From: John Correia <jcorreia@biochem.umsmed.edu>
  To  : rasmb@alpha.bbri.org
  Date: Thu, 27 Sep 2001 16:31:02 -0500

Re: Keq from sedimentatin velocity

Judith

I presume you are using weight average as determined from DCDT or DCDT+ analysis.  You cannot use an average S.  The conc to use is the one you get from the the DCDT+ analysis.  see Correia (2000) Methods Enzymol vol 321: 81-100.

Of course other boundary analysis methods exist like sedfit from Peter Schuck for monomer-dimer.



>>> <judithk@vax2.concordia.ca> 09/27/01 04:22PM >>>
Dear RASMBers, I am trying to measure the equilibrium constant for a
monomer/dimer system using sedimentation velocity. I feel reasonably sure
of the s20,w values for the monomer and dimer and reasonably sure that
there are no higher order mers. However, when calculating Keq, what
protein concentration do I use? Is it the concentration of the solution
that I loaded? Or is it the concentration at some point in the cell? If
the later - at what point in the cell do I measure it and when during the
run? Many thanks.

Judith Kornblatt
Dept of Chemistry and Biochemistry
Concordia University
1455 de Maisonneuve Ouest
Montreal, Qc H3G 1M8
Tel: 1 514 848 3384   FAX: 1 514 848 2868