[RASMB] velocity sedimentation

[pascal egea]

Greetings,

I am currently doing some velocity sedimentation experiments using absorbance optics on a 33 kDal protein and I am processing my data with DC/DT plus.
I have several questions to ask to the g(S) function specialist.
first I was spinning at 50.000 rpm and scanning 3 replicates with a radial increment of 0.02 this was resulting in a scan every 3:30 minutes (roughly).
my g(S) function is very nice clearly indicating a single component system with a S of about 2.3 S.
As It seems that the more frequently you scan the better it is, I therefore tried only 2 replicates and still a radial increment of 0.02 and now it allows me to scan every 2 minutes (approximately). nevertheless my function does not look as nice (this is the same sample). I also increased the speed to 55.000 rpm.

so is it a result of a lower number of replicates (more noise)?. Is it best to scan more frequently with more noise versus less frequently with more replicates?
Is there for sedimentation velocity a really optimal speed (I know the reference curve) or the faster you spin the better it is?

Thanks in advance for your answers.

Pascal Egea
UCSF department of Biophysics and Biochemistry
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