[RASMB] Radial-dependent noise in Beckmann XL-I

[Tom Laue]

Hi Anna-
This is a bit surprising. Can you post a couple of scans for us to look at?
It seems unlikely that thermal gradients are the cause. At 4 deg, the 
density of water (or aqueous solvents) is at a maximum, and the 
temperature-dependence of the density is at a minimum- that is, changes 
in temperature have a minimal effect on the density. This is why a lot 
of the early free-boundary electrophoresis work was done at 4 C.
What solvent are you using? Is there enough salt to create the density 
gradient that will stabilize against convection?
Best wishes,
Tom


On 1/26/2012 7:33 AM, anna vitlin wrote:
> Hello,
> We have a Beckmann XL-I running a An-60 Ti rotor.
> When running sedimentation velocity experiments at 4 deg. we have 
> noticed protein-independent, time-independent, radial-dependent noise, 
> consistently between 6.2 and 6.4 Radius.
> This phenomenon occurs using different cell assemblies, different 
> wavelengths and different velocities but does not occur at 20 deg.
> Has anyone detected behavior like this and how do we troubleshoot it?
> Should we call for service?
> Thank you
> Anna Vitlin
> Tel-Aviv university
>
>
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Department of Biochemistry and Molecular Biology
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