[RASMB] Strange AUC noise

[David Hayes]

Hi Karl,
Please note that the two scan sets are from the same cell, same sample, on different machines, and the cell was not in any way cleaned up between the two.  Any dirt on the outside of the cell would show up in both.  Also, the noise moves around the cell and is time dependent.  
A while back I had a cell with a big splatter on just the sample window and it made a baseline that was around 0.2 A280 at the base of the cell.  SEDFIT did fine fitting this data set, though it looked like a curvy rainbow at the bottom of the cell:  the baseline did not change with time, so SEFIT could fit it.
We always have sample/dirty cell discussions with our Beckman repair man, so we are well trained in making sure the noise comes from the instrument and not the cell or sample.
Kind Regards,
David
      From: Karl Maluf <Karl.Maluf at ap-lab.com>
 To: 'David Hayes' <drdavidbhayes at yahoo.com>; 'RASMB' <rasmb at rasmb.org> 
 Sent: Monday, October 19, 2015 4:12 PM
 Subject: RE: [RASMB] Strange AUC noise
   
David, Are you sure there wasn't a smudge on one the windows from someone's thumb as they assembled the cell? Karl


From: RASMB [mailto:rasmb-bounces at list.rasmb.org] On Behalf Of David Hayes
Sent: Monday, October 19, 2015 11:14 AM
To: RASMB
Subject: [RASMB] Strange AUC noise

Hi all,
We had some strange AUC noise in a recent experiment.  In the pictures below from SEDFIT, the first two runs produced data as in the picture NNBekman1 (the IT guys name our instruments and they pruposely mispelled Beckman as Bekman years ago). A strange noise pattern showed up in the scans that were produced on day one.  Then the sample was loaded into a new cell and run again on the same centrifuge producing the strange noise pattern in the picture called NNBekman1.   the filled cell was taken and gently mixed and then run on another centrifuge Bekman17 and made a perfectly fine patter shown in picture Beckman17.
We have seen the strange noise before on our NNBekman1 centrifuge, but this is the first time on NNBekman2.
Has anyone seen noise like this?  Any theories on the cause of the noise?
It certainly looks like an optical artifact of some kind, but the time dependence is hard to explain.
Kind Regards,
David Hayes
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