From: dr. jack correia <jcorreia@fiona.umsmed.edu>
  To  : rasmb@bbri.eri.harvard.edu
  Date: Mon, 16 May 94 13:08:25 -0500

Re: Differential sedimentation.

>
>Geoff-
>I haven't tried, but have a couple of projects that are good candidates
>for this sort of analysis. I'll be paying close attention to this
>discussion since there isn't any written records on how to use the XLA in
>this fashion. The potential sensitivity to conformational changes is
>enormous, but I have always been concerned about mismatches in viscosity
>causing misinterpretations (causing me to chicken out). Does anyone have
>experience with this?
>Best regards-
>Tom Laue
>
Tom,
      If you reread the Schachman papers on this method you will find it was
applied to APCase and the effect of small substrate concentrations, [c]'s
that would not change density or viscosity!  Matching density and viscosity
is a requirement of this method!!  Thus, it is limited to high affinity effector
s!
It also requires extremely precise filling to perfectly match the menisci!