[RASMB] upper concentration limit AUC

Mon Sep 1 06:40:08 PDT 2008

Hi Joris,

How high you can go before you will have to model concentration
dependent nonideality will depend on your protein (charge, anisotropy),
the buffer, speed and the type of experiment you will run. In general,
because of the absence of flow, equilibrium experiments are not as much
affected by hydrodynamic non-ideality as velocity experiments.
One thing to be aware of is that both XLI and XLA, but especially 
XLI can be subject to refractive problems when the gradients become
too steep. For high concentration measurements I would definitely recommend
investing in 3 mm centerpieces. Check RASMB archives on messages about
Wiener Skewing if you plan to measure with interference. If so, make sure
your optics are focussed on the 2/3 plane.

Regards, -Borries

> 
> Dear all,
> 
> =20
> 
> A colleague asked me whether analytical ultracentrifugation has an upper =
> limit with regard to the concentration of the protein. They want to =
> measure the protein at the same concentration as the NMR experiments (> =
> 1 mM). I am not entirely sure but I thought this should be no problem. =
> One could easily measure off-peak at another wavelength than 230nm, e.g. =
> 235nm or 280nm, right?! Or does one run into non-ideality phenomena when =
> doing sedimentation equilibrium at these high protein concentrations?!
> 
> Thanks a lot in advance for any feedback.
> 
> Best wishes,
> 
> =20
> 
> Joris Beld
> 
> =20
> 
> Hilvert Group
> 
> ETH Z=FCrich
> 
> Switzerland
> 
> 
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> 
> <p class=3DMsoNormal>Dear all,<o:p></o:p></p>
> 
> <p class=3DMsoNormal><o:p> </o:p></p>
> 
> <p class=3DMsoNormal>A colleague asked me whether analytical =
> ultracentrifugation
> has an upper limit with regard to the concentration of the protein. They =
> want
> to measure the protein at the same concentration as the NMR experiments =
> (> 1
> mM). I am not entirely sure but I thought this should be no problem. One =
> could
> easily measure off-peak at another wavelength than 230nm, e.g. 235nm or =
> 280nm,
> right?! Or does one run into non-ideality phenomena when doing =
> sedimentation equilibrium
> at these high protein concentrations?!<o:p></o:p></p>
> 
> <p class=3DMsoNormal>Thanks a lot in advance for any =
> feedback.<o:p></o:p></p>
> 
> <p class=3DMsoNormal>Best wishes,<o:p></o:p></p>
> 
> <p class=3DMsoNormal><o:p> </o:p></p>
> 
> <p class=3DMsoNormal>Joris Beld<o:p></o:p></p>
> 
> <p class=3DMsoNormal><o:p> </o:p></p>
> 
> <p class=3DMsoNormal>Hilvert Group<o:p></o:p></p>
> 
> <p class=3DMsoNormal>ETH Zürich<o:p></o:p></p>
> 
> <p class=3DMsoNormal>Switzerland<o:p></o:p></p>
> 
> </div>
> 
> </body>
> 
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> 
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