[RASMB] Urea question

[pjgb at mrc-lmb.cam.ac.uk]

Dear Borries and RASMBers,

A number of years ago, I was involved in following the unfolding of the 
HPV-16 E2 protein DNA-binding domain with increasing urea concentrations, 
up to 5M (Mok, Y.-K., de Prat Gay, G., Butler, P.J. and Bycroft, M. 
Equilibrium dissociation and unfolding of the dimeric human papillomavirus 
strain-16 E2 DNA-binding domain. Prot. Sci., 5, 310-319, 1996).
While tha analysis is crude by modern standards, this publication does 
contain the denisty of urea solutions, at various concentrations, measured 
in the Paar density meter.
Moreover, from the regularity of behaviour of the protein with urea 
concentration, there was no obvious evidence of any problem with urea 
gradients - and that with long column equilibrium.

Yours,

Jo

--On Tuesday, April 20, 2004 11:32 am -0500 Borries Demeler 
<demeler at biochem.uthscsa.edu> wrote:

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> Hi,
>
> I was wondering if someone has experience with performing equilibrium
> experiments in 1 M urea. I am concerned that in high speed experiments
> there may be a density gradient forming that may affect buoyant density
> and cause problems with standard model fitting. I haven't tried it yet and
> would like to know if I should expect problems before I waste the sample.
> I know that high NaCl concentrations can cause quite a problem in velocity
> experiment, but there viscosity is also a problem. Peter, you have done
> some work on this, any comments about urea? Or is the short column
> reducing any effect to where it could be neglected?
>
> Thanks,
> -Borries
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P.J.G. Butler,
MRC Laboratory of Molecular Biology,
Hills Road, Cambridge, CB2 2QH, UK.
Tel. +44 (0)1223 402296