From: Jo Butler <pjgb@mrc-lmb.cam.ac.uk>
  To  : =?ISO-8859-1?Q?Helmut_C=F6lfen?= , rasmb@bbri.harvard.edu
  Date: Fri, 05 Oct 2001 09:52:20 +0100

Re:

Dear Helmut,

You say that you know the v-bar for these charged spheres.  While this may be true in vacuo, do you actually know the apparent v-bar which will be relevant when they have bound counterions/solvent due to their charge?
This could have a significant effect on the precision of your calculations.

Jo

--On Thursday, October 4, 2001 11:14 pm +0200 Helmut Cölfen <coelfen@MPIKG-GOLM.MPG.DE> wrote:

> Hi my friends out there,
>
> I seem to have a quite trivial problem but nevertheless seek your
> advivice if you are aware of more recent theories.
>
> I  have a close look at strongly charged colloids - all of them are more
> or less the ideal of a monodisperse solid hard sphere. The sedimentation
> behaviour of their uncharged counterparts is precicisely known as all of
> you will aggree. OK, I know the VBAR, the molar mass from their diameter
> from dynamic light scattering, Field flow fractionation and transmission
> electron microscopy. The world should be fine to describe everything so
> far.
> But as you can imagine, there are strong charge influences on
> sedimentation and I wonder if this "ideal" case has not yet been treated
> in dependence of particle charge.
>
> Now the charge comes into play. I have started reading the classical AUC
> textbooks and surprisingly, I found the best answer in Svedberg/Pedersens
> classical book. But this is almost 70 years old so  I guess there are
> more recent theories of charge influence on sedimentation underway. OK,
> there are many papers treating the sedimentation of polyelectrolytes but
> the thing I look for is: Can I determine the average particle charge
> QUANTITATIVELY once I know the VBAR and particle dimension ???
>
> I have the feeling that the answer is trivial but nevertheless, I believe
> that there must be a more recent treatment than that of Svedberg in
> 1940's.
>
> Any hints towards more recent theories for SOLID CHARGED SPHERES are
> highly appreciated.
>
> Thanx a lot
>
> Helmut
>
>
>
>
>
>
>
>
> _______________________________________________________________
> Dr. Helmut Cölfen
> Max-Planck-Institute of Colloids and Interfaces
> Colloid Chemistry
> Am Mühlenberg 2
> 14424 Potsdam
> Germany
>
> Tel: --49 331 567-9513
> Fax: --49 331 567-9502
> http://www.mpikg-golm.mpg.de/kc/coelfen/
> _______________________________________________________________
>



P.J.G. Butler,
MRC Laboratory of Molecular Biology,
Hills Road, Cambridge, CB2 2QH, UK.
Tel. +44 (0)1223 402296