Antw: [RASMB] Am I missing something?

[Holger Strauss]

Dror,

if you're after scanning speed, it might be worthwhile trying out pseudo-absorbance, i.e. scanning each channel in intensity mode and taking the log of the intensity, which is linearly proportional to the concentration, and that's all you need for your analysis. You can fill two samples in one cell, one in the ref and the other in the sample sector. Aquisition takes the same time as for a conventional experiment in absorbance mode, because you're always scanning the ref sector. There's a paper in Anal. Biochem., check Kar (or Khar?)/Schuck/Laue. Accidentally, your S/N is better in pseudo-absorbance, because you're not dividing two noisy datasets.  
This is great in combination with 12 and 3 mm Cps - you can do almost two orders of magnitude with Abs-optics in one exp AND run up to 6 samples (sometimes 8, though I haven't figured out yet how to make that reliable) in a four whole rotor.

Cheers, Holger

>>> Dror Noy <dror.noy at weizmann.ac.il> 06.06.05 21.57 >>>
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Dear all,
I'm running sedimentation velocity experiments on our XLA where a 
typical scan (no replicates, r=6.0 to 7.2) takes about 1 min. If I try 
to scan two cells or more, the time interval between scans increases 
proportionally because the XLA software scans the cells one at a time 
(i.e. scans the whole radial range for cell 1 then cell 2 etc.). This 
makes scanning several cells unreasonably slow. Does anybody know if 
it's possible to scan multiple cells simultaneously a radial step at a 
time (i.e. measure at r=x for all the cells then for r = x+dx for all 
cells etc.)?
Thanks,
Dror
=========================
Dror Noy, Ph.D.
Structural Biology Dept.
Weizmann Institute of Science
Rehovot 76100
Israel

e-mail: dror.noy at weizmann.ac.il
Tel: (972)-8-934 2525
Fax: (972)-8-934 4154
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