[RASMB] difference between experimental and modelled sed coef for

[Borries Demeler]

> Dear RASMBers,
> 
> I am working with a protein-DNA complex for which I did sedimentation 
> velocity experiments (interference and absorbance) to determine its 
> sedimentation coefficient (using c(s) and finite elements to calculate 
> <s> from the experimental data). I have done the experiments a number of 
> times at different concentrations.
> 
> The buffer  in which the complex is contains D2O (43->65%) and Glycerol 
> (about 20%). I measured the densities of the buffers and estimated the 

Marcello,

that's quite a bit of glycerol. Depending on the speed, I'd be concerned
about building up a glycerol gradient inside your velocity experiment
which would also give a gradient of density and viscosity, causing the
sample to slow down towards the bottom of the cell (it hits a glycerol
cushion?). Just another variable to think about. One thing you might want
to do to verify this is to run glycerol against water to see if the effect 
is large enough ito worry about at the speed you are running it. Should be
possible with and XLI.

Regards, -Borries