ul and get equilibrium times down to 2-3 hours for a 100 kD protein.


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 Dr. John J. "Jack" Correia
 Department of Biochemistry
 University of Mississippi Medical Center
 2500 North State Street
 Jackson, MS  39216
 (601) 984-1522                                 
 fax (601) 984-1501                             
 email address: jcorreia at biochem.umsmed.edu     
 homepage location: http://biochemistry.umc.edu/correia.html  
 dept homepage location:    http://biochemistry.umc.edu
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