[RASMB] buffer components and IF optics

[Peter Schuck]

Irene,
I doubt that 1 mM DTT could have been the problem.  If you see only noise, 
that would point towards strong scattering, either from the sample or from 
the surface of the window, degrading the contrast of the fringes.  I've 
done many runs with DTT concentrations in the low mM range, and never 
noticed anything unusual.  I don't know, though, what happens at 200 mM...
Peter


At 03:10 PM 5/12/03 +0000, you wrote:
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> >
> > Regarding high concentrations of DTT, I have no hands-on experience
> > with this situation in particular, but if it's not possible to
> > precisely match the sample and reference sectors in the buffer
> > composition, you'll see the sedimentation of DTT.  Also, I'm not sure
> > if the refractive index increment of DTT could possibly change with
> > oxidation state, and in this way create a mismatch between the two
> > sectors.  But again, it should be no problem to take this into account
> > in the data analysis (assuming that you have an excess signal from DTT
> > in the sample sector), by treating this as an extra sedimenting
> > species.
> >
>In my limited experience I have come across one problem with DTT. A 
>Student supplied
>me with a sample and buffer containing 1mM DTT for an SV run. On the 
>3000rpm run all
>I saw was noise. Initially we thought  azide was the problem, but it 
>turned out to be
>oxidised DTT. This was  solved by adding the same concentration of TCEP.
>
>Irene
>
>
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